why cant i install TRV's?

[bhm1712]

I would like to install TRV's in my bedrooms, bathroom and kitchen.

However, if i isolate just one of my radiators my boiler starts to kettle within about 5 minutes. So in theory if i install TRV's and they close down then my boiler is likely to implode on itself. (maybe not that bad but...)

Any ideas as to why this might be the case?

System info:

Glow-worm Space Saver Mk 2, 40BR
C-Plan (Feed and Vent before the DHW MV)
Siemens Wireless room thermostat
Siemens cylinder stat
Siemens RWB29 controller/programmer
22MM feed and return pipes
15mm spurs to radiators upstairs and 8mm microbore to downstairs
7 Single bar radiators

No pumping over, no kettling usually, clean system - flushed annually and inhbitor added. System water exceptionally clean for the age of the system. F&E tank clear and no sludge.

THANKS!

 

[bhm1712]

should perhaps mention that the boiler thermostat has been recently changed and works fine.

 

[muggles]

You most likely have a one pipe system, only solution is a re-pipe if you want TRVs

 

[bhm1712]

It's a two pipe system with 22mm flow and return pipes. The system although not new is a late eighties system.

 

[rpevans]

Suggest that you need to install a pressure relief bypass valve. Sounds like you have only just enough water flow through the boiler when all rad valves open.
Hope this helps.
Rich

 

[45yearsagasman]

You sure it's a C plan, with that boiler?

 

[bhm1712]

Yes because I installed the c plan myself about 4 years ago.

Previous to that it was just an on or off system. No room stat or cylinder stat and a basic timer with just on or off twice a day!

C plan was wired to Honeywell diagrams

 

[stem]

You most likely have a one pipe system, only solution is a re-pipe if you want TRVs

A one pipe system has a constant flow regardless of the TRV's shutting. Even with every radiator off, the water will continue to circulate around the one pipe which is formed as a loop.

Also, all my rads have standard Terrier TRV's (except the hall where the room thermostat is) and they all work perfectly.

 

[Nige F]

However, if i isolate just one of my radiators my boiler starts to kettle within about 5 minutes. So in theory if i install TRV's and they close down then my boiler is likely to implode on itself. THANKS!

No , it would EXplode

 

[Agile]

All boilers should have an autobypass valve.

A higher head pump might help too.

8 mm is not easy to use !

Tony

 

[bhm1712]

the boiler is 25 years old so i dont think it has an auto bypass valve.

Where would an auto bypass valve need to be fitted on a system like mine?

 

[Agile]

Yes, if you want TRVs!

 

[rpevans]

See the installation guide here:

http://www.honeywelluk.com/products/Valves/Bypass-Valves/DU145/

Rich

 

[bhm1712]

Thanks gentlemen for your advice.