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Author Topic: ASHP setup temperatures  (Read 12832 times)
Bodidly
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« Reply #75 on: November 24, 2019, 07:13:25 PM »

A complete hyjack as interesting as it is.

I value the expertise on here, but perhaps I should have started a new thread.

Am I correct in thinking that GSHP is of little use in the depths of winter with below-zero ground temperatures?

Do they switch to heating via the grid automatically or is it down to the owner to switch over?

 

Our GSHP ground loop is a bit short so in dry cold weather temps around our ground loop will get below freezing but it causes no problem with high running costs. Pretty sure they use them in permafrost in parts of Scandinavia. Any ground that is above absolute zero still has energy in it  Smiley
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marshman
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« Reply #76 on: November 24, 2019, 07:46:39 PM »

A complete hyjack as interesting as it is.

I value the expertise on here, but perhaps I should have started a new thread.

Am I correct in thinking that GSHP is of little use in the depths of winter with below-zero ground temperatures?

Do they switch to heating via the grid automatically or is it down to the owner to switch over?

 

Depends on the size of loop, depth in the ground, how much energy is taken out and where you are in the country.  I am fortunate in that I am in the supposedly sunny south east, have 4 x 300m  ground loops, don't take massive amounts of energy from them. Lowest ground loop temperature I have seen in 4 winters since install is 8 deg C. The lowest temps in terms of ground loops are in February, by the beginning of March they start climbing again. By the end of April they are 10 deg, last year they were at 11 deg C at the end of April. So with properly sized loops, efficient low temperature heat emitters and high levels of insulation and draught proofing a GSHP (and ASHP for that matter) will work throughout the entire heating season.

Having said all that I live in a remote rural area and have a large collection area covering the best part of an acre which is totally impractical for the majority of housing stock  in the UK (and elsewhere). The average domestic garden will not be big enough and installation of ground loops is massively disruptive and possible only where access is available for large machinery. Bore holes would be impracticably expensive. I personally think that a lot of UK housing stock would need a lot of work in terms of insulation before gas boilers could be replaced with any sort of heatpump, and the practical reality is in many places only ASHP could be used - you then have the issue of noise!  Here I am thinking of urban areas with rows of close knit Victorian Terraces or even later developments of post war semi's.  When looking at new builds then the developers need to understand how heatpumps work and build the houses accordingly, i.e. higher levels of insulation, thermal mass, UFH, careful siting of ASHP units, and maybe redesigning the layout of the development to allow the use of ground collection loops to run into adjacent fields or under access roads to utilise all available land for energy harvesting. The public also need educating away from the thinking of turning heating on and off and letting it run at a low level 24/7.

Roger
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« Reply #77 on: November 24, 2019, 08:35:03 PM »

The siteing of the outdoor ASHP unit is vital and rarely, if at all, taken into consideration. I expect your outdoor unit is fitted with the fan up tight against a wall stuck in a corner of the garden out of sight. This is the worst possible place to put it. The fan creates an area of low pressure behind the unit and of course the only air that can be drawn into the fan is the cold air coming out the front. Virtually all ASHP compressors are installed like this, WRONG.   The unit should be perpendicular to the wall so the cold air can freely flow down and away from the unit and the fan will be drawing fresh warm air only from the rear. They should be installed in the clear with any prevailing movement of air going in the same direction of the fan. ASHP's ice up continually if you are in a damp environment, like a valley in the country, this causes them to defrost every 20 minutes or so. The ice is an insulator and causes high pressures in the compressor because the liquid cannot evaporate quick enough.
In the uk the ground temp is the annual average of the air temperatures and is usually around 8 to 10 degrees. Thats why GSHP's work far better than ASHP,s. The governments idea of having all new builds with an ASHP is a recipe for disaster, as usual they do not know what they are talking about.
ASHP's work in Scandinavia because the houses are properly, and carefully, built to passive house standards where they need negligible heating anyway. Can you see any British Property Developers doing that.  Also the air is cold and DRY there is very little humidity like we have here in Damp Britain.

http://www.yougen.co.uk/blog-entry/1560/Common+problems+with+Air+Source+Heat+Pumps/
« Last Edit: November 24, 2019, 08:48:47 PM by rogeriko » Logged

DonL
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« Reply #78 on: November 25, 2019, 12:16:38 PM »

