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Getting a new boiler

Does what it says on the tin
dspp
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Re: Getting a new boiler

#382379

Postby dspp » January 31st, 2021, 10:28 am

Mike4 wrote:
UncleEbenezer wrote:It's a Baxi Combi 80Eco.


Ok I've had a look in the manual, and this was Baxi's most basic "Ford Escort" of a boiler, and comes with a wide variety of different badges on it including Baxi, Potterton and Main. A massive seller and a non-condenser killed off by the regs in 2005 which made steamers mandatory. A cheap and cheerful boiler which generally works quite well but is subject to a number of faults that should have designed out 15 years earlier. It is generally easy to fix and all parts are freely available.

It has a hydraulic diverter valve that is particularly troublesome which needs to fully divert in order for the HW to work. If it is sticky or has a perished diaphragm it only partially diverts and the boiler fails to fire in HW mode. Turning the CH on disguises the problem by making the boiler fire anyway so I reckon this is your problem causing the cold showers. There is a possible alternative but related cause. There is a pin which extends from the diverter valve when it diverts into HW position and presses a microswitch to fire the burner. The water seal around the pin degrades with age and water gets in the microswitch stopping it working. You could have either problem, or both. I prescribe a new diverter valve and switch assembly. Parts are about £150 plus mebbe 90 mins on site to fit and test.

Regarding the pressure loss, this could be a failed or flat expansion vessel causing the pressure to rise excessively then discharge via the pressure relief valve to outside. This should have been checked in the service you had done though, particularly if you reported the pressure loss to the bod. He should really have been able to tell you about the diverter problem too as is is really common on this really common boiler. If this is the problem, a plastic bag tied over the end of the PRV discharge pipe will collect some tell-tale water after the next time you re-pressurise the system. I think though, you may have mentioned NOT getting wide pressure swings so this still points to a slow system leak.

At the same time I suggest demanding a new domestic water-to-water heat exchanger if you are feeling flush as it is hardly any more work to fit this at the same time, and yours may well be contaminated which causes the HW temperature to swing up and down over about a 45 to 60 second cycle, which I think you also mentioned happening.

Finally, these boilers have a single NTC thermistor to control all the temperature functions and this too is a common fail, so at only about £25 for the part I recommend getting this changed at the same time too.

Cost to do that lot will probably be £500-£600 by a local bod, unless you decide to cut your losses and get a new one.


That is a masterly remote diagnosis, I am very impressed. It reminds me only too well of UK-designed & UK-manufactured cars from the 1970s given the known but unaddressed faults. I am encouraging my boiler, and my GF's boilers to last as long as possible so that ASHP get beyond the equivalent stage !

regards, dspp

Mike4
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Re: Getting a new boiler

#382391

Postby Mike4 » January 31st, 2021, 10:56 am

dspp wrote:That is a masterly remote diagnosis, I am very impressed. It reminds me only too well of UK-designed & UK-manufactured cars from the 1970s given the known but unaddressed faults. I am encouraging my boiler, and my GF's boilers to last as long as possible so that ASHP get beyond the equivalent stage !

regards, dspp


Thank you kindly sir!

Post the makes and models of your and your GF's boilers and I'll give you potted reviews of them....

UncleEbenezer
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Re: Getting a new boiler

#382398

Postby UncleEbenezer » January 31st, 2021, 11:18 am

Mike4 wrote:
UncleEbenezer wrote:I have a different problem. Finding any tradesmen at all willing to return my calls, let alone take on work.


Trouble is, you've chosen a really dumb time to break your boiler. Silly UncleE!


I've had the same problem in other seasons. Starting shortly after I moved in here when I found water from the shower coming through the kitchen ceiling, and needed urgent work done: then it was October 2019 I struggled to get quotes from plumbers. A typical reply was "booked up for the next six months".

I also spent all seasons last year looking for various other jobs, of which the biggest (five-figure £££££) is my new kitchen, to include new floor, new sash window, etc. The folks in the showrooms are happy to draw pretty visualisations and quote me for units and worktops, but the folks who actually do the work are elusive. Even the ones who did a great job next door two years ago!

Thanks too for the boiler diagnosis: if you were my local plumber I'd have much more confidence. I might just arm myself with that and see if I can figure out the parts you're talking about: if I can get it to fire independent of the heating then I'm back to happy-to-live-with-it-until-heatpump-season. But that cost is not something I want to bear for what may very well be a boiler that'll just limp on.

Mike4
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Re: Getting a new boiler

#382405

Postby Mike4 » January 31st, 2021, 11:39 am

UncleEbenezer wrote:Thanks too for the boiler diagnosis: if you were my local plumber I'd have much more confidence. I might just arm myself with that and see if I can figure out the parts you're talking about: if I can get it to fire independent of the heating then I'm back to happy-to-live-with-it-until-heatpump-season. But that cost is not something I want to bear for what may very well be a boiler that'll just limp on.



You're welcome. There is a workaround (better described as a mega-bodge) you could try if my diagnosis turns out to be right and the pin is simply not moving quite far enough. Devise and glue a spacer onto the end of the pin!

