6 Red Flags to Avoid When Considering a Heat Pump Installation

6 Red Flags to Avoid When Considering a Heat Pump Installation

As someone that’s deeply involved in the design and installation of heating systems, I want to share essential advice for consumers considering an air source heat pump. My business partner, Luke, and I run Optimus Heating, and we’ve achieved recognition in the industry, winning Vaillant’s heat pump challenge last year and being one of 10 chosen projects in Viessmann’s Top of the SCOP’s competition. We specialise in creating highly efficient heating systems, often achieving efficiencies over 500%.

This guide is not a pitch for business but a genuine attempt to help consumers navigate the misinformation surrounding heat pump installations. If you’re looking for a system with long-lasting efficiency, low running costs and minimal noise, here are the six red flags to avoid when considering a heat pump installation.

Red Flag 1: Design Flow Temperature

If you’re being sold a heat pump with a flow temperature of 50C, be cautious. A higher flow temperature can limit the efficiency of your heat pump and shorten its lifespan. Some manufacturers offer a 7-year warranty, which is far shorter than the potential lifespan of a heat pump installed with the correct parameters.

The reason for this limited warranty is that manufacturers have no control over how the heat pump is installed, particularly concerning flow temperature. Many mass-market installations are designed for 50C flow temperatures, which can significantly reduce the lifespan of the compressor and increase noise levels. Additionally, for every degree increase in flow temperature, you may experience a 3% loss in efficiency. A heat pump designed with a 35C flow temperature can be up to 45% more efficient than one designed for 50C.

Lowering the flow temperature naturally enhances efficiency, reduces running costs, extends the lifespan of your heat pump and minimises noise. Always question any company promoting flow temperatures above 45C.

Red Flag 2: Rooms Designed at Different Temperatures

CIBSE design guides recommend different temperatures for different rooms, such as 18C for kitchens and 21C for living rooms. However, designing emitters for varying temperatures in adjacent rooms can lead to inefficiencies.

According to thermodynamics, heat will always move from hot to cold areas. This means that the warmer room will lose heat to the cooler room, causing your system to become unbalanced and your heat pump to work harder than necessary. It’s nearly impossible to maintain different temperatures in different rooms unless they’re vacuum-sealed.

Your home should be designed with a single consistent temperature, with a setback temperature for cooler bedrooms overnight. Always question any company that doesn’t use one consistent design temperature across your property.

Red Flag 3: Third Party Controls, Zoning & TRVs

Imagine a simple two-up, two-down house, where each room has a 2.5kW heat loss/load, totalling 10kW for the entire house. If you install a 10kW heat pump and then zone the house into upstairs and downstairs, shutting off the upstairs zone during the day, you’ve essentially halved the water volume in the system. This reduction in water volume can cause your heat pump to cycle on and off, reducing efficiency and potentially shortening its lifespan.

Heat pumps operate most efficiently when they can modulate their power to maintain a steady temperature. However, third party ‘smart’ heating controls often act like on/off switches, which can cause the compressor to cycle inefficiently. These controls were originally designed for combustion heating (boilers) and are not ideal for vapour compression heating (heat pumps).

The best approach is to use weather compensation controls, which allow your heat pump to adjust its power output based on outdoor temperatures, maintaining a consistent indoor temperature without cycling the compressor. Always question any company that suggests using third party or ambient controls.

Red Flag 4: Buffers, Hydronic Separation & Fixed Speed Circulation Pumps

In 99% of the UK housing stock buffers are not necessary. A buffer is essentially a cylinder of water connected to both the heat pump and the central heating system. The use of a buffer with a fixed speed circulation pump and third party controls leads to huge inefficiencies. The circulation pump on the heating side of the buffer will work at a different speed to the circulation pump inside the heat pump causing distortion across the buffer.

Most heat pumps are designed to operate with a temperature differential (ΔT) of 5C between the flow and return. However, when a buffer is used, the differential on either side of the buffer can become different. This means the heat pump may have to work harder to reheat more than 5C. This can result in huge inefficiencies and reduce the life of your heat pump.

