Halstead 102 losing pressure when hot water running

[wolf66]

Hi there,
You have already helped me here, as a couple of weeks ago, my DHW was running intermittently hot and cold - the boiler was cutting out after about 30 seconds, then re-firing. After reading advice here, I got the boiler engineer in, and he removed the heat exchanger, etched it with acid and refitted it. He also put more inhibitor in the system, and fitted a magnabooster. That solved the original problem completely.

However, now it has a new problem. The pressure gauge is showing a loss in pressure. After all the work done last week, the boiler was refilled to 1 bar pressure, but I noticed the next day it had dropped again, only a little about 0.1 bar. So I duly topped it up again, thinking that it was because we had bled the radiators, and the system was settling and have since been watching like a hawk! It falls a tiny bit most days, only when the hot water is running, and I've checked for leaks around radiators, the boiler... also checked that there is no water coming out of the pipe outside (there isn't'). I rang the engineeer again yesterday, and he told me I had a leak (!), asked me to top up the pressure with water again, which I did, and look for water in the bowl I had placed outside (there is no water there). Prior to the work I had done on the boiler, this problem did not exist. I still have hot water, and the boiler is not failing to fire. One particular tap seems to cause a more regular pressure drop than others - whether that's just a coincidence, or significant, I don't know.

Boilers are not my speciality, but I would like to have some idea of what's going on, not only because I'd like to get it sorted, but also because I'm catastrophising, imagining huge leaks under the floor, which will wreck my home and cost a fortune - not to mention the fact that I'm going away for a few days, and don't want the worry of coming home to a) a flood, or b) knackered boiler!!
I'd really appreciate any help you guys can give me,
Thanks,
Wolf

 

[bellairaphon]

sounds like a possible split inside the plate to plate.

Nath

 

[wolf66]

Thanks for your reply, bellairaphon, I really appreciate it. Can a split be fixed, or is it a replacement job? By the time you add on labour, this could be really expensive, if it needs replacing - the boiler must be at least 6-8 years old, not sure as it was in the house when I bought it 2 years ago.

 

[45yearsagasman]

A split in the plate heat exchanger would cause the pressure to rise as it will be allowing mains pressure to cross to the boilers primary circuit

 

[picasso]

If your sure the leak isint external to the boiler then I would go for a split in the main heat exchanger, isolate the boiler by turning off the flow and return valves under the boiler,turn the boiler off at the mains and leave it overnight,if the pressure drops you know its in the boiler.

 

[wolf66]

Thanks, I'll speak to the engineer on Monday, and see if we can figure it out. I'm starting to avoid using hot water at all, since that stops the pressure from dropping any further! I thought I'd cracked it last night, when I can home and discovered a puddle in the upstairs bathroom, and drops of water coming from one of the light fittings... but examination of the loft showed no damp, no leaks in any of the defunct pipes, nothing. So it seems I just the unlucky one at the moment, with a leaky roof, dodgy boiler, and who knows what the next thing will be?

 

[wolf66]

Over the weekend, I've avoided using the hot tap in the bathroom, where the boiler is - and there's been no pressure drop at all. Everything is the same - I haven't done or not done anything differently, apart from avoid using this tap. Can't see why it should make a difference, or even IF it should. But it clearly does make a difference - the pressure was dropping every day, when the tap was used. No drop when it is unused.
Anyone able to figure this out?