Onoff

Gearing Up For A Temporary UFH Buffer

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Bear with me as this might sound a bit mental!

 

Current downstairs heating is a 50 year old 3/4" nominal bore system.

 

New bathroom refurb has x1 UFH loop in the floor and a second loop purely for a towel rad.

 

I don't really want to connect a manifold to the old single pipe system and get it and the new loops crudded up. Now for the mad bit...

 

Thinking that as I've a spare copper cylinder I could divert the single pipe CH through the coil of the cylinder. Then fill the cylinder and pump that via a manifold around my two loops. I've an in slab stat I could use to control the pump. 

 

Thus I'd keep old and new systems separate. An aside is that the room where the "buffer" cylinder would be sited would get some heat from the cylinder as there's no heating there at the mo aside from the single pipe across the floor that I'd look to tap off of to feed the cylinder. Thinking it'd also maybe put less strain on the oil boiler.

 

So stat calls for heat and pump simply circulates some hot through the loop (s). But would it be too hot as there's no blending?

 

???

 

Cheers 

 

 

 

 

Edited by Onoff

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That sounds like a good plan.  You will need a header tank would that go in the loft or just above the cylinder?

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8 hours ago, ProDave said:

That sounds like a good plan.  You will need a header tank would that go in the loft or just above the cylinder?

 

Cheers. A daft question I'm sure but do I have to have a header tank?

 

Could I maybe treat the water in the cylinder as a semi sealed system, add inhibitor and put an AAV on top of the cylinder?  Is there really any need for an expansion pipe?

 

Rough sketch shown less the manifold. As the sketch stands I'm thinking there's an issue as the UFH loop would run too hot i.e. at the temp of normal rads. 

 

20190116_165135.thumb.jpg.9e1c065712d0ff0c7ff80c2590fb235c.jpg

 

Appreciate it's bit off the wall.

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Maybe add a 2 port valve to stop the UFH loop getting too hot? Have it cutting off via the floor stat?

 

20190116_171259.thumb.jpg.a740cb941e36dec44a91d75cafe08843.jpg

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Better would be a 2 port on the input to the tank, driven by a tank stat so it only heats the buffer to the required temperature.  Normal "1 pipe" system bypass when the 2 port is closed.

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Without an expansion tank, where would the water expand to as it warms up? Why wouldn't the tank burst? Or crinkle up as it cools down?

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1 hour ago, ProDave said:

Better would be a 2 port on the input to the tank, driven by a tank stat so it only heats the buffer to the required temperature.  Normal "1 pipe" system bypass when the 2 port is closed.

 

Ta. I want though the UFH and towel rail at two different temperatures I'm thinking.

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3 hours ago, Ed Davies said:

Without an expansion tank, where would the water expand to as it warms up? Why wouldn't the tank burst? Or crinkle up as it cools down?

Agreed it needs a header tank.

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Does the header tank need to be fed a supply via a ball cock like "usual"?

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5 minutes ago, Onoff said:

Does the header tank need to be fed a supply via a ball cock like "usual"?

Just add a small EV and fill it up manually. Sealed kit

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19 minutes ago, Nickfromwales said:

Just add a small EV and fill it up manually. Sealed kit

Surely only if it is designed as an unvented cylinder.

 

A header tank, even without a ballcock would seem better. Just keep an eye on the level if you do that.

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Just now, ProDave said:

Surely only if it is designed as an unvented cylinder.

 

A header tank, even without a ballcock would seem better. Just keep an eye on the level if you do that.

If its sat directly above the 'buffer' and needs no lengthy pipework ( wasted time and fittings / pipe ) then yes, will do the job.

You should know by now that I hate header tanks / open pipe systems 😛

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1 minute ago, Nickfromwales said:

If its sat directly above the 'buffer' and needs no lengthy pipework ( wasted time and fittings / pipe ) then yes, will do the job.

You should know by now that I hate header tanks / open pipe systems 😛

This is only temporary.  @Onoff definition of temporary may be a bit longer than mine.

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55 minutes ago, Nickfromwales said:

Just add a small EV and fill it up manually.

