boiler fan and other boiler questions

[Stephen]

Hello,

This morning the boiler started making noises. When the fan starts spinning it makes a noise. I don't know how to describe it. A howl is the best I can describe it but that suggests it is loud and high pitched and it isn't exactly either of those. Once the fan has been spinning for a while, the noise seems to go away. Perhaps the fan expands as it gets hotter and that somehow stops the noise?

I can get to the back of the fan and I have sprayed some white grease onto the bit of the fan I can see but it doesn't seem to have had any effect. Where is the bearing that I need to lubricate? Is it at the "far end" of the fan, that would involve having to dismantle things to reach?

Are these known symptoms of a failing fan? I presume the grease has dried out with age? I know Geoff is recommended in these parts. Is it time to buy a new one from him?

I would like to get a new boiler one day but I currently have a combi and I would like to change it either to something with a cylinder, so that I have backup hot water, or possibly I might look into a heat bank. I would also like to move it to the other side of the kitchen. I was hoping I could re plumb the water bits, add the cylinder and header tank etc. myself, before buying a new boiler, to keep the costs of the replacement down. As it will take me months to get round to it, I was hoping to keep this boiler going for a bit longer.

My question is, how could I get a gas qualification, so that I would be able to do all of the replacement when the time comes? A quick google suggests I need a to start with an NVQ level 1, then do NVQ level 2, then NVQ level 3, and then spend several hours under the supervision of a plumber. That's great if you want to go into it professionally, but I think it would take too long and be too expensive for a DIYer.

Thanks, Stephen.

[Andrew Gabriel]

There's a bearing on each end of the motor, which the armature shaft goes through. You can only temporarily lubricate it once this has happened - it needs new bearings which are impregnated with lubrication - you can't impregnate old bearings, so you can't get any lubrication to work long term.

BTW, they use oil and not grease at these speeds.

You can always just ignore the combi/hot water side and use it as a system boiler with a hot water cylinder, or perhaps use the combi part for a top floor shower for pressure, and the hot water cyclinder for everything else.

You don't need qualifications to do it yourself, although you do need to be competent. When I did mine, I had read though the gas regs and Corgi book at the time, and was already competent at plumbing with end-feed soldered fittings, and had serviced gas boilers before.

How much plumbing have you done before, and what type of pipe and fittings have you used?

Most expensive part was that I bought a flue gas analyser, although that was only after realising the supposedly preset gas mixture was actually miles off. (Everyone found the same with that boiler model.)

[TomSawer]

Are you sure its the fan?

I had the same ssymptoms/problem with mine and it turned out to be the heat exchanger coil. This is small bore and easily starts to fur up. This can cause a kettling/rattling noise and sounds just like a fan.

[Stephen]

That explains it then, I have only sprayed one end.

What sort of speed do they rotate at? Which way round is the use of oil/grease: do slow fans use grease or do slow fans use oil?

Thanks, I will have to see what is available to read.

I started off using compression, doesn't everyone? I've since "upgraded" to end-feed. I'm not perfect at it though, I still use too much solder but better safe than sorry ;)

I've mainly used copper but also polybutylene pipe (the latter obviously not with end feed!).

Thanks, Stephen.

[Stephen]

No, I just assumed it was since it started at the same time the fan starts spinning.

I don't know how long the boiler has been here, nor how well the water was maintained with additives etc, so it could be. I did put a magnaclean on it and replaced the inhibitor when I moved in.

I guess it is a process of elimination: try a reconditioned fan and if that doesn't work some sort of anti-kettling additive? Or perhaps the other way around to save on cost?

Thanks, Stephen.

[Stephen]

That's what I was thinking, and how could I afford to spend x months working as a plumber's apprentice.

That's good news, I was worried that competent meant qualified

I think the testing for leaks is the bit I have never done before. Is that using that leak detector spray? Don't you have to pressure test it too?

Thanks, Stephen.

[John Rumm]

He will do you a recon exchange - you buy a rebuilt one, and send yours back when you are done.

[Chris French]

In message , Stephen writes

You need to do a pressure drop test.

The process is detailed in Ed's Gas Fitting Faq:

[Andrew Gabriel]

Sleve bearings with sliding parts are oiled. OTOH, if it has ball bearings (which have rolling parts with very little sliding), then these are greased.

Seems to be common with some plumbers too - not satisfied until there's a puddle of solder on the floor underneath. Not thinking there might well be a similar amount inside the pipe too...

Ideally, you see a shiny ring of solder just around the join. If you use more than that, it might just be hiding part of the join which is not soldered.

[Stephen]

Yes, I found that and found it very helpful. Are there any other online sources to read?

[Stephen]

I hadn't thought of that. I'll have to be more careful in the future. I hope practice will make perfect.

I guess that's where the leak tester fluid comes in? Would you see a water leak or would it be too small to notice?

As an update, I have fitted a new fan and it is much quieter now.

I found an exploded diagram here:

You have to hover the cursor over it to enlarge, I would have preferred something I could have enlarged manually.

There is a seal between the fan and the flue, it is part 23 on that diagram. I have moved the old one across as a temporary measure but it is looking like it is starting to dry out, so I think a replacement is advised.

There is a smaller washer, part 22, that sits beneath it. That is dry and brittle looking too. I can't work out what that is for. Is it a back-up in case the other seal leaks?

I think they are about £17 each at the plumbers merchants. It seems a lot for small rings of plastic: together the two of them will cost almost as much as the replacement fan!

Thanks, Stephen.

[newshound]

That sounds like the standard cheap squirrel cage motor bearing failure noise. I've currently got it on my halogen cooker but I have had it in boiler fans in the past (and numerous other things).

The bearings at each end of the armature are little phosphor bronze spheres, in a shaped clamp so that they are self-aligning. They have a diametral hole which carries the armature which should spin with respect to the bearing. Actually they are a porous bronze impregnated with mineral oil, "Oilite" is one proprietary name.

A drop of 3 in 1 or a spray of WD40 will normally silence them, which provides a 100% positive confirmation. They should last a while after adding oil, less long after using WD40. You can recover them by dismantling and soaking in oil (3 in 1 is good) but you may have corrosion on the shaft or wear and/or debris deposited in the bore so slightly more fettling may be necessary. Some are easier to strip than others.

[newshound]

You can buy a commercial manometer, but it is easy enough to make one up with clear flexible tube, the sort which is used to feed airstones in fish tanks. Add a drop of ink or food dye to make it easier to read. ISTR that boiler installation manuals usually quote the leak criterion which is something like 10 mm water gauge loss of pressure in a minute (JUST MY BALLPARK RECOLLECTION, THE FIGURE IS ON-LINE).

[John Rumm]

Your local library card number may allow online access to the British Standards documents[1]... If so, looking at the various BS docs about gas fitting is very informative.

BS 5440 - flues BS 5482 - code of practice for butane and propane (domestic) BS 5871 (3 parts) gas fires BS 6172 cooking appliances BS 6798 boilers BS 6891 gas pipework in general BS 7593 code of practice for water treatment in CH systems

If you have a search of some of the torrent search engines, you may be able to track down a copy of Tolley's Domestic Gas Installation Practice book - (one of the industry key reference manuals)

[1] If not, there may be some folks on the group who would be prepared to email you some of them.

[Stephen]

Thank you. As the fan is fixed, I am hoping to leave changing the boiler for a while. Lots of other DIY to do in the meantime! I will try and find these and have a good read.