Y-Plan vented heating - Banging from the boiler

[Mike Dodd]

CH/HW system is a Y-Plan design, Baxi Solo 40PF boiler.

Yesterday there was a hell of a racket coming from the boiler - a series of bangs maybe a second apart, a bit of wheezing etc., there's also sounds of bubbling through other parts of the pipe system. I'm not sure, but the boiler may cut out for a few minutes (I'm not sure of its characteristics before this started - I would have thought it'd be on continuous whilst there was a demand for heating the HW cylinder?)

My thoughts are that with the temperature dropping recently, the CH has kicked in, and disturbed the last 8 months of static water in the radiators, kicking up sediment, and presumably kicking this into the boiler clogging it up (heat exchanger