Buffers are often used by installers to simplify the installation process, but this can lead to a lazy and inefficient system. If you really need additional system volume to reduce cycling consider a volumiser. This is essentially the same tin can as a buffer but ideally sits in line on the flow pipe from the heat pump. This adds system volume without the need for hydronic separation.


However, its worth nothing that a well designed system at a low flow temperature with the correct sized heat pump, pipework and emitters will have enough system volume that you most likely do not need to install either a buffer or a volumiser.


If your designer/sales person is specifying either of these things ask they to prove why they are needed. Put simply, buffers massively reduce efficiency and make your system more costly to run.

Red Flag 5: Central Heating Pipe Sizing

Proper pipe sizing is crucial for the efficient operation of your heat pump. The designer should always be able to provide calculations to ensure that your house’s pipework is capable of transporting the full power output of the heat pump. If the pipework isn’t large enough, upsizing radiators will be pointless, as the energy won’t be able to reach them efficiently.

A good designer will consider this and prove their design mathematically, leaving nothing to guesswork.

Red Flag 6: Power Output Size of the Heat Pump

The heat pump you choose should be matched to the specific heat loss of your home. If the heat pump is oversized, it will cycle on and off, leading to inefficiencies and potential damage. On the other hand, if it’s undersized, it will overwork and struggle to maintain the desired temperature, especially in colder weather.

As a crude example, if your heat loss is 3.8kW and you are being sold a 6.9kW heat pump, this heat pump is probably oversized and will potentially cycle.

Proper sizing is essential to ensure that the heat pump operates efficiently and lasts as long as possible.

Closing Thoughts

These are the six red flags to watch out for when purchasing a heat pump. Luke and I are passionate about sharing our knowledge to push the industry in the right direction. We want consumers to be empowered to ask the right questions and choose a system that works efficiently, doesn’t cost a fortune to run and lasts a long time.

Recently, I discussed these points on a Facebook thread about a heat pump installed by a large nationwide company. After someone from that company viewed my LinkedIn profile, the post was removed. I don’t think that’s fair to consumers, so I’m sharing this content here, unaffiliated with anyone.

The marketplace is full of tempting offers, clever marketing and glossy adverts, but many big players are selling you a lie. By asking these red flag questions, you can uncover the truth about what you’re being sold. And if you’re still unsure, leave a comment below or on the Renewable Heating Hub Forums and we’ll try to guide you in the right direction.

Also, please feel free to share this information widely and use it to hold salespeople and designers accountable. Remember, buying a cheap system might cost you more in the long run, with higher energy costs and potential failures from overworked heat pumps.

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bontwoody
4376 kWhs
3 months ago

Nice to see an installer being honest and open as to the potential pitfalls that can befall an installation. 
I would certainly recommend you to a friend looking to install a heat pump. 

JamesPa
Editor
7597 kWhs
Reply to  bontwoody
3 months ago

How refreshing to hear someone in the industry telling us what everyone needs to hear.  The things you are saying have become pretty clear to the minority who join forums like this to discuss these things, exchange experiences and focus on logical explanations, but seem (by repute) so far to have escaped too much of the industry.
Just a couple of matters for clarification/information.
In your bit about buffer tanks you state (as a red flag) ‘Buffers, Hydronic Separation & Fixed Speed Circulation Pumps’.  The first two undoubtedly are red flags.  My question is about fixed speed circulation pumps (in systems without hydronic separation).  Assuming you have avoided the other red flags, does fixed speed actually matter if the pump is set up for about 5C deltaT at the design temp?  At higher OATs the deltaT will drop if the pump speed is fixed, but does this actually affect the efficiency of the heat pump?  I genuinely don’t know and haven’t actually seen any data either way despite pouring over manufacturer data books.  Obviously it’s a minor point but it would be good to see some data to support this (or not).
 
 

Majordennisbloodnok
Editor
6625 kWhs
3 months ago



Assuming you have avoided the other red flags, does fixed speed actually matter if the pump is set up for about 5C deltaT at the design temp?


