Baxi 30/85 "low pressure/pump fault"

[Billy Bob Bob]

are you saying the pressure wont go over 0.5 bar? is cold water pressure good there?

 

[SanClerDave]

Water pressure is good, I can top up the pressure to any point i wish, but as soon as the filling loop is turned off, the pressure drops back to 0.5bar. There are no obvious leaks in the boiler, or in the system, however some of the pipework is under floors. Circulation appears good, all radiators get hot quickly!

 

[aatkins]

I have had a similar problem in that the micro switch would not make on startup but also had poor circulation problems in that all the rads would not heatup together, changed the diaphragm but no use. I made sure that there was no air in the CH supply/return pipes that could be causing a low flow. I recently changed the pump and that solved the problem with the circulation , all the rads are piping hot now. However the micro switch seems to be operating in the reverse now, i have to break the switch for the pump to start, anyone experience this before?
Anyway in answer to your problem, make sure the system is air free, make sure mesh on pump suction is not clogged, if those two things are ok then i would say the pump is the problem. I thought my pump was operating ok, was spinning ok and the circulation was ok ish, it was still faulty, remember its the flow that causes the differential pressure accross the hydraulic assembly valve and if you haven't got enough flow it won't push the pin out to make the switch. I bought a Grundfos UPS 25 60 and fitted it into the casing of the old pump (UP 15 50), fits perfect and alot cheaper. Now all i have to do is solve my micro switch problem!!

 

[Mbear]

We have a new block of flats up here full of these. I've had this fault many times, the 1st few times I changed the dia, both jobs came back in within the wk. it turns out that the small differential hole is slightly choked on the left hand/dia manifold. We've been replacing the whole manifold when it occurs now, its pointless beating about the bush. Just replace it

 

[aatkins]

When you say you are replacing the whole manifold do you mean the hydraulic outlet assembly?