The siteing of the outdoor ASHP unit is vital and rarely, if at all, taken into consideration. I expect your outdoor unit is fitted with the fan up tight against a wall stuck in a corner of the garden out of sight. This is the worst possible place to put it. The fan creates an area of low pressure behind the unit and of course the only air that can be drawn into the fan is the cold air coming out the front. Virtually all ASHP compressors are installed like this, WRONG.   The unit should be perpendicular to the wall so the cold air can freely flow down and away from the unit and the fan will be drawing fresh warm air only from the rear. They should be installed in the clear with any prevailing movement of air going in the same direction of the fan. ASHP's ice up continually if you are in a damp environment, like a valley in the country, this causes them to defrost every 20 minutes or so. The ice is an insulator and causes high pressures in the compressor because the liquid cannot evaporate quick enough.
In the uk the ground temp is the annual average of the air temperatures and is usually around 8 to 10 degrees. Thats why GSHP's work far better than ASHP,s. The governments idea of having all new builds with an ASHP is a recipe for disaster, as usual they do not know what they are talking about.
ASHP's work in Scandinavia because the houses are properly, and carefully, built to passive house standards where they need negligible heating anyway. Can you see any British Property Developers doing that.  Also the air is cold and DRY there is very little humidity like we have here in Damp Britain.

http://www.yougen.co.uk/blog-entry/1560/Common+problems+with+Air+Source+Heat+Pumps/

The installation instructions for my ASHP specify minimum clearances of 300mm behind and 1000mm in front. As it happens mine is installed 450mm from a wall and the performance is excellent (results published on this site). Subjectively, the stream of cold air coming out of the front of the device induces surrounding air into it and dissipates several meters from it; there seems little probability of the cold air short-circuiting back to the inlet. The unit defrosts as needed and this is more frequent in cool, damp, conditions but less frequent during very cold spells.

When choosing the ASHP I found a study comparing actual results between GSHP's and ASHP's and the difference was small. What was notable was the wide spread of results for both technologies showing the importance of designing and running either technology properly. The capital cost of the ASHP is considerably less.

Irrespective of heating source, our houses, and particularly new builds, should be built to high standards of insulation and air tightness and we need to aspire to that.

I would see the combination of well designed and built houses combined with well designed and installed ASHP's as being an excellent ambition, particularly as we continue to de-carbonise our grid electricity.

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chris wills
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« Reply #79 on: November 25, 2019, 12:25:27 PM »

Sorry guys. All interesting stuff but really nothing to do with this topic.
Please start a fresh topic.
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DonL
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« Reply #80 on: November 25, 2019, 01:16:46 PM »

Sorry, quite right. Don
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« Reply #81 on: November 25, 2019, 09:44:13 PM »

Sorry guys. All interesting stuff but really nothing to do with this topic.
Please start a fresh topic.

It has a lot to do with your installation. You say your heat pump cycles a lot, how do you know if it defrosting a lot and thats the cycling you are talking about. The compressor has to stop, wait for a few minutes to depressurise and the valves to change over then it will run at full power in reverse for 5 minutes and stop again. Strangely the defrosting cycle is not counted by any manufacturers in their efficiency calculations. The only way you can tell if its defrosting is to put a digital thermostat on the pipework to the fan coil.
A properly installed ASHP should run all day non-stop in the cold weather if there is enough demand.
« Last Edit: November 25, 2019, 09:45:55 PM by rogeriko » Logged

chris wills
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« Reply #82 on: November 26, 2019, 07:50:30 AM »

Sorry guys. All interesting stuff but really nothing to do with this topic.
Please start a fresh topic.

It has a lot to do with your installation. You say your heat pump cycles a lot, how do you know if it defrosting a lot and thats the cycling you are talking about. The compressor has to stop, wait for a few minutes to depressurise and the valves to change over then it will run at full power in reverse for 5 minutes and stop again. Strangely the defrosting cycle is not counted by any manufacturers in their efficiency calculations. The only way you can tell if its defrosting is to put a digital thermostat on the pipework to the fan coil.
A properly installed ASHP should run all day non-stop in the cold weather if there is enough demand.

It is definitely not on a de-frost cycle, there is a symbol for that on the pump and it never appears. My issue is I cannot tell the CH pump to go off when the rooms reach the correct temp.
I don't understand that it runs all day comment. It has a set point of return temperature and when it hits that it goes off. Of course if its really cold then it will run and run as it struggles to reach the setting.
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DonL
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« Reply #83 on: November 26, 2019, 04:59:53 PM »

Sorry guys. All interesting stuff but really nothing to do with this topic.
Please start a fresh topic.