Obviously everyone’s interpretation could be different, but my understanding is that a red flag is a warning – an indicator – not a rule; if you see a red flag, you pick up on the need to check further, but the circumstances of the red flag aren’t in themselves an absolute blocker. I have no idea if fixed speed pumps are an issue or not but I’m very happy to accept the advice that if they’re included in a design that I should cross-check that design very carefully. I understand you’re just picking up on a statement to do some technical brain-picking and am not suggesting you’re saying anything more than that, btw.
Personally, I would add some more to the red flag list.
Discussions steering the inquirer to the overall cost after subsidies
If the installer keeps trying to steer the inquirer’s questions about cost back to a “when you take off the Government subsidy (BUS/RHI etc), this is what it will cost" and trys to avoid straight cost discussions that make comparisons easy, the inquirer is likely being “sold to" and the installer may well be trying to hide unpalatable details. For sure, the net cost to change is a valid discussion point but it shouldn’t be the only one.
Installer telling the inquirer what they need
As the old adage goes, God gave us two ears and one mouth so we may hear twice as much as we speak. In order for the potential installer to make recommendations they need to know what the customers needs and wants are, and to find that out the installer has to listen. If they start recommending before asking a lot of fact-finding questions, their advice is not fit for purpose. When they do start making recommendations, they ought to be linking those recommendations back to what the customer has been asking for. It doesn’t, for instance, matter if the rule of thumb is to design a house temperature of 20degC if the customer wants to live in a warmer environment than that and if the installer doesn’t check first then they’re not listening. If they don’t listen to that, what else won’t they be listening to and taking into account?
Plans for the long term
Does the installer have long-term relationships with most of their customers? If the installer is looking to foster a long term relationship with the customer they’re far less likely to be installing something that’s difficult to maintain or costly to run.

JamesPa
Editor
7597 kWhs
3 months ago


Personally, I would add some more to the red flag list….
Installer telling the inquirer what they need
 

How dare you.  The customer for a heat pump has absolutely no right at all to have an opinion on what they need because the installer is the expert.  I’ve seen this stated quite clearly on this forum on more than one occasion and was recently asked ‘would I tell a surgeon what to do?’ when I had the temerity to suggest that my own view as a customer might have some validity.  Surely you have learned that by now!
 

Plans for the long term
 

Well that will rule out many, perhaps most, of the current players in the industry which, just as happened solar panels, will disappear as the grants dry up because their business model is essentially grant harvesting not customer service.
 
You will of course appreciate that these comments are tongue in cheek, but at the same time have an element or seriousness!

I understand you’re just picking up on a statement to do some technical brain-picking and am not suggesting you’re saying anything more than that, btw.

You are correct, I asked the question for that reason alone.  Its a statement I have seen before, but I have also seen that statement that 5C delta T isn’t critical.  Since both cant be true (or can only be true if they refer to different circumstances) I’m genuinely interested in some fact/technical explanation why heat pump efficiency might degrade if delta T differs materially from 5C, most particularly if its less. 

Majordennisbloodnok
Editor
6625 kWhs
3 months ago


How dare you.  The customer for a heat pump has absolutely no right at all to have an opinion on what they need because the installer is the expert.  I’ve seen this stated quite clearly on this forum on more than one occasion and was recently asked ‘would I tell a surgeon what to do?’ when I had the temerity to suggest that my own view as a customer might have some validity.  Surely you have learned that by now!


😆 😆 
Having had the need many times throughout my life to deal with the medical community on behalf of family members, that’s a very interesting question.

Would I tell a surgeon what to do? No.
Would I tell him or her how to do it? No.
Would I tell him or her what we needed to achieve? Yes, absolutely.
Have I ever done any of the above? No, because every surgeon I have ever dealt with has been guided by the patient’s wishes first and started off by asking questions.

As a result, this hypothetical surgeon’s position is no different from that of a heat pump installer; the customer (patient) decides what should be done, the expert (surgeon or installer) fleshes out the detail and decides how to tackle it, the customer has the plan explained to them and gives the go-ahead (signing the contract or the consent form) and the expert then carries out the agreed plan.
Any “expert" trying to distance the customer from what they intend to do (and charge for) is, in effect, a surgeon playing God with a patient’s life without the patient’s consent. How quickly do you think it would take for the General Medical Council to deal with that high-handed behaviour? On the other hand, any expert accepting a customer telling them how to do their job is absolving themselves of their moral and sometimes legal duty which is equally unethical.



