Megaflow/solid fuel - wiring

richy3333 · Oct 15, 2013

Hi all.
Plumber has installed a Megaflow unvented system with a neutralizer and a back boiler working off a stove. We've been discussing how to wire it up electrically and I wondered if anyone has experience/ could direct me to a wiring diagram?

The stove was trial run and gravity was not causing the heated water to rise properly so a small pump has been added. An initial thought was to use a stat to 'sense' the pipe heating up to start the small pump to help gravity along, but this needs to then stop when the tank comes up to temperature and the motorised valve and main pump 'kick in'.

Megaflow won't help as they say their tank shouldn't be used with this set up but the plumber considers it OK as a neutraliser has been installed?

Constructive thoughts welcomed...

Benjamiin · Oct 15, 2013

I've done a lot of solid fuel systems, although no megaflow, but we used to take a cable from the heating load of the programmer into a high limit pipe stat and low limit pipe stat, the load of the high limit stat fed the pump, and the load of the low limit stat fed the room stat which fed the pump, meaning if temp got too high it automatically sent water round the radiators to stop overheating of the back boiler, and the low limit stat only allowed the room stat to activate when the water was over 40 degrees! Hope this helps, can email you a drawing if you p.m me your email address

snowhead · Oct 15, 2013

Look on the Dunsley neutraliser site, they have loads of example wiring diagrams.

But the most important issue is to manage the potential excess heat from the solid fuel boiler.

The system MUST gravity without the aid of a pump in case of a power cut, and you can't put valves or pumps in the gravity circuit which may restrict that flow, any zone valve must be normally open (powered closed)

The plumber should have put heat a leak radiator circuit in the system.

richy3333 · Oct 15, 2013

Thanks for your comments both.

The plumber doesn't want to use a programmer or room stat and as I said has added the small pump to the gravity feed.

I wired the system up as per Dunsley's (before the small 'gravity assist' pump was installed and the plumber asked me to take it all out as 'I had over complicated matters'.