Heat pumps - What’s your experience of the benefits and downsides to an ASHP?

Just a few observations.

TRVs and zoning

Turning radiators down or off, zoning parts of the heating, or running the heating intermittently will reduce the average temperature of the house and hence reduce the heat losses from the house.

Operating the heat pump at a higher flow temperature will reduce its efficiency, so running it for longer at a lower temperature should make it more efficient.

The question is does the increase in efficiency outweigh the increase in house losses?

In some ways this is like comparing taking a bath or a shower. Baths are much more efficient because the energy in the bath far exceeds the losses in the pipework, but showers use maybe a quarter of the energy, so they are by far the most economic.

If the load on the heat pump is much less than its rating (excessive zoning), then the heat pump will be continually cycling, pulsing heat in, then waiting for the return flow to cool. Think filling a bowl with hot water in the kitchen, then taking it upstairs to fill the bath, then returning to the kitchen to repeat the process.

Heat up times.

The time for a room to re-heat is determined by the power output from the radiator. If the radiator has been resized so that it outputs the same power (at the reduced flow temperature) as the original radiator (operating at gas boiler temperatures) then the room will reheat in the same time.

Weather compensation may mean that the (initial) flow temperature may be less than the design flow temperature (for -3°C ambient), so the cooler radiator outputs less power and the room heats slower. 

However a "TPI" thermostat on a gas boiler system will adjust the heating duty cycle to run the boiler cooler (to increase efficiency), so it too will heat slower on warmer days.

Those are some really thoughtful observations @BeePee. 

I don’t know if you have seen this article yet but I would definitely recommend giving it a read 

• Air Source Heat Pump (ASHP) cost analysis - how does it compare to a gas boiler? VIDEO

Keep us updated with your findings

I Iive in a terraced house. Could I have a heat pump installed?  If so where would it go?

On the revised App there is a Heat Pump section on the Home page and you register your interest. It doesn’t commit you to a course of action but it does take you down the path where by the Heat Geeks can establish where the best place for all the elements of the system need to be.

If you commit to going ahead with the survey then I think the fee is £350 which I believe is refunded as part of the cost of the installation. I followed that process but for practical reasons I didn't complete but the house heat loss survey was very useful and I opted to stay with my gas boiler for the time being but I've upgraded a couple of large windows to triple glazing and upsized a radiator in the hallway which was an extension to the house and hadn't been sized properly.

Peter

Whereabouts on the home page?  I can't see it. Can you send a screen shot?

Hi, our new heat pump (not from OVO) has a COP of about 2.5 for water and 1.1 for room heating, so I’m looking for ways to improve it. I hope this is a good place for this question.

The installer quoted and agreed to link a Honeywell Evohome to it: it controls each radiator separately (i.e. a multi-zone system). I realised that this would mean the COP was not the best it could be, but we don’t want to loose the ability to leave some bedrooms unheated and save that way. The Evohome is an on-off control to the heat pump - Opentherm could give a graduated control system (as it does with boilers), but doesn’t seem to be implemented on heatpumps. Apart from going to single zone, does anybody have any suggestions about what to do? The pump is an Ecodan R32. I’m trying to get the installer to help, and asking here to help me talk sensibly with him. Thanks in advance.

If I was you I’d try running it without the zoning and see how it improves. Set the heat pump to run on a weather dependent setting. Unfortunately as we’re coming to the end of the heating season it’s going to be difficult to set this up now. Do you know how to set up the weather curve ? 
1.1 for space heating is dreadful though 2.5 for hot water is not bad. 
Search for the heat geek video which explains why you shouldn’t zone rooms with a heat pump.

Thanks Julia. It was left on constant flow temperature at 50C, it’s on temperature compensation mode now. I’ll need to install the wireless room thermostat they left before I can change zoning. It’s difficult to set a specimen room for the thermometer. I’ve seen the heat geek video. I get the point but there are rooms in an extension that are thermally separate from the rest so I will exclude some rooms. I’ll need to balance the system too, as with remote TRVs it wasn’t necessary. I know there’s a heatgeek video for that too. I can’t quite believe that we’d have warmer rooms all the time and it not cost more, but we’ll see. We were quite frugal with the Evohome and boiler. Thanks again.

Hey @Johnc99 

Welcome to the OVO Forum.

I hope the advice juliamc left you was helpful, keep us updated with how you get on with things. I’m sure it could be helpful to others in the community in future to learn from your experience.🙂

Hi Julia. I have installed the Mitsubishi room temperature monitor and watched quite a few heat geek videos. There is also a document of his that gives a specimen calculation for cost with and without zoning, which is quite convincing. The weather has warmed so, as you say, it’s difficult to set it up now and see what’s happening. We really only need the bathroom warmed first thing and late evening. Our single zone is the dining room, lounge, kitchen and bathroom. Our heat pump can modulate down only to 60%, so with a low load it must cycle and so it will have a low COP. I have lowered the pump flow maximum temperature (which sets when it turns off) and minimum temperature (which decides when it turns back on), trying to slow the cycling. The energy used, morning and evening, is only a few kWh, so it may not be worth trying to improve COP for this time of year, when the dominant effect should be in the heating season. If anybody is still interested I will try to remember to update this if I get anywhere. Thanks

@Sandyeyes Sorry for the delay. I missed your message. I tried to find it again but it isn’t there any more. Possibly bypassing a few hurdles, try emailing Anna Gunstone directly at upgrades@heatgeeks.com to see if you can get some information on how you get started on this. It is dependent on Heat Geeks carrying out work in your area so you may not have the link if they aren’t. I hope that helps.