Well that will rule out many, perhaps most, of the current players in the industry which, just as happened solar panels, will disappear as the grants dry up because their business model is essentially grant harvesting not customer service.


My point precisely, put rather more concisely and probably more clearly.
 

Johnmo
2245 kWhs
3 months ago


Would I tell a surgeon what to do? No.Would I tell him or her how to do it? No.

My answered isn’t the same. And here is an example.
I had a sore ear lobe, and an area that would bleed if I picked it. It appeared in April. Went to the doctor, he sent me to a clinical specialist/surgeon, he said not sure what it is, but what we’ll do is take a section out of your ear and do a biopsy, when it’s healed it’ll look ok. This was in September and the surgery booked for December. Come November the area had healed up, so cancelled the surgery. The next April came along, same thing. My mother said put sun block on your ear, and wear a hat, which I thought was worth a ago. Issue went away a few weeks later and has never returned. Always wear a hat always put sun block on my ear. Now have a similar area on my cheek, so do the same with sun block.
So I don’t do everything the medical professionals say. 
 

Project_Electrify
239 kWhs
3 months ago

The rooms at a consistent temperature is interesting and makes perfect sense because with our existing gas setup the hallway is colder than the living room and every time the door between the two is opened the living room cools and anyone sat near the door gets a chill.
The ASHP design we are going ahead with did as you said and has a consistent temperature but other quotes we had didn’t and rigidly stuck to 21, 18, 22 etc..
We’re looking forward to our installation in the coming weeks.
 
 

Toodles
9485 kWhs
Reply to  Project_Electrify
3 months ago

@project_electrify Even though MCS guidelines ‘suggest’ these different temperatures – they are merely that, suggestions and furthermore, they are not living in your house nor are they likely to be paying your bills!
Once the installers have commissioned the system, it is down to you – and this is where the interesting bit starts! Each of the emitters (radiators) is furnished with a lock shield valve which you employ to control the flow thus the heat in each room. Please see: 
https://renewableheatinghub.co.uk/how-to-balance-radiators-the-role-of-the-lockshield-valve
for my method. Regards, Toodles.

Jancold
1611 kWhs
3 months ago

Interesting that none of my two surveys asked me what room temps I would like/prefer and as for design temp (you get what we offer)! However they were both from who energy suppliers fully expect to get their money back long term.  It seems like “we will put in what we want and that is it".  Customer? or Victim! One more resurvey and one by an actual installer (I hope). Sadly I expect his price may be out of my budget. Sometimes I wonder why I am bothering.

Lucia
1443 kWhs
Reply to  Jancold
3 months ago

@Jancold I changed things a bit with 🐙 by insisting rooms had other functions – spare bedroom = office. 
I’ve accepted their install won’t be perfect (as in for my needs) but they are so much cheaper it is all I can afford.
Hopefully, over time, it is tweakable one way or another. 

JamesPa
Editor
7597 kWhs
Reply to  Lucia
3 months ago


@Jancold I changed things a bit with 🐙 by insisting rooms had other functions – spare bedroom = office. 
I’ve accepted their install won’t be perfect (as in for my needs) but they are so much cheaper it is all I can afford.
Hopefully, over time, it is tweakable one way or another. 

I think this is the right way to do things in the current market. Tell them what thet need to hear so you get what you want.  It seems to me you are getting a good deal.
 

Johnmo
2245 kWhs
3 months ago


Sometimes I wonder why I am bothering.

I get that. I just did DIY.
It’s almost as if they, the installer, are doing you a favour, somehow they believe the money is theirs, not a tax payer contribution. They are looking for you to pay a bulk of the costs, so really need to minimise what they ‘give’ you otherwise they dilute how much of the £7500 they keep themselves. And somehow they are are getting away with it – criminal 
 

Ian McKay
3 months ago

Interesting thoughts Simon. One thing that troubles me about the recommendation to avoid using TRVs is that the user then has little control over individual room temperatures. How would you suggest the occupant makes those kinds of fine tuning adjustments?

