new boiler losing pressure

Possibly. Have you got lots of rads? Are more being used now if TRVs are opening?

its a 3 bed bungalow with a normal sized rad in each room. pretty sure the filling loops properly off.

seems strange that its been fine tho for 3 weeks, then just goes again.

pretty sure the filling loops properly off.

The valve taps might be turn fully off but that doesn’t mean it isn’t faulty slowly leaking into the boiler.

Filling loop should be disconnected when not in use to prevent the possibility of the water in your heating system getting back into drinking water supply.

What exactly did the engineer change / repair / tweak. If you can’t tell us that all we’re doing is guessing. Unless your engineer replaced the pressure vessel completely I would guess all he did was recharge it hence the fact it’s now gone again. We had ours replaced before Christmas and it’s been fine since, it did work for a while after I pumped it up despite the membrane having completely failed but it would have slowly lost the charge.

So disconnect the filler loop (legal requirement anyway) and work out exactly what was fixed last time around.

If you can’t tell us that all we’re doing is guessing.

yeah, fair point. he recharged it i know that, but didnt replace it. all he replaced was the PRV.

We had ours replaced before Christmas and it’s been fine since, it did work for a while after I pumped it up despite the membrane having completely failed but it would have slowly lost the charge.

sounds a possibility then, fits in with whats happened here.

So disconnect the filler loop (legal requirement anyway) and work out exactly what was fixed last time around.

i dont know how to do this. if its a legal requirement then surely hes done that himself?

thanks chaps, ill be on the phone to them this morning…..

Can you just get the system hot and turn off, then try releasing pressure from the expansion vessel. If it’s dud then there will be very little air to release?

Not sure thats a good idea unless the OP wants to get scalded.
Better to check the pressure when COLD.

Sadexpunk where you?
I’ll have a look if your near enough.

Not sure thats a good idea unless the OP wants to get scalded.
Better to check the pressure when COLD.

how exactly are you meaning for me to do this?

Sadexpunk where you?
I’ll have a look if your near enough.

im in lincoln mate. thanks for the offer, very kind of you.

ive got a call booked for tuesday now.

Bigyinn… Should just be air but fair point. But when cold there would be less pressure in the expansion vessel anyway. Suppose you could achieve the same by just taking a reading from a bike pump.

ive been an engineer for 20 years

first off can we stop calling this guy an engineer. Unless he designs the boilers I very much he is an actual engineer.

OP first thing I would do is get the installer out (if you trust him) to drain the system and move the filter to the boiler inlet. Give it all a good flush and replace the PRV again and check the expansion vessel is adequate. I wonder if it would be possible to fit one where the splice in the boiler outlet piping will have to be when the filter is removed.

Do you have 1 radiator without a TRV where the thermostat is? If not you could be shutting off all the rads but the boiler still thinks it needs to be on, I would have thought it would detect the return flow was too hot before it did any harm though.

Did the installer supply the boiler or did you buy it and have him install? If the former then after so many faults I would think you soon have grounds to reject the boiler and ask for another brand to be fitted if the fault is due to the boiler and not some old part of your system. The filter in the wrong place does complicate things a lot but only as far as the manufacturer warranty is concerned, the installer on the other hand does seem to be responsible for putting it right.

just spoken to the installer andy, before i read your post. i asked about the filter placement and he said there was no room to put it on the return side near the boiler. the only other place would have been in the loft, and they tend to get forgotten about up there and not cleaned out yearly. not quite sure about that explanation myself, but for now ill accept it.
1. what are you suggesting goes in the ‘splice’? another expansion vessel? should that really be needed?

2. all radiators have TRVs. the thermostat is on the wall in the hall. theres 1 radiator also in the hall with a TRV.

3. installer ordered the boiler from internet, delivered to our house and then installed it. obviously a legit sale tho as ideal have it on their records and are honouring the warranty.

thanks

The rad in the hall MUST NOT have a TRV on it.
The two will not get on and cause you issues as neither one knows which one is switching.

really?? ive had these thoughts to myself before….. whats best, crank the thermo up to max and control with TRVs individually, or set the thermo at reasonable temperature and then the TRVs and hope each one gets hot enough….

ive never heard that a hall radiator shouldnt have a TRV on it tho. and why just that one?
and why would they get confused? the wall mount will switch off as soon as it hits a certain temperature, and surely the rad will do the same, hit a temperature then switch off. in fact why would they need to know what the other is doing?

oh, and i assume this is nothing to do with the boiler no? that shouldnt be happening regardless of whether the hall rad has a TRV….

thanks

1. Just a precaution if it did turn out you needed one. As you will already have a break in the plumbing there (if moving the filter to the correct location) then it could reduce the work. You shouldn’t really need one though.

