HVAC Questions? Ask an HVAC Expert for Answers ASAP
Hello, I can help you with this.Firstly, dispel any idea that the leak is within the boiler casing. If it was, you would see water dripping from its lowest point.You might be on the right track with the expansion vessel, but first please check the pressure relief valve outlet - there should be a 15mm pipe with an open end outside. If you increase the system pressure to 2.0 bar, does this drip at all? If it's raining and making that difficult to judge, then place a balloon or a plastic sandwich bag over the end, held in place with an elastic band, and see if it fills up.If it isn't dripping, then you have a leak from a pipe or a connection, somewhere else. Ideally you need to find where the water is going, then you can trace where it's coming from.If none of the above yields an obvious cause, then closely inspect every radiator valve joint, and every vent and every plug, to check for water. Everything should be bone dry.
I don't think the loss of pressure at night isn't really a clue, but I'll bookmark it.When you say "check on the boiler", I'm really not sure what you mean. If pressure is dropping then water must be coming out, and if it was coming out of the boiler itself then you would see water.The only thing that might be near the boiler, but it might not, that could let water out is the PRV (pressure relief valve). That's why you need to locate the outlet from the PRV. Trust me - I've been presented with this symptom hundreds of times.Now a small apology - I ignored the model of your boiler earlier, and I shouldn't have done. So now I realise that the PRV for your boiler is within the casing, also the tundish, so you will have to remove the front panel from the boiler and locate the tundish. Please see the attached diagram and see how far you get.I'm not abandoning you - don't panic! If you're in Hertfordshire or London then I could help you, otherwise you will need to do this next step as part of the diagnosis, or call a heating engineer to diagnose the problem.
Apologies - that attachment was nonsense. Try this one.
OK. That a pity, as it would have been easy.The 170 model is identical in all ways except power.It's intriguing that turning off the boiler appears to have an effect.Let me have a think for an hour and I will get back to you :-)In the meantime, does the pressure ever go above 2.5 bar?
A quick follow-up...Were you able to see the tundish during the period after turning off the boiler, when the pressure was dropping?An idea - if you place a strip of folded kitchen paper across the tundish opening, you won't have to stand there watching it. After increasing the pressure you can go back later and see if the paper is wet.They probably don't need to see the QC stickers, but I'll send that photo too.
What was the pressure just before turning on the boiler?
I was using "opening" as a noun, not a verb - there should be a 'window' in the tundish which is where the drip or flow of water would be visible. Vertically above the tundish should be the PRV, which often has a red plastic knob (but sometimes black or blue).
OK. I'll describe a commonplace problem and you can see which facts fit this theory...
The purpose of the expansion vessel is to absorb increases in pressure. The EV can lose its charge pressure over months and years, and then it does nothing. Equally, it can fail internally, and then it does nothing.If the EV has lost its pressure, for whatever reason, the system pressure can rise from around 1 bar to around 3 bar when the boiler heats up. This is a problem, because the PRV will often open slightly and let some water out. When the boiler shuts off and the system cools down, the loss of water becomes evident in a lower pressure than at the beginning of this sequence.So, the clue is in whether or not there is any loss of water, through the tundish, between the boiler starts from cold, then heats up, then cools down again. Since there is more than one tundish, you need to make sure that you're looking at the correct one, or do the paper test on both of them.
I need to go out for about an hour, but I'll check in here when I get back.
OK hang on - I'll send a photo...
The tundish in this photo has water trickling through it - that's the abnormal condition.
If you could post a photo of the entire area around and below the 'TPR 15' valve, I can see what you're looking at.
I'm back sooner than I thought. Please could you attach a photo?
Excellent photos, and they explain everything.One minute, I just need to check a fact...
If you need to call me, please feel free: 07753 637786.This isn't your fault, but your Promax has been installed wrongly.It's not dangerous, as far as I can tell, but it needs inspecting and correcting. It contravenes Part G of the Building Regulations, which is illegal. Whoever installed it should be reported to the HSE, along with whoever has worked on it since.In terms of fixing your problem, it's my belief that the EV has no pressure. This is easy for a heating engineer to check , and I can guide you through it. If the EV hasn't failed then it can be recharged; if it needs to be replaced I could guide you, but you'd be better of hiring a heating engineer to do it and to correct the problems.It's also commonplace for the PRV to have to be replaced when it has been opening a lot - they tend to get sediment trapped on the sealing washer and then the washer will never seal again. PRVs are cheap, but again this is something better done by a professional.
In 35 years of working on heating systems, this is the first time I've ever seen an installer do this. I thought I'd seen everything, but this has amazed me.How old is the flat?
1. There's no tundish.2. There isn't a continuous fall in the pipework from the PRV and the T&PV.3. There might not be any visible indication where the discharge pipe emerges.4. It's illegal to install any invented vessel unless competent to do it.5. The manufacturer's warranty is immediately invalidated.The tundish is actually supplied by Potterton with the boiler, and they still didn't use it. They couldn't possibly have completed the certification, or notified Building Control about it, unless they lied. The whole installation needs inspecting.
If they didn't know what they were doing, they might have made dangerous mistakes in other flats. I can't see anything that makes me say "don't use it", but like I say it needs inspecting.
The most urgent thing is to find out where this pipe (see the green arrow) goes.
I'm certain that the CH expansion vessel has lost its pressure. I don't know about the DHW EV, but the whole installation needs checking. If any inspection is done when selling the flat, then this will be revealed at that stage and will be a problem.If any British Gas engineer has ever taken the cover off and seen what I can see in that photo, they should be sacked.
Since the flat is less than 10 years old, you could make a claim under the NHBC warranty.
Ah. 20 years. I drew the wrong conclusion.Yes - the marked pipe is the discharge pipe, so an outlet. It must be full of water, which is VERY wrong - that's a risk of Legionella bacteria growth right there.Shall I send you an extract of the relevant part of the installation instructions, so you can read what they should have done?
I'm having trouble with my PDF generator, so here's the entire manual.The pages that underpin what I've been saying are: 3, 4, 9, 25, 26, 59.Please ask if you need anything explained further.