Pressure problems on Firebird Combi

[Ianm]

Hello

I've read through related topics on the board but none seem to fit my problem. Just under 3 years ago I had a Firebird Combi boiler installed as part of a complete refurbishment of the property. From the very beginning we had problems with pressure dropping over a period of a few days and I would need to top up regularly. This winter it has got worse in that the boiler pressure drops so low, so quickly that the boiler cuts out and I have to go outside (in the cold and rain) to restart. The plumber that put this in admitted that he didn't know much about oil boilers, but he was under contract to the builders that did the work. Since then I have had 2 other heating engineers investigate, the first put on a second expansion tank and the second tried re-pressurising the tanks. None of this works. There are no signs of a leak anywhere that anyone can find (the builder did try and find a leak in the early days) and I would have thought that if there is one it would be noticable by now.

Related to this is the fact that I do have to bleed one particular radiator fairly regularly and I know this will be a contributing factor, but I don't bleed it nearly enought to be the sole cause.

A final point that I have mentioned to the heating engineers (and is thought to be irrelevant by them) is that the water feed to the boiler is from a bore hole via a pump and treatment plant that introduces some aeration into the water.

I could really do with trying to find the cause as it's starting to become a real hardship keeping it going.

Thanks for any help.

Ian

 

[Burnerman]

Whether the boiler is fired by oil or gas is irrelevant in this case...if your pressure is dropping you have a leak somewhere, unfortunately.
As your system is sealed, I think that any oxgenated water from the well or whatever would quickly disperse and would be bled away. If you are having to bleed a radiator frequently then there is likely to be some amount of dirt in the system. This dirt is called magnetite and it produces its own hydrogen gas...often the water when you bleed the rads is black in this case.
Popular places for boilers to leak are the pressure release vlve and any automatic air valves that the boiler may have.
John

 

[Ianm]

Thanks for the reply.

No black water when I bleed the radiatior - all rads and pipework are also only 3 years old.

If one of the valves was leaking wouldn't I be able to see the leak and wouldn't one of the engineers have spotted it - or is it hard to find?

 

[Burnerman]

You would certainly see the leak if its bad enough.....but if its only a tiny amount then the water could be evaporating as soon as its produced. There would be traces of minerals though, if that were the case. However, the water is going somewhere....!
How long does it take for the pressure to fall?
John

 

[Ianm]

It varies - during the summer it didn't need any attention, which is not surprising as the heating wasn't on, but may be relevant.

Just now I an topping up once a week at least, if I leave too long the amber light comes on and it cuts out.

This morning when I topped up there was a lot of gurgling noise and despite the taps still being open the pressure stopped rising at a little below 1 bar. I left the taps open for a while, but the pressure refused to increase.

Should also say (just in case it's relevant) that the house is split with ground floor being underfloor heating and other floors being normal rads.

 

[Burnerman]

Surely the water pressure coming from your bore hole is greater than one bar? It seems that the pressure within the system, and the pressure of the water supply was the same - assuming that the filling loop valves are working ok.
John

 

[Ianm]

Bore Hole pressure is generally higher than 1 bar, I can't remember without checking at what pressure the pump from the borehole kicks in. I suppose it's possible that it was just starting to fill the water supply pressure tank and the pressure had equalised at that point. I hadn't thought of that.

As I understand it though you are saying there is a leak somewhere, just not obvious.

 

[Burnerman]

Yep, if the pressure is dropping I'm afraid there is.....at least your boiler isn't old enough to have water jacket / heat exchanger problems, I think.
John

 

[GodKnows]

Hi all,

Could be your underfloor heating is suffering from osmosis. Have you set the CH temp above 60 Degrees? Also, the type of pipe can be of detriment to your system. Also, someone could of put a nail through the underfloor pipework

 

[Ianm]

Well when we first had the problem the buidlers crawled all over looking for a leak in the underfloor heating system. It was pressure tested to 3 bar without a leak on installation. Haven't had the temp up that high at all. If it was leaking under the floor surely I would notice tiles lifting or carpet discolouration after 3 years?

I wonder if I'm coming at it the wrong way. There is no overt sign of any leakage, I know I am bleeding one radiator more than is normal. I didn't think this could cause the drop in pressure I'm seeing, but would it take a while to work through? Is this the real problem and not the boiler? How could I cure this problem to see if it is the root cause?

Thanks for all the help so far.