[Closed] Another geothermal and UFH question.

How hot can we expect the hot water to be?

As hot as you set it to be.

The geothermal bit only preheats the water, it then gets topped up by conventionally heating it.

Instead of heating mains cold water that's been run at 750mm below the surface and is subject to ambient temperature and could be 3 or 4 degrees, You're heating water that's been prewarmed by passing it underground but it'll be lukewarm, not hot, Until your heating system tops it up

The water heating is entirely electric. How much is that going to cost? Omigawd.

They're usually pretty efficient and cheap to run

STOP. WORRYING. ABOUT. EVERYTHING.

IT'S. GOING. TO. BE. FINE.

Thanks PP. In my current state of mind everything is a catastrophe.

THis is a catastrophe

Presuming we're talking Ground Source Heat Pump? A bit like a fridge in reverse, they draw heat from the ground and make it warmer - usually for UFH with a solid screed floor they heat to 30-45 degrees C. Domestic hot water uses a different circuit and can be adjusted to suit your needs.

Why are you not asking your architect/contract administrator all these questions? That's their job.

THis is a catastrophe

No it isn't. This is:

The water heating is entirely electric. How much is that going to cost? Omigawd.

Here have a play with this - Water Heating Calcs Spreadsheet

why would you want to shower in water that is 60C?

Ah no of course you wouldn't but you can edge the mixer slowly round so you're close to boiling then step out of the shower feeling faint.

The water heating is entirely electric. How much is that going to cost? Omigawd.

No solar, either thermal or electric to help out? Odd on a new build.

Nope.

Okay so unless you have a pipeline out to Reykjavik I doubt it's geothermal. Big difference.

I'd not be relying on it alone for hot water, apart from anything else you need to get it up to 60deg or risk the likes of legionella. Given where you are solar probably wouldn't be much use either unless you had a decent input and some sort of storage device (heat or electrical).

So really it comes down to electrical heating for domestic water, again that can be stored either in a tank or heat storage (salt based) which is 4x the price of a tank but 1/4 the size and good for a claimed 50yrs. Also heats the water on demand rather than just sitting there.

I did actually tell you how it works on your other thread (as did several others). Either re-read it or simply google "how do heat pump systems heat domestic hot water"

No solar, either thermal or electric to help out? Odd on a new build.

Against advice or a poor situation (ley of big hill or wooded area )

Seems an odd choice to invest so much in ground source and not have the less expensive forms of energy generation already covered. I guess ground source gets you the green wash ticket in one swoop for your planning and building warrent if there isn't a physical reason for not going along the solar side of things. Would have complimented the ground source nicely I'd have thought

Just to correct a few misconceptions here, the GSHP can heat your ho****er to above the levels where you need to be concerned about legionella... but indirectly. For my build last year I (had) installed a CTC GSi 12 which uses a heat exchanger to heat the DHW. You can set the temperature and volume of this, effectively setting how much energy you wish to retain stored in this part of the system. Happy to discuss further if it would be useful.

Against advice or a poor situation (ley of big hill or wooded area )

/Stalker alert
I'm fairly sure I know where his build site is, we know some of his new, next door but a few in the valley, neighbours... 🙈

I'm sure the 'neighbours' have solar.

A 4kw PV system would look after the DHW for about 6 months of the year on its own.

4kw PV system would look after the DHW for about 6 months of the year on its own.

So when is the break-even point? Genuine question. (Do they still have feed in tarriffs in Scotland?)

10 years as of yesterday based on today's electric prices. And a 57 degrees north nigh on due south facing challet style roof. With 98% unshaded panels inclusive of the SEG payment. FIT is long gone

I don't believe electric will get cheaper any time soon as demand rockets

From memory the OPs system needed 3 wells 150m deep drilled through bedrock for the heating system. I’d like to think that the long term costs of the system were explained fully before he paid for that.

^^^ I guess at least it’ll be a nice deep repository for the mice 🤣

I dont wish to be rude but this 'saga' is one of the most bizarre things I've followed on stw this year, globalti have you lost the phone number for your architect? These are ALL questions you can and should be asking them, that's what theyre paid the big bucks by YOU for.

Every time someone asks why you havent asked them about it you avoid that specific question. If you're spending the kind of money I can imagine you are you really need to be kicking ass with those you're employing.

For my build last year I (had) installed a CTC GSi 12 which uses a heat exchanger to heat the DHW.

Do you mean a heat battery like a Uniq? (a heat exchanger doesn't store heat)

Yeah that would work, I just meant using the loop to heat a hot water tank. I mean, you could, but you're gonna destroy the Cop at decent temperatures.

So did your architect answer your question then?

airvent
Free Member
So did your architect answer your question then?

Jakester
Why are you not asking your architect/contract administrator all these questions? That’s their job.

Posted 23 hours ago

Thanks all. Meeting architect tomorrow.

Couple of things to add....

Most GSHP will get domestic hot water to 60degC (depending on the model) and will do it with better efficiencies than an ASHP due to the fairly constant tempeature of the heat source (12-14degC given that its a borehole system). the majority of GSHP will have a coefficient of performance of 3 or 4:1 when delivering DHW, rather than space heating where it can get more efficient. You'll want a hot water cylinder specifically designed to work with a heat pump. if your heat pump manufacturer doesnt do one, PM me and I can help.

Air Source heat pumps struggle with DHW provision due to the variable temperature of their energy source - they have to work really hard when the air is at or below freezing (in the UK in particular)and their COP can fall to 2:1 or less, which is why a lot of them limit DHW temps to 55 or below, and have to top up with a direct electrical element.

A UNIQ heat battery was mentioned. steer clear.

A UNIQ heat battery was mentioned. steer clear.

Any reason? The case studies seemed to vary between not good and really good, how much of that was down to behavioural use I don't know.

SquirrelKing - site wont let me PM you. not sure why.

I'm in the same industry so could be seen as having a vested interest in slagging them off - prefer to PM you if poss.

Are you trying through mobile? I can only post at home on Firefox.