Combi system loosing pressure

[Bob Hill]

Hi all,

Have searched on the forum for past posts on this topic and wanted a bit more info...

I've got a greenstar 24i Junior combi boiler. I've recently added two rads and a towel rail. Pressure tested the system up to 2 bar to check for leaks and fixed any I found meaning that the pressure held indicating no further leaks.

The boiler than had a service and a new fan fitted (not done by me)

Since then the pressure drops both when the heating is on and when it isn't. I repressurise the system via the filling loop and it then looses pressure again. It may or may not be related to the work done by the guy who came in...

I've also bled the rads so that there is no air in the system as far as I can tell.

It seems the suggested causes are:

1. Leaking pipe somewhere - How small a leak could cause the pressure drop?
2. Something to do with the PRV - Though no water is discharging - how could I test if this is a potential cause of pressure loss?
3. Something to do with the expansion vessel - How could I test this?
4. The filling loop is letting water go back into the mains

Have I missed any possibilities? What can I try in order to fix it?

I'm assuming it's a bad thing to just keep filling with water - I don't really understand where the water is going.

Thanks for help in advance.

 

[diamondgas]

Hi Bob Hill 🙂

1) Any loss of water will bring about an indication of pressure loss.
2) Tie a plastic bag around the prv outlet, see if it collects anything
3) Good indicator to a deflated EV is large pressure fluctuations when the heating is switched on. Rising from 1bar to 3ish kind of thing 🙂
4) not likely but disconected it if it's a concern...!

5) Heatexchanger leaking - check condensate for constant running/filling

Hope that helps Bob 🙂

 

[mountainman]

You've done pretty well so far Bob.
Perhaps it's now time to get a heating engineer in.
If you suspect that the person who serviced your boiler has caused the problem maybe call them back.
MM

 

[Bob Hill]

Thanks for info so far. I was quite pleased with having installed the rads so it's frustrating to have problems right at the end

I'll check those things suggested and if no joy I'll give the guy a call back as it did seem to be holding pressure (though with the boiler off due to broken fan) before the guy came in.

Cheers

 

[dboi78]

Fill up boiler to 2 bar isolate flow and return and if pressure goes down leak is in the boiler and rules out pipe work, won't exactly locate leak but helps to narrow it down.

 

[Bob Hill]

Stupid question: How do I isolate the flow and return- are there service valves built into the connection on the bottom of the boiler? or will I need to find another way to isolate.

 

[diamondgas]

Stupid question: How do I isolate the flow and return- are there service valves built into the connection on the bottom of the boiler? or will I need to find another way to isolate.

Touch them at your peril!! 🙂 for some reason I've yet to find a manufacturer with reliable iso valves but do get some comfort out of the more modern boilers 🙂

When you mention the pressure held in your first post, for how long did you test?

 

[stratplus]

Hi Bob,

Just a thought Bob but sounds possible to me that it could be leaking from a soldered fitting perhaps when the heat gets to it! It may be ok on a cold fill but as the pipework heats up to temperature the fitting will expand and if the solder hasnt ran properly it will leak. Have you used soldered fittings on the new rads?

I'm not a boiler engineer but don't think changing a fan will have anything to do with the wet side! It dosen't take much water for a pressure drop.

Hope this helps.

 

[Bob Hill]

Hi guys.

I found the leak hiding behind one of the rads I'd installed - Lesson, never try to solder in a chimney it doesn't work well!

System now working fine - Thanks for the advice 🙂

 

[Centralheatking]

Hi Bob

Your prob is of interest to us so if you have time can you go on to

centralheatking@btinternet.com and we will reply with a few
questions


Thank you