Conversations with my boiler...

[Itsallaguess]

Me - You're very quiet lately

Boiler - I've decided not to work

Me - Well, it's the age we seem to be living in at the moment - is there anything in particular you're not happy about?

Boiler - You need to replace your pump

Me - Now, steady on old chap, that seems a little premature at this stage - can you give me any more details as to what's actually wrong with it?

Boiler - It needs replacing...

Me - Yes, but why, exactly?

Boiler - Because I said so...

Me - Right. You're going to be like that, are you?

Boiler - I'm afraid so...

Me - I think I'll just isolate you from the electrics and remove the cover on the pump shaft, to see if I can turn the pump impeller manually with a screwdriver and check for a seized shaft...

Boiler - Well, that's entirely up to you, but I've told you it needs replacing already...

Me - Thanks - well, I've just looked at the pump, and I can turn the impeller with a screwdriver, so that's always a good sign - are you absolutely sure it needs replacing?

Boiler - Read the fault-code, dimwit - that's what it's telling you, isn't it?

Me - Well, it is, but there's lots of things that can stop the pump working, and some of them can be fixed without necessarily needing a replacement, so I'm just making sure, if that's OK with you?

Boiler - Fill your boots. Let me know when it's been replaced won't you...

Me - Thanks - now we know the impeller, bearings, or the shaft aren't fully seized, it's going to be worth checking the pump winding resistance, to see if there's a short or an open circuit on the windings, so I'll keep you electrically isolated whilst I check, if that's OK?

Boiler - You could have ordered a new pump by now - you know that right?

Me - Yes, but they're quite expensive, and would need opening up the water-circuit to replace, which can get a bit messy, so I'm just making sure we do need to go to that trouble first...

Boiler - Well, if you continue not to trust my diagnosis, that's entirely up to you, of course...

Me - Thanks - I've dropped off the 240v supply to the pump and tested across the pump terminals, and it's showing a reading of around 125 Ohms on my multi-meter, which is about right for a working set of windings of a pump of this size, so the windings look fine from here...

Boiler - Whoopy-do. Have you ordered a new one yet?

Me - Well, let's not rush into this....Now the boiler is electrically isolated and the normal pump supply has been dropped off the terminals, I think it's probably worth setting up an external 240v supply from a socket, using a 1A fuse and a switched extension near to the pump, and we can try a very quick operation of the pump from a 'known good' electrical supply, just to see if it'll very briefly turn...

Boiler - Well, it's up to you, of course, but I've already told you that it needs replacing...

Me - Thanks - I've just briefly switched the external 240v supply to the pump on, and it buzzed a little but didn't turn...

Boiler - I told you a while ago it wasn't working - are those ears painted on?

Me - Ah, but I'm interested in the 'why it's not working', which your current 'replace the pump' error code isn't giving me any details for...

Boiler - Well that doesn't really matter to me - if you replace the pump, I should start working. What could be simpler than that?

Me - Well, not having to replace the pump might be simpler, but you're not entirely helping me with that pursuit, are you?

Boiler - I'm not sure I want to be helpful to someone who won't listen to me...

Me - Be like that then....but at the moment, we've made sure the shaft, bearings, or impeller aren't seized, and we've checked the pump windings for continuity and appropriate resistance, and we've concluded that the pump won't run from an external 240v supply.

Boiler - That's because it needs replacing, you dolt....

Me - Hang on though....what's this tubular item inside the pump connection box?

Boiler - I'm not telling you...

Me - Well, it's the starting capacitor, which most AC pumps need to initially get going.

Boiler - That's interesting - the new pump will come with one as well then, probably...

Me - Well, it would, but given how the temporary-supply test went, I now suspect that we're just looking at the starting capacitor being faulty to be honest...

Boiler - You don't seem too confident...

Me - I'm not 100% confident, no, but I've got a very strong suspicion now, given the previous test results....I've just checked on Amazon, and a 2.5µF replacement capacitor is about £6, and with another £2.50 delivery charge, a brand new starting-capacitor can be here in two days...

