Keep one radiator without TRV, even on Evohome zoned system?

25 Apr 2017
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United Kingdom
Hi all,

We have a Worcester Bosch Greenstar 30CDi Combi boiler, and are installing the Honeywell Evohome system with HR92 wirelessly controlled TRVs.

My plan had been to have a TRValve fitted to the radiator in our hallway, where there currently isn't one as the thermostat is based there. In the newer system, I'd rather the hallway was a zone we could configure (and on top of that, it's one of 12 radiators with the HR92s coming in packs of 4, so I'll already have a TRV head for it).

However, I noticed in the manual for the Worcester that it states "The remaining radiator... should be uncontrolled and must be left open" and have read elsewhere online that "one radiator should be left without a TRV and left permanently switched on, unless the boiler is fitted with a flow meter to detect when all the radiator valves are closed."

Any thoughts on this? If I leave that radiator with no TRV, can I then set the Evohome controller across from it in the hall and still have a 'hallway' zone, but where the sensor for that zone is the controller itself (which does have a built in sensor you can use for such things) - even with no actuator on that single radiator?
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Hi, just wondering how you got on with the Honeywell system and your 30CDi boiler. I have the same boiler and thinking of getting the same Honeywell system. Any advice would be great (mainly want to know it’s actually compatible and how easy it is to install). Cheers.

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