This is rather overdue. My plan is to check the safety PRV, clean the filter in the combination valve, check/adjust the air pressure in the expansion vessel, and check the operation of the over-temp stat. What didn't I think of? Are there any gotchas when getting at the filter?
Bah! Typo alert! "safety PRV" should, of course, be "over-pressure release valve".
I would say you have all the required bits covered in a general case:
IME many are fairly simple strainer type arrangements - designed to catch large particulate stuff mostly. Normally a case of unscrewing a cap on the enclosure, withdrawing a mesh basket and giving it a clean.
Don't do it on a day where you can't get a new PRV/"overpressure relief valve"?
They like to leak after being tested/disturbed, and this is exacerbated by doing it on day where there are no spares available.
Thomas Prufer
How are you going to test the overheat stat?
Tim
Just check if it's gone open circuit
Mine's adjustable so I'll just turn it down a little
:-) I've had that problem once before, but got it to seal eventually
I had a problem with some corrosion / hard water scale on the metal mating surface of the PRV that was causing it to let by very slightly. And yes this was on a day where getting a spare (which was manufacturer specific) would have been tricky!
I fixed it by resurfacing the metal part. I had a set of small dremmel style tools - one was a ~15mm grinding wheel on a mandrel. I put that in a pillar drill, and used light even pressure to grind the surface of the valve using the side of the grinding stone.
Hmm, getting to the strainer in the Caleffi multibloc valve is defeating me at the moment. The only info I can find says that the cartridge can be pulled-out by pulling on the bolt head once the grey plastic cap has been removed, but the cartridge won't budge.
I'd prefer not to remove the whole valve and work on it on the bench because it's in an awkward place that would be hard to protect from water loss, and the pipework around it is quite tight.
I presume the bolt sets the operating pressure, rather than retaining the cartridge(?), so do I just pull harder?
Are you sure? Isn’t that just a regular immersion stat? The overheat stat is a secondary stat that needs manual resetting.
Tim
I'm sure.
I'm sure. The emergency stat has both a tweakable and a fixed stat in series. The immersion heater has its own stat, so has the DHW controller (and, FWIW, the DHW circulation pump) ...
I've found a cross-section drawing now which confirms that the answer
*is* to pull harder ... but the damn thing still won't budge. I'm beginning to think that I'm going to have to remove the whole valve - unless someone has a bright idea ... ?
Is the valve working? If so, I’d just leave well alone.
Tim
The hot flow has decreased so the filter screen needs cleaning, and to do that the cartridge needs to come out :-( Slightly annoyingly, the cylinder PRV is functionally redundant because I fitted a PRV that limits the pressure in the whole house ...
I gave-up trying to pull the cartridge out so decided to replace the whole combination valve - the job was much simpler than I'd anticipated and the valve only cost £41. I needed to release some pipe clips to get enough movement but the job was done without draining the tank and without *any* water loss - hydraulic locks can be useful. With the old valve on the bench I still couldn't pull the cartridge out of the housing but a quick tap with a punch through it's rear end (a secondary regulated pressure outlet) and it came out easily. The filter had a fair amount of crud in it but the moving part had scale around the shaft and I suspect that was upsetting its operation. It's all cleaned-up now and in a box in case it's needed in the future. It was good to tackle a job and find it much easier than I'd expected.
Good to hear!
Which reminds me I ought to service mine!
What has surprised me is how great the showers are now - when things degrade slowly over a long period it isn't easy to spot the degradation ... until it's rectified. The improvement can't be explained by the amount of crud on the filter so it must have been the scale affecting the piston "thing"'s movement. Note to self: it is worth cleaning and descaling the magic PRV gubbins annually.
Yup. I was noticing that I could not get my shower as hot as I would like. The cylinder was still heating to the correct temp. I was about to look at the thermostatic shower valve, but then SWMBO mentioned that she did not think the water from the hot taps was as hot as it once was. So I looked at the thermostatic blending valve I had installed on the outlet of the cylinder. I had left it set at its maximum output (low 50s IIRC - just enough limit to protect against scalds but leave enough "headroom" in the hot water to allow mixing down at point of use.
So I cranked that all the way down to minimum and then all the way back up to max, and the hot water was back to normal. So it seems that was getting stuck somewhere as well.
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