Underfloor Heating

[jstephens]

Hi everyone,

I'm a sparky so my plumbing knowledge is limited.

I was asked to go out to a new underfloor heating system last week as the last 2 sparkys apparently couldnt get it working.
Its a baxi combi boiler with rads upstairs and underfloor downstairs.
the rads are controlled via a honeywell wireless stat.
The underfloor looks to me a basic set up, its not a manifold just one zone and i might be wrong here but a mixing valve with a pump next to it.
The underfloor again has its own wireless stat.
The problem they are having is whichever stat is called it all comes on together, no separation at all.
The is a 2 port valve (not connected) on the flow going to the rads upstairs.
now obviously at the moment its not going to separate as the valve hasnt even been wired.
Whats confusing me is there is only 1 valve for the rads and nothing for the underfloor. from what i can see the flow going from boiler has a tee which also flows to the underfloor, surely there should be a valve there too?
sorry for lack of knowledge on the plumbing side but i can't see much point wiring it correctly if it needs 2 valves.

cheers, Jon

 

[Chalked]

Easiest way is two valves, then use each end switch for the boiler. But if the manifold has a wiring Center with a relay, you can switch through that for underfloor and the end switch in the m/v.
You need to make sure tha pipework to the underfloor has been taken off before any radiators and the motorised valve to control the heating is just after.

 

[jstephens]

hi thanks for response.
the boiler is right above the manifold so looks like its going down from boiler, teeing to underfloor then up, through a valve and then to upstairs. to me though I'm seeing that if i switch the valve off for example i can shut down the rads and have underfloor on its own but if i want just rads then the underfloor will come on too? or will it off if the underfloor pumps not running?

cheers

 

[jstephens]

my main question really is can this system work as it is with only one valve for the rads or does the plumber need to fit one?


cheers

 

[dancinplumba]

got any pics of underfloor set up ? single zones usually have a temp sensor on pipe to it, which switches u/f pump on

 

[jstephens]

Hi mate
no pics unfortunately
i could switch the pump through the ufh stat. My main concern was that when the rads are on the ufh would still heat up without a valve in place

 

[dancinplumba]

if the u/f pump isn't running then it wont come on

 

[jstephens]

Cheers for help

 

[walterwhite]

I would add another 2 port for the UFH. Particularly as the branch is so close to the CH pump.

 

[jstephens]

the only separate pump is right next to the ufh, that sound odd?

 

[jstephens]

it is a combi boiler though

 

[walterwhite]

The pump in the boiler will be pumping to the manifold when rads call for heat. Even if the UFH pump isn't on you may get some flow through it

 

[dancinplumba]

is it like this ?

 

[jstephens]

Yes, or very similar.
So looking at previous comments there should be another valve for ufh?

Thanks for help much appreciated

 

[dancinplumba]

valve not really needed, I have this at the moment, if u/f pump not running then it don't heat up,
but no reason not to have a valve. check this out

http://www.polypipe.com/cms/toolbox/1339_Polypipe_FH_ZRU_Installation_Guide_V1_AW_WEB.pdf

 

[chris watkins]

http://www.johnguest.com/wp-content/uploads/2014/07/UFH-Room-Pack-Install-Guide.pdf

The above is another popular make of single room U/F

 

[stevetheplumber]

if the underfloor pump is close to the boiler you will get some heat passing through so better control with a valve

 

[jstephens]

if the underfloor pump is close to the boiler you will get some heat passing through so better control with a valve

bit of conflicting info lol

in my head (I'm no way a plumber) the water in the same pipe will then flow to the ufh but makes sense that it won't go far without the pump.
To have the valve installed would involve the plumber coming back so i was more concerned that if i wire it as it should be it still would heat both areas up.

cheers for help guys

 

[jstephens]

http://www.johnguest.com/wp-content/uploads/2014/07/UFH-Room-Pack-Install-Guide.pdf

The above is another popular make of single room U/F

cheers for that Chris, this is the exact make installed.
Interesting read, the one diagram shows the flow from boiler and states

Connecting to existing heating circuit will not allow independant control of the UFH heating
circuit

so they are saying that there should be 2 valves in place?

 

[dancinplumba]

if rad valve is off but your stat for u/f turns on boiler and u/f pump, then u/f heating, no rads on


if rad valve on but u/f stat off you have rads only ???