Boiler - So could a new pump...

Me - Yes, but with a huge increase in costs, and a much bigger job to then fit...

Boiler - Well, if you're continuing to ignore my suggestion, then that's entirely up to you....

<two days later...>

Me - The new starting-capacitor is here!

Boiler - Excuse me - I'm trying to sleep over here...

Me - I'll just swap the old one out, and put this new one inside the pump connection box.

Boiler - You do seem to like fiddling with that duff pump, don't you...

Me - Well, it's not taken too long really you know, and I do like to make sure I really do need to spend hundreds of pounds on a replacement pump...

Boiler - Suit yourself...

Me - I'm just going to turn you all back on now - can you let me know how things look?

Boiler - Slave driver...

<switches boiler on>

Me - How are you feeling now?

Boiler - Fine, why are you asking?

Me - Well you seem to be running brilliantly now, and you kept telling me that you needed a new pump...

Boiler - I said a new pump would get me going again, if you'd have listened properly, and it would have...

Me - Yes, but only because the new pump would have come with a new starting-capacitor, which is the only bit that was actually broken...

Boiler - I wasn't wrong then...

Me - Well, you weren't wrong, but you also weren't as helpful as you might have been, but as I'm in such a good mood after an £8 boiler-repair, I suppose I can let you off just this once, but before I go, are you able to tell me how many expensive pumps get swapped out when they're actually fine, and they only really need a new £6 starting capacitor?

Boiler - I wouldn't tell you if I could...

Me - No, I'm sure you wouldn't...

Cheers,

Itsallaguess

[GoSeigen]

Just been having a similar conversation with two or three old laptop adaptors, now expecting a shiny new £80 adaptor to be delivered in a couple of days...



GS

[DeepSporran]

Excellent. A very entertaining tale with a happy ending.Thank you !

[BullDog]

A terrific story. So sad in these days of environmental awareness that 99.9% of the time a plumber would be called, a new pump fitted and the old one sent to landfill.

I recently had a not dissimilar experience with a washing machine motor. The machine was still under warranty. I said to the repair guy "new carbon brushes?". The reply was that new carbon brushes would almost certainly fix the fault but he was fitting a new motor anyway. He did. I kept the old motor and this thread has just reminded me to buy a set of carbon brushes for the removed motor which is now my spare.

[Boots]

Thanks for such an entertaining tale. It's really nice to fix something, rather than throw money at a solution with a lot of waste.

[Tedx]

Very often I find youtube comes up with answer to queries similar to IAG's

For example, many years ago, I had a Samsung flatscreen telly. One morning I turned it on to fid the picture leaping all over the place. Google/Youtube directed me to a small screw in panel on the rear/side of the tv. Behind the panel there was a small circuit board with plug in socket. Unplug that, Youtube said, and you won't be able to change channels using the buttons on the TV (who does that these days!?), you'll only be able to use your remote....but you're problem will be fixed.

And it was. For nothing. I'm just glad it wasnt the other way around and I'd have to get up and change the channel. I might have had to adopt a child to lie on the floor and change channel for me (because that was my job when the old man was watching the box)

[stewamax]

If the impeller was irreparably seized, the head - the part that does the work - is probably all you need. So before you buy a new pump, it's worth checking if a replacement head is available, as they are for the ubiquitous Grundfos and Wilo domestic pumps.

And it is easier to fit: unplug the power supply at the head, shut the gate valves either side, unscrew the head (typically four hex bolts needing a standard Allen key), screw in the new head, open the valves and plug in the power supply.
Job done.

Cheaper, and no need to disturb the 28mm valve fittings that need big wrenches.

And your boiler will never know the difference...

[Mike4]

I'd say about 50% of old skool pump failures are start capacitor failure. The only puzzling bit is where you got a new one for six quid! The caps that fit inside Grundfos pumps are slightly smaller in diameter than standard start caps and generally cost me about thirty quids.

