TurboMax 824e short cycling

[nkt]

Hi,

I'm in a studio flat with the above boiler feeding 3 radiators, 1 large and 2 small. I've been trying to balance the radiators but, even from cold, the boiler will not fire for more than about 3 minutes before the internal stat kicks in, which is not long enough to make adjustments. Once the radiators are hot, the boiler often fires for as little as 15 seconds at a time. The flow is currently set to 70°C and, even with all the lockshields wide open the internal bypass pipe heats up immediately whereas the return flow pipe never gets anywhere close to 50°C. Is it possible that the bypass is operating to readily or is my system just too small to work efficiently? I've tried reducing d.0 to the lowest setting but it made no difference.

 

[flameport]

The system is far too small for the boiler output.
However the return from the radiators should be hot, if not then the bypass is open, which could indicate it's broken, or there is a blockage in the radiator circuit.

It's rather pointless trying to balance such a small system.

 

[nkt]

Thanks for the reply. The bypass is definitely opening as soon as the boiler fires, but I assumed that this was because the circuit is so small. Would reducing the pump speed help? It's currently on the higher setting.

 

[flameport]

Possibly. The point of the bypass is that it only opens when the rest of the system is closed - normally when TRVs are fitted and they close due to the rooms being hot enough.
With the radiators open, the bypass should be closed.

 

[nkt]

I just tried the lower pump speed; no difference except a bit of squealing. I've removed the TRVs altogether (I have Tado and there's only 2 rooms!) and the lockshields are fully open. I had my hand on the bypass and I could feel water flowing through it as soon as the pump started running. I'll try removing the bypass valve tomorrow to see if it's sticking.