2. As hammy says above, you will get stuck in a feedback loop where they compete against each other. if the TRV is set lower then the thermostat will never shut off and the boiler keep going and going until it detects the return flow is too hot as the heat is not being dumped. Fully open the TRV or take the top off completely and put a cover cap over it so no one can adjust it.

3. My concern was just that he could try and walk away and claim no responsibility if you supplied the boiler. As he has supplied the boiler you may have more rights to have him make sure it all works correctly.

2. struggling to get my head around this one…. 😀

if every TRV is set low say, then you say the thermostat will never shut off as the ‘set temp’ on the wall is never reached and the boiler will keep going. firstly, why would the boiler keep going? nothing is calling for any further heat. and secondly, i have a TRV on the hall rad and the boiler isnt running all the time. so does that not disprove that theory? (not that im trying to disprove you :-))

EDIT: come to think of it its not on all the time as its on a timer too, 2 hrs morning, 2 hrs evening.

EDIT EDIT: so youre saying that for those 2 hrs on the timer, the boiler will be running all the time even if the rads have all reached their desired temp? whats happening to the hot water? just circulating around the system but bypassing the rads?
so the boiler is only ever doing what the wall stat is asking, doesnt listen to the rads at all.

thanks

with regards to the filter position – there is a reason you filter engine oil before it goes into your engine. Same principle here. Little bits of rust will come off the inside of your rads and find their way into the heat exchanger of the boiler where they may well get stuck before the filter on the outlet so by moving the filter to the return the water gets filtered just before it accesses the boiler. The inlet and outlet pipes are close to each other on the boiler so I don’t see why it couldnt have been done properly first time round.

As for cleaning the filter it’s part of the service. Put a sticker on the boiler saying the filter is in the loft and make sure he or whoever else does the service goes up there to flush it when doing the service.

the TRVs are mechanical with no electrical feedback to the boiler (unless you have a smart electronic system).

The boiler is controlled by the thermostat/programmer so is on when the timing says it needs to be on and only until it gets to temp. It will then fire up as and when needed to maintain that (I am simplifying so ignoring modulation etc)

If the TRV is set low then it shuts off the hall radiator so the hall doesnt reach the thermostat cut-off temp so, assuming your timer is still in an on period, the boiler will keep going. The other rads will then get more flow and eventually they will shut off. Then you have no rads dumping heat which the boiler doesnt like. It should self protect though before it needs to vent, or at least that is my limited understanding and how I would expect one to be designed. The PRV should be there in case of a more serious fault.

It would be worth a check though by removing the top off the hallway TRV and seeing how it goes. Also remove the fill loop if you can to rule that out. Might also be worth checking all the rads are hot to rule out air locks etc.

yeah good point. ill do that anyway, no matter what ideal bloke says. ill take a pic of the boiler when im there tuesday (just about to move into the house again after period of renting it out) so you can see the location.

thanks a lot

EDIT EDIT: so youre saying that for those 2 hrs on the timer, the boiler will be running all the time even if the rads have all reached their desired temp? whats happening to the hot water? just circulating around the system but bypassing the rads?
so the boiler is only ever doing what the wall stat is asking, doesnt listen to the rads at all.

You got it.

Only feedback is a mechanical one where the boiler can go “hang on, the water is coming back just as hot as it went out” Maybe on a system with a small expansion tank that is enough to trigger the PRV?

thanks, very interesting. not much of a plumber meself, is it easy to take the top of a TRV or do i need special ‘plumber tools’ 🙂

and is it the same result if i just crank the valve to max and leave it there?

It’s a “hand job” if you’ll pardon the expression.

No tools required 🙂

Just grab the ring and twist 😆
Thats the little one under the big knob…

I’m not knowledgeable at all when it comes to plumbing, so apols if this make no sense, but:

We had similar issues with a brand new pressurised system in our last house. Turned out that the previous ownners (or their plumber) had not added any corrosion inhibitor stuff to the water in the system. This caused corrosion in the pipes and the release of bubbles, which meant that the system was regularly over-pressuring when hot (air expands more than water when hot). The system then dumped excess pressure by releasing water though an overflow pipe and then dropped to a very low pressure once cold again. Queue me topping it up again, and again, and again.

