Posted by: @editor

I have found the heat pump industry as a whole to be very divisive, and approaches to thinking and installations are binary. It's either 1 or 0. Buffer tank or no buffer tank. Open loop systems versus controllers (thermostats, TRVs, etc.). There appears to be  no middle ground. I'm not saying that what Brendan does is not better – he is just in the minority because every quote we received (six in total) had a buffer. Most users on the forums that have had heat pumps installed in the last 2-3 years will have buffer tanks. Quick show of hands – who has a buffer tank as part of their heat pump system?

If buffer tanks are installed because installers are "lazy" and don't want phones ringing because flow is insufficient leading to heat pump errors, that's inexcusable. These systems cost a lot of money and they should be installed to the highest, most efficient standard. 

I will invite installers to have a look through this forum, and hopefully some will respond, and we'll see where this conversation goes.

 

 

Mars, and who has rubbish COP's, high running costs and poor performing systems? Every one of you that has buffer tanks and system separation. Most would be here if they were happy with their systems.

"If buffer tanks are installed because installers are "lazy" and don't want phones ringing because flow is insufficient leading to heat pump errors, that's inexcusable"

This is exactly why buffer tanks (system separation) are installed and for no other reason.  Ask Graham Hendra.

"These systems cost a lot of money and they should be installed to the highest, most efficient standard."

I could not agree more. I started doing it their way then found that it did not work, spent many years developing and proving the simple systems I have given you. As I say, if you do not take my advice, you are the looser. However, I hope you do dig in to this and expose this scam. It is nearly as bad as the condensing boiler scam perpetuating today.

@caroline2000 Who is saying that you cannot change the compensation curve settings?

Posted by: @heacol

Posted by: @editor

I have found the heat pump industry as a whole to be very divisive, and approaches to thinking and installations are binary. It's either 1 or 0. Buffer tank or no buffer tank. Open loop systems versus controllers (thermostats, TRVs, etc.). There appears to be  no middle ground. I'm not saying that what Brendan does is not better – he is just in the minority because every quote we received (six in total) had a buffer. Most users on the forums that have had heat pumps installed in the last 2-3 years will have buffer tanks. Quick show of hands – who has a buffer tank as part of their heat pump system?

If buffer tanks are installed because installers are "lazy" and don't want phones ringing because flow is insufficient leading to heat pump errors, that's inexcusable. These systems cost a lot of money and they should be installed to the highest, most efficient standard. 

I will invite installers to have a look through this forum, and hopefully some will respond, and we'll see where this conversation goes.

 

 

Mars, and who has rubbish COP's, high running costs and poor performing systems? Every one of you that has buffer tanks and system separation. Most would be here if they were happy with their systems.

"If buffer tanks are installed because installers are "lazy" and don't want phones ringing because flow is insufficient leading to heat pump errors, that's inexcusable"

This is exactly why buffer tanks (system separation) are installed and for no other reason.  Ask Graham Hendra.

"These systems cost a lot of money and they should be installed to the highest, most efficient standard."

I could not agree more. I started doing it their way then found that it did not work, spent many years developing and proving the simple systems I have given you. As I say, if you do not take my advice, you are the looser. However, I hope you do dig in to this and expose this scam. It is nearly as bad as the condensing boiler scam perpetuating today.

I don't have a buffer; my installer said they were a waste of time. He also told me to stick to weather compensation. The system has been fine up till now. I do have TRVs, although they are all turned up full. I also have thermostats, although I'm going to experiment with not using them. I've got MMSP so can see the effects easily and I'll post them here.  

@heacol, if your design is better (and I'm definitely not qualified to say either way) are other countries with more experience of ASHPs doing it like you say?  If they are, isn't that a way to persuade those in power here?  If ASHPs could rival gas in running costs, why wouldn't Ofgem/the UK government want that?

One point I'd make in defence of suppliers.  A lot of customers will not readily accept a system that is a lot less controllable that their boiler. If the sales person tells them they can't have a thermostat with their ASHP and will have to mess around with weather compensation curves and thermometers to get the right temperature, they might just not bother. 

Posted by: @heacol

@derek-m You are wrong, there are a lot more peramiters involved than you think, the inverter system running at low load is increadably efficient as the collector can be up to 6 times larger than at peak. All measurements are done at peak. In addition,the inverter it'self can reduce efficiency by up to 60 % from most efficient point to worst (just like an engine as it goes up the rev rainge).

The manufacturers do not give you this data, I have spent many years working it out in rela life scenarios to get the best possible output and performance for my customers.

Brendon,

Could you please clarify the part about which I am wrong.

I would be very interested to learn about all these additional parameters, please enlighten me. I can take it, I'm an Engineer.

