Any domestic heating engineers here?

[Hobgoblin]

Hi all

 

I have a problem with my combi boiler;

 

It is a Glow Worm Betacom 30c

 

Only 2 years old, and it keeps losing pressure, when it gets below 1 bar, it will not start.

 

Every few days I have to turn a water tap (it is on a U piece of hose which comes from one port on the boiler, and back to the adjacent one), which I imagine replenishes a header tank, to get it back above the minimum pressure, to enable it to restart. I can find no leaking radiators.

 

It has been doing this for only the last few weeks, last year I think I only had to do this operation once.

 

Does anyone have any wisdom on this, I am a capable DIY man, and happy to fix it myself if it is straightforward?

 

Cheers

[SupraD06]

Hiya mate, if you find that you have checked all radiators and still have to keep filling the pressure up via the filling loop, then it may be that it is over due a service, the good news is that your problem is an easy fix, inside the boiler or nearby there will be an expansion vessel ( bright red in colour ) this is a large can that has a large bag inside that is filled with air, and over time the air escapes. The air is usualy there to absorb the pressure rise by the water temp, when the air has been lost in the bag, the pressure relief valve opens up and discharges the water, thus why you have a drop in pressure. What you need is a bike pump with a guage on, somewhere on the red cover will be a label/stamp with what pressure it should be, if not maybe worth a google or a phone call to the manufacturer, once you know what it should be you can remove the vessel cover, and check what pressure you have, if its low then simply top it up, if it wont hold any pressure, the bag maybe split, and it will need replacing.

 

Hope this is useful, and its an easy fix.

[Hobgoblin]

Excellent, cheers for that, I am now gonna have a look.

[Hobgoblin]

OK have found it.

 

Its a bit fiddly to get at as it is behind the boiler, but with the aid of a mirror I found it, so now I just need to get a footpump or such like to blow it up.

 

I have found the instruction manual; it says Expansion vessel pre-charge pressure 1 bar (14.6lbf/in2).

 

Does this mean I should set at this pressure with the water at normal pressure (it is currently 1.5 bar), or must I reduce the water pressure first?

 

Cheers

[Havard]

OK have found it.

 

Its a bit fiddly to get at as it is behind the boiler, but with the aid of a mirror I found it, so now I just need to get a footpump or such like to blow it up.

 

I have found the instruction manual; it says Expansion vessel pre-charge pressure 1 bar (14.6lbf/in2).

 

Does this mean I should set at this pressure with the water at normal pressure (it is currently 1.5 bar), or must I reduce the water pressure first?

 

Cheers

 

Have you pressurised the system with the U shaped pipe to 1.5 Bar? If so the water pressure will be giving you a false reading on the "tyre" valve on the vessel. You are best to drain all the water out of the boiler till it reads near zero. Put a gauge on the vessel and get a true reading of the air/gas charge. I imagine it will be zero when you get all the water out. Pump up the vessel to 1.0/1.1 Bar and then refill the boiler as you have before.

 

You will find that the pressure will remain constant for a while.

 

When the boiler heats up, the pressure should be between 1.5 and 2 Bar depending upon the size of the system.

 

H.

[Hobgoblin]

Cheers, will do that tomorrow, as I have arranged to borrow a pump with a guage.