I didn’t believe the plumber to be honest, but adding the inhibitor fixed the problem. Problem was spotted because the water was always milky in appearance when bleeding the rads (full of little bubbles).

Hope you get it sorted – my system was driving round the bend when it was playing up.

ok, update time.

different engineer this time, and he thinks hes found the problem. hes thinking there was a pinprick hole in the expansion vessel, allowing water to get in slowly. he said there was water in the bit where it shouldnt be. id have thought the first engineer would have spotted that, but no matter, we’re hopeful its sorted.
he also talked about the ‘one rad with no TRV’ but instead of the hall rad, he suggested the dining room, some distance away from the wall stat. something about if you do the hall rad then itll tell the wall stat that the house is hot enough too quickly, and the rest of the house may feel cold. seemed to make sense at the time and he took the valve off.

he also changed the vessel for a smaller one as he didnt have correct size. he looked at the system and how many rads i have (10 i think) and said that the 8 ‘something or other’ should still be fine rather than the 10 that he removed.

he didnt make much of the incorrect placement of the filter, but said ideally it should be moved. i forgot to take a pic to post but he agreed space would be tight, and that if it was in the loft then theres access issues(?). he would suggest extra pipework in the tight spot to bring it out from the wall a bit. i asked if the extra 90 degree elbows would cause any ‘flow issues’ which he said was a fair point, maybe.
so im no better off with that really, but im still thinking it would be better off on the return side. dont think the original fitter will be too keen to move it at no extra cost tho and theres certainly no way i can force him to if its not a mistake as such. even some gas safe engineers are saying its no big issue :-/

thanks

Sounds like (or, I hope) you’re sorted now. Only just seen your thread, but FWIW, we had the same problem for about 12 months, since we had the system drained for a bathroom refurb. Our local CH plumber (also a keen MTBer:)) serviced the boiler last week and fixed it – it was the pressure vessel. He said it’s a fairly common problem and he see’s a lot of people where other CH ‘engineers’ haven’t spotted it – so people can end up throwing a lot of money at the problem. I’d got so worried about potential leaks that I’d been under some of the floors checking – the local fella fixed the problem with a new valve core (about 10p worth!) and a bike track pump.

HTH
p.s. If you need the number of our local guy, gimme a shout. He’s in NE Sheffield but I guess he might cover Lincoln(?)

he also talked about the ‘one rad with no TRV’ but instead of the hall rad, he suggested the dining room, some distance away from the wall stat. something about if you do the hall rad then itll tell the wall stat that the house is hot enough too quickly, and the rest of the house may feel cold. seemed to make sense at the time and he took the valve off.

Put the TRV back on. The bloke doesn’t understand how a thermostat works.

If you find that the hallway reaches temperature before the rest of the house, what you need to do is adjust the lockshield valve on the hall radiator to reduce the flow, and hence increase the time it takes to heat the room.

And this “engineer” is allowed to work with gas and unvented cylinders…

p.s. If you need the number of our local guy, gimme a shout. He’s in NE Sheffield but I guess he might cover Lincoln(?)

thanks mate, ill mebbes need to take you up on that sometime.

Put the TRV back on. The bloke doesn’t understand how a thermostat works.

If you find that the hallway reaches temperature before the rest of the house, what you need to do is adjust the lockshield valve on the hall radiator to reduce the flow, and hence increase the time it takes to heat the room.

And this “engineer” is allowed to work with gas and unvented cylinders…

haha, its never simple is it!! not having much luck with these engineers…..anyways, a new word for me to get my head around now, lockshield valve? me not know what that is or how to adjust it.
also, how do i know if the hallway reaches temp before the rest of the house? may seem obvious, but is it? hall rad heats hall to 62 say, knocks off wall stat cos ‘house is now required temp’. if another room feels a little too cool, i wouldnt know whether it needed its own TRV turning up a notch, the ‘lockshield valve in the hall reducing’, or whether that room is indeed ok and im being a donut. open plan lounge/diner with a rad in each section, is it just cool here cos its near an outside wall? without a temp gauge going round each room saying “ah, still 1 degree short here” itd be hard to know how to balance everything.

whats his mistake then, cos it sounded reasonable when he explained it. ‘a radiator remote from the wall stat needs to be able to ‘waste excess heat’ rather than the one near the wall stat doing so and knocking off the stat prematurely’…..

thanks a lot