Heat Sink Radiator

[Mickjohn]

Hi
I have an 8 Rad system....7 with Evohome HR92’s on and one rad in bathroom acting as a heat sink ( lock shield valves ) all working fine.....not sure i should have said that anyway I understand need for heat sink rad on system that just has thermostatic valves in case all close and boiler is still running but on evohome if all HR92’s are shut then boiler shouldn’t run so could I add HR92 to the bathroom rad which is acting as the heat sink rad

Hot water is heated from a separate instant water heater.

Many thanks in advance

Mick

[anniesboy]

i had a new system installed last year,initially the plumbers planed to install my bathroom radiator exactly as you describe.

I explained I wanted HR92s on all radiators (10),which was easily achieved by installing a by pass valve,this was installed in my loft along with the boiler.

I guess you need the same,however I am not a plumber ,Im sure someone else will clarify or correct if I'm wrong

I like you have water heated via immersion heater.

[CT1]

I have HR92s on all radiators and my boiler includes an ABV. The system has been working without problems for 6 years. Fitting an external ABV might be necessary depending on your boiler but should not be difficult to install.

[filbert]

Hi
.... I understand need for heat sink rad on system that just has thermostatic valves in case all close and boiler is still running but on evohome if all HR92’s are shut then boiler shouldn’t run so could I add HR92 to the bathroom rad which is acting as the heat sink rad
Mick

I have the same question. Why would the pump or boiler run when the valves are all shut? Especially an old fashioned system like mine (Ideal Mexico, no fancy controls). I just can’t understand why any sort of bypass would be needed.

[Mickjohn]

i had a new system installed last year,initially the plumbers planed to install my bathroom radiator exactly as you describe.

I explained I wanted HR92s on all radiators (10),which was easily achieved by installing a by pass valve,this was installed in my loft along with the boiler.

I guess you need the same,however I am not a plumber ,Im sure someone else will clarify or correct if I'm wrong

I like you have water heated via immersion heater.

Thank you for reply seems by pass valve will be the way to go btw i have instant water heater not emersion heater

Mick

[anniesboy]

Here is a link to why a bypass is installed.
https://www.youtube.com/watch?v=7sp78lBoSPw&t=93s

[BuxtonJim]

I'd be thoughtful about that. My boiler apparently has an ABV but, as belt and braces, I use a large towel rad as a bypass in case of pump overruns.
The bonus is that towels are always bone dry.

[Mickjohn]

Thank you for the above replies much appreciated but instead of ripping up floor boards to fit an automatic bypass valve what about setting a custom schedule at set point say 5 degrees add all present HR92's ( in summer) and install a single zone thermostat (Y87RF) in bathroom and bound to my evohome controller.
Wouldnt that effectivley control the bathroom rad? or am I missing something?

Many thanks in advance

Mick

[DBMandrake]

I don't understand why you would need to rip up your floor boards to install an automatic bypass valve. They're usually installed within about a metre of the boiler so unless you have a very short pipe run from the boiler before the pipes disappear into the floor installing an ABV shouldn't be a problem.

[DBMandrake]

I have the same question. Why would the pump or boiler run when the valves are all shut? Especially an old fashioned system like mine (Ideal Mexico, no fancy controls). I just can’t understand why any sort of bypass would be needed.

Most boilers have pump overrun so when the boiler demand signal is turned off (BDR91 etc) the pump will continue to run for a few minutes. If all the valves are closed and there is nowhere for that overrun to flow the pump will not be very happy trying to pump into a dead end...

Also you can't trust the Evohome system to never allow the boiler relay to turn on when all HR92's are closed and blocking water flow - it actually happens in certain normal circumstances (for short periods of time) let alone if there is any intermittent wireless comms which could let it happen for a long period of time.

If you want all radiators controlled in an Evohome system you need an automatic bypass. Personally I think it's worth it and I had an automatic bypass installed so I could control all radiators on our system.