Connecting underfloor heating to CH System.

27 Mar 2024
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United Kingdom
Hi Everyone,

I'm installing a wet underfloor heating system for my in laws in a bathroom revamp for them, at the moment they just have a Worchester Bosch Greenstar 25Si combi boiler with 12 radiators connected to the system all controlled by a room stat and various TRV's.
I'm going to cut into the CH Flow and return to connect the manifold in & put a 2 port valve so they can control the bathroom UFH separately to the rest of the house, from my research and understanding there should be an automatic bypass valve between the Flow & Return, if that is the case is there a minimum distance the bypass valve need's to be from the boiler?

Any advice welcome
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The Si has an internal bypass but if the system is an S plan or all TRV's then ideally an auto bypass would be fitted, it needs to be before the CH's 2 port valve.
Hi Madrab
The current system is a two pipe system with no zone valves and TRV's on all radiators other than where the room stat is currently situated.
Yeah my plan was to install a 2 Port valve feeding the manifold and put an automatic bypass before the 2 port.

Thanks for coming back to me really appreciate it.
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Yep. Was going to say what @cross thread said.

You need to spilt pipework at boiler to 2 zones with separate f&r else you'll not be able to ufh on only.

Or, you could do it if you put multi room zoning in with eTRVs.
Thanks guys appreciate your help I'll split into two zones with valves for the heating & UFH with an automatic bypass valve between the flow and return before the zone valves.

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