Zone valve wiring into existing CH system

[FirmButton]

Hi chaps, I am building an extension for the outlaws it will have underfloor heating. I want to link it to the existing CH system by linking into the main feeds and fitting a zone valve to the CH supply so the rads don't heat up when the ufh is calling for heat. The ufh will call for heat and kick the boiler into action, which is simple enuf, but how the ufh call for heat without powering up the zone valve?

Here is a simple answer but just can't get my head round it just this mo!

Cheers

Steve

 

[bhm1712]

probably better asking this in the plumbing and central heating part of the forums. Im sure a mod will move it as soon as they see it.

 

[bernardgreen]

The controller for the under floor heating system should have provision to control the "zone" valve.

Or have you missed the point that you cannot simply feed the CH hot water directly under the floor as a zone of the CH system. You need a constant temperature control and pump to circulate water under the floor while taking enough of the CH hot water to maintain the correct temperature.

The water under the floor should not be as hot as the CH water unless your boiler is set for a low temperature CH ( circa 25 deg C ) which would require very large radiators to heat rooms.

 

[FirmButton]

Actually the answer was obvious, I need to go standard y plan with a three port valve!

don't worry Bernard , I'm not planing to heat the floor to 70c

Cheers chaps

Steve

 

[ban-all-sheds]

So what surface temperature do you plan to have?

What are the radiant properties of the flooring?

How much heat will you get out of each square m?


And since this is, for now, still in the Electrics forum, are you aware of the Building Regulations requirements for electrical work?

 

[Lectrician]

Actually the answer was obvious, I need to go standard y plan with a three port valve!

don't worry Bernard , I'm not planing to heat the floor to 70c

Cheers chaps

Steve

Really?

You would normally use three two port valves, one for the cylinder, one for the rads and one for the underfloor. The "boiler" terminals of the underfloor controller would "fire" the UFH zone valve. All zone valves would fire the boiler.

You cannot use a three port valve and then add a two port valve too, unless you also fit a blocker valve, and if you do that, you may as well whip out the three port and replace it with two two ports.

 

[RF Lighting]

S plan plus. Easy as peas.

 

[Lectrician]

Exactly...

 

[FirmButton]

There is no hot water cyclinder, so surely a y plan set up as if the ch stat was the HW stat and the ufh call set up as if it were the CH stat would do the job?

Steve

 

[bernardgreen]

ufh call set up as if it were the CH stat would do the job?

I would suggest that the differences between heating a floor and heating a tank of water are so great that a control system for a hot water tank will not be very efficient for controlloing the heating of a floor. I can see the boiler doing a lot of short cycling when only the floor is being heated unless it modulates its output over a large range.

 

[matt1e]

Hi chaps, I am building an extension for the outlaws it will have underfloor heating. I want to link it to the existing CH system by linking into the main feeds and fitting a zone valve to the CH supply so the rads don't heat up when the ufh is calling for heat. The ufh will call for heat and kick the boiler into action, which is simple enuf, but how the ufh call for heat without powering up the zone valve?

Here is a simple answer but just can't get my head round it just this mo!

Cheers

Steve

the ufh zone will power its own zone valve
as will the other zones
the valves themselves will fire the boiler as req
s-plan/s-plan plus is what you need to be looking at as others have said

Matt

 

[Lectrician]

There is no hot water cyclinder, so surely a y plan set up as if the ch stat was the HW stat and the ufh call set up as if it were the CH stat would do the job?

Steve

NO.

A 3 port Y valve does not spring closed - You have to drive it to the shut water position by giving it a "hot water off" signal from the timeclock, and a "hot water satisfied" from the stat.

Fit two two port valves.

 

[FirmButton]

The CH stat has two poles so I can emulate a hot water stat. I thought three port valve return to HW off without power?

Anyway, I do actualy have two two port valves but have never done an s plan. Do I need a bypass in the system though with s plan?

Originally I had in mind a simple single two port setup, only letting the CH zone valve open when the room stat calls. The ufh manifold I imagined didn't need any zone valve as it will only take hot water when the thermostatic valve on it opens?

Steve

 

[bernardgreen]

only letting the CH zone valve open when the room stat calls. The ufh manifold I imagined didn't need any zone valve as it will only take hot water when the thermostatic valve on it opens?

What happens when the room stat calls for heat and the floor thermostatic valve is closed because UFH pipework is at maximum temperature. You would have a boiler firing on the room stat but no load as the thermostat valve is closed.

 

[FirmButton]

If the room stat calls for heat the zone valve would open, the rads have no trvs so there will be no issues. I think u are thinking the ufh thermostatic valve is like one on a radiator? It isn't it is incorporated in the ufh manifold, it has no influence on the radiators.

Steve