Combi Boiler Drain/Refill Question

[redbike]

Hi,

This combi boiler has an integral, allbeit conventional, water pump. It also has a mechanism for bleeding air out of the boiler via a plastic tube at the top of the boiler which has a twist type stopper at the end.

This Worcester Bosch Greenstar 30SI boiler is in the loft, i.e. at the highest point of all pipework. If the system is drained and refilled, it is therefore likely to have air trapped in the boiler.

I have heard that these boilers are supposedly 'self-bleeding' and therefore require no special activity to bleed air out of the boiler or the pump.

Can anyone confirm whether this really is the case? Also, in a similar vein, would the integral water pump need to be primed before starting the boiler up to prevent the pump running dry for a few seconds before it primes itself?

Thanks

 

[ianmcd]

First of all no the boiler is not self priming you need to turn that bayonet fitting with the hose on it a quarter turn untill water comes out, as a side note if the boiler has been fired and has hot water in it put a larger section of pipe over the hose as it may spurt extremely hot water and even steam out, once the pipe runs freely of water the pump should be primed if not just slacken the large slot screw in the centre of the pump till water comes out then tighten again, hope this helps


Ian

 

[redbike]

First of all no the boiler is not self priming you need to turn that bayonet fitting with the hose on it a quarter turn untill water comes out, as a side note if the boiler has been fired and has hot water in it put a larger section of pipe over the hose as it may spurt extremely hot water and even steam out, once the pipe runs freely of water the pump should be primed if not just slacken the large slot screw in the centre of the pump till water comes out then tighten again, hope this helps ?

Ian

Thanks for your advice Ian,

Just to clarify, you say that once water flows from the bayonet/hose the pump should have been primed. Is there a way to tell for sure that the pump has been sucessfully primed without actually priming the pump to check? If not, does this mean the pump should always be bled/primed separately after bleeding the boiler?

 

[ianmcd]

If the pump has air in it after you prime the top bayonet connection it will only be noisy it wont do any harm , if you are in any doubt release the large screw a quarter of a turn that I talked of earlier before firing the boiler, you wont harm the pump in any way