I carried out a similar fix on the air circulation fan on a BRINK warm air boiler in a church hall a few weeks ago. A new fan was over £1,400 but all it needed was a new start capacitor for a tenner. Happy church.

[servodude]

I'd say about 50% of old skool pump failures are start capacitor failure. The only puzzling bit is where you got a new one for six quid! The caps that fit inside Grundfos pumps are slightly smaller in diameter than standard start caps and generally cost me about thirty quids.

I carried out a similar fix on the air circulation fan on a BRINK warm air boiler in a church hall a few weeks ago. A new fan was over £1,400 but all it needed was a new start capacitor for a tenner. Happy church.

Why do they always fail? Built in obsolescence?
Under rated? By everyone, always?
Old pumps taking longer to get to speed so the start cap is in use longer than it was "designed" for?
Just one of those "that's how it is" things?

[BullDog]

I'd say about 50% of old skool pump failures are start capacitor failure. The only puzzling bit is where you got a new one for six quid! The caps that fit inside Grundfos pumps are slightly smaller in diameter than standard start caps and generally cost me about thirty quids.

I carried out a similar fix on the air circulation fan on a BRINK warm air boiler in a church hall a few weeks ago. A new fan was over £1,400 but all it needed was a new start capacitor for a tenner. Happy church.

Why do they always fail? Built in obsolescence?
Under rated? By everyone, always?
Old pumps taking longer to get to speed so the start cap is in use longer than it was "designed" for?
Just one of those "that's how it is" things?

Capacitors have a finite life before they stop working.

[88V8]

Capacitors have a finite life before they stop working.

I have a 'soft-start' in-line extractor fan, I'll try to remember this thread if ever it stops working.

V8

[Itsallaguess]

I'd say about 50% of old skool pump failures are start capacitor failure.

The only puzzling bit is where you got a new one for six quid!

The caps that fit inside Grundfos pumps are slightly smaller in diameter than standard start caps and generally cost me about thirty quids.

Sizing of the starting capacitor was important for my Vaillant pump as well, as it looked quite stubby and there was a round securing clip inside the terminal box that I was keen to make continued use of if possible, rather than having things floating around inside the box.

This was the 450v rated 2.5μF starting capacitor I bought in the end, which had exactly the same dimensions (25 x 51mm) as the one being replaced -

Miflex 312765 Start-up capacitor motor capacitor, 2.5μF, 450V (£6.04) -



https://www.amazon.co.uk/Start-up-capacitor-motor-25x51mm-Miflex-grey/dp/B01CSXOMZA

There's a wide range of other capacitance ratings available on the above link, so I hope it might come in handy as a cheaper equivalent option for you.

I'm glad that people enjoyed the story. I should probably add that my Vaillant boiler is about 25 years old at this stage, and it's been a great and reliable workhorse throughout, with only a few relatively minor maintenance issues over that time.

It might be a grumpy old bugger, but I'd buy another Vaillant in a flash when it eventually grumps out completely on me...

Cheers,

Itsallaguess

[jfgw]

If your boiler is talking to you, you should probably stop taking those tablets that the doctor has recently started prescribing for you

Technical point:

A start capacitor is connected in series with the start winding and a switching device, usually a centrifugal switch or an electronic start relay. Once the motor is up to speed, the capacitor is disconnected. It is rated for about 275V.

A run capacitor is connected permanently in series with the start winding. It is rated for about 450V.

A motor may have either of these, or both. A start capacitor has a much higher capacitance than a run capacitor and provides a higher starting torque.

The pre-electronic central heating pumps had permanent capacitor motors, i.e., they had run capacitors but did not have start capacitors.


Julian F. G. W.

[servodude]

Why do they always fail? Built in obsolescence?
Under rated? By everyone, always?
Old pumps taking longer to get to speed so the start cap is in use longer than it was "designed" for?
Just one of those "that's how it is" things?

Capacitors have a finite life before they stop working.

True - but its measured in more than purely time.

