Bypass Radiator Question

[MikeGrahamT21 59]

Hi,

 

Is there a size requirement for the Bypass Radiator? Or can it be any radiator? I was thinking of making it the towel radiator in the bathroom. We have a combi condensing boiler.

 

Thanks for any info.

 

Regards

Mike

[JSHarris 4,017]

Do you need a bypass radiator at all? 

 

We don't have one on our combi system in our old house, just a bypass valve that allows the flow and return to be short circuited if all the rad  TRVs happen to be closed.  The same goes for the ASHP at the new house, we fitted a standard heating system bypass valve to deal with the short delay whilst motorised valves open and adjusted it until it only opened when needed.

[MikeGrahamT21 59]

Well, I'm not really sure. I also fitted a bypass on part of the pipework a few years back as a just in case all the radiators were turned off for whatever reason, so in terms of flow, there is a path even if everything is off (though the bathroom towel rad doesn't have a TRV currently, so is also a bypass). I was just thinking from a boiler perspective.

 

I'm about to invest in a Honeywell Evohome System with connect radiator TRVs, currently the back of the house tends to be cooler (thermostat lives in living room where the TV and home cinema gives off quite a bit of heat), so ideally i'd want a TRV in the room too (even though its not recommended to have one where the stat is, evohome doesn't really work like that though), to close off the room radiator while still allowing heat into the back radiators, without cooking us

[MikeGrahamT21 59]

Checked manual, boiler definitely needs a bypass, but that should suffice with both the pipework, and the bathroom radiator, so TRV in the room is possible.

[Nickfromwales 2,613]

The likelihood of the TRV's all being closed automatically is pretty much zilch. I would just put the hallway / lobby rad on bypass and fit TRV's everywhere else. 

Unless you go around and physically shut them all off to the zero position the issue won't arise, so basically if you can discipline yourself to not turn every radiator in the house off and then go and turn the heating on you'll be absolutely fine. . 

 

[MikeGrahamT21 59]

Yeah I'm sure I'll manage that lol. We don't have a hallway radiator, as it's too small, so I'll go with the bathroom on bypass, as it can get as hot as it likes in there. Now all I need is black Friday to come along and hopefully a bit of luck that the evohome has a discount, I can hope lol

[JSHarris 4,017]

We've had the situation once where all the TRVs were closed, and the towel rail valve was shut off, when we'd been away for a few days.  I turned the heating system back on when we came home, but forgot to go around opening all the TRVs and the towel rail (it wasn't me that had closed them, I didn't even know they were closed -  someone who thought it was a good idea as we were going away closed them all without telling me..............). 

 

All that happened was that the bypass opened and the boiler shut down again, as normal, a minute or two later, because it had reached the set flow temperature very quickly.  It then just sat for the duration of the anti-short cycle delay before firing up again and shutting off again.  It didn't flag any faults, or give any indication that there was a problem, the only give away was that the pump over-run stayed on a long time, plus if you opened the front and entered the first level diagnostics you could watch it fire up,  shut down, go to pump over-run then enter the anti short cycle delay.

[MikeGrahamT21 59]

That's good info thanks, I'll definitely incorporate one of these into the new circuit