Won't that need annual inspections and all that stuff?

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Thanks all.

 

Back to the main issue as I see it:

 

The boiler is set at 65 deg. As is then the radiators run at 65 deg. 

 

If I run that through the coil in the cylinder it'll transfer the heat to the water in the closed system which I assume will get to 65 deg. 

 

That's fine to feed the towel rail directly.

 

But the UFH loop? From reading I believe the temperature presented to the UFH loop needs to be in the region 35 to 45 deg? I'm worried if I feed it at 65 it could be detrimental to the slab, tiles etc.

 

So say I fit a manifold, how would that work, one side gets 65 deg and the other goes back to the buffer? I don't get how it reduces the temperature from 65.

 

Cheers

 

 

 

Edited by Onoff

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37 minutes ago, dpmiller said:

blending valve?

 

Don't know. What I can't get my head around with UFH is where it "gets it's cold" from to bring the boiler temp down to something more acceptable to the loop. Or is it that the hot is restricted to that loop by adjusting individually? Do all the loop "returns" just common up?

Edited by Onoff

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the loop doesn't "get" any cold. The loop/ loops just circulate, the blending valve opens to let sips of hot in and this pushes the cold out, back into your return pipe...

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I can't visualize how a blending valve could be set up for the UFH loop but with the towel rail running at full temperature without having separate pumps for each circuit.

 

Alternatively, what about wiring the towel rail and UFH in series so the towel rail drops the temperature a bit then the rest goes into the UFH?

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Run the towel rail direct off the 1 pipe system, and just the UFH off the buffer with my idea of a 2 port valve and tank stat to limit the temperature in the buffer.  Then for now you don't need a manifold and blending valve.

 

You can add a proper manifold and blending valve when your next room is refurbished and ready to go, some time about 2025? :ph34r:

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2 hours ago, ProDave said:

Run the towel rail direct off the 1 pipe system, and just the UFH off the buffer with my idea of a 2 port valve and tank stat to limit the temperature in the buffer.  Then for now you don't need a manifold and blending valve.

 

You can add a proper manifold and blending valve when your next room is refurbished and ready to go, some time about 2025? :ph34r:

 

Tbh I don't want to be contaminating the new rad and loop.

 

Should be getting a manifold early Feb! ;)

 

Need to finish the tiling, get the sanitary ware in and working then convince SWMBO I need to dig up  build back up the complete floor in the stairs room to run ducts for all future UFH loops! :)

 

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14 hours ago, Ed Davies said:

Won't that need annual inspections and all that stuff?

:ph34r:

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15 hours ago, Ed Davies said:

Won't that need annual inspections and all that stuff?

 

It’s temporary. He’ll be done by then 😂 🤔

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14 hours ago, Onoff said:

 

Don't know. What I can't get my head around with UFH is where it "gets it's cold" from to bring the boiler temp down to something more acceptable to the loop. Or is it that the hot is restricted to that loop by adjusting individually? Do all the loop "returns" just common up?

It’s not “where does it get its cold from”....it’s “there’s my blending valve that only allows X amount of heat in” ;)  

The ‘cold’ is the heated water in the loops which needs topping back up ( an exchange takes place in the blending valve where cooled water is ejected by fresh heated water being allowed in under the pressure of the pump flow ). 

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37 minutes ago, Nickfromwales said:

The ‘cold’ is the heated water in the loops which needs topping back up ( an exchange takes place in the blending valve where cooled water is ejected by fresh heated water being allowed in under the pressure of the pump flow ). 

 

So the cold water blends with the hot to produce water of the right temperature that is sent back into the loops and then some cold goes back to the boiler for reheating? I assume that initially the water in the store may be lower than in the floor (potentially if someone has just had a bath for example). 

 

Is there a decent diagram that explains it? I don’t want to fiddle with anything but would like to understand how it works. Or is my setup different? 

 

If the UFH is off all summer for example doesn’t the water in the loops go manky? And then you’re potentially showering with that water when it eventually feeds back into the TS? Or have I got that wrong too lol? 

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