What can cause boiler to not heat water properly?

JustAnotherSaver

Wife has just ran the bath and the water is just coming out warm. Actually it's probably more lukewarm as warm suggests it's not too bad. I could hold my hand under the hot tap fine enough without it even coming close to uncomfortable never mind actually burn. The boiler pressure when the hot tap was running was 2bar which on this boiler is getting towards the upper end of the green section.

We've had issue in the past where the shower would be hot and then go literally stone cold before going hot again and then stone cold and it may even stay stone cold for the rest of the shower. This was maybe 2-3 years ago now. Plumber came out and wouldn't you know it - like when you take the car to the garage, the water didn't act up when he was out. He flushed some radiator looking thing with chemicals that was inside the boiler and it was fine after that.

Typically we're coming to the end of our time off which means unless things go really bad then it's going to be March before we can get anyone out and tie it in with annual leave. Just wondering what can cause this from a curiosity standing as unless it's a simple case of push this button then i'm not about to start messing with it.

The boiler is a Worcester 25Si Greenstar https://www.screwfix.com/p/worcester-bosch-greenstar-25si-gas-combi-boiler/2277h.

From looking at paperwork i think the previous owner had this installed around 2011-2012. We bought the house late 2013 but only moved in in early 2015.

Jeepers_Creepers

Almost certainly the original hot/cold fault was caused by a partially blocked Plate-to-Plate exchanger. These have very fine channels in them, and are prone to blocking up if there's sludge in your system.

(The P2P exchanger is a series of flat plates with water channels squished tightly together.  The heated water from the main exchanger (the 'boiler') is circulated through every second plate in this P2P exchanger, and the cold mains water is passed through the others and is therefore heated up instantly. Because the channels are so small, any sludge builds up on the surface and eventually stops the boiler water getting through - the boiler overheats, turns off the flame, cools, turns on the flame, overheats, turns off the flame, cools, etc.)

Your current symptoms are different - the water seemingly just not getting very hot rather than 'cycling' - but chances are it's the same issue.

Do you have a magnetic filter fitted? (Not that they are the full answer, as I've found to my cost...)

JustAnotherSaver

Yes that's what it was. Now you've said it it rings a bell and it was that.

Back then i think we had been running the central heating with no inhibitor as we had had a leak (caused by myself) the whole thing had drained out and when the emergency plumber came out and sorted it, when i found out about this additive called inhibitor way later i realised he hadn't added any, neither had we (as we were ignorant to it all) so it had been running for months without.

Then we had that guy come and sort that P2P exchanger you mention.

He sorted that on the day and then he came back IIRC a couple week later and did a total flush of the system. They were banging the radiators throughout and had some machine to flush them. At this point they also added in that Adey magnetic filter but i since learned on YouTube that Adey must do at least two of these and we got the midget size and not the full size one.

Jeepers_Creepers

Ah, they did a decent job, then by the sounds.

Has that filer been checked and cleaned regularly?

I fitted a GlowWorm combi on to an old system, and had cleaning chemicals running through it before the install. I've still had repeated problems with P2P exchangers blocking since then, even tho' I fitted a Magnacleanse (the professional 2- cylinder device) and had various chemicals added to give it a further clean for a couple of months. I'd always collect a fair amount of sludge with this device, and then I fitted an Adey Pro as a permanent fixture. Despite all this, new P2Ps block up every year or so!

Two things I've discovered: (1) it doesn't take much sludge to block a P2P given a year or so of build up, and (2) a magnetic filter doesn't catch everything - it can allow enough through to still cause a gradual blockage. (I keep my filter clean - checked every 6 months or so, and the small deposits wiped away.)

Oh, and (3) I can now swap the P2P in this boiler in about 20 minutes... :-( 

JustAnotherSaver

The Adey? No I wouldn't say it's been cleaned regular.

I don't know how much pressure loss is 'acceptable' over a given timeframe. IIRC he put us at 1.5bar and over some months we had dropped to either 1 bar or the red zone, i can't remember now. So i pressurised the system. It started losing pressure so perhaps 6-8 months in i dosed the Magnaclean pot with some inhibitor. This is when i found out that it was smaller because on the YouTube video the guy put a full pot in and i could only put say half a pot in or whatever it was.

There wasn't really a lot of dirt on the magnet. There was some that washed off but i was expecting quite a lot and there was nothing really.

Then i booked the guy in December 2019 ish for a service as the boiler had started making a right noise. The same guy that fitted it. I wasn't in for this so i couldn't honestly tell you whether he checked the filter or not but if not then the only time it has been checked since being fitted late 2018.

Hmm that's worrying. I've got my dates all wrong here. I was just typing that out going off memory. I'll leave it in all the same. I've just checked my emails and the flush and magnaclean were done Dec-2017.

He came out again for a service Dec 2018 by the looks of the invoice.

I've only checked the Magnaclean once myself and i thought it was about 6 months after they fitted it, but perhaps it was mid 2019.

I'm pretty sure that he came out December 2019 for a service because i remember him being quite difficult to track down and he no longer replied to emails as quickly as he had done ... but i don't have an invoice which is strange.

