Talk:Heat pump - Revision history

Designing Buildings at 13:12, 5 January 2015

2015-01-05T13:12:00Z

← Older revision		Revision as of 13:12, 5 January 2015
Line 1:		Line 1:

−	~~These text in [] are comments on The Future of Electricity in Domestic Buildings~~ a ~~review by BRE Group.~~	+	I attach a set of very recent test results on my A2A heat pump. Heat pump 'under-sizing' destroys the rationale for running heat pumps and there is a lot of it about. Have you heard the stories about heat pumps costing £2000 per winter to run and they do not heat the house properly? The stories are true
−		+	:-
−	~~1: Heat pumps, as opposed to air conditioning (cooling), are an important part~~ of ~~the effort to meet the UK’s carbon reduction target.~~	+
−		+
−	~~[DECC reported that a~~ test of about 280 RHI heat pumps in December 2013 achieved an average SPF of about 2.4 which falls below the EU threshold of 2.5 for renewability. In other words this sample of pumps achieved nothing with respect to emissions.]	+
−		+
−	~~2: The theoretical performance for heat pumps can be in the region of 4:1 but in practice it is often closer to 3:1 or even 2:1 in cold weather.~~	+
−		+
−	[My pump, a Mitsubishi SRK20ZJX, has a rated CoP of 5.7 at A7/A20 and actually delivers it. The most efficient pump that I know of is an Hitachi RAS8SX with a rated CoP of over 6. As the last winter's average temperature was 8.2C here in Gloucestershire, the SCOP was better than 5.0. My pump normally runs 24/7 in the 270 to 400watt range, so costs 6.48*0.15=£0.97 to £1.44 per day in the coldest months. The total electricity bill for last winter's space heating by heat pump was £144. The gas-fired boiler supplied the DHW and some supplementary heat for the lounge.]	+
−		+
−	~~Because this pump runs 24/7, it places no fluctuating demand~~ on ~~the grid beyond that caused by the ambient temperature variation. I also received a quote for an RHI pump for~~ my house. That would have been a 10kW(electrical) air-to-water pump. That is something like 22 times bigger and the generation has to be 22 times bigger as well. If people treat these big pumps like a fossil-fired boiler and they all get switched on as people come home from work, the evening peak demand on the system will go through the roof. This will need major grid reinforcement and will also need a total rebuild of the distribution system. Local 415V transformers are sized stochastically for current loads. None of this seems to have been thought about by anyone in authority.]	+
−		+
−	3: Many of these are likely to be air to water systems as despite their lower performance than ground sourced heat pumps they are relatively easy to install in existing buildings as they don’t need large and disruptive earthworks normally associated with ground sourced heat pumps.	+
−		+
−	~~[Big mistake]~~	+
−		+
−	~~4: As with many high power applications associated with heating purposes heat pumps can consume a large amount of electricity.~~	+
−		+
−	~~[Too right but nobody in DECC or Parliament seems the slightest bit interested.]~~	+
−		+
−	~~5: This can become a particular concern during switch-on and switch-off when voltage fluctuations must say within recognise limits as specified by the Electricity Supply Act 1988.~~	+
−		+
−	~~[This problem may not arise if every house on a supply transformer has a big~~ heat pump. ~~The transformer (and its associated cabling) will have tripped on high overcurrent long before all the pumps have started at 5o'clock of an evening.]~~	+
−		+
−	~~----~~	+
−		+
−	~~A2A~~ Heat ~~Pump~~ 'under-sizing' ~~Performance Test on 29/12/2014.~~	+
−		+
−	~~The appended test report demonstrates~~ the ~~complete economic failure that attaches to~~ running ~~in the 'under-sized' condition. 'Under-sizing' is a physical condition where the~~ heat ~~pump loses its ability to generate sufficient heat to prevent the the actual temperature falling below the desired temperature.~~	+
−		+
−	~~When a pump slips into 'under-sizing' its electrical power rises to a maximum whilst its heat output falls. The crucial point~~ is ~~that to remove the pump from this 'under-sized' state without shutting down requires~~ a ~~major reduction in the heat demand~~ of ~~the house~~. ~~In other words, the 'under-sized' condition is unstable. If you go a little bit into 'under-sizing',~~ you ~~go all~~ the ~~way and stay there until you do something fairly drastic. That is where these ridiculously high~~ heat ~~pump bills(mentioned above) come from.~~	+
−		+
−	~~I am confident that a lot of the poorly performing A2W~~ pumps ~~in DECC's test report spend a lot of time in the 'under-sized' condition. The A2W I tested last~~ winter ~~certainly did. It ran 'under-sized' continuously in ambient temperatures of 5C at a cost of 4240.15=£14.40 per day or £432 per 30 day month. My A2A, running properly~~ and ~~continuously at about 333watts, uses 0.33240.15=£1.20 per day or £36 per 30 day month.~~	+
−		+
−	~~Chose your poison: An 'under-sized' 4kW A2W or an efficient 0.45kW A2A; just a factor of 12 difference in running cost at 5C ambient. The A2W failed to~~ heat the house properly~~, whilst the A2A was fine. Also the A2W cost about eight times as much as the A2A.~~	+
−		+
−	~~________________________________________________~~	+
−		+
	Ambient temperatures were -1.5C at 0600.<br/>The sky was cloudless and ambient temperatures rose steadily throughout the test.		Ambient temperatures were -1.5C at 0600.<br/>The sky was cloudless and ambient temperatures rose steadily throughout the test.

Designing Buildings at 13:10, 5 January 2015

2015-01-05T13:10:20Z

← Older revision		Revision as of 13:10, 5 January 2015
Line 1:		Line 1:

	These text in [] are comments on The Future of Electricity in Domestic Buildings a review by BRE Group.		These text in [] are comments on The Future of Electricity in Domestic Buildings a review by BRE Group.
−	1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.	+
		+	1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.

	[DECC reported that a test of about 280 RHI heat pumps in December 2013 achieved an average SPF of about 2.4 which falls below the EU threshold of 2.5 for renewability. In other words this sample of pumps achieved nothing with respect to emissions.]		[DECC reported that a test of about 280 RHI heat pumps in December 2013 achieved an average SPF of about 2.4 which falls below the EU threshold of 2.5 for renewability. In other words this sample of pumps achieved nothing with respect to emissions.]

Designing Buildings at 13:10, 5 January 2015

2015-01-05T13:10:07Z

← Older revision		Revision as of 13:10, 5 January 2015
Line 1:		Line 1:

		+	These text in [] are comments on The Future of Electricity in Domestic Buildings a review by BRE Group.
	1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.		1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.

Designing Buildings at 13:07, 5 January 2015

2015-01-05T13:07:40Z

← Older revision		Revision as of 13:07, 5 January 2015
Line 1:		Line 1:

−	1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.~~<br/><br/>~~[DECC reported that a test of about 280 RHI heat pumps in December 2013 achieved an average SPF of about 2.4 which falls below the EU threshold of 2.5 for renewability. In other words this sample of pumps achieved nothing with respect to emissions.]~~<br/><br/><br/>~~2: The theoretical performance for heat pumps can be in the region of 4:1 but in practice it is often closer to 3:1 or even 2:1 in cold weather.~~<br/><br/>~~[My pump, a Mitsubishi SRK20ZJX, has a rated CoP of 5.7 at A7/A20 and actually delivers it. The most efficient pump that I know of is an Hitachi RAS8SX with a rated CoP of over 6. As the last winter's average temperature was 8.2C here in Gloucestershire, the SCOP was better than 5.0. My pump normally runs 24/7 in the 270 to 400watt range, so costs 6.48*0.15=£0.97 to £1.44 per day in the coldest months. The total electricity bill for last winter's space heating by heat pump was £144. The gas-fired boiler supplied the DHW and some supplementary heat for the lounge.]~~<br/><br/>~~Because this pump runs 24/7, it places no fluctuating demand on the grid beyond that caused by the ambient temperature variation. I also received a quote for an RHI pump for my house. That would have been a 10kW(electrical) air-to-water pump. That is something like 22 times bigger and the generation has to be 22 times bigger as well. If people treat these big pumps like a fossil-fired boiler and they all get switched on as people come home from work, the evening peak demand on the system will go through the roof. This will need major grid reinforcement and will also need a total rebuild of the distribution system. Local 415V transformers are sized stochastically for current loads. None of this seems to have been thought about by anyone in authority.]~~<br/><br/>~~3: Many of these are likely to be air to water systems as despite their lower performance than ground sourced heat pumps they are relatively easy to install in existing buildings as they don’t need large and disruptive earthworks normally associated with ground sourced heat pumps~~<br/><br/>~~[Big mistake]~~<br/><br/>~~4: As with many high power applications associated with heating purposes heat pumps can consume a large amount of electricity.~~<br/><br/>~~[Too right but nobody in DECC or Parliament seems the slightest bit interested.]~~<br/><br/>~~5: This can become a particular concern during switch-on and switch-off when voltage fluctuations must say within recognise limits as specified by the Electricity Supply Act 1988.~~<br/><br/>~~[This problem may not arise if every house on a supply transformer has a big heat pump. The transformer (and its associated cabling) will have tripped on high overcurrent long before all the pumps have started at 5o'clock of an evening.]~~<br/>~~	+	1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.
		+
		+	[DECC reported that a test of about 280 RHI heat pumps in December 2013 achieved an average SPF of about 2.4 which falls below the EU threshold of 2.5 for renewability. In other words this sample of pumps achieved nothing with respect to emissions.]
		+
		+	2: The theoretical performance for heat pumps can be in the region of 4:1 but in practice it is often closer to 3:1 or even 2:1 in cold weather.
		+
		+	[My pump, a Mitsubishi SRK20ZJX, has a rated CoP of 5.7 at A7/A20 and actually delivers it. The most efficient pump that I know of is an Hitachi RAS8SX with a rated CoP of over 6. As the last winter's average temperature was 8.2C here in Gloucestershire, the SCOP was better than 5.0. My pump normally runs 24/7 in the 270 to 400watt range, so costs 6.48*0.15=£0.97 to £1.44 per day in the coldest months. The total electricity bill for last winter's space heating by heat pump was £144. The gas-fired boiler supplied the DHW and some supplementary heat for the lounge.]
		+
		+	Because this pump runs 24/7, it places no fluctuating demand on the grid beyond that caused by the ambient temperature variation. I also received a quote for an RHI pump for my house. That would have been a 10kW(electrical) air-to-water pump. That is something like 22 times bigger and the generation has to be 22 times bigger as well. If people treat these big pumps like a fossil-fired boiler and they all get switched on as people come home from work, the evening peak demand on the system will go through the roof. This will need major grid reinforcement and will also need a total rebuild of the distribution system. Local 415V transformers are sized stochastically for current loads. None of this seems to have been thought about by anyone in authority.]
		+
		+	3: Many of these are likely to be air to water systems as despite their lower performance than ground sourced heat pumps they are relatively easy to install in existing buildings as they don’t need large and disruptive earthworks normally associated with ground sourced heat pumps.
		+
		+	[Big mistake]
		+
		+	4: As with many high power applications associated with heating purposes heat pumps can consume a large amount of electricity.
		+
		+	[Too right but nobody in DECC or Parliament seems the slightest bit interested.]
		+
		+	5: This can become a particular concern during switch-on and switch-off when voltage fluctuations must say within recognise limits as specified by the Electricity Supply Act 1988.
		+
		+	[This problem may not arise if every house on a supply transformer has a big heat pump. The transformer (and its associated cabling) will have tripped on high overcurrent long before all the pumps have started at 5o'clock of an evening.]

	----		----
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	Time_ _ Pwr_ _ Blr In_ ''Out _ _Set Pt _Amb _<br/>0950'' _ _300 _ _ 19.2 _ _ 28.5 _ _ 21 _ _ 1.0 _ _ All doors shut except 3<br/>1000_ _ 293 _ _ 19.0 _ _ 27.4 _ _ 21 _ _ 2.0 _ _<br/>1005_ _ 295 _ _ 18.9 _ _ 27.2 _ _ 21 _ _ 2.5 _ _ All doors opened<br/>1010_ _ 385 _ _ 18.7 _ _ 29.0 _ _ 21 _ _ 2.5 _ _		Time_ _ Pwr_ _ Blr In_ ''Out _ _Set Pt _Amb _<br/>0950'' _ _300 _ _ 19.2 _ _ 28.5 _ _ 21 _ _ 1.0 _ _ All doors shut except 3<br/>1000_ _ 293 _ _ 19.0 _ _ 27.4 _ _ 21 _ _ 2.0 _ _<br/>1005_ _ 295 _ _ 18.9 _ _ 27.2 _ _ 21 _ _ 2.5 _ _ All doors opened<br/>1010_ _ 385 _ _ 18.7 _ _ 29.0 _ _ 21 _ _ 2.5 _ _

−	1015_ _ 480 _ _ 18.6 _ _ 32.4 _ _ 21 _ _ 3.0 _ _ Whole house heated~~<br/>…~~ stable at high load ~~...~~<br/>1050_ _ 470 _ _ 18.7 _ _ 34.0 _ _ 21 _ _ 5.5 _ _	+	1015_ _ 480 _ _ 18.6 _ _ 32.4 _ _ 21 _ _ 3.0 _ _ Whole house heated, stable at high load<br/>1050_ _ 470 _ _ 18.7 _ _ 34.0 _ _ 21 _ _ 5.5 _ _

−	Set Pt +1 → 22C. Fan noise up.<br/>'Under-sized' condition starts<br/>1055_ _ 645 _ _ 18.8 _ _ 35.9 _ _ 22 _ _ 6.0 _ _<br/>1100_ _ 675 _ _ 18.8 _ _ 36.2 _ _ 22 _ _ 6.0 _ _<br/>Set Pt -1 → 21C<br/>1105_ _ 560 _ _ 18.7 _ _ 33.7 _ _ 21 _ _ 6.5 _ _<br/>1110_ _ 640 _ _ 18.7 _ _ 35.0 _ _ 21 _ _ 6.5 _ _ No recovery of normal running<br/>1115_ _ 665 _ _ 18.7 _ _ 36.3 _ _ 21 _ _ 7.0 _ _<br/>1120_ _ 665 _ _ 18.8 _ _ 36.5 _ _ 21 _ _ 7.0 _ _<br/>1125_ _ 665 _ _ 18.8 _ _ 36.4 _ _ 21 _ _ 7.5 _ _ Pump stuck in 'under-sized' condition<br/>1130_ _ 665 _ _ 18.9 _ _ 36.4 _ _ 21 _ _ 7.5 _ _ Lounge door shut<br/>1135_ _ 655 _ _ 18.9 _ _ 36.4 _ _ 21 _ _ 8.0 _ _<br/>1140_ _ 670 _ _ 19.0 _ _ 36.7 _ _ 21 _ _ 8.0 _ _ 3 bedroom doors shut<br/>1145_ _ 630 _ _ 19.0 _ _ 36.4 _ _ 21 _ _ 8.0 _ _ Fan noise down<br/>1150_ _ 605 _ _ 19.2 _ _ 36.0 _ _ 21 _ _ 8.5 _ _<br/>1155_ _ 605 _ _ 19.5 _ _ 36.0 _ _ 21 _ _ 9.0 _ _<br/>1200_ _ 560 _ _ 19.6 _ _ 34.7 _ _ 21 _ _ 9.0 _ _<br/>1205_ _ 535 _ _ 19.6 _ _ 34.4 _ _ 21 _ _ 9.5 _ _ 4th bedroom door shut<br/>1210_ _ 430 _ _ 19.7 _ _ 33.3 _ _ 21 _ _ 9.5 _ _<br/>1215_ _ 315 _ _ 20.0 _ _ 31.6 _ _ 21 _ _ 9.5 _ ~~_<br/>'Under~~-sized' condition ends	+	Set Pt +1 → 22C. Fan noise up.<br/>'Under-sized' condition starts<br/>1055_ _ 645 _ _ 18.8 _ _ 35.9 _ _ 22 _ _ 6.0 _ _<br/>1100_ _ 675 _ _ 18.8 _ _ 36.2 _ _ 22 _ _ 6.0 _ _<br/>Set Pt -1 → 21C<br/>1105_ _ 560 _ _ 18.7 _ _ 33.7 _ _ 21 _ _ 6.5 _ _<br/>1110_ _ 640 _ _ 18.7 _ _ 35.0 _ _ 21 _ _ 6.5 _ _ No recovery of normal running<br/>1115_ _ 665 _ _ 18.7 _ _ 36.3 _ _ 21 _ _ 7.0 _ _<br/>1120_ _ 665 _ _ 18.8 _ _ 36.5 _ _ 21 _ _ 7.0 _ _<br/>1125_ _ 665 _ _ 18.8 _ _ 36.4 _ _ 21 _ _ 7.5 _ _ Pump stuck in under-sized condition<br/>1130_ _ 665 _ _ 18.9 _ _ 36.4 _ _ 21 _ _ 7.5 _ _ Lounge door shut<br/>1135_ _ 655 _ _ 18.9 _ _ 36.4 _ _ 21 _ _ 8.0 _ _<br/>1140_ _ 670 _ _ 19.0 _ _ 36.7 _ _ 21 _ _ 8.0 _ _ 3 bedroom doors shut<br/>1145_ _ 630 _ _ 19.0 _ _ 36.4 _ _ 21 _ _ 8.0 _ _ Fan noise down<br/>1150_ _ 605 _ _ 19.2 _ _ 36.0 _ _ 21 _ _ 8.5 _ _<br/>1155_ _ 605 _ _ 19.5 _ _ 36.0 _ _ 21 _ _ 9.0 _ _<br/>1200_ _ 560 _ _ 19.6 _ _ 34.7 _ _ 21 _ _ 9.0 _ _<br/>1205_ _ 535 _ _ 19.6 _ _ 34.4 _ _ 21 _ _ 9.5 _ _ 4th bedroom door shut<br/>1210_ _ 430 _ _ 19.7 _ _ 33.3 _ _ 21 _ _ 9.5 _ _<br/>1215_ _ 315 _ _ 20.0 _ _ 31.6 _ _ 21 _ _ 9.5 _ _Under-sized condition ends

	1220_ _ 316 _ _ 20.0 _ _ 30.1 _ _ 21 _ _ 10.0 _ _ Normal running.<br/>1225_ _ 319 _ _ 20.0 _ _ 30.3 _ _ 21 _ _ 9.5 _ _ 4 bedroom doors opened<br/>1230_ _ 310 _ _ 19.5 _ _ 29.0 _ _ 21 _ _ 10.0 _ _ Lounge door opened<br/>1240_ _ 312 _ _ 19.1 _ _ 29.1 _ _ 21 _ _ 10.0 _ _		1220_ _ 316 _ _ 20.0 _ _ 30.1 _ _ 21 _ _ 10.0 _ _ Normal running.<br/>1225_ _ 319 _ _ 20.0 _ _ 30.3 _ _ 21 _ _ 9.5 _ _ 4 bedroom doors opened<br/>1230_ _ 310 _ _ 19.5 _ _ 29.0 _ _ 21 _ _ 10.0 _ _ Lounge door opened<br/>1240_ _ 312 _ _ 19.1 _ _ 29.1 _ _ 21 _ _ 10.0 _ _

−	1250_ _ 445 _ _ 18.9 _ _ 33.7 _ _ 21 _ _ 9.5 _ _ Whole house heating~~<br/>…~~ stable at high load ~~...~~<br/>1400_ _ 415 _ _ 19.0 _ _ 33.0 _ _ 21 _ _ 9.0 _ _ Test ends. All doors open	+	1250_ _ 445 _ _ 18.9 _ _ 33.7 _ _ 21 _ _ 9.5 _ _ Whole house heating stable at high load<br/>1400_ _ 415 _ _ 19.0 _ _ 33.0 _ _ 21 _ _ 9.0 _ _ Test ends. All doors open

	Notes:<br/>1: 'Doors' means internal doors(8 in total) that connect to the hall where the pump is located.<br/>2: From stable high load at 1050 at Set Pt 21C, a Set Pt increase of 1C increased Pwr from 470 to 675watts. This increase started the 'under-sizing' test.<br/>3: Recovery from 'under-sizing' lasts from 1100 to 1215. Progressively the Set Pt was reduced back to 21C, the lounge door shut, 3 bedroom doors shut and finally a 4th bedroom door shut to get back to normal running.<br/>4: With normal running achieved at 1220, all doors were open at 1400 when the test ended. By then the ambient temperature had increased from 2.5C at 1005 to 9.5C which should have assisted the recovery of normal running.<br/>5: This test provides an indication of the large heat load reduction required to recover a pump in the 'under-sized' condition.<br/>6: The quick reversal of the Set Pt increase of 1C failed to return the pump to the previously stable condition. Five more doors had to be closed to recover normal running whilst the ambient temperature also rose by about 6.5C between 1005 and 1250.<br/>7: The 'under-sized' condition is an instability that requires considerable intervention to reduce heat loads to recover the normal operation.<br/>8: The 'under-sized' condition destroys the economics of running a heat pump.		Notes:<br/>1: 'Doors' means internal doors(8 in total) that connect to the hall where the pump is located.<br/>2: From stable high load at 1050 at Set Pt 21C, a Set Pt increase of 1C increased Pwr from 470 to 675watts. This increase started the 'under-sizing' test.<br/>3: Recovery from 'under-sizing' lasts from 1100 to 1215. Progressively the Set Pt was reduced back to 21C, the lounge door shut, 3 bedroom doors shut and finally a 4th bedroom door shut to get back to normal running.<br/>4: With normal running achieved at 1220, all doors were open at 1400 when the test ended. By then the ambient temperature had increased from 2.5C at 1005 to 9.5C which should have assisted the recovery of normal running.<br/>5: This test provides an indication of the large heat load reduction required to recover a pump in the 'under-sized' condition.<br/>6: The quick reversal of the Set Pt increase of 1C failed to return the pump to the previously stable condition. Five more doors had to be closed to recover normal running whilst the ambient temperature also rose by about 6.5C between 1005 and 1250.<br/>7: The 'under-sized' condition is an instability that requires considerable intervention to reduce heat loads to recover the normal operation.<br/>8: The 'under-sized' condition destroys the economics of running a heat pump.

Designing Buildings: Created page with " 1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.

[DECC reported that a test of ..."

2015-01-05T13:04:52Z

Created page with " 1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target. [DECC reported that a test of ..."

New page

1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target. [DECC reported that a test of about 280 RHI heat pumps in December 2013 achieved an average SPF of about 2.4 which falls below the EU threshold of 2.5 for renewability. In other words this sample of pumps achieved nothing with respect to emissions.] 2: The theoretical performance for heat pumps can be in the region of 4:1 but in practice it is often closer to 3:1 or even 2:1 in cold weather. [My pump, a Mitsubishi SRK20ZJX, has a rated CoP of 5.7 at A7/A20 and actually delivers it. The most efficient pump that I know of is an Hitachi RAS8SX with a rated CoP of over 6. As the last winter's average temperature was 8.2C here in Gloucestershire, the SCOP was better than 5.0. My pump normally runs 24/7 in the 270 to 400watt range, so costs 6.48*0.15=£0.97 to £1.44 per day in the coldest months. The total electricity bill for last winter's space heating by heat pump was £144. The gas-fired boiler supplied the DHW and some supplementary heat for the lounge.] Because this pump runs 24/7, it places no fluctuating demand on the grid beyond that caused by the ambient temperature variation. I also received a quote for an RHI pump for my house. That would have been a 10kW(electrical) air-to-water pump. That is something like 22 times bigger and the generation has to be 22 times bigger as well. If people treat these big pumps like a fossil-fired boiler and they all get switched on as people come home from work, the evening peak demand on the system will go through the roof. This will need major grid reinforcement and will also need a total rebuild of the distribution system. Local 415V transformers are sized stochastically for current loads. None of this seems to have been thought about by anyone in authority.] 3: Many of these are likely to be air to water systems as despite their lower performance than ground sourced heat pumps they are relatively easy to install in existing buildings as they don’t need large and disruptive earthworks normally associated with ground sourced heat pumps [Big mistake] 4: As with many high power applications associated with heating purposes heat pumps can consume a large amount of electricity. [Too right but nobody in DECC or Parliament seems the slightest bit interested.] 5: This can become a particular concern during switch-on and switch-off when voltage fluctuations must say within recognise limits as specified by the Electricity Supply Act 1988. [This problem may not arise if every house on a supply transformer has a big heat pump. The transformer (and its associated cabling) will have tripped on high overcurrent long before all the pumps have started at 5o'clock of an evening.] 

----

A2A Heat Pump 'under-sizing' Performance Test on 29/12/2014.

The appended test report demonstrates the complete economic failure that attaches to running in the 'under-sized' condition. 'Under-sizing' is a physical condition where the heat pump loses its ability to generate sufficient heat to prevent the the actual temperature falling below the desired temperature.

When a pump slips into 'under-sizing' its electrical power rises to a maximum whilst its heat output falls. The crucial point is that to remove the pump from this 'under-sized' state without shutting down requires a major reduction in the heat demand of the house. In other words, the 'under-sized' condition is unstable. If you go a little bit into 'under-sizing', you go all the way and stay there until you do something fairly drastic. That is where these ridiculously high heat pump bills(mentioned above) come from.

I am confident that a lot of the poorly performing A2W pumps in DECC's test report spend a lot of time in the 'under-sized' condition. The A2W I tested last winter certainly did. It ran 'under-sized' continuously in ambient temperatures of 5C at a cost of 4*24*0.15=£14.40 per day or £432 per 30 day month. My A2A, running properly and continuously at about 333watts, uses 0.33*24*0.15=£1.20 per day or £36 per 30 day month.

Chose your poison: An 'under-sized' 4kW A2W or an efficient 0.45kW A2A; just a factor of 12 difference in running cost at 5C ambient. The A2W failed to heat the house properly, whilst the A2A was fine. Also the A2W cost about eight times as much as the A2A.

________________________________________________

Ambient temperatures were -1.5C at 0600. The sky was cloudless and ambient temperatures rose steadily throughout the test.

Time_ _ Pwr_ _ Blr In_ ''Out _ _Set Pt _Amb _ 0950'' _ _300 _ _ 19.2 _ _ 28.5 _ _ 21 _ _ 1.0 _ _ All doors shut except 3 1000_ _ 293 _ _ 19.0 _ _ 27.4 _ _ 21 _ _ 2.0 _ _ 1005_ _ 295 _ _ 18.9 _ _ 27.2 _ _ 21 _ _ 2.5 _ _ All doors opened 1010_ _ 385 _ _ 18.7 _ _ 29.0 _ _ 21 _ _ 2.5 _ _

1015_ _ 480 _ _ 18.6 _ _ 32.4 _ _ 21 _ _ 3.0 _ _ Whole house heated … stable at high load ... 1050_ _ 470 _ _ 18.7 _ _ 34.0 _ _ 21 _ _ 5.5 _ _

Set Pt +1 → 22C. Fan noise up. 'Under-sized' condition starts 1055_ _ 645 _ _ 18.8 _ _ 35.9 _ _ 22 _ _ 6.0 _ _ 1100_ _ 675 _ _ 18.8 _ _ 36.2 _ _ 22 _ _ 6.0 _ _ Set Pt -1 → 21C 1105_ _ 560 _ _ 18.7 _ _ 33.7 _ _ 21 _ _ 6.5 _ _ 1110_ _ 640 _ _ 18.7 _ _ 35.0 _ _ 21 _ _ 6.5 _ _ No recovery of normal running 1115_ _ 665 _ _ 18.7 _ _ 36.3 _ _ 21 _ _ 7.0 _ _ 1120_ _ 665 _ _ 18.8 _ _ 36.5 _ _ 21 _ _ 7.0 _ _ 1125_ _ 665 _ _ 18.8 _ _ 36.4 _ _ 21 _ _ 7.5 _ _ Pump stuck in 'under-sized' condition 1130_ _ 665 _ _ 18.9 _ _ 36.4 _ _ 21 _ _ 7.5 _ _ Lounge door shut 1135_ _ 655 _ _ 18.9 _ _ 36.4 _ _ 21 _ _ 8.0 _ _ 1140_ _ 670 _ _ 19.0 _ _ 36.7 _ _ 21 _ _ 8.0 _ _ 3 bedroom doors shut 1145_ _ 630 _ _ 19.0 _ _ 36.4 _ _ 21 _ _ 8.0 _ _ Fan noise down 1150_ _ 605 _ _ 19.2 _ _ 36.0 _ _ 21 _ _ 8.5 _ _ 1155_ _ 605 _ _ 19.5 _ _ 36.0 _ _ 21 _ _ 9.0 _ _ 1200_ _ 560 _ _ 19.6 _ _ 34.7 _ _ 21 _ _ 9.0 _ _ 1205_ _ 535 _ _ 19.6 _ _ 34.4 _ _ 21 _ _ 9.5 _ _ 4th bedroom door shut 1210_ _ 430 _ _ 19.7 _ _ 33.3 _ _ 21 _ _ 9.5 _ _ 1215_ _ 315 _ _ 20.0 _ _ 31.6 _ _ 21 _ _ 9.5 _ _ 'Under-sized' condition ends

1220_ _ 316 _ _ 20.0 _ _ 30.1 _ _ 21 _ _ 10.0 _ _ Normal running. 1225_ _ 319 _ _ 20.0 _ _ 30.3 _ _ 21 _ _ 9.5 _ _ 4 bedroom doors opened 1230_ _ 310 _ _ 19.5 _ _ 29.0 _ _ 21 _ _ 10.0 _ _ Lounge door opened 1240_ _ 312 _ _ 19.1 _ _ 29.1 _ _ 21 _ _ 10.0 _ _

1250_ _ 445 _ _ 18.9 _ _ 33.7 _ _ 21 _ _ 9.5 _ _ Whole house heating … stable at high load ... 1400_ _ 415 _ _ 19.0 _ _ 33.0 _ _ 21 _ _ 9.0 _ _ Test ends. All doors open

Notes: 1: 'Doors' means internal doors(8 in total) that connect to the hall where the pump is located. 2: From stable high load at 1050 at Set Pt 21C, a Set Pt increase of 1C increased Pwr from 470 to 675watts. This increase started the 'under-sizing' test. 3: Recovery from 'under-sizing' lasts from 1100 to 1215. Progressively the Set Pt was reduced back to 21C, the lounge door shut, 3 bedroom doors shut and finally a 4th bedroom door shut to get back to normal running. 4: With normal running achieved at 1220, all doors were open at 1400 when the test ended. By then the ambient temperature had increased from 2.5C at 1005 to 9.5C which should have assisted the recovery of normal running. 5: This test provides an indication of the large heat load reduction required to recover a pump in the 'under-sized' condition. 6: The quick reversal of the Set Pt increase of 1C failed to return the pump to the previously stable condition. Five more doors had to be closed to recover normal running whilst the ambient temperature also rose by about 6.5C between 1005 and 1250. 7: The 'under-sized' condition is an instability that requires considerable intervention to reduce heat loads to recover the normal operation. 8: The 'under-sized' condition destroys the economics of running a heat pump.

Talk:Heat pump - Revision history

Designing Buildings at 13:12, 5 January 2015

Designing Buildings at 13:10, 5 January 2015

Designing Buildings at 13:10, 5 January 2015

Designing Buildings at 13:07, 5 January 2015

Designing Buildings: Created page with " 1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.[DECC reported that a test of ..."

Designing Buildings: Created page with " 1: Heat pumps, as opposed to air conditioning (cooling), are an important part of the effort to meet the UK’s carbon reduction target.

[DECC reported that a test of ..."