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1.There is the guarantee if you need it dont worry.
2.ΔT50 only refers to the radiator spec but yours will be taken at lower figure.(not mentioned anywhere on the document)
3.Heat geek taken the whole house radiators combined as heat flows from hot to cold so there should be equalisation.
To me this shows that they are, as I suggested up thread, winging it a bit/playing the numbers game based on their accumulated experience.
We don't ask for detailed design specs of a car engine, we ask how many miles per kWh it does (or per gallon for fossil cars). It's thus only a matter of conditioning that we ask for heat pumps. Given the state of the industry it's sensible conditioning, but in a more mature industry it would be unnecessary.
Ultimately only you can decide if you are happy with this. If other similarly priced quotes involve replacing more radiators and are otherwise similar technically you can be pretty certain that these will in fact deliver a higher scop
That is unless they are both under estimated, the Heat Geek guarantee is invoked, and the result is that they are forced to better the alternative at no cost to you.
Unfortunately the underlying problem, which is not readily fixable, is that heat loss estimates have a significant degree of uncertainty attached to them.
This post was modified 3 weeks ago 3 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@l8againagain I think you need to look into it in depth.Heat geek proposal says the heat loss are for -3.6 deg C outdoor and 21 deg C indoor temp
Vaillant spec for 5kW attached shows the unit can indeed do 6.4kW (my heat loss according to heat geek). But they can do 6.4kW at -3 deg c only if flow temp is 40deg C or below.
My existing T11 radiators cannot output 6.4kW at 40deg C.
Not overthinking here. My exisitng radiators wont work with 5kW unit from Vaillant for 6.4kW heat loss
@jo2255, you’re absolutely on the money here IMO. This isn’t overthinking it... you’re simply checking whether both sides of the design work at the same time, and this is something honestly makes my head hurt.
The Vaillant table you provided shows the 5kW unit producing 6.4kW at -3C only when the flow temperature is 40C. Your design temperature is actually slightly colder at -3.6C, so even that operating point looks marginal. Once the flow rises to 45C, the available output drops to 6.1kW, then to 5.9kW at 50C and 5.8kW at 55C.
Meanwhile, your radiators cannot emit the required 6.4kW with a 40C flow. Based on the figures you previously posted, a conventional radiator correction calculation would put their combined output at only a fraction of that figure. They would appear to need a flow temperature somewhere around the high 50s or 60s to meet the stated heat loss, but at that temperature the 5kW Vaillant no longer produces the required output. That is the gap that I think needs explaining.
Heat Geek may believe the calculated 6.4kW heat loss is substantially higher than the house will experience in reality, and they may have enough installation data to support that judgement. That is possible, but if the proposal states a 6.4kW heat loss at -3.6C, I think it is entirely reasonable to ask how the chosen heat pump and existing radiators meet it. The headache is getting stronger.
People/installers will also understandably point out that we only get a limited number of days at the design temperature. That is true, but those are precisely the days when the design really makes a difference IMO. Trust me, from experience, an extended cold spell is deeply unpleasant when the heat pump cannot replace the heat the house is losing. The temperature gradually slips, the heat pump runs relentlessly, defrosts and hot water cycles take more capacity away, and increasing the flow temperature in an attempt to catch up can cost a small fortune without necessarily restoring comfort. A fortnight of that in January feels considerably more important than its small percentage of the year suggests. Just speaking from experience having had a unit that couldn't deliver the required heat when we dropped below zero.
This is also where the guarantee’s fine print re-enters the picture. A good annual efficiency figure does not necessarily prove that every room will remain comfortable during the aforementioned coldest fortnight. I would want Heat Geek to confirm in writing that all the intended rooms will maintain their specified temperatures at -3.6C, including the effect of defrosting and hot water reheating, while still meeting the promised efficiency. I would also ask what happens if comfort can only be restored by increasing the flow temperature and that then pulls the annual efficiency below the guaranteed figure. The guarantee could still make this a very good consumer proposition, but it needs to guarantee both outcomes together... a warm house during the design conditions and the promised efficiency over the year. One should not be achieved at the expense of the other IMO.
If heat geek had mentioned that traditional calculation would have your house at 6.4kW heat loss but our 1000's of installs and algorithm estimates that actually your heat loss is close to 5kW and hence we are recommending the 5kW unit. Everyone else is going the traditional route and suggesting 7kW unit and we are suggesting 5kW for the above reasons. If for any reasons we have got it wrong you have our guarantee.
I wouldn't have questioned them at all if they had said the above.