If a specific component is going to have a lifespan noticeably shorter than the rest of the design then there really should be a good reason.
Especially when that component is in a module that forms part of a bigger system which apparently suggests changing the entire pump when it fails.

perhaps I'm just being grumpy cos I keep forgetting to pickup a 1uF Polypropylene I need for a repair (the one I took out is measuring nowhere near that now) when I ride pass the local parts shed

-sd

[quelquod]

I recently had a not dissimilar experience with a washing machine motor. The machine was still under warranty. I said to the repair guy "new carbon brushes?". The reply was that new carbon brushes would almost certainly fix the fault but he was fitting a new motor anyway. He did. I kept the old motor and this thread has just reminded me to buy a set of carbon brushes for the removed motor which is now my spare.

You’re probably both doing the right thing. Expiring brushes often give the commutator a hard time so the repair man is guarding against a short-term repeat call out. Probably a good idea to give the commutator a check and maybe a polishing with wet ‘n dry.

[BullDog]

I recently had a not dissimilar experience with a washing machine motor. The machine was still under warranty. I said to the repair guy "new carbon brushes?". The reply was that new carbon brushes would almost certainly fix the fault but he was fitting a new motor anyway. He did. I kept the old motor and this thread has just reminded me to buy a set of carbon brushes for the removed motor which is now my spare.

You’re probably both doing the right thing. Expiring brushes often give the commutator a hard time so the repair man is guarding against a short-term repeat call out. Probably a good idea to give the commutator a check and maybe a polishing with wet ‘n dry.

Yep. Agreed. The comm is in very good condition with no visible wear. I'll give it a clean to remove most of the carbon track deposit. Leaving some behind as a dry lubricant for the new carbons to run on.

[Watis]

You’re probably both doing the right thing. Expiring brushes often give the commutator a hard time so the repair man is guarding against a short-term repeat call out. Probably a good idea to give the commutator a check and maybe a polishing with wet ‘n dry.

Yep. Agreed. The comm is in very good condition with no visible wear. I'll give it a clean to remove most of the carbon track deposit. Leaving some behind as a dry lubricant for the new carbons to run on.

I cleaned the commutator on a washing machine motor with methylated spirits once.

For the rest of the life of that machine, it chewed through brushes every few months. I don't know whether they were cheap brushes or whether the meths damaged the commutator.

Watis

[Mike4]

Capacitors have a finite life before they stop working.

True - but its measured in more than purely time.

If a specific component is going to have a lifespan noticeably shorter than the rest of the design then there really should be a good reason.
Especially when that component is in a module that forms part of a bigger system which apparently suggests changing the entire pump when it fails.

perhaps I'm just being grumpy cos I keep forgetting to pickup a 1uF Polypropylene I need for a repair (the one I took out is measuring nowhere near that now) when I ride pass the local parts shed

-sd

I fixed a boiler for a bloke once who explained to me capacitors are less like inanimate devices than living, breathing organisms with finite lives, depending on how well they are understood and looked after or abused. He reckoned human beans expend whole careers specialising in capacitors still without fully understanding them.

I got on really well with him and I suspect he was right.

On the other hand, perhaps he was really taking the ****

[servodude]

True - but its measured in more than purely time.

If a specific component is going to have a lifespan noticeably shorter than the rest of the design then there really should be a good reason.
Especially when that component is in a module that forms part of a bigger system which apparently suggests changing the entire pump when it fails.

perhaps I'm just being grumpy cos I keep forgetting to pickup a 1uF Polypropylene I need for a repair (the one I took out is measuring nowhere near that now) when I ride pass the local parts shed

-sd

I fixed a boiler for a bloke once who explained to me capacitors are less like inanimate devices than living, breathing organisms with finite lives, depending on how well they are understood and looked after or abused. He reckoned human beans expend whole careers specialising in capacitors still without fully understanding them.

I got on really well with him and I suspect he was right.

On the other hand, perhaps he was really taking the ****

Yeah they are little houses for the pixies that look after the magic smoke and they can get upset if you don't treat them well. Throw in the need to derate them for voltage, and the effects of package size, and it's amazing anything ever works