I am quite familiar with Variable Speed Drives (VSD) or Inverters as they are often called. The VSD is supplied with 240v 50Hz electrical power which is rectified to produce direct current (DC) normally in the range 600 to 800 volts. The DC voltage is then converted back to AC voltage, normally at 240v but with variable frequency, normally in the range 5Hz to 50Hz. By varying the frequency, it is therefore possible to vary the speed of an induction motor that is powered from the VSD. Since there are always losses in electrical and electronic circuits, the output from the VSD may be close to 100%, but can never exceed the input power.

In an ASHP, a VSD powers the motor, which in turn drives the compressor. The slower that the compressor runs, the lower pressure it develops in the refrigerant gas, the less energy that the motor uses, but the less heat energy absorbed by the refrigerant gas in the process. Because the refrigerant gas is at a lower temperature and hence contains less heat energy, it is limited in the amount of heat energy that can be transferred to the water in the heat exchanger. The heat loss of a property, and hence heat demand will determine how much heat energy a heat pump would need to provide. The number, size and type of the heat emitters will determine the water flow temperature required to meet the heat demand, so reducing the heat demand and/or increasing the output of the heat emitters will have a direct effect on the performance of any heat pump supplying the heat energy.

I do not disagree with your statement that ASHP's operate more efficiently at lower water flow temperatures, and that quite high COP values can be achieved under the optimum operating conditions, the problem being that these optimum operating conditions do not exists at low ambient air temperatures.

@kev-m They do not install buffer tanks in any European country in single house systems (large commercial is different). It is purely a UK phenomenon because plumbers/pipe fitters/boiler bashers refuse to upgrade their knowledge. Heating engineers have attempted to upgrade, but unfortunately they are only a tiny minority, therefore, for the industry to sell the units, they had to come up with a way to overcome the arrogance. Hence, Buffer tanks.

"@heacol, if your design is better (and I'm definitely not qualified to say either way) are other countries with more experience of ASHPs doing it like you say?  If they are, isn't that a way to persuade those in power here?  If ASHPs could rival gas in running costs, why wouldn't Ofgem/the UK government want that?"

We are a very small minority, on our own, doing it properly. Most of the guys only install heat pumps and have been doing so for many years. Unfortunately our industry representatives and associations (including the manufacturers and MCS) are all of the opinion that the user is not important, shunting a box is. I have made a lot of noise over the years and still do, hence, I am not very well liked.

One point I'd make in defence of suppliers. A lot of customers will not readily accept a system that is a lot less controllable that their boiler. If the sales person tells them they can't have a thermostat with their ASHP and will have to mess around with weather compensation curves and thermometers to get the right temperature, they might just not bother.

I think you would have found the same complaints when customers went from an open fire to a boiler, including the high installation costs. If you want to install a heat pump, it is not a boiler, be prepared to change or live with the consequences and do not complain that your bill has doubled. I have little sympathy for people who will not accept the change and will not install systems for people who insist on individual room control, zoning and other options. I walk away as I will not do a bad job, just to get a job.

The better units are very east to adjust, but most are difficult. I only install Nibe for ground source and Panasonic for air source for that reason.

@derek-m It does not work like that, When we talk about inverter technology we are talking about the variable speed compressor/inverter drive unit as a whole. They operate in a similar way and has a similar performance curve to a car engine (starts off at about 80% of best efficiency, climbs to 100 % of best efficiency then can drop to 30% of best efficiency at maximum RPM), the pressure and temperature are actually controlled by the expansion valve, not the speed of the compressor. The compressors are positive displacement, so can produce the maximum 40 bar (depending on the refrigerant, it can go up to 160 bar) pressure at 10 % of maximum speed. There are 2 other variables, they are the evaporator and condenser which are both designed to provide high levels of performance at maximum output based on economies of scale. When the load reduces, the ratio between surface area and output increases resulting in an increase in performance. It is imposable to calculate this as every manufacturer has different ways of doing things.

Your maths may have worked on the old fixed speed compressors, which had an output the varied only by the variation of supply and delivery temperatures.

Not simple any more. That is one of the reasons you should not use a third-party thermostat with a modern inverter unit, when the thermostat switches on, the unit runs at full capacity (the worst possible performance level for the compressor, evaporator and condenser)all the time until the thermostat switches it off again. You could do it with the old on-off compressors as they were either 100% or nothing. Thermostat is 100% or nothing.

This is the simple explanation, not a simple as people make out.

@heacol question? Could I simply get a plumber in and installer a manual diverter around the parts you note? It's something I might consider as it's reversible if needed. I did speak to a plumber the other day and he was very hesitant to change anything as he wasn't sure if it might impact (or damage) the HP.