Heat loss estimation is not simple to get right. But sizing once you have the heat loss estimate and design temp is relatively straightforward based on heat pump manufacturers spec.
In my case they have confirmed 6.4kW heat loss. I dont have any more info.
If heat geek had mentioned that traditional calculation would have your house at 6.4kW heat loss but our 1000's of installs and algorithm estimates that actually your heat loss is close to 5kW and hence we are recommending the 5kW unit.
That might be sailing too close to the wind in terms of MCS rules. They are trying to break the mould within a set of rigid rules the principal effect of which is (arguably) to protect poor installers. I am guessing that's a difficult balancing act.
That's not defending Heat Geek, just a possible explanation
This is also where the guarantee’s fine print re-enters the picture. A good annual efficiency figure does not necessarily prove that every room will remain comfortable during the aforementioned coldest fortnight. I would want Heat Geek to confirm in writing that all the intended rooms will maintain their specified temperatures at -3.6C, including the effect of defrosting and hot water reheating, while still meeting the promised efficiency. I would also ask what happens if comfort can only be restored by increasing the flow temperature and that then pulls the annual efficiency below the guaranteed figure. The guarantee could still make this a very good consumer proposition, but it needs to guarantee both outcomes together... a warm house during the design conditions and the promised efficiency over the year. One should not be achieved at the expense of the other IMHO
Completely agree with @editor here, the fine print matters and those questions need to be asked before you consider them. It would be instructive to see the actual text of the guarantee.
Anyone who claims their heat loss estimate is right is telling a porky. The only way to be certain is a proper measurement of demand under controlled conditions. All surveys are approximations based on assumptions which may not be correct! If they are correct to within 10% that's probably as good as you can expect.
This post was modified 3 weeks ago 3 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@jo2255 — I agree with @editor, you are definitely not over-thinking this. There is a mismatch between apparent heat loss and apparent capacity. I say apparent because most if not all of the numbers are estimates. Even the aroTHERM data sheet says as much. But on the face of it, there is a mismatch, and it needs to be dealt with.
Given my recent post about MCS requirements, I am sure @jamespa is correct when he says Heat Geek are 'winging it a bit'. To my mind, there is just too much black box stuff about it, too much don't worry, the guarantee is there if you need it. But what is that guarantee? According the Heat Geek website it is:
The Guarantee: Heat Geek guarantees the overall efficiency of your heat pump system at the figure stated in your quotation, measured over 12 months of real operation. This is for both heating and hot water. If your system doesn't hit that number, we will fix it at our cost.
To me, that raises more questions than it answers - though they do give some of the answers'
(1) how do you measure 'real operation'? Answer: you don't (unless you do so independently), Heat geek monitor your system remotely. From their website:
How We Verify It: After installation, your heat pump transmits performance data every 15 minutes. We monitor overall efficiency continuously. If something is not right, we know.
OK, they know. But do they tell you? This also raises the old chestnut, whose data is it anyway, not to mention the fact that this is the designer/installer marking their own homework.
(2) what happens if the system is clearly failing before 12 months of operation?
(3) how long does the guarantee last? Answer: "Your Guarantee remains valid as long as the system is operated as installed and settings have not been altered." I read that as meaning you have to relinquish control of your system to keep the guarantee. I'm not sure I would be content with such a restriction.
All in all I suspect the guarantee might not be that robust in practice. It also, as @editor has pointed out, only covers efficiency, and leaves out another very important consideration, whether the property stays warm in cold weather. A system can meet an efficiency target, but still be ineffective.
I very much doubt they will tell us, but I wonder how many guarantee claims have Heat Geek dealt with, and what were the outcomes?
Midea 14kW (for now...) ASHP heating both building and DHW
I was also curious about the specifics of the guarantee, and here's what HG sent to me by email:
Regarding the guaranteed efficiency, That is exactly right regarding the efficiency guarantee. It is an annual seasonal average (SCOP), which includes hot water. As you noted, the efficiency will naturally be lower during a cold snap in January and significantly higher in the shoulder months, with the guarantee applying to the 12-month average. To answer your question about indoor temperatures: yes, the efficiency guarantee and the comfort guarantee are linked. We guarantee that the system will achieve your designed room temperature (typically 21°C unless specified otherwise) in every room, ±1°C, even on the coldest day of the year. If the system achieves the efficiency target but fails to keep the house at the agreed temperature, or if it keeps the house warm but fails to meet the efficiency target, the Heat Geek Guarantee is triggered.
