Underfloor heating via an s plan system

[piz]

hello
Can anyone help am looking for a diagram I have an splan system with an extra valve for the u /f heating

 

[telectrix]

trigger the ufh valve from ufh stat. use valve microswitch to fire boiler via the stat input terminal in boiler (and ufh pump if fitted)

 

[Meggerman]

As above or If you have UFH manifold take controller output to 2PV valve and then onto boiler. Google Honeywell for S Plan Diagram.

 

[davesparks]

trigger the ufh valve from ufh stat. use valve microswitch to fire boiler via the stat input terminal in boiler (and ufh pump if fitted)

You shouldn't connect a dedicated ufh pump directly to the boiler sw live or else it will run when either of the other valves are open regardless of whether the ufh valve is open or not.
Connecting the boiler fire signal from the valve to the pump and the coil of a relay and use the relay to switch a live to the boiler.

 

[davesparks]

If you look in the heating controls section of the forum you will find a PDF of the wiring diagrams in a sticky at the top of the page.

 

[Lagentium]

You may need a pair of relays to stop back feeding from when one system calls everything will turn on. If a plumber isn't involved be aware of the UFH running temperatures compared to a system with radiators on. If this has already been thought about please excuse me!!

 

[davesparks]

Pair of relays? If the underfloor has its own pump he'll need one relay to isolate it from the boiler switched live as I described above, why do you need a second relay to prevent backfeed?

If it was necessary to isolate the pumps so that the normal pump doesn't run whilst the ufh is on its own then you'd need a second relay. But that's a whole other matter and I've heard many arguments for and against that one.

 

[Lagentium]

I was thinking along the lines that if there is a pump for existing loops for the radiators, theirswitch wires would need to be separated through a relay or two depending on the setup of the system as they could just be trying to pump against a closed zone valve.

 

[telectrix]

I was thinking along the lines that if there is a pump for existing loops for the radiators, theirswitch wires would need to be separated through a relay or two depending on the setup of the system as they could just be trying to pump against a closed zone valve.

then again, the ufh valve will be open so the pump will pump through that.

 

[Lucien Nunes]

Even if there isn't a manifold controller (i.e. the UFH is a single zone) is there any reason why its stat output can't feed the UFH pump and valve motor? In this case the valve microswitch can simply be paralleled with the others to feed the boiler s/l without backfeeding.

 

[telectrix]

Even if there isn't a manifold controller (i.e. the UFH is a single zone) is there any reason why its stat output can't feed the UFH pump and valve motor? In this case the valve microswitch can simply be paralleled with the others to feed the boiler s/l without backfeeding.

that's how i'd do it. then if it worked, fine. if not, back to the beermat for a revised diagram.

 

[D Skelton]

Even if there isn't a manifold controller (i.e. the UFH is a single zone) is there any reason why its stat output can't feed the UFH pump and valve motor? In this case the valve microswitch can simply be paralleled with the others to feed the boiler s/l without backfeeding.

I often find them wired this way, it is the simplest way of doing it, but then you've got the pump firing before the valve opens. It will shorten the life expectancy of the pump. A relay is the only option if you want the UFH valve to open, then the UFH pump and boiler to fire, but keeping the UFH pump control seperate from the main pump.

 

[telectrix]

surely if the pump is triggered by the valve microswitch when the valve opens, that sorts the problem.

 

[D Skelton]

surely if the pump is triggered by the valve microswitch when the valve opens, that sorts the problem.

But the boiler is also triggered by that microswitch, and the main pump, which means you'll have backfeed from the DHW or CH when they are energised firing up the UFH pump when it's valve is closed. The only two options available is to put the UFH pump on the valve feed (not ideal), or on a relay operated from the valve's orange

 

[davesparks]

The pump needs to be connected to the valve orange along with the relay coil, the switch side of the relay should work the boiler sw live.