Two boilers in domestic situation

dougalmaguire

Hi all, I came across a job today where the installation had two boilers for the heating system plumbed tru a manifold with two pumps off manifold one for upstairs and one for down....when downstairs heating switched on the rads upstairs were coming on to...even when upstairs pump was electrically isolated...bar pressure on each boiler was 2 half bar...I know the pressure is way to high so would this force the water tru the upstairs pump and in turn onto the rads?? Also to solve any "creeping" if two motorized valves are fitted before each pump would this solve the problem?? Rads were still warm when pump was reconnected and bar pressure returned to normal....I am not a plumber by the way just a sparks!! Any info would help I'm just curious!!!

SmallBalls

I know with systemlink manifolds, they recommended non-return
valves on any zones that are at a higher level than the manifold.

Motorized valves would work but a more expensive solution.

dougalmaguire

What would u recommend as a soulution?? Also if valves were used am I right in saying the stat would wire to the valve and the auxiliary contacts on the valve would switch the boiler off when temp is met?? Just looking for as muck info as possible so any ideas or info is all of help!! Cheers

Pete67

It's probably gravity circulation through the upstairs pump when the downstairs heating is on and the manifold hot. Motorised valves would definitely work, I would put them on the discharge side of the pump personally but it probably does not matter. Check valves would also work and are cheaper as said already and require no wiring. Either option requires draining and refilling.

If using motorised valves, switch the valve with the zone thermostat, use aux contacts to switch the appropriate zone pump and enable boilers - you may need an additional relay or two. Is there a third pump or a zone valve for DHW?

dougalmaguire

The hot water is actually fed tru yet another boiler!!! I've never come across a system like this...heating wise that is.I always taught that the use of manifolds with pumps is more suited to commercial/industrial use....

@pete 67.... The plan is to put m.valves on discharge side of each pump...stats to open close the valves and aux contacts on valves to switch boiler on or off when temp is reached...it makes sense to me...but I'm not a plumber. In my head it would totally isolate the both pumps when one circuit is on....hope I'm making sense here!!

Pete67

Makes sense, what switches the pumps on/off, is it the stats? Some boilers need a permanent mains supply, if this is the case use the aux contacts to make the boiler enable contacts rather then power on/off the boiler. Pretty unusual heating system you have there, 3 boilers :eek:

dougalmaguire

I know!!! It's a disaster!!! I was gona wire the valves and pump on same sw wire so when clock calls for heat valve opens and pump kicks in at same time then aux contacts kill boiler/pump when stat reaches temp.... Am I right???

oikster

How big is this "domestic situation"?:eek:

dougalmaguire

Its a big house!! Needs to be sorted quick! I think I'm on the right track...well the wiring!! Just want to get a laymans understanding of the plumbing end as it makes my job easier then! I've never come across anything like this before it's bizarre!!