Toodles
9485 kWhs
Reply to  Ian McKay
3 months ago

@Ian McKay Assuming you don’t require dynamic temperature changes and are happy with a constant temperature in any one room, please carry out the control of temperature using the lock shield valve at the opposite end of the radiator from the TRV (which should be fully open, then the lock shield valve will control the flow.) If you wish to follow my routine, please read:
https://renewableheatinghub.co.uk/how-to-balance-radiators-the-role-of-the-lockshield-valve
Regards, Toodles.

JamesPa
Editor
7597 kWhs
3 months ago


Interesting thoughts Simon. One thing that troubles me about the recommendation to avoid using TRVs is that the user then has little control over individual room temperatures. How would you suggest the occupant makes those kinds of fine tuning adjustments?

As @Toodles says above.  Basically you don’t except as a one off when the system is commissioned (or over time) by balancing the radiators using the lockshield valves.
Low temperature heating, whether by gas, oil, or heat pump, is a different design and control philosophy to the high temperature heating we are used to.  The basic idea is to dispense with most controls and run the ‘boiler’ (gas, oil or heat pump) more or less constantly at the lowest possible temperature so that the heat loss from the house is just matched by the heat emitted from the radiators.  This gives both the maximum efficiency and the maximum comfort (the latter principally because temperature gradients are minimised).  The efficiency gain is more with heat pumps than with fossil fuel boilers, which is why it is emphasised in heat pump installations, but is present even with fossil fuel boilers.  The supposed gains from micro-controls, much touted by the manufacturers, are largely wholly illusory and certainly well over stated. 
You may need to read a bit more fully to understand this as there are a few interacting factors some of which are counter intuitive.  It boils down to keeping most emitters open all of the time gives you a nice constant temperature with minimal temperature gradients in the room (hence maximum comfort) for the least expenditure of energy.  The reason that this is the most efficient boils down to the fact that the heat loss from the house is determined by the insulation between the house and the outside walls and insulation between rooms is negligible.  The upshot of this is that the amount of heat loss (from the house) saved by zoning a room or an area is quite small, and the reduction is more than offset (in many cases) by the loss in efficiency due to the reduced emitter area which means that the flow temperature must be increased to compensate, resulting in a higher energy consumption (which is what you pay for) even though the loss from the house is less. Heat Geek has some good videos on why not to zone (and when zoning might be a good idea), with some worked examples to prove the point.
Most of us should really be running our gas boilers this way too, but unfortunately the UK (unlike some other countries) didn’t mandate weather compensation, so it wasn’t applied even though most boilers support it because the industry in Europe is centred on Germany which does mandate it.  As a consequence most of us are probably paying 10% more for our heating than we need to and have been suckered by the control industry into buying way more ‘bits’ than we really need to.

Ian Cruickshank
Ian Cruickshank
2 months ago

Hi I am thinking of having a heat pump fitted the installation company is MPC Titan Business Park 1 Aurora Avenue Queens Quay Glasgow.
I currently have oil-fired heating and is a 25 KWH the house is a 3-bed detached bungalow with a solid 9-inch thick wall what size pump would be required and can they use the existing pie work for the radiators they will replace the radiators
I consume 1800 liters per year

1 do you have any experience with MPC
2 would it be cheaper to run a heat pump
3 the house is a constant 20c
any advice would be appreciated thank you, Ian.

bontwoody
4376 kWhs
Reply to  Ian Cruickshank
2 months ago

@Ian Cruickshank
We would need some more details to answers all your questions on heat pump size and pipe diameters, but it is possible to give you a rough idea from the 1800 litres of oil per year. There are various methods that can be used but as a rough guide I would estimate that you would require a heat pump with a maximum output of between 6-8 kW.
If you have 15mm copper pipes to your radiators then thats a good first indicator.
An installer would do a full heat loss survey, which might be higher (they frequently are) but be wary about going too large. bigger is not always better in heat pumps.
With respect to running costs, a well installed heat pump should beat oil and gas, but well installed are the key words. there are a lot of installers out there who just harvest the grant without really knowing what they are doing. I would try and get quotes from heat geek installers as a first option.