It has a lot to do with your installation. You say your heat pump cycles a lot, how do you know if it defrosting a lot and thats the cycling you are talking about. The compressor has to stop, wait for a few minutes to depressurise and the valves to change over then it will run at full power in reverse for 5 minutes and stop again. Strangely the defrosting cycle is not counted by any manufacturers in their efficiency calculations. The only way you can tell if its defrosting is to put a digital thermostat on the pipework to the fan coil.
A properly installed ASHP should run all day non-stop in the cold weather if there is enough demand.


It is definitely not on a de-frost cycle, there is a symbol for that on the pump and it never appears. My issue is I cannot tell the CH pump to go off when the rooms reach the correct temp.
I don't understand that it runs all day comment. It has a set point of return temperature and when it hits that it goes off. Of course if its really cold then it will run and run as it struggles to reach the setting.

The heat pump is at it's highest efficiency when the temperature difference between the source and the heated water is as low as possible. So the most efficient operation is to have the water temperature as low as possible so that the system runs all the time. This is why it is better to vary the recirculating temperature according to demand (inversely proportional to outside temperature). In your case, the setpoint temperature for the buffer tank should vary in this manner. The recirculating pump to the underfloor heating/radiators should run nearly all the time and the underfloor heating/radiators get hotter or cooler depending on the outside temperature.
The heat pump (and it's re-circulating water pump) should run as necessary to maintain the  varying set temperature in the buffer tank. If the heat pump is of the simple on/off type you will need enough hysteresis (difference between the temperature it turns on at and temperature which it turns off at) to give a reasonable run time for the heat pump which depends on the rating of the heat pump and the size of the buffer tank.

I think this is what Rogeriko is getting at and it is certainly the way I control mine in principle.

Don
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chris wills
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« Reply #84 on: November 29, 2019, 06:33:12 PM »

Sorry guys. All interesting stuff but really nothing to do with this topic.
Please start a fresh topic.

It has a lot to do with your installation. You say your heat pump cycles a lot, how do you know if it defrosting a lot and thats the cycling you are talking about. The compressor has to stop, wait for a few minutes to depressurise and the valves to change over then it will run at full power in reverse for 5 minutes and stop again. Strangely the defrosting cycle is not counted by any manufacturers in their efficiency calculations. The only way you can tell if its defrosting is to put a digital thermostat on the pipework to the fan coil.
A properly installed ASHP should run all day non-stop in the cold weather if there is enough demand.


It is definitely not on a de-frost cycle, there is a symbol for that on the pump and it never appears. My issue is I cannot tell the CH pump to go off when the rooms reach the correct temp.
I don't understand that it runs all day comment. It has a set point of return temperature and when it hits that it goes off. Of course if its really cold then it will run and run as it struggles to reach the setting.

The heat pump is at it's highest efficiency when the temperature difference between the source and the heated water is as low as possible. So the most efficient operation is to have the water temperature as low as possible so that the system runs all the time. This is why it is better to vary the recirculating temperature according to demand (inversely proportional to outside temperature). In your case, the setpoint temperature for the buffer tank should vary in this manner. The recirculating pump to the underfloor heating/radiators should run nearly all the time and the underfloor heating/radiators get hotter or cooler depending on the outside temperature.
The heat pump (and it's re-circulating water pump) should run as necessary to maintain the  varying set temperature in the buffer tank. If the heat pump is of the simple on/off type you will need enough hysteresis (difference between the temperature it turns on at and temperature which it turns off at) to give a reasonable run time for the heat pump which depends on the rating of the heat pump and the size of the buffer tank.

I think this is what Rogeriko is getting at and it is certainly the way I control mine in principle.

Don


I just can't see anyway to vary the ASHP output, the only option is to fix its output or return temp.
I really need the stats in the house to switch the CH pump off, that will crack it i think.
Any ideas how to do this....can it be automated so i do not have run cables all over the house?
This is how my stats are wired into the manifold, not good....just looks like a simple on/off circuit for the manifold only and not the pump - another way i guess is fit the pump to manifold or something similar

Need a switch on the CH pump to turn it off/on when the all the manifolds are closed to the rooms.


* IMG_0625.JPG (113.75 KB, 768x1024 - viewed 245 times.)
« Last Edit: November 29, 2019, 07:08:01 PM by chris wills » Logged
Countrypaul
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« Reply #85 on: November 29, 2019, 07:07:11 PM »

There are two clear ways in my mind to try and automate your pump, one is simply to use a thermostat in a suitable room and have that turn the pump on/off (a wireless one can be used to avoid having to run more cables), this won't give you exactly what you want but is fairly cheap and easy to implement. The second way is to use a wiring centre - that will do exactly what you want, it would be located close to the manifold and the existing thermostats would be wired into it and the existing manifold actuators would also be wired into it, as would the pump - though this might require a new cable from current pump location to manifold location - although you could move the pump though how that would affect your radiators I have no idea.

