Powermax 155x Low Pressure Lock Out

[teataster]

Hi

Can anyone help with some advice please?

My Mum has a Powermax 155x which is about 3 years old. Pressure falls every six weeks and she tops up the system to 1.0 bar. The boiler was turned off for two weeks in January while she was away, and the pressure dropped to zero. It locked out when she tried start it. She has called British Gas on a one-off repair basis, but in the meantime I thought it would be useful to do some research.

What causes pressure to fall to zero when cold? There is no evidence of a leak from the central heating circuit. Is it normal to have to top up so frequently? Are these boilers prone to this kind of problem?

Any help much appreciated.

Teataster

 

[superdupergasman]

Could be anything from a passing Pressure relief valve and flat expansion vessle to a leaking pipe some place under a floor or even a cracked heat exchanger allowing the water leak inside the combustion chamber and evaporate!

Lots of things on a sealed system can leak.

 

[Agile]

Expensive to call BG for such a simple problem!

An independent would probably solve the leak for less than £100 !!!

Tony

 

[Onetap]

What causes pressure to fall to zero when cold? There is no evidence of a leak from the central heating circuit. Is it normal to have to top up so frequently? Are these boilers prone to this kind of problem?

It's a leak; it could be under the floor. It could be several small leaks.

I'd suggest checking whether there is water dripping from the pressure relief valve (aka safety valve); fix a food bag over it with a rubber band; do not plug it, it's a safety device.

The safety valves will often fail to reseal when they have opened, due to particles of dirt getting under the seat, and usually need to be replaced.
The usual reason for them opening in the first place is that the expansion vessel has lost its air charge or is undersized for the system water volume. The expansion vessel is quite often undersized on the Range Powermax, because it has a water capacity of 100 or 150 litres (I forget which) of water.

Also check radiator valve glands, they often drip, but the water evaporates whilst the system is hot, so the leak isn't immediately apparent.

 

[Londoner1980]

Seems like there is always a problem with this boiler. Mine is doing the same, pressure dropping very quickly when not used. Also I seem to be getting a dripping sound in my sitting room (one floor up). Intermittent drip sound, which goes off when the boiler stops, I only move din 3 weeks ago and the boiler should only be 5 yrs…. Should I just replace.