As an experiment it might be very interesting

Posted by: @heacol

@derek-m It does not work like that, When we talk about inverter technology we are talking about the variable speed compressor/inverter drive unit as a whole. They operate in a similar way and has a similar performance curve to a car engine (starts off at about 80% of best efficiency, climbs to 100 % of best efficiency then can drop to 30% of best efficiency at maximum RPM), the pressure and temperature are actually controlled by the expansion valve, not the speed of the compressor. The compressors are positive displacement, so can produce the maximum 40 bar (depending on the refrigerant, it can go up to 160 bar) pressure at 10 % of maximum speed. There are 2 other variables, they are the evaporator and condenser which are both designed to provide high levels of performance at maximum output based on economies of scale. When the load reduceand s, the ratio between surface area and output increases resulting in an increase in performance. It is imposable to calculate this as every manufacturer has different ways of doing things.

Your maths may have worked on the old fixed speed compressors, which had an output the varied only by the variation of supply and delivery temperatures.

Not simple any more. That is one of the reasons you should not use a third-party thermostat with a modern inverter unit, when the thermostat switches on, the unit runs at full capacity (the worst possible performance level for the compressor, evaporator and condenser)all the time until the thermostat switches it off again. You could do it with the old on-off compressors as they were either 100% or nothing. Thermostat is 100% or nothing.

This is the simple explanation, not a simple as people make out.

Brendon,

I don't disagree with many of your statements and I certainly agree that thermostats are not ideally suited for use with ASHP's and would certainly like to support you in your quest to improve the operation and control of ASHP based heating systems.

Where I find great difficulty is your claim that a COP of 7.4 can be achieved when an ASHP is operating with an outside air temperature of 3C and an inside air temperature of 21C. It may be possible to achieve such figures under specific operating conditions for a short period of time, but I cannot see how such levels of efficiency can be produced consistently. Please provide data for longer periods if you wish to convince me.

Your claim that the level of insulation, and hence heat loss, is of no importance, totally contradicts the laws of thermodynamics, and hence gives me reason to doubt.

I agree that the pressure and temperature are controlled by the expansion valve, but as the heat demand on the heat pump increases, so must the pressure and temperature, which in turn means that the compressor/inverter must work harder and hence draw more power. This occurs at a time when there is less energy to be absorbed from the ambient air.

Hi, any thoughts on using an electric boiler as a back up/ booster for an ashp in the cold (sub 4°) weather? I don't have gas at the property ( although could get it at a cost) and thought I'd hit upon a solution.

However, can't actually find any installers to ask. Do they actually exist?

Sam. 

Posted by: @sam

Hi, any thoughts on using an electric boiler as a back up/ booster for an ashp in the cold (sub 4°) weather? I don't have gas at the property ( although could get it at a cost) and thought I'd hit upon a solution.

However, can't actually find any installers to ask. Do they actually exist?

Sam. 

Hi Sam,

Back again. You would be much better either buying an electric fan heater, which you can move around the house, or having an Air to Air ASHP installed to support your present A2W ASHP>

@heacol, I can certainly see (based on our debate and interaction) why you wouldn't be liked by the industry. I do, however, respect your perseverance and stance, and this site was always supposed to be a forum for discussion and differing views. I'm not sure that I'm fully convinced that you can maintain the extremely high COP scores over 7 with ambient temperatures of 3C and keep a moderately insulated home warm at 21C. But that's neither here or there, and my personal opinion based on our heat pump experience. 

I would, however, like to understand why the buffer tank and controls make heat pumps so inefficient and why bypassing these makes your systems operate better. Where (and why) does the system lose so much performance with the buffer tank and thermostats?

On the subject of MCS, as homeowners, this is the only entity that provides any assurance and a fallback position for dodgy installations of which there are many in the UK. Sam, who actually posted earlier today is a prime example of that. She had an awful heat pump system installed by a non-MCS accredited installer and she had zero recourse and to my understanding they've had the heat pump, in a new build removed. For me, that is an unacceptable situation. 

While the MCS is far from perfect, I would rather have the MCS than not have them because at least there's a structure in place where the industry can grow from and evolve, and maybe they can be the driving force to get better installation standards in place if enough pressure is applied. I'm curious – does the MCS have a guideline pertaining to buffer tanks?

I will be more than happy to interview Ian again and raise the many points that we've discussed here – if they are at fault, they should be accountable, 100%. They are supposed to be safety net in the system to protect homeowners and consumers from rubbish installations. And if the installation criteria needs to be rectified and updated, they have to be especially in light of the net zero targets. We all need to be consuming far less energy, and if the systems installed could be better designed and installed, then this must be brought to light, and we'd be happy to raise this awareness. 

From your perspective Brendan, as a guesstimate, how many installers are in your camp (buffer-less systems)? 

@kev-m, that's super interesting. I didn't know you were buffer-less and that your installer was adamant about this. We had six quotes and each one recommended a buffer tank. If one or two had suggested otherwise, this would have prompted us to dig deeper, but when all six go down the same route, there's no need to question anything.