A couple of boiler questions

[GMM]

'tis the season for this topic, so I thought I would get one in.

1 I woke up this morning to a squealing noise running through the house, which I tracked down to the boiler. Turning the boiler off then on again, the noise took a minute or two to restart. Since it was early, I resolved to leave it for a while (expecting it to persist so I could investigate later) but it stopped after about an hour. My first impression was that it could be a fan bearing, though I can't see how that could resolve itself, short of the fan stopping entirely. Is tehre any other explanation for this?

2 I have two boilers in series (fitted before my time). I have set the second one for a lower temperature than the first, so it should only cut in when the first struggles. My first thought this morning was to turn the first one off and run on the second while I sort things but the second was showing a fault that indicates it's not firing properly. Listening to it try to start after a reset, it's clearly igniting but not holding. Less than a year ago, I replaced the flame supervision device. It's easy enough to do and I'll replace it asap but do these things really have such a short life? If so, it's worse than the old thermocouples.

Is it likely that not being used very often leads to premature fauilure in these controls? I can easily make it run more often (by turning the first one off from time to time).

FWIW, these boilers are both Ideal icos HE24 and, before anyone says, it's not a setup I would choose, by a long stretch, but it's what's there and I'm not inclined to spend thousands rippng them out right now.

[harryagain]

Commercial boiler installations are often multiple and usually the lead boiler is automatically changed say once a week to "excercise" the components.

[John Rumm]

Fan or pump bearing seems most likely. You may find it gets quiet once its warm.

It could be the PCB rather than the sensor - the icos/isar have a bit of a reputation.

Probably not a bad idea to spread the wear and also that way you get to know about failures of the backup before you need it.

From what I saw of the one I had, they were actually nicely made mechanically (if a little cramped to work on), but it transpired the electronics let them down.

[GMM]

I couldn't see any mention of an internal pump in the manual, so assumed the external ones were all I had. The trouble with these squealy noises is that they're not easy to tell apart: My first thought when I heard it in the house was that it was something like water under pressure trying to get through a small gap and I didn't think it was the boiler but the plumbing. A new fan appears to be about 40 quid, so not the end of the world, but I'd like to be sure before diving in and changing it.

Despite my best efforts, I haven't been able to reproduce the noise during the course of the day, so it's clearly going to be a problem that only occurs at the most inconvenient times... (hence I'd like to fix the other one, below).

My recollection from last time was that it's not simple to differentiate the two, so I swapped the easier/cheaper part and that fixed it for then. I'll take the same strategy this time as it's 15 quid and 20mins work to change the sensor, compared with serious cash for the PCB. If that doesn't fix it, then it will be time for plan B.

I feel that must be right, and was what I intended to do but, of course, it's one of those things that get forgotten when there are always plenty of other things to do. I'm a bit surprised the same fault has occurred again though, as I'd have expected any 'lack of use' probem to be with a moving part, somehow.

Indeed - the electronics have to be a concern but then again, even a few hundred on electronics could be worthwhile if necessary, compared to the cost of a total replacement, so I'll try to stick with these for a while yet. Fortunately, pretty much all spares seem to be widely available still.

[John Rumm]

I take it you have looked at Geoff's web site for fans (and PCBs)?

[GMM]

I have now :-) Thanks for the steer, John. At first sight, there didn't seem to be any of the right parts listed but I will look more closely if and when I need them. Cheers

[John Rumm]

Usually worth giving them a call - they may have more stock than the web site claims, and even if not, you may find they can repair your PCB and return it even if they don't have a repaired one in stock to swap yours for. (assuming you can cope without it for a few days)

[george]

Could it be this noise?

[Andrew]

is this Drivels old house ???.

[www.GymRatZ.co.uk]

I had a similar problem on my completely different boiler recently. Fortunately the handbook came with an extensive fault diagnosis check list...

In my instance on first power-up the fan would purge the burner chamber then the gas would ignite but with a small "explosion" the sort that makes the case distort slightly which then appeared to blow out the flame after which the igniter would keep sparking but no gas/flame.

The problem was actually diagnosed by the handbook as a blocked condensate syphon.

Even after draining the syphon of cack the problem still persisted so I had to remove the combustion chamber and pour water into the top of the syphon which was still blocked, but a bit of tapping and woosh... it cleared. Since then all has been good.

I don't know the in's and outs of why a blocked condensate syphon should cause the flame to blow out but I put it down to a high back-pressure which would normally escape down the syphon.

Might be worth investigating before looking at anything else?

Pete@

[GMM]

Fortunately not as scarey as that sounds. Mine was/is reminiscent of the squeal you get from a car fan belt/duff water pump bearing (not that I've heard that on a car of my own for a long time!)

[GMM]

No - it can't be, as I don't have a combi! My observations around the place lead me to believe it was the house of someone who was highly trusting (/gullible) of less scrupulous tradesmen. To add to that, a lot of jobs were done in the 70's and

80's, when standards were not at their best....