Download the manual here https://www.freeboilermanuals.com/asset ... 80-Eco.pdf

Have a careful look at Fig 82 on page 34, and find the "DHW pressure differential valve" inside your boiler. When you turn the hot tap ON the pin in the centre shoudl emerge and operate that microswitch in the same diagram. I bet on yours, the pin doesn't quite operate the switch. In fact if you operate the switch yourself with say a screwdriver, you should get a fright as the boiler will light! Try this to test if the microswitch is working, then turn on the shower and see if it fails to operate the switch.

Do post with the results of this experiment if you decide to try it...

dspp
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Re: Getting a new boiler

#382422

Postby dspp » January 31st, 2021, 12:30 pm

Mike4 wrote:
dspp wrote:That is a masterly remote diagnosis, I am very impressed. It reminds me only too well of UK-designed & UK-manufactured cars from the 1970s given the known but unaddressed faults. I am encouraging my boiler, and my GF's boilers to last as long as possible so that ASHP get beyond the equivalent stage !

regards, dspp


Thank you kindly sir!

Post the makes and models of your and your GF's boilers and I'll give you potted reviews of them....


That is an offer I just can't refuse :).

Mine is a gas job, never given a moment of trouble:
- Viessmann Vitodens 100-W

The GF has two oil boilers, running separate parts of the vast crumbling pile ..... :
- Worcester-Bosch Greenstar 32/50
- Grant Vortex Pro

The WB is frankly an antique, and apparently is one of the few that has escaped all the many recall/retrofits on this model, and amazingly is still going despite the last set of plumbers' attempts to kill it (not all plumbers are equal, we relocated it internally a few years ago, and they even managed to install the flue upside down ! and now it is lovingly tended by a very different plumber).

So, tell me the worst.

regards, dspp

Mike4
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Re: Getting a new boiler

#382583

Postby Mike4 » January 31st, 2021, 10:03 pm

dspp wrote:Mine is a gas job, never given a moment of trouble:
- Viessmann Vitodens 100-W


Hmmm.... Viessmann first hit the market back in about 2002 with a massive press effort with all manner of hyperbole claiming to be a whole new way of thinking about boilers and taking things to a whole new level of quality. Trying to do a "Worcester Bosch" basically but not quite pulling it off.

For example I booked myself onto one of their early technical training courses to find out all about them. 9am in somewhere stoopid like Telford and I was there on the dot, in a room with 30 other gas bods all there for the same reason. 10.30am and MD of company comes in and apologises saying training bloke hasn't turned up and he will have a bash at showing us all about it. Set the tone for the whole day and the whole company. The example boiler they had (a Vitodens 100W) didn't look a great deal different to me from a bargain basement Baxi, and the short day of training didn't change my mind.

So, sorry to say the Vitodens 100W is not a great piece of kit, but then neither is it a disaster. Just an average boiler sold for slightly above average price. The troubling bits are twofold. Firstly parts for Viessmanns are rarely stocked by boiler spares merchants and everything is mail order and secondly, parts are nosebleed money, i.e. twice the price of the equivalent part for say a Vaillant So great news that yours has never missed a beat!

They tend to suffer from a pair of rubber hoses inside, one or the other of which splits randomly. This half fills the boiler with water as per this photo posted in The Combustion Chamber a couple of days ago...

Image

But bear in mind this is all relative. I'd choose a Viessmann any day over a Halstead, Ariston, Keston, Powermax or Gulfstream any day. Loads of Viessmanns out there giving sterling service as you have illustrated, it's just that when they pack up, they cost a packet to fix.

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Re: Getting a new boiler

#383482

Postby redsturgeon » February 3rd, 2021, 10:21 pm

As luck would have it my three year old Vaillant stopped working tonight!

Showing fault F75 pump water shortage!

Texted my plumber who says it is a known pressure sensor fault and I should ring Vaillant who will send round an engineer to fix it.

He also suggested boosting the water pressure to 2.2 bar and a reset to restore heat tonight.

All working again. I'll let you know how good Vaillant after sales is.

John

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Re: Getting a new boiler

#383562

Postby UncleEbenezer » February 4th, 2021, 9:35 am

redsturgeon wrote:As luck would have it my three year old Vaillant stopped working tonight!

Showing fault F75 pump water shortage!


Thanks for sharing. A timely reminder that modern more-computerised boilers may be subject to a whole new class of problems!

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Re: Getting a new boiler

#383628

Postby redsturgeon » February 4th, 2021, 12:37 pm

UncleEbenezer wrote:
redsturgeon wrote:As luck would have it my three year old Vaillant stopped working tonight!

Showing fault F75 pump water shortage!


Thanks for sharing. A timely reminder that modern more-computerised boilers may be subject to a whole new class of problems!


So far, so good on Vaillant.

Emailed them, they called me within 30 minutes and an engineer is coming tomorrow.