In either scenario, the remedy is the same:
1. We will return to investigate the system.
2. We will carry out any necessary upgrades or rectified works at no cost to you.
3. We will continue until both the temperature and efficiency guarantees are met.
The reason we can be so confident is that we don't just rely on theoretical models; we back our designs with monitored performance data.
If heat geek had mentioned that traditional calculation would have your house at 6.4kW heat loss but our 1000's of installs and algorithm estimates that actually your heat loss is close to 5kW and hence we are recommending the 5kW unit. Everyone else is going the traditional route and suggesting 7kW unit and we are suggesting 5kW for the above reasons. If for any reasons we have got it wrong you have our guarantee.
I wouldn't have questioned them at all if they had said the above.
Heat loss estimation is not simple to get right. But sizing once you have the heat loss estimate and design temp is relatively straightforward based on heat pump manufacturers spec.
In my case they have confirmed 6.4kW heat loss. I dont have any more info.
Yes, yes and more yes.
Earlier, I gave @jamespa's post a "bang on" emoji because I absolutely believe installers should be focusing on what really matters. A good SCOP is not a target in itself; it's merely an indicator. Whether your radiators are warm or you've got a particular flow temperature is also irrelevant if the core function (a comfortable home at reasonable running costs) is delivered.
However, anyone following my posts for a reasonable time on this forum will know just how much I detest the "trust me, I'm a doctor" approach. Not only does it cut a perfectly intelligent customer (who knows the vagaries of their home better than anyone else) out of the loop, it introduces a dependency on the installer that discourages independent homework-checking. If, as you say, @jo2255, HG had backed up their stance with some open explanation you wouldn't have batted an eyelid. As it is now, what they want you to accept is being picked over in fine detail on a public forum. I'll freely admit that there's a difference between the Aira "accept what we say and don't ask questions" approach and HG's "we're right and we'll back it up with a guarantee" stance, but the person holding the purse strings really should be able to get all the information they need to be happy they're making an informed choice.
To put it into context, I cannot remember the last time I encountered a doctor taking the "trust me, I'm a doctor" stance. The explanations to all the questions a patient may ask are quite likely to be simplified so as not to have technicalities obscuring a key point, but that's true of heating systems too. If a doctor dealing with a far more complex collection of estimates, variables and experiences related to a far more complex system than some central heating and with far more riding on their being right can be open and straight with a "customer", why can't a heating engineer. The answer, as various professional members here demonstrate (@ashp-bobba springs to mind but is not alone), is that they can and should.
105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs
"Semper in excretia; sumus solum profundum variat"
I think the reason for my frustration is i started my journey of heatpumps watching all the heat geek videos on YouTube. They basically got riled up about all the right topics of flow temp, questions to ask installers, run away if flow temp isnt mentioned, zero disrupt and save money etc etc
When my turn came for heat geek no questions were answered. Maybe I had set my expectations too high and that caused the disappointment with heat geek. They came close to £8.5k with no rads after BUS which was on the high side of the quotes I recieved.
No disappointment with Aira for me as I expected it to be a sales driven visit and compulsory buffer and they didn't disappoint. The guy from Aira made me watch 4 long videos of the company. The same company I have researched to book the visit which he is on.
Like you mentioned. I didn't give a single thought on heating system before delving into heatpumps.
I think the reason for my frustration is i started my journey of heatpumps watching all the heat geek videos on YouTube. They basically got riled up about all the right topics of flow temp, questions to ask installers, run away if flow temp isnt mentioned, zero disrupt and save money etc etc
When my turn came for heat geek no questions were answered. Maybe I had set my expectations too high and that caused the disappointment with heat geek.
You are quite right to be riled and no, your expectations are not set too high.
However it is still an evolving industry and we all need to cut some slack for the thought leaders as they evolve their business (and the market) whilst trying not to fall foul of rigid MCS rules designed 'by the industry for the industry', not necessarily for the customer.
@majordennisbloodnok is spot on with his aversion to 'trust me I'm a doctor', but try asking for design details of any other consumer product and you may be disappointed!
It's an interesting one and perhaps 'horses for courses'. Maybe Heat Geek are now focused on people who aren't, and don't want to be, heating geeks and trying to deliver what they need not necessarily what those who want the detail need.
It would be good to hear from Heat Geek themselves, but there may be very good commercial reasons not to give away too much.
However you look at this it's an alternative 'sales' model which may appeal to many and may not appeal to others. That has to be good for market diversity even if it doesn't suit everyone
