Electric+ASHP Underfloor Heating in passivhaus bathrooms - madness? =)

[Post and beam]

13 hours ago, puntloos said:

Nibe if I wanted to (my installer carries the brand

Would you mind letting me know who in Hertfordshire you use. My planned build is in North Herts and i have failed so far to get quotes that are not  stupidly high.

[puntloos]

2 hours ago, Dan F said:

I don't know that it does make them more efficient at 60C to be fair.  Also, as I said elsewhere 75C doesn't mean DHW at 75C.  My aroTherm gets up to around 73C, so the max DHW temperature is really not much more than 65C.  We sometimes heat the tank to 65C if we know DHW is going to get a lot of use, and it makes the 300L UVC go further.

This is an interesting point - my DHW cylinder is 400L so perhaps I don't need to worry too much about low water temperature. Of course the legionella cycle will be costly but there you go.

[markocosic]

2 hours ago, puntloos said:

This is an interesting point - my DHW cylinder is 400L so perhaps I don't need to worry too much about low water temperature. Of course the legionella cycle will be costly but there you go.

 

Business partner, in Hertford, has an ASHP.

 

Vaillant jobbie. 7kW nominal into their 250 litre nominal cylinder. DHW nominal setpoint 45C. In practice this means a max of 53-55C from the heat pump and the top of the tank at a shade over 50C. (the coil-through-tank arrangement results in a stratified charge) The 250L cylinder was chosen for its coil size not because he needs 250L, but in practice this allows for a lower operative temperature without running out.

 

Summer COP for charging like that is of the order 4.5; winter (average in UK is 7C; DHW reheat timed for hottest part of day) ought to be over 3.

 

You can use the zoom function on that heatpumpmonitor dataset to see how other units perform. Suppressing reheat until the tank is materially emptied materially bumps COP (3.5>4.5 in this weather)

 

Legionella disabled. Tanks turned over often enough are not at risk. It shouldn't be a major part of your usage anyhow.

[puntloos]

On 17/07/2023 at 12:05, Post and beam said:

Would you mind letting me know who in Hertfordshire you use. My planned build is in North Herts and i have failed so far to get quotes that are not  stupidly high.

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