Investigating Ideal Combi Logic+ C24 losing pressure

grumbler

macci85 said:

Both discharge pipe go to the same pipe outside into the soil. I cut them last year....

Do you mean both the condensate pipe and the pressure relief pipe?

It's OOT, but AFAIK the relief pipe outlet is supposed to be visible - either inside ('tundish') or outside.

And condensate, unless it goes to drain, normally goes to a limestone soakaway, not directly to soil (because it's slightly acidic).

ThisIsWeird

macci85 said:

I've kept track of the pressures this morning with times and F/R temperatures:

 06:40   1.5bar   18 -> Turned heating on
 07:10   2.0bar   60 -> Turned heating off
 07:15   1.6bar   50 -> Shower used
 08:22   1.2bar   50
 08:52   1.1bar   44
 09.02   1.0bar   42
 09:32   0.7bar   38
 09:38   0.6bar   35
 10:02   0.4bar   35
 10.32   0.2bar   32

  I turned the boiler off and closed the F/R valves yesterday night with a starting pressure of 1.2bar and this morning it was at 0bar. Not sure they are at full 90deg, this is the max I can turn them: 

Both discharge pipe go to the same pipe outside into the soil. I cut them last year and there was no water from the PRV for a few days. Some drops from the condensation pipe with boiler off and cold. For both experiments the pressure was still going down.
I could try to check that again if helpful.

That is a very significant drop in pressure, so should amount to a good few cupfuls of water, I'd have thought = more easy to notice.

Do these isolating vales turn fairly smoothly? Ie, they may be 'stiff', but should turn smoothly, and stop with a firm 'end'?

I'm guessing you are turning them the right way, but the position shown in that pic would normally suggest to me 'open', but the valve is an angled type, so could be different.

Anyhoo, could you show us the pipe outside the house, please? And, yes, after you shut off the boiler for the night, and isolate these three valves (F,R & mains in), a rubber-banded bag over the pipe would be useful. There should only be a couple of spoonfulls left from remaining condensate, if anything, but I'd expect that sort of pressure loss to produce a very noticeable amount of water.

When the boiler is cold, repressurise to 1.5 last thing.

jefaz07

grumbler said:

macci85 said:

Both discharge pipe go to the same pipe outside into the soil. I cut them last year....

Do you mean both the condensate pipe and the pressure relief pipe?

It's OOT, but AFAIK the relief pipe outlet is supposed to be visible - either inside ('tundish') or outside.

And condensate, unless it goes to drain, normally goes to a limestone soakaway, not directly to soil (because it's slightly acidic).

Correct. It’s incorrect. It needs to go into a tundish, and an approved one such as a TeslaTun or HotUn. The condensate can go to soil via a soak away.  

macci85

Yes, they turn smoothly and then they are firm.

Yes, both the condensate and the copper PRV pipe go into the same pipe that goes outside of the house down from the first floor to the ground and then in the soil.

I've done the test suggested last week, without closing the F/R valves, the pressure went down an only a few drops went out of the condensation pipe (I had to cut it to check any water coming out). I can retry closing the valves.

ThisIsWeird

Wow. I'll let other comment on whether that whole discharge and condensate pipe setup conforms to regs.

You are sure you can capture all the contents from that pipe end? If so, yes, worth trying that again.

A thought - you had to cut that pipe as it went into the soil? Does it look as tho' it goes into a buried perforated container full of lime chippings? If there is a container there, it should be openable. If it doesn't, expect all these pants to die horribly...

It's a shame you cannot separate the discharge from the cond, but repeat your test regardless. All three stop valves (not the gas...) closed.

If the pressure has fallen, then note the level and repressurise to the 1.5 'test' pressure, and then open an isolating valve.

Ganga

ThisIsWeird said:

Wow. I'll let other comment on whether that whole discharge and condensate pipe setup conforms to regs.

You are sure you can capture all the contents from that pipe end? If so, yes, worth trying that again.

A thought - you had to cut that pipe as it went into the soil? Does it look as tho' it goes into a buried perforated container full of lime chippings? If there is a container there, it should be openable. If it doesn't, expect all these pants to die horribly...

It's a shame you cannot separate the discharge from the cond, but repeat your test regardless. All three stop valves (not the gas...) closed.

If the pressure has fallen, then note the level and repressurise to the 1.5 'test' pressure, and then open an isolating valve.

Why are their trousers in trouble ? 

macci85

Thanks for the comments! Pretty annoying that the surveyor didn't tell me anything about this boiler piping when I bought the house.

Anyway, I managed to run the test:
1. Wait for boiler cold 
2. Repressurised to 1.5 bar
3. Closed the isolation valves
4. After 3h the pressure dropped to 0.8bar, no water coming out from both PRV and condensation pipe
5. Repressurised to 1.2 bar
6. Opened the isolation valves, no movement on the gauge.
7. Pressure started dropping again as usual.

ThisIsWeird

A 1.5 to 0.8 bar drop in 3 hours is clearly significant. That usually makes it easier to trace!

I'm stumped.

You isolated three valves? Now't is coming out from the cond/safety pipe, and now't is dripping out the actual boiler. (your cond/safety pipe cannot possibly be leaking out via a joint, so giving a false reading.)

So, where is the pressure loss taking place?! 

Assuming that the F&R isolating valves are not letting-by, and that would be unlikely, I can only see two remaining options. One is that the EV diaphragm is perforated, so the air side is seeping through to the water - system - side, and that air is then being expelled via the auto air vent, but this issue has surely been going on for far too long for this to still be a possibility - the EV must surely be empty of air by now, and full of water, so cannot keep being responsible. And the other is that there's a perforation in the P2P exchanger. This could allow the system water to seep out into the DHW pipes, but for this I'd expect some signs to be visible in your hot water if you, say, fill a basin - I'd expect some signs of chemicals. And, when the mains feed to the boiler is reinstated, I'd expect the system pressure to fluctuate, and rise to whatever your mains pressure is.

None of these possibilities seem plausible, so I'm stumped. :-(

macci85

Thanks for the support!  

It could be that the the valves were not actually well closed (I can't force more than I did) and that there is a real leak somewhere in the property, I would guess downstairs as as you say there should be a lot of water leaking and there should have been some signs in the ceilings had it been upstairs.

I guess I'll have book a leak detection to try to solve the mystery!

ThisIsWeird

macci85 said:

Thanks for the support!  

It could be that the the valves were not actually well closed (I can't force more than I did) and that there is a real leak somewhere in the property, I would guess downstairs as as you say there should be a lot of water leaking and there should have been some signs in the ceilings had it been upstairs.

I guess I'll have book a leak detection to try to solve the mystery!

These valves do (should) shut off pretty securely in normal use. They should in fact shut fully off before they are turned the full 90o. Unless they are truly faulty - and this would usually be detected by 'sloppiness' in their movement - then you can be fairly certain that they are shutting off. (By 'sloppiness', you might find that, during a mid-turn, you will find 'play' if you then turn it backwards. Ie, you'll sense a looseness where turning the handle back and forth is having no effect - it is 'loose'.)

As you say, you'd expect such losses to show up somewhere, but if some pipes are under the downstairs floor, then it wouldn't be obvious.