Peter

I’m in the process of going back through this thread along with reaching out to some who have now had experience of a Heat Pump over some months or years. 
I’m part way into the process - there’s a few offers around at present - and have had a surveyor visit to assess our current situation. They said it all looked positive (awaiting sign off for the Gov Grant) and now looking for an install plan. 
Once the project begins, I will try to track the installation progress and report back

Hey ​@BPLightlog,

Please keep us updated on your journey ⚡

If you’d like to share it as a blog you could post it as a new thread and give everyone an idea of the different challenges and victories that you have. Excited to see the end result!

This is a very good reference to heat pumps. I’ve been through the entire series myself and it was for this reason that I became sufficiently knowledgeable in order to make a decision on whether to go for an ASHP or not. The other consideration is that heat pump technology is changing all the time and it is worth seeing if the early limitations have been eliminated or reduced with more modern designs.

https://www.heatgeek.com/category/knowledge/

I thought I'd add in a few notes here while it's fresh in my mind. I had a Samsung EHS heat pump installed in late November, a very well done physical installation although terrible communications. A cold snap at the end of the installation didn't help with getting it properly tuned and caused a bit of panic. I'm pretty sure there were a few settings wrong which because of Christmas and new year I've corrected myself with much research. I'll get the installer back to check and confirm what I've done.

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Things I've learnt:

Proper settings are really important

Proper design of the system is too

Heat pumps take a lot more effort to understand

My heat pump is quiet but my water pumps are as noisy as with the old system

The efficiency depends on a pile of things, not just the heat pump, including the volume of water hitting radiators. Sometimes it's better to have more of the house heated. Get it set right and then tamper as little as possible. 

A poor installer can ruin what should be a good investment. Get someone who knows what they are doing and who will make sure it's working well.

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Costs

Yes, your house will be heated more. This is a benefit and disadvantage. It may reduce the cost saving but it also enables it and less used rooms are already comfortable to spend time in.

Think of the capital cost as a long term one. Heat pumps are likely to last much longer than modern boilers. 25 years is quoted, although time will tell.

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Overall I love it and expect it to be better and easier in the long term.

Jon

​@Countrylad it's good to get your experience with a heat pump on here for other people to see.

The issues that concerned me were:

The intial cost. Not just the capital but the cost of replacement parts and the cost to insure it against faults. It's worth carefully researching those.

Longevity. My old gas boiler lasted 24 years with only one replacement part. In the end it was the heat exchanger that was failing so it was game over but everything else was fine because it was in an indoor environment. A significant part of an ASHP sits outside in all weathers. I think the jury is still out on how that will last and what that will look like in 25 years time. Screening the unit can cause a microclimate issue.

There is a risk of damage to the outside unit if you have a simultaneous fail of the mains power during sub zero temperatures. Some designs have antifreeze valves that drain the water in an emergency should that occur but not on the system I was offered. They wouldn't add glycol antifreeze either to the outside water circuit as they said it increases the viscosity of the water and reduces the COP.

I had a disagreement with the installers about the size of the unit required and they specified a 7.5kW unit against my detailed GCH records of only needing 4kW peak at the specified lowest temperature. A 5kW unit was available but they wouldn't budge on that. A 7.5kW would have been constantly cycling, reducing the efficiency.

In the end I installed an A2AHP rated at 3kW for a small fraction of the price and it replaces about 85% of my gas use. I call it a discrete hybrid system and hybrid systems are common in the USA and worth considering. But, if you just want a direct replacement for the gas boiler then make sure you do your research.

Peter

I agree that lots of information from anyone with experience is useful .. I’ve been following a whole host of both installed and about to be installed projects and most have been positive (albeit needing some questions and direction).
My own reflection so far is that with the gov grant, many installations are not that expensive at all. Couple that with an included insurance policy, warranty and offer on including any radiator upgrades in the standard price has made me progress towards a purchase and install. 
An oversized HP is definitely a negative but my survey has shown heat losses (we have a void underneath the wooden floorboard) which suggest the need for a 9kW unit. 
I'm still not committed to the install but most of my research is pointing towards the positives to go ahead. We will see what happens!

Oversizing can be bad but, of course, so can under-sizing! I've got a 16kW high temp heat pump and I'm almost sure my house could have got away with a smaller model. If you play around with the heat curve you should be able to minimise cycling. Even with a large unit I'm still getting around 340% efficiency for heating.

340% efficiency? Mind if I borrow some of that? XD

340% would be good. Going by the system info it varied daily from 2.2 to 3.7 from late November to now. Do you have any idea how yours went over the same period ​@Blastoise186?

In terms of capital cost, after replacement and decommissioning cost for my oil system (23 years old) it cost 3500 which I’m happy to spread over 20 years and that included putting in an insulated underground hot water pipe.

My system has 0% efficiency as I unfortunately don’t have a heat pump. I run on an all-electric Communal Heating system which has underfloor heating in my flat hooked up to a central electric boiler that covers the entire building. That means the heating and hot water is also wired into the landlord electricity supply and meter rather than my own.

It’s great for me because I can turn my flat into a 24/7/365 sauna and not pay a penny for it. :D

Alexa. <boing> Room temperature 25

Oops I tagged the wrong person so … 

340% would be good. I don’t really have a sense of what real-life figures I might get

Going by my system info mine varied on a daily summary from 220% to 370% from late November to now (SW Oxfordshire). This included water heating. Over the same period the average daily outdoor temperature was -0.8 to 12.5 

Do you know the range of  yours daily over the same period ​@nealmurphy ? I’m trying to figure out how much I need to poke the installer 😏

​@Countrylad I've not looked at individual months as it's easiest to look at the usage since installation which was 3 years ago. I'll take a note of the numbers today and report back in a couple of days to give an idea how it's doing in current conditions. 

Did you get any guarantee of COP or a suggestion of what it may be from your installer?

I'm not sure that it's a guarantee but the scop quoted is 4.4, my average is 2.9 from about 33 days recorded