On my setup the manifold is downstairs in the utility room with the wiring centre and the pump is upstairs near the thermal store, there is a cable from the utility room upto the pump.
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chris wills
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« Reply #86 on: November 29, 2019, 07:20:55 PM »

There are two clear ways in my mind to try and automate your pump, one is simply to use a thermostat in a suitable room and have that turn the pump on/off (a wireless one can be used to avoid having to run more cables), this won't give you exactly what you want but is fairly cheap and easy to implement. The second way is to use a wiring centre - that will do exactly what you want, it would be located close to the manifold and the existing thermostats would be wired into it and the existing manifold actuators would also be wired into it, as would the pump - though this might require a new cable from current pump location to manifold location - although you could move the pump though how that would affect your radiators I have no idea.

On my setup the manifold is downstairs in the utility room with the wiring centre and the pump is upstairs near the thermal store, there is a cable from the utility room upto the pump.

2 very good options, I already have the room stats in place and want to utilise these, I think if I fitted a single stat to control the whole of downstairs then it could get a bit tricky for it to represent each room. The latter suggestion is what I need, can you provide some links/images to what is needed? Don't think I would try it myself, maybe get a plumber in. With regards to radiator effects I see little it would affect tbh

Basically like this:



« Last Edit: November 29, 2019, 08:14:50 PM by chris wills » Logged
Countrypaul
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« Reply #87 on: November 30, 2019, 12:21:46 AM »

As I see it, unless you want to move your pump, an electrician maybe more relevant than a plumber- ideally you want a part P registered plumber of course who could deal with both aspects.

I think this would be suitable: https://www.heatmisershop.co.uk/6-zone-underfloor-heating-wiring-centre/?gclid=EAIaIQobChMImumIxtSQ5gIVhbTtCh2pHAosEAQYASABEgLc_PD_BwE
but mainy because I have the 8 port version, there are other makes. Port 6 on this one appears to support either UFH or radiators which may or may not be an advantage for you.

Download the instructions and make sure it does what you require before committing yourself. Others on here may be able to make better recommendations.

As highlighted earlier in this thread therea are also other options that include a manifole complete with valves, pump and TMV, but if all you require for the moment is the wiring centre the one above would I believe be adequate. Note I just choose the first supplier I found on google, there  may be others cheaper and your plumber/electrician may be able to supply you also.
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chris wills
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« Reply #88 on: December 01, 2019, 07:01:47 PM »

As I see it, unless you want to move your pump, an electrician maybe more relevant than a plumber- ideally you want a part P registered plumber of course who could deal with both aspects.

I think this would be suitable: https://www.heatmisershop.co.uk/6-zone-underfloor-heating-wiring-centre/?gclid=EAIaIQobChMImumIxtSQ5gIVhbTtCh2pHAosEAQYASABEgLc_PD_BwE
but mainy because I have the 8 port version, there are other makes. Port 6 on this one appears to support either UFH or radiators which may or may not be an advantage for you.

Download the instructions and make sure it does what you require before committing yourself. Others on here may be able to make better recommendations.

As highlighted earlier in this thread therea are also other options that include a manifole complete with valves, pump and TMV, but if all you require for the moment is the wiring centre the one above would I believe be adequate. Note I just choose the first supplier I found on google, there  may be others cheaper and your plumber/electrician may be able to supply you also.

OK I get the wiring system but how do I tell
It to switch the CH pump off if the rooms are to temp?
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rogeriko
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« Reply #89 on: December 01, 2019, 10:00:25 PM »

All those manifold wiring centres have outputs to turn pumps and boilers on and off. Your system has been wired directly from thermostat to actuator. Whoever installed like that dosn't know what they are doing. Get a simple cheap 6 port wiring centre and you will have your pump output that will turn on the pump when any thermostat calls for heat and turn it off when all the thermostats are up to temperature.

https://www.ebay.co.uk/itm/UFH-8-Way-230v-Underfloor-Heating-Wiring-Centre/142945939731?hash=item21483df113:m:mgJyLVmMjoIPhnKihlb3zzA

45 pounds and it has 8 ports. Six for your underfloor actuators and two more for the upstairs radiators one for each floor. It will control your entire house.

Let the controller operate the 2 port valves for the upstairs and the 2 port valves will operate the pump. You do not need a 2 port valve on the underfloor heating circuit because you have the actuators to control the flow.
« Last Edit: December 01, 2019, 10:06:52 PM by rogeriko » Logged

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