UFH Water Flow

[Big Neil]

having a bit of a blonde moment - I'm sure it'll seem obvious when someone clarifies for me but;

 

When the hot water goes into the UFH manifold to be distributed to the various circuits so as to  flow around them, once circulated and back to the manifold, where does it then go? Does it just feed into the drains?

[joe90]

The water is fed in a loop going back to the boiler/buffer tank, it’s temp will still be above room temp ready to be topped up again and recirculated. 

[Big Neil]

riiiiiiiigghttttt - so in the case where one has a 'monoblock ASHP' mated to a cylinder with supplementary Coil to utilise excess PV generation, where that cylinder also feeds the rest of the hot water system, one of the feeds coming FROM the cylinder should be into a buffer tank for the UFH? Or does it all just go back into the cylinder anyway as it's all drinkable?

[Big Neil]

Its the same tank in either case is it, not one for hot water and another for the UFH. Have i read it correctly that the UFH has a hot and cold feed to mix down to the correct temp?

[joe90]

In my case I heat a buffer tank 90ltr through a coil with my ASHP. the water in this buffer tank is circulated through the UFH manifold by a pump (when the room stat calls for heat). In the pipework from the ASHP (flow) there is a diverter valve which when there is a call fir DHW the valve operates and the DHW tank is heated (as a priority) when the DHW tank is up to temp the valve releases and is available to heat the buffer again. I have no P.V.

[Big Neil]

Riiiiiiggght - Thanks Mr 90. I still need to get to a house mid-build, where I can actually see a setup involving ASHP and wet UFH in action. I'm terrible it seems with plumbing stuff, understanding exactly how everything is routed, when it comes to the hot water generation.

[joe90]

@Big Neil I could draw you a diagram of our setup if you want but as you have P.V. It might be better if you list what you have/want and there are plumbing guru,s on this forum that will give you better advise ?

[Big Neil]

A diagram would be very helpful please sir, I just want to get an idea in my head, understand that, then when I take more specific advice I can ammend my understanding much more easily

[joe90]

Will do later mate?

[Ed Davies]

8 hours ago, Big Neil said:

Or does it all just go back into the cylinder anyway as it's all drinkable?

It's not drinkable. Well, it is but whoever did would probably get at least a bit ill. Any water that goes through the ASHP and/or the UFH has to be kept completely separate from the “wholesome” (DHW) water that'll get fed to taps, showers, etc.

 

For the cylinder you have a choice: it can be full of DHW and heated by a coil containing the primary water (from the ASHP, boiler, solar thermal, whatever) with inhibitors and anti-freeze as required for the source. This is a conventional hot water cylinder. Or the cylinder can contain primary water and heat the DHW via a coil through it. Terminology varies but that's usually referred to as a thermal store. Other combinations are available: e.g., tank-in-tank or using plate heat exchangers.

 

With a conventional hot water cylinder you may or may not have a separate smaller buffer tank containing primary water which is there to stop the ASHP from short cycling. If you have a thermal store then there's typically no need for a separate buffer as the thermal store does that function.

[TerryE]

The water flowing in the UFH loop has CH inhibitor in it so it is definitely NOT potable and is entirely separate from the potable supply.  In our case our potable circuits are at 3 bar and the UFH circuit at 1 bar.  I do have a filler connection form one to t'other but this uses a two one-way filler valve in series and  a separate small expansion vessel on the  UFH side.  If you need to transfer heat from one circuit type to another without  mixing the supplies then you can use some form of heat exchanger such as an internal coil in tank or a plate heat exchanger (PHE).

 

In the case that Ed is discussing were you also have another ASHP circuit, this is going outside and needs to be cold tolerant in a way not needed for a UFH circuit and so the ASHP circuit will typically have an anti0freeze content and will typically be separated from the UFH circuit by coil HEs in a buffer tank or thermal store, or by a direct PHE.

[Nickfromwales]

@Big Neil

The cold water going into the DHW cylinder and the hot feed coming out to supply the taps have been omitted for definition of whats heating and whats DHW.

 

[joe90]

After the professionals have posh diagrams on here mine seems very DIY, but hey ho here we go. The inhibitor water is limited to the ASHP, and tank coils (with their connected pipework). The UFH loop is pressured to about 1 bar. As is the ASHP loop. As I said tho, I have no PV .

[Nickfromwales]

4 minutes ago, joe90 said:

After the professionals have posh diagrams on here mine seems very DIY, but hey ho here we go. The inhibitor water is limited to the ASHP, and tank coils (with their connected pipework). The UFH loop is pressured to about 1 bar. As is the ASHP loop. As I said tho, I have no PV .

What’s there not to like ? ?

[joe90]

Just now, Nickfromwales said:

What’s there not to like ? ?

 

Thanks Nick at least it works (now that you guru’s have helped me so much).

[Nickfromwales]

Ps the image I posted was a simple net grab  

[Dreadnaught]

@joe90, very helpful. Thank you. I didn't realise how the buffer tank for the UFH worked, with the coil within. Your diagram was instructive.

[Big Neil]

To be honest Mr 90 i prefer it to the amateur scribble nick grabbed. I like the personal touch.

 

One thing I don't quite get is that if the cold feed from the mains goes into the hot water tank then out to the ASHP plus to the UFH via the diverter valve, how the return from the UFH doesn't get mixed up with the water one might otherwise drink/shower in. Have i read something wrong somewhere

 

Or should i be reading that coil looking think inside the DHW tank as a sealed loop?

[Big Neil]

got it  (maybe) - sealed loop. Combined a bit of corssover from my other thread about heat batteries. So the ASHP heats a closed loop filled with antifreeze to give the heating. It's not actually water which goes through those loops no?

[joe90]

10 minutes ago, Big Neil said:

got it  (maybe) - sealed loop. Combined a bit of corssover from my other thread about heat batteries. So the ASHP heats a closed loop filled with antifreeze to give the heating. It's not actually water which goes through those loops no?

 

Yes mate, I have two sealed loops, one for the ASHP with antifreeze/inhibitor and one for the UFH with no additive. Mains water only flows into the bottom of the DHW tank and hot out the top to taps.

[Big Neil]

ahhh, so the coil looking thingey going into the DWH tank is a loop of pipe aswell.. good stuff. So You can supplement that with a heating element taking excess PV generation (or simply straight from the mains) if required to be hotter.

 

So now i'm a fully qualified heating engineer who wants me to do their whole installation gratis??

[joe90]

2 minutes ago, Big Neil said:

ahhh, so the coil looking thingey going into the DWH tank is a loop of pipe aswell.. good stuff. So You can supplement that with a heating element taking excess PV generation (or simply straight from the mains) if required to be hotter.

 

So now i'm a fully qualified heating engineer who wants me to do their whole installation gratis??

 

Yes, I also have two immersions In my DHW tank which I used to supply hot water whilst I got  my ASHP working, it would be easy to wire the lower one to use excess PV.

 

YES I did mine but it was a steep learning curve (see my threads on ASHP set up) and thanks to many guru’s on here I managed it ?

[Big Neil]

Booom. That's a win for the day - small maybe but i'm counting it. Needed that. Thanks to everyone. @joe90 i'll be on to you the next time i need a diagram for something.

 

If in return anyone wants to know anything about kebab shops in Salford, the Lotus Elise between 1995 and 2001 or the pitfalls of women from the Stoke region... I'm your Man!

[joe90]

 

23 minutes ago, Big Neil said:

Thanks to everyone. @joe90 i'll be on to you the next time i need a diagram for something.

 

I’ll get my pencil sharpened ?.

Edited December 11, 2018 by joe90