I'm not sure this directly answers your question as the GSHPs in use in North America seem to be somewhat differently configured than those in Europe.

First point: what water temperature do you use in your shower? In our case, the thermostatic mixing valve is set at 38C - I would be surprised if you needed anything above 40C.

We have a gas hot water tank where the thermostat is set at 51.5C (125F) - this is considerably below the 60C that I've seen mentioned for tanks in the UK and is done this way to avoid scalding - we're not worried about Legionnaire's disease as the tank is at mains pressure. The GSHP has a de-superheater which preheats the bottom of the tank and I think the output is 55C. When the heat pump is running (either in the depths of winter or when we have it in airconditioning mode) the hot water is noticeably hotter (and the gas consumption also goes down). Note, though, that our GSHP is not set up to provide all our DHW, just to supplement it. Main heat distribution is through forced air.

I would say anything above 40C is fine - and the higher you go above 40C the lower your coefficient of performance. (The de-superheater works on a different principle which is why the output temperature is so high).

Hope this helps,

Paul in Montreal.

I installed a GSHP in the summer with a 300 litre main pressure cylinder
and set the water temperature to around 45C , I cant remember the exact figure ,
I was trying to get it as low temperature as possible
that they were happy with at there kitchen hot tap with out the need to add cold
the customer are very happy with this
The heat pump supplies all the hot water and they are a family of 5
The pumps controller automaticially brings the water up tp 60c once a week ,as discribed in the manual, to pasturise the water

Jim

Posted By: tonygetting scolded

Tony, your mis-spellings are sometimes hilarious - I'm guessing you used scolded deliberately rather than scalded

Paul in Montreal

Posted By: jamesingramWhats the deal with a mains pressure cylinder and legionella

No one mentions it over here in Canada where everyone has a mains pressure water cylinder. People are being advised to turn the thermostat down to 51.5C to avoid being scalded - no-one mentions legionella. I think there's enough chlorine in mains water that it's not a problem - at least, I've never heard of any cases in all the 14 years I've been here - not from domestic water at least.

Paul in Montreal.

Our GSHP is "upto 55C" as well. This is the maximum that it can output and is settable via controls. The "upto" just means that you can have it set lower if you want.

Get a thermal store to allow for future upgrades via coils for solar hot water/log burning stove.