Backfeed issue?

[cj.dodgson]

Hello,

I am currently wiring up an wet underfloor heating system to an existing oil fired boiler, with gravity feed hot water and pumped central heating.

The underfloor heating is on its own programmerable stats and has a s/l to the boiler.

The Hot water has s/l to boiler.

The central heating has a s/l to the pump and boiler. How do I stop the pump for the central heating coming on with the HW or underfloor heating?

 

[Sintra]

Use a relay

 

[cj.dodgson]

What type and where would it be placed?

 

[snowhead]

Do you intend trying to run the Underfloor without the existing Central Heating?

Depending on how the Under floor pipework is connected, you may have to have the existing heating pump on with the boiler to get hot water to the under floor manifold and pump.

Are there any Zone valves existing or proposed?

 

[cj.dodgson]

The central heating pump is t'd off so doesn't need to run for the underfloor heating. There is a zone valve for the underfloor heating. So they can run separately if i can stop the central heating pump coming on.
If a relay will work that's fine but i have never used one so don't know what type/size etc... And where to place it.

 

[snowhead]

The enable/call signal from the Thermostat for the Under floor will open the U-F Zone valve.
The boiler will be enabled by the switch in the Zone valve.

You need a Normally open relay contact connected to the boiler, with the coil for that relay connected to the S/L from the heating.
The heating S/L can still connect directly to the pump.

 

[chopper76]

Sorry have I missed something here? Surely the underfloor heating will require a pump to pass the water through the system. And as you've got a valve in situ for the underfloor just wire it as a three channel boiler system, just as you would if you had a seperate zone for towel rails