Once more unto the breach

[speedyharry]

I am preparing to fit a replacement central heating water pump. Please see Diagram A, which shows the main components of the existing central heating and indirect hot water installation.

The existing installation uses a conventional gas boiler (Glo-worm SpaceSaver), a hot water cylinder with a heat exchanger, a single pump and two cisterns (one of which is shown on the diagram A.) So far as I know, the boiler does not have over-heat protection.

All pipes are 22mm throughout except for an open discharge over the cistern. This is a 15mm branch from the 22mm F/E pipe. This feature bothers me, given what I have read here that boiler safety relies on a dedicated open vent from behind the pump.

I would like to ask if the assembly shown on diagram A is a recognised working. By the way, any other advice about fitting a new pump will also be gratefully received.

 

[Hugh Jaleak]

As long as there is a clear, open, constantly rising path from the boiler to the Vent, that satisfies the safety aspect. Ideally the vent needs to be in 22mm pipework, given you seem to have a 22mm pipe up to the point where it tees to go into the Feed and Expansion Cistern it may be worth upgrading the last section if not too ridiculously difficult a task.

I would assume it has worked up to this point in time without too much issue, ensure Pump is correct orientation when fitting new and dont rely on the Pump Valves to shut off, you will probably be better to drain the system before attempting to remove the old pump. Refill and add inhibitor as required when finished and satisfied no leaks.