I do remember asking him how long I should leave between services and he said something on the lines of 12 months but should be ok with 18 months because i remember thinking that's ok - i'll book him in with a May holiday then. I just can't figure out why i've no invoice for December 2019.

Depending how often you should keep on top of it, it hasn't been kept on all that regular i guess.

If i pressurise to 1.5 bar then for it to get in to the red zone (so maybe 0.6 bar loss) could take maybe 4-6 months at a guess, thereabouts.

Myser

You may want to empty the Magnaclean more often.  The state of the contents will give you an idea of whether there is sludge system.  Plenty of videos online showing you how to isolate the valves either side and detach the filter housing.

Your gradual pressure loss may be a weeping joint or from the pressure relief valve pipework.  Have a look for any green staining near radiator valves and also see if the discharge copper pipework (outside) has any signs of water exiting from it.  The best way to confirm, is to put a plastic sandwich bag around it sealed with an elastic band and monitor it over a few months.

Jeepers_Creepers

As Myser says, checking the Magnaclean ain't hard and could be interesting  :-)

However, my own experience is that they ain't a panacea. I still get blocked P2Ps even with one fitted, and that's one that doesn't get that dirty either. Thankfully, I can get new P2Ps for around £30 - and am about to try an experiment restoring them using a liquid rust remover (the sludge being an iron oxide, I believe).

The pressure loss is at the 'annoying' level but not disastrous. There's pretty clearly a drip or weep somewhere, tho', and Myser's advice is good. The pipe to check outside is the 15mm copper one, not the 22mm plastic.

JustAnotherSaver

Myser said:

You may want to empty the Magnaclean more often.  The state of the contents will give you an idea of whether there is sludge system.  Plenty of videos online showing you how to isolate the valves either side and detach the filter housing.

Your gradual pressure loss may be a weeping joint or from the pressure relief valve pipework.  Have a look for any green staining near radiator valves and also see if the discharge copper pipework (outside) has any signs of water exiting from it.  The best way to confirm, is to put a plastic sandwich bag around it sealed with an elastic band and monitor it over a few months.

I had to pressurise the system last week. I was going to dose the pot again as i knew i had half a bottle from last time but i can't find it at all. I know i didn't put it all in because that's how i found out it was only a half size and i thought i'll put the rest in the next time i have to check it. Since i couldn't find it and the system needed pressurising then i just went ahead without checking the magnaclean. I'll have to have a gander in there.

2 questions regards inhibitor:

1) Can you mix? Right now there's some MC1+ in there. Could i for example, just chuck some Sentinel X100 in?

2) Can you add too much inhibitor? Obviously i'm not talking about putting 50 bottles of the stuff in. It will have had 1ltr in, then it's been pressurised a few times, then it's had another 500ml to 1ltr in, pressurised a few more times.

I've had a look at some of the pipework and the only bit i can tell is the drain off tap in the kitchen which will be the only radiator that has a drain off tap. Where this meets the radiator it's not clear as anything but i always see it and think, is that more green than last time? Am i seeing things? I get a wonder wipe and wipe it to see if anything transfers and not really.

Myser

You can't really have too much inhibitor, not sure about mixing different brands though?  Best to check with Sentinel.  It can be topped up via the Magnaclean housing.

If you do see some green marks near the drain off, try tightening it a little.  It may not have been fully closed when it was last used.

JustAnotherSaver

Jeepers_Creepers said:

The pipe to check outside is the 15mm copper one, not the 22mm plastic.

Will it definitely be those two?

I ask as i remember talking to someone who said to me "just have a go" about some 'basic' plumbing job.

I told them the story about how i had to call an emergency plumber out due to flooding my living room, then the following weekend i had to call him out again for doing pretty much the same in the upstairs bedroom and having the water come through the ceiling in the living room below. All i was doing was connecting the radiator back up.

My problem is my take on 'nipping up;. It's a phrase i absolutely despise. What actually is 'nipping up'? It's why when i work on a car i pester someone for the torque settings. What's the torque settings on the sump plug on that car? Oh you just nip it up and then give another slight nip.

NO! Just give me the bloody torque settings. I have a torque wrench, i'll set it to the number and job done without disaster.

Because i have a tendency to overtighten - and that's what happened with the radiators. My thinking was that i don't want these things to leak, so is this tight enough? What if it isn't. I'll give it another turn. Hmm it may leak, turn it again, and again and oops i've just bent the pipe.

The plumber said in my defence, the pipes are 10mm, not 15mm and he's seen many damaged with hoovers.

Myser

Ah you have 10mm pipework.  That is more prone to blockages due to sludge, so all the more reason to empty the Magnaclean more often.

In terms of how much to tighten the drain off, it's difficult to give you a torque setting as it's a rubber washer that seals against the seat.  Just tighten it a little until you feel some resistance.  Once you've used the drain off a few times, you usually have an idea of how much to tighten it.  You shouldn't need to lever it much so if you have a key for it, then hand tight should be fine:

https://www.amazon.co.uk/Monument-2056d-Three-Legged-Radiator/dp/B0001P0FHM