John

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Re: Getting a new boiler

#383680

Postby UncleEbenezer » February 4th, 2021, 4:09 pm

Mike4 wrote:Have a careful look at Fig 82 on page 34, and find the "DHW pressure differential valve" inside your boiler. When you turn the hot tap ON the pin in the centre shoudl emerge and operate that microswitch in the same diagram. I bet on yours, the pin doesn't quite operate the switch. In fact if you operate the switch yourself with say a screwdriver, you should get a fright as the boiler will light! Try this to test if the microswitch is working, then turn on the shower and see if it fails to operate the switch.

Do post with the results of this experiment if you decide to try it...


I got around to trying that today. The boiler was last used yesterday evening.

I opened it,. found the part in question, and turned on the hot tap in the kitchen (which is near the boiler). I saw something moving, and was trying to figure out whether it should have moved further - hadn't touched anything - when the boiler fired up. It went out briefly (the up/down/up-and-stay-up cycle), but basically worked without having turned the heating on. Is it possible the nearer/greater flow of the kitchen tap made a difference there?

A couple of days ago I tried another experiment: turned the heating on, then went directly upstairs and started the shower. No hot water, so I left it 20 minutes and retried. Still no hot water and the radiator was cold! Fixed that by turning the boiler off and on again, whereupon the heating slowly and reluctantly fired up and I got my shower a bit later.

UncleEbenezer
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Re: Getting a new boiler

#383779

Postby UncleEbenezer » February 4th, 2021, 11:49 pm

UncleEbenezer wrote:
Mike4 wrote:Have a careful look at Fig 82 on page 34, and find the "DHW pressure differential valve" inside your boiler. When you turn the hot tap ON the pin in the centre shoudl emerge and operate that microswitch in the same diagram. I bet on yours, the pin doesn't quite operate the switch. In fact if you operate the switch yourself with say a screwdriver, you should get a fright as the boiler will light! Try this to test if the microswitch is working, then turn on the shower and see if it fails to operate the switch.

Do post with the results of this experiment if you decide to try it...


I got around to trying that today. The boiler was last used yesterday evening.

I opened it,. found the part in question, and turned on the hot tap in the kitchen (which is near the boiler). I saw something moving, and was trying to figure out whether it should have moved further - hadn't touched anything - when the boiler fired up. It went out briefly (the up/down/up-and-stay-up cycle), but basically worked without having turned the heating on. Is it possible the nearer/greater flow of the kitchen tap made a difference there?


repeated the experiment a couple of hours later. It fired up briefly (maybe 30 seconds), then stopped and stayed off. So the water warmed up then went cold, like my unsuccessful showers.

The microswitch appeared connected all the time, both when the boiler fired and when it had stopped. My (timid) poking with a screwdriver did nothing. So I don't think that's the culprit.

There was a sound - which I've heard before - of something like a relay clicking on and off. That also happens when the heating is stuttering. So some kind of internal switch would seem to be implicated. So I did what has become my usual this year: turned on the heating for a while before my shower.

Oh well, the weather forecast tells of another cold snap just coming, so no great hardship with the heating. Summer I could perhaps(?) work it by turning all radiators off. But I really don't fancy this when we get alternating warm and cold snaps around March/April!

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Re: Getting a new boiler

#385313

Postby redsturgeon » February 10th, 2021, 8:32 am

Just to update on my Vaillant boiler experience.

The boiler has now all been fixed under warranty. The boilerman was extremely efficient and polite. All done with strict covid compliance. Masks to be worn by all parties, pets locked away, windows open in room the boiler was in.

First visit booked for next day, but access to boiler was restricted by built in shelf underneath. New visit booked for two working days forward while I tackled the shelf.

They asked if the boiler was actually functioning when I phoned so they possibly would have been even quicker with the fix if I'd had a non functioning boiler.

John

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Re: Getting a new boiler

#400022

Postby UncleEbenezer » March 29th, 2021, 11:34 am

Just a postscript here. I cut-and-run, and got a Worcester Bosch Greenstar 2000 installed on Feb. 13th, since when my daily hot shower has felt mercifully secure. The boiler is right for this house, and having the (cheapest option) thermostatic/programmable control in the hallway is a little extra luxury.

I realise that by going to a big box-shifter I took pot-luck (but surely the same applies to a local firm if you don't know them already), but I was very pleased to get it done at an all-inclusive price of £1589, against my expectation of £2k-if-I'm-lucky. The man Warmzilla sent was from Plymouth - our nearest big city, and a very easy drive for him, and seemed very happy to be contracting for them.

Oh, and after a month and a half, the pressure hasn't sunk back into the red, so that problem appears to have been the old boiler, or something else within the scope of what he fixed/serviced.

I also got some impression of how these folks operate in lockdown: he seemed to be under some strict instructions. I said to him something like:
Normally I'd offer cups of tea/coffee to a tradesman working here, but since you're working in the kitchen and we should keep apart, better I show you where things are and you just help yourself.

But it was evidently part of his covid training not to accept anything from the customer. He'd brought his own refreshments, including a thermos.


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