had new combi boiler fitted and thermostats on all radiators except one. Think plumber forgot one but he said that you have to leave one without thermostat is this true

[cheerschuck]

[Hawkwalk]

yes, one is left without the thermostat to act as a heat leak. Something to do with releasing pressure to protect the warter pump. I asked the very same question on here last year.

[Buenchico]

It's normal for one radiator not to have a thermostatic valve. The most likely place to site that radiator is probably in a bathroom.

Chris

[askyourgran]

Yes it's true. we had the radiator in the bathroom without a thermostat, but since we've had a new combi boiler we had the radiator changed to the one in the hallway, we found that it got too hot in the bathroom and we couldn't control it (our bathroom is small).

[AlBags]

You CAN have a TRV on EVERY radiator .. so long as you fit a bypass valve ... like the Honeywell DU145 here ...

http://www.honeywellu...duct.aspx?r=by&p=2344

It lets a controlled amount bypass hot to cold return to avoid stressing the pump and cycling boiler for no reason .

[pilotlight]

The probable reason for your installer leaving the radiator without a thermostatic radiator valve is that the radiator in question is serving the room / space where the room thermostat is sited. This is recommended practice by heating installers.
Most boilers manufactured in the last few years have a built-in bypass, although some installers will still fit a automatic bypass to the system.
If you ask your installer what the reasoning is regarding the 'missing trv ', i'm sure he would explain.
Hope this helps.

[cheerschuck]

Thank you all very much - very helpful each of you.

[gucciman]

even with a bypass fitted if all your rads are turned off then the heat cannot circulate away from the boiler properly and the over heat stat could keep triggering.

and it is good practice to not have a trv in the same room as a room stat as the 2 will work against each other and cause problems.