GSHP - I need help with making it as efficient as possible!

countryhouse39

Reed_Richards said:

shinytop said:
I don't have a GSHP but have an ASHP so similar.  The three things that make my ASHP work inefficiently are (1) cold weather (2) high flow temperatures and (3) working hard.  I get the best efficiency when the HP is running steadily at low-mid power and the flow temps are 35-40C.  I try and avoid letting the house heat up and cool down too much because that makes my ASHP work hard to warm it up and so keep the heating on most of the time.  I use weather compensation, which varies the flow temp according to the outside temperature; I don't know if you have this. ... 

(1) You have a GSHP so it will be much less sensitive to the weather outside than an ASHP.
(2) This is an intrinsic property of all heat pumps, the higher that water flow temperature the less efficiently and economically they perform.
(3)  This is true for @shinytop but it may or may not be true for all heat pumps.

The thing that you can do that will work for all heat pumps is to make sure the water temperature you are using is not higher than it needs to be.  Since the temperature it needs to be will depend on the outside temperature hopefully your heat pump will incorporate 'Weather Compensation' which automatically adjusts the maximum water temperature according to the outside temperature.   This feature may or may not have been engaged and may or may not have been set-up optimally.

we have weather compensation - how do I ensure it is set-up optimally?

shinytop

countryhouse39 said:

Reed_Richards said:

shinytop said:
I don't have a GSHP but have an ASHP so similar.  The three things that make my ASHP work inefficiently are (1) cold weather (2) high flow temperatures and (3) working hard.  I get the best efficiency when the HP is running steadily at low-mid power and the flow temps are 35-40C.  I try and avoid letting the house heat up and cool down too much because that makes my ASHP work hard to warm it up and so keep the heating on most of the time.  I use weather compensation, which varies the flow temp according to the outside temperature; I don't know if you have this. ... 

(1) You have a GSHP so it will be much less sensitive to the weather outside than an ASHP.
(2) This is an intrinsic property of all heat pumps, the higher that water flow temperature the less efficiently and economically they perform.
(3)  This is true for @shinytop but it may or may not be true for all heat pumps.

The thing that you can do that will work for all heat pumps is to make sure the water temperature you are using is not higher than it needs to be.  Since the temperature it needs to be will depend on the outside temperature hopefully your heat pump will incorporate 'Weather Compensation' which automatically adjusts the maximum water temperature according to the outside temperature.   This feature may or may not have been engaged and may or may not have been set-up optimally.

we have weather compensation - how do I ensure it is set-up optimally?

Can you see from your controller how it's set up now?  It's likely to be a pre-selected 'curve' or one you can specify yourself.  Details will be in your manual.  The way most people do this is to set thermostats a couple of degrees higher than normal and let the heating run continuously.  If your house heats up to the new thermostat settings the flow is too high so adjust the curve to lower it.  You have to keep doing this until the flow temperature maintains your desired temperature without the thermostat.  You'll probably have to do this on days of different temperatures outside.  A 'quick and dirty' method is just to lower the flow temp and see what happens.  If the house then is still warm you'll almost certainly be saving money. Keep doing until you're too cold.
 
However... if you use a weather compensation curve that will just keep the house warm then if you allow the thermostats to switch it on and off then the house will take ages to warm up. If you want to run the system like this then you'd be better using a weather compensation curve that's a little hotter.

I run my ASHP continuously with the thermostats turned up to 30C. This keeps the house at a constant 21C.  This might not work for everyone but it does for us.  It took a couple of weeks tinkering to get it right.



 

Reed_Richards

Do you know how to change the weather compensation settings?  It  may be in an "installer" menu that you would need to know how to access.

Do you have the heat pump on 24/7?  Do you know how it copes with the mixture of UFH and radiators, which might require different water temperatures?

Can you see what water temperature your heat pump is using at any given time?

In principle you wait for a day when the outside temperature is expected to remain fairly stable.  You note what it is then you manually reduce the set water temperature a bit and see if the house manages to keep warm enough.  If the house stays warm then you repeat this exercise for a range of different outside temperatures.  Then you adjust the weather compensation settings to match these new reduced temperatures.

For example, when my ASHP was set up it was programmed to make the leaving water temperature 50 C when the outside temperature was 5 C or less.  I have found that I only need 50 C water when the outside temperature is about -3 C or less and if it's 5 C outside I can get away with about 42 C water and my house remains perfectly warm.  Only having to heat the water to 42 C improves the economy of operation of my heat pump.     

ccbrowning

countryhouse39 said:

We have a GSHP for our heating and hot water. the RHI payments end this year and so we have the double whammy of no longer getting that alongside rising energy costs, and its worrying me. Our GSHP was installed by previous occupants of the house who then got divorced and sold house to us shortly after completing the works (I sometimes wonder if the stress of the heating system aggravated any problems they were having!) The reason why this is relevant is that in all the time we have been here we have had lots of issues with it and the main stress we have is that there are so few people in our area willing to service / repair it or any part of the heating system, that any time anything goes wrong it take a lot of time and money to fix; so much so i am seriously contemplating retraining as a renewables engineer!!

Anyway, we are lucky that we have a lovely big house (5bed,3living) but this means our energy use is high. Despite being resigned to our usage being higher than average, I still feel that its also higher than it should be, even taking the size of property into account. During winter we regularly use 100kwh a day, and we need to bring this down. I am hoping there is someone on here who can help me identify where/how we can make things more efficient. Thanks!

Mind my asking what county you’re in? We’re buying a home with a GSHP up in Lancashire and it seemed like a number of companies are around that can service GSHPs. 

markin

The night set back of 15c seems far to low to me, they have to work very hard to get back up and underfloor heating makes it far worse as they can take 6+ hrs to days to get back up to temp, i think 18c would be far better.

Reed_Richards

I have my night set back at 17.5 C but only on the coldest nights does it actually get down to 17.5 C before the heating comes on again.  

matelodave

My set back is 17.0 and it still takes a couple of hours to get back up to temp with underfloor heating. Probably faster with a radiator set up.

michaels

I guess the general principle must be that a lower night temp = less heat loss, however the specific factor may be that to provide the extra energy required to recover to the day time temp may result in less efficient running due t the system efficiency parameters.

countryhouse39

ccbrowning said:

countryhouse39 said:

We have a GSHP for our heating and hot water. the RHI payments end this year and so we have the double whammy of no longer getting that alongside rising energy costs, and its worrying me. Our GSHP was installed by previous occupants of the house who then got divorced and sold house to us shortly after completing the works (I sometimes wonder if the stress of the heating system aggravated any problems they were having!) The reason why this is relevant is that in all the time we have been here we have had lots of issues with it and the main stress we have is that there are so few people in our area willing to service / repair it or any part of the heating system, that any time anything goes wrong it take a lot of time and money to fix; so much so i am seriously contemplating retraining as a renewables engineer!!

Anyway, we are lucky that we have a lovely big house (5bed,3living) but this means our energy use is high. Despite being resigned to our usage being higher than average, I still feel that its also higher than it should be, even taking the size of property into account. During winter we regularly use 100kwh a day, and we need to bring this down. I am hoping there is someone on here who can help me identify where/how we can make things more efficient. Thanks!

Mind my asking what county you’re in? We’re buying a home with a GSHP up in Lancashire and it seemed like a number of companies are around that can service GSHPs. 

we are in Scotland... not so well covered it seems!

countryhouse39

markin said:

The night set back of 15c seems far to low to me, they have to work very hard to get back up and underfloor heating makes it far worse as they can take 6+ hrs to days to get back up to temp, i think 18c would be far better.

ok - thanks - will see how we go raising this slightly.