JamesPa
Editor
7597 kWhs
Reply to  Ian Cruickshank
2 months ago


Hi I am thinking of having a heat pump fitted the installation company is MPC Titan Business Park 1 Aurora Avenue Queens Quay Glasgow.I currently have oil-fired heating and is a 25 KWH the house is a 3-bed detached bungalow with a solid 9-inch thick wall what size pump would be required and can they use the existing pie work for the radiators they will replace the radiatorsI consume 1800 liters per year
1 do you have any experience with MPC2 would it be cheaper to run a heat pump3 the house is a constant 20cany advice would be appreciated thank you, Ian.

On the basis that oil is 10kWh per litre, 1800 litres is about 18MWh.  That very roughly translates to a 7-9kW heat pump.  You will need to have a proper heat loss calculation done to size the pump, but if it differs widely from this then question it.  You may need to replace some or all radiators depending on their sizes, heat loss calc will indicate.  You should get a scop of 3 or better so will consume 6MWh electricity per year or maybe less.  You can work out how much that costs.  
Heat pumps are all about the system design not the unit itself.  Many installers simply dont understand how to design a low temperature heating system and will add in lots of unnecessary controls, a buffer tank and miscellaneous other things which cost money and compromise performance.  Simple is best, no buffer, one zone, no TRVs on the majority of rads (or TRVs turned up to 2-3 degrees above the target temperature).  No third party ‘smart ‘ controls (with one possible exception – homely), just weather compensation driven by the heat pumps own controller.  Diverter valve so either DHW or CH is fed never both at once.  Initially run 24*7 for most of the season with possibly a modest set back at night.  You can vary this either end of the season.
Its worth following this forum to understand the technology better, sadly many installation companies, set up especially to harvest the grant, don’t. 
I know nothing about MPC.
Hope that helps.
 
 
 
 
 

Toodles
9485 kWhs
Reply to  Ian Cruickshank
2 months ago

Please keep us posted with any progress and if there is anything you are unsure about, there are numerous very knowledgable and helpful people who subscribe to this hub – and advice is unbiased and free! Remember, there is no such thing as a silly question – personally, I have gained a great deal of understanding from subscribers questions and the replies on this group! Regards, Toodles (I’m just here for the free ride m’self😉)

JamesPa
Editor
7597 kWhs
2 months ago

PS.  I should have added that the heat pump capacity you need may be up to 25% less if you have a very old (ie inefficient) boiler.  In the range 6-9kW is probably a good assumption (subject to survey), anyone trying to sell you say 10+ KW is, as @bontwoody says, suspect.  One cowbow lot tried to sell me 2*16kW pumps for my 8kW house!
Be aware, however, that heat pump sticker capacities arent necessarily representative of their actual capacity and the actual capacity depends on the design temperature.  Vaillant, for example, sell a sticker 7kW model which, in the South of England, is good for 8.5kW.  Mitsubishi and Samsung seem to clamp their output at the sticker value in firmware, as it is suspiciously constant over a range of outdoor temperatures.  Daikin, who sell half a dozen models in any given ‘range’ seem to do fairly weird things.  Other manufacturers have other variants.  This is part o0f the selection process that your designer will go through.

GT22
63 kWhs
2 months ago

First posting.
I have had an ASHP since 2009 and sometimes I think I know less now than I did then.
I read and appreciated the article on the 6 flags. It did prompt a couple of questions.
I think questions first and then a bit of info to help if someone wants to try and explain to me.
Red Flag 1: Design Flow Temperature.
If the system is set to produce 35’C. How do you get water sufficiently hot for DHW?
I have found from experience that 45’C at the tank is fine for showers, but 40’C and it might start to run cool at the shower by the end. ASHP cannot keep up with demand?

Red Flag 4: Buffers, Hydronic Separation & Fixed Speed Circulation Pumps.
This is the big question.
Is the buffer that is referred to, the same as my cylinder? Or did I misunderstand?
All the ASHP systems that I see advertised have an external fan unit plus an internal cylinder.  

