Underfloor heating help

[dlt27]

Hi, hope somebody can help. I am currently wiring a new wet underfloor heating system for builder. The plumber has fitted a 2 port valve and the pump that is part of the manifold.
The existing system is a y plan.
I was going to leave existing system how it is and fit a wireless programmable stat to underfloor heating. To keep it separate I was going to fit a contactor to the switch live to the boiler
Ie from switch live of existing y plan to first A1 of 2 pole contactor and switch live from underfloor heating to 2nd A1 of contactor. This way both systems are kept seperate.
Could anybody with more experience tell me if this would work or better still another way it could be done. Thanks again

 

[dlt27]

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[dlt27]

That looks a bit better than mine. Thank you again. All makes sense now.

 

[Last plumber]

If you are altering this to an S Plan, you need to make sure you have an auto bypass installed. There may already be one but I thought I'd mention it, it should have one anyway really but not everyone installed them on a Y plan

 

[dlt27]

Ok. Thanks