GSHP for heat AND hot water

[Alister84]

Looking for advice or real world examples of GSHP as the main source for both heat and hot water. 
 

House is new build, will be ICF construction and approx 420 square meters.

 

We are a family of 5 with three teenagers who (when the world is functioning normally) all do clubs/sports so shower 2/3 times a day. My concern is the GSHP won’t be able to keep up with demand, everyone having showers in the morning then 2/3 people having showers in the afternoon then the same again in the evening. 

Hot water tank would be 300+ litres and we plan on having solar thermal in addition to the GSHP and obviously the tank will have an immersion heater should all else fail, but feel that defeats the purpose.

 

Real world advice/examples appreciated 

[Onoff]

I seem to recall @Barney12 at least installing a ground loop. Not sure if it's connected / running.

[SteamyTea]

Is this thread been doubled up?

 

 

Can't help with real world examples.

 

Have you measured the amount of water you use and at what temperatures?

 

There is a bit of a myth that heat pumps cannot deliver 'enough'.

It is totally wrong and is really down to sizing properly.  An 8 kW HP, of any sort, is still delivering the same power as an 8 kW gas or oil boiler.  It is what the watt actually means.

Edited July 2, 2020 by SteamyTea

[IanMcP]

On 02/07/2020 at 21:48, Alister84 said:

Looking for advice or real world examples of GSHP as the main source for both heat and hot water. 
 

House is new build, will be ICF construction and approx 420 square meters.

 

We are a family of 5 with three teenagers who (when the world is functioning normally) all do clubs/sports so shower 2/3 times a day. My concern is the GSHP won’t be able to keep up with demand, everyone having showers in the morning then 2/3 people having showers in the afternoon then the same again in the evening. 

Hot water tank would be 300+ litres and we plan on having solar thermal in addition to the GSHP and obviously the tank will have an immersion heater should all else fail, but feel that defeats the purpose.

 

Real world advice/examples appreciated 

hi 

 

I’m starting my build soon and the spec / demands are similar. 
 

have you installed your system yet , keen to learn more 

 

thx 

[Nickfromwales]

A little 5kw ASHP would suffice, if a big enough hot water tank was fitted, and the heating load was equal to or lesser than, it would simply take much longer to recover after depletion.

Why a GSHP? Seems a massive ball-ache and no support from RHI = big capital costs and a far longer break-even period. ASHP seems far more practical and attractive for a number of reasons.

Forget solar thermal, go for more solar PV as ST is a PITA to own and maintain, has significant losses, and is a one-trick pony. PV can be converted to heat with an immersion, and when the tank is satisfied the excess electricity can go towards the house base loads. ST just heats and heats, and then carries on doing that all summer which is of little or no use if you're not there to keep drawing off DHW.

Needing bags of DHW is not necessarily managed by the heat source, more the hot water device, so the position of the horse and the cart may need a bit of adjusting here   

[jfb]

3 hours ago, Nickfromwales said:

 

A little 5kw ASHP would suffice,

 

I’m confused why you say this with no details about the build quality. A house of 400m2 seems very unlikely to work with a 5kw ashp unless it is a passive build maybe. Particularly if hot water use is high.

 

agree with ashp over gshp though.

[Nickfromwales]

4 hours ago, jfb said:

I’m confused why you say this with no details about the build quality. A house of 400m2 seems very unlikely to work with a 5kw ashp unless it is a passive build maybe. Particularly if hot water use is high.

 

agree with ashp over gshp though.

Was referring to the OP   not your build. ICF as above. 
5kw will suffice regardless of DHW consumption, as you’d just size the UVC a lot bigger and accept longer recovery times. No ASHP can replenish DHW linear to it being consumed, so the point is academic to be fair. 
But it would work, just slowly. It would only be 1kw behind a direct UVC with 2x 3kW immersions. 

[Alister84]

On 19/12/2021 at 20:32, IanMcP said:

hi 

 

I’m starting my build soon and the spec / demands are similar. 
 

have you installed your system yet , keen to learn more 

 

thx 

Hi,

 

Yeah, things moving in the right direction for us. System hasn't yet been commissioned but we have ground loops in, underfloor, manifolds, tanks and heat pump on site. Fingers crossed we get to switch it on Febuary/March time.

 

Feel free to PM me if you need more info or have specific questions.

[IanR]

What size UVC did you go with?

 

We have a similar demand, although not quite as high as children are a little younger, but have a 12kW ASHP combined with a 500l UVC. While the 500l tank has never left us short and the 12kW ASHP seems to heat it back up relatively quickly, ie. 3 or 4 showers in a row without a problem and back up to full temp in around 1 or 1.5 hours, I'm not sure I'd want to go smaller than 500l.

[Alister84]

On 05/01/2022 at 10:07, IanR said:

What size UVC did you go with?

 

We have a similar demand, although not quite as high as children are a little younger, but have a 12kW ASHP combined with a 500l UVC. While the 500l tank has never left us short and the 12kW ASHP seems to heat it back up relatively quickly, ie. 3 or 4 showers in a row without a problem and back up to full temp in around 1 or 1.5 hours, I'm not sure I'd want to go smaller than 500l.

We went with 1,000L for the UVC. We have six bathrooms in the house plus 2 WC and two kitchen spaces so more is more apparently!