Background info. Probably too much?
2009 a 4.5kW Sanyo monobloc system installed.
223 litre cylinder. The DHW coil running through it is 5 litre capacity. The ASHP dumps into that tank. The CH radiators run from the same tank.
The pump for the external ASHP fan unit is Fixed speed. The pump for the CH radiator system is set on a low fixed speed, just because that seems to work.
A small 3-bedroom Victorian terrace in London. Now, well insulated. For example all windows and external doors either DG or TG. 100mm PIR internal insulation on some external bedroom walls. 150mm PIR insulation at Loft floor level. Started to insulate at ground floor level, 100mm PIR between joists. Still insulation work to be done.
Radiators all upgraded. (No radiators in two bedrooms. Those are being renovated and have the benefit of IWI (internal wall insulation).

Impossible to state exactly the ASHP electric consumption but from the detailed meter readings that I take, I would work it out at about 10kW per day, for a Feb 2024 period in inner London.
Occupancy – 1 person.
I leave the ASHP as ON 24/7. The heating is programmed for morning and evening periods. Manually boosted if I get chilly outside of those periods.

Unfortunately, I don’t know my Heat Loss calc. Nor do I know the Heat/Temp Curve for the Sanyo. The user interface is horrible.

I want to learn because the unit is not going to last for ever. One day I must make a big decision.

Right now I am NOT looking for recommendations, just guidance on the two points above. 

Mars
Admin
22762 kWhs
Reply to  GT22
2 months ago

@GT22 Welcome to the forums! Here are my thoughts on your questions:

Red Flag 1: Design Flow Temperature – When your system runs at a 35°C flow temperature for space heating, domestic hot water (DHW) is generally handled separately. Modern systems are designed to use different flow temperatures for heating and hot water. The heat pump will typically boost its output to around 50–55°C specifically for DHW, so they don’t interfere with each other.

Red Flag 4: Buffers, Hydronic Separation & Fixed Speed Circulation Pumps – The buffer tank being referred to here is separate from your hot water cylinder. In the heating circuit, the buffer tank helps “smooth out” the ASHP’s operation and reduces short cycling, particularly with fixed-speed pumps. Your hot water cylinder is dedicated solely to DHW and doesn’t interact directly with the buffer.

If you’re open to it, sharing a photo of your plant room where the hot water cylinder is located could help determine if you’ve got a buffer tank in place.

You’ve really been a trailblazer with your 2009 ASHP! Ours is only six years old, and the control panel already feels outdated, so I can imagine the quirks of your Sanyo. Would love to see a photo of the unit if you’re willing to share.

GT22
63 kWhs
Reply to  Mars
2 months ago

As requested a couple of photos. Many thanks for the information. It is so helpful to get that sort of clear information.

Sanyo display 20240924 174119
Sanyo landing unit 20240924 174046

 

GT22
63 kWhs
2 months ago

@Johnmo Thank you for providing that clarification.

GT22
63 kWhs
2 months ago

If I had a new ASHP installed I would still have to have a hot water cylinder. I watched the relevant video on this site. But I don’t need any buffer unit. 
Can I get clarification on this point. 
Can the ASHP External unit, supply heat for Central Heating radiators or UFH at one temperature and one set of F&R pipes and do that supply directly? Bypassing the cylinder?
Or have I got that completely wrong and need to go away and do some serious reading? 🤔 

Mike@MH
126 kWhs
Reply to  GT22
4 days ago


If I had a new ASHP installed I would still have to have a hot water cylinder. I watched the relevant video on this site. But I don’t need any buffer unit. 
Can I get clarification on this point. 
Can the ASHP External unit, supply heat for Central Heating radiators or UFH at one temperature and one set of F&R pipes and do that supply directly? Bypassing the cylinder?
Or have I got that completely wrong and need to go away and do some serious reading? 🤔 

 

JamesPa
Editor
7597 kWhs
Reply to  Mike@MH
4 days ago

If I had a new ASHP installed I would still have to have a hot water cylinder. I watched the relevant video on this site. But I don’t need any buffer unit. 

Can I get clarification on this point. 

Can the ASHP External unit, supply heat for Central Heating radiators or UFH at one temperature and one set of F&R pipes and do that supply directly? Bypassing the cylinder?

Or have I got that completely wrong and need to go away and do some serious reading? 🤔 

 

The ASHP, just like a boiler, can supply water at only one temperature at any time.  So it switches between space heating and DHW.  There will be one set of F&R from the heat pump, which splits into two sets at a diverter valve. 

The reason that boilers (as we set them up in the UK) can do both simultaneously is that they run the heating at a high flow temperature, resulting in both reduced comfort and a 10% increase in energy consumption and therefore cost.  Boilers, like heat pumps, are actually best run at a low temperature with weather compensation (best both for comfort and cost!), but in the UK we rarely do this, unlike some more enlightened countries in mainland Europe.

 

benson
545 kWhs
2 months ago

Nothing like a government grant to bring out the bandits for sure. An absolute minefield and as per my other post our current installation is hardly going smoothly. The company we went with however were one of the few who didn’t want a massive amount of money (in effect the whole cost of the job minus the grant) up front, so at least I have some leverage to try and ensure it is completed to a decent standard.
As for optimus heating, came across as knowing their onions but I booked an initial home survey after a fair bit of back and forth communications (mainly telling me how good they were) and after all that they didn’t turn up or contact me to tell me they weren’t coming. Red flag #7?

Mars
Admin
22762 kWhs
Reply to  benson
2 months ago

@benson Optimus didn’t turn up?

benson
545 kWhs
Reply to  Mars
2 months ago

Nope. Made a firm appointment, and they didn’t turn up or make any contact. I was slightly miffed.

Mars
Admin
22762 kWhs
Reply to  benson
2 months ago

@benson that’s very disappointing indeed.

JamesPa
Editor
7597 kWhs
2 months ago


Can the ASHP External unit, supply heat for Central Heating radiators or UFH at one temperature and one set of F&R pipes and do that supply directly? Bypassing the cylinder?
Or have I got that completely wrong and need to go away and do some serious reading?

ASHPs (and fossil boilers running at a low flow temperature or with weather compensation – rare in UK, common in more enlightened countries) supply at one flow temperature at any one time and thus the installation will invariably include a three way diverter valve (or two two way valves) so that space heating or dhw can be fed, but not at the same time.  The unit switches flow temperature and the diverter valve according to whether space of dhw heating is required.
If you need, in addition, two flow temperatures for space heating you must supply the space heating at the higher temperature and mix down for the lower.  Again same for boilers and ASHPs.  The ASHP COP will be determined by the higher, because that is the temperature it is required to produce.
Hope that clears matters up.

GT22
63 kWhs
Reply to  JamesPa
2 months ago

@JamesPa Many thanks. You are adding to my education on the current ASHP approach. So different from my 2009 Sanyo configuration, hence my questions.

JamesPa
Editor
7597 kWhs
Reply to  GT22
2 months ago


@JamesPa Many thanks. You are adding to my education on the current ASHP approach. So different from my 2009 Sanyo configuration, hence my questions.

My ashp journey is only 3 years old and in that time it’s clear that thinking has matured quite significantly, albeit by no means universally.  I can only imagine how much change there might have been since 2009.
Please continue to ask questions, people here are very willing to help and no question is silly.
 

Erik Verne
6 days ago

Great article! You’ve highlighted essential red flags to watch out for when considering a heat pump installation. One innovative idea would be to include tips on how to verify the credentials of installers, ensuring both quality and reliability in the installation process. Keep up the informative work!

JamesPa
Editor
7597 kWhs
6 days ago

One innovative idea would be to include tips on how to verify the credentials of installers, ensuring both quality and reliability in the installation process. Keep up the informative work!

@mars That could be a whole discussion in itself.  I don’t personally think its simple!

 

Mars
Admin
22762 kWhs
Reply to  JamesPa
5 days ago

@JamesPa it is a good idea, but not easy as you say. We actually have something along these lines scheduled in for recording next week Friday for the podcast.

Clover Rayner
5 days ago

This article highlights important factors to consider when installing a heat pump. Identifying red flags, such as poor sizing, improper installation, and lack of maintenance plans, ensures you avoid costly mistakes and achieve optimal system performance.

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