Air source heat pumps

[Steve Skelton 1Participant @steveskelton1]

Simon, you would definitely need batteries, as in the winter, you are unlikely to get sufficient power from the panels to drive an ASHP. You would need at least 10kWhr of battery to give you a sensible running time before depletion of the batteries.

Steve

[David JuppParticipant @davidjupp51506]

I have ASHP and solar panels and nominally 10kWh of storage (in winter more storage would be good).

Unless you specify it – most solar/battery installs won’t provide power during a power cut.  To do that you’ll need extra equipment to handle the changeover (at extra cost), and most likely an additional local earth connection.

The installer I used said if grid is reliable at your location, then it’s not worth the extra costs – in areas supplied by overhead lines, it could well be worth spending the extra.

[John MCParticipant @johnmc39344]

[Steve Skelton 1Participant @steveskelton1]

John, we would charge the batteries up from the grid using an off peak tariff. We currently only pay 7p per kWhr for 6 hours overnight so we charge the car, run the dishwasher and dryer at night along with anything else that has a high power consumption. There are a number of special tariffs that charge less at certain times of the day.

Steve

[simondavies3Participant @simondavies3]

[noel shelleyParticipant @noelshelley55608]

An interesting point is how do you convert DC to an acceptable 50 c/s Without the grids stable 50c/s as a starting point – in some cases you can’t ! So when the grid goes down the wind and solar may go with it – NOT so clever ? Our grid system is very fragile and could easily be taken down. Noel.

[SillyOldDufferModerator @sillyoldduffer]

[John MCParticipant @johnmc39344]

[John MCParticipant @johnmc39344]

[pmm1Participant @pmm1]

I have a 6kW ground source heat pump – installed 2010.

 

The house, a converted threshing barn, was designed with a heat pump in mind.

 

The walls are basically 18” stone, 2” gap, 8” closed cell insulation, 1”gap (to facilitate wiring) and plasterboard, with double or triple glazed windows according to size.

 

A warm roof is fitted with insulation similar to the walls.

 

The downstairs floor is insulated.

 

Underfloor heating is fitted, both upstairs and down, with stone flooring downstairs and low tog carpets upstairs.

 

The ground source is 2 off 200 metre U shaped loops laid at least 2 metres deep in the field in front of the house. The field conveniently slopes down away from the house so the pipes were laid in sand with a constant gradient so as not to allow any air traps to occur.

 

The heat pump is installed in an outhouse so noise is not a problem.

 

The heat pump works on a 3 degree differential and the lowest temperature in the output pipe is about 4 degrees C in winter, so there is not any significant surface cooling due to the heat pump.

 

The heat pump works very well, but is usually only used to produce hot water (52 degrees) as the house is usually heated using a 6kW wood burning stove (as I have a near inexhaustible supply of hardwood logs).

 

The heat pump soft start module failed during Covid and it took about 8 months to acquire an (upgraded) replacement which, when fitted showed the compressor had failed and killed the soft start module, which explained why the module had been upgraded.

 

The local heat pump installers said they only installed and did not repair. They did, however, point me to a local firm who maintain commercial refrigerators who had a suitable unit in stock and soon fitted it.

 

So, for any heat pump compressor failure look to commercial fridge repairers to get a replacement compressor.

 

Paul

[BazyleParticipant @bazyle]

Is the 6kW input or output?

[pmm1Participant @pmm1]

6kW is the rated output

Paul

[duncan webster 1Participant @duncanwebster1]

Manchester science museum have installed a ground source heat pump but drilled down 135 metres to an aquifer as the heat source. This sounds sensible. Friend of mine has a house backing onto a biggish river. I wonder if the powers that be would notice if he diverted some of the flow.

They have also installed electric fired boiler to run the steam engines. This doesn’t sound as sensible, CCGT system is 60% efficient, whereas a gas fired boiler can be higher. Whichever, I hope the condenser cooling water is used by the heat pump. Got to be warmer than groundwater

[Martin KyteParticipant @martinkyte99762]

Significant gains can be made when large new builds have green tech designed in. Our new Lab opened in 2013 with 4 deep bore wells to service the heat pumps.

“The building is glass-clad, providing a light and spacious design. Heat build-up is reduced by automatic venetian blinds, between the standard double glazing and an outer glass skin. Other energy-saving features include heat recovery wheels that exchange energy between outgoing and incoming air, a ground source heat pump, and automatic control of lights to reduce intensity when daylight is available.”

The heat exchanger wheels achieve a typical 5 to 6 degree temperature change between incoming and exhaust air in winter which significantly reduced the heating demands. The Lab is a rock solid 21 degrees all year and I am convinced that staff actually choose to come in during heatwaves even if they would normally have the day off.!

Our electricity bill is still over a million quid.

https://www2.mrc-lmb.cam.ac.uk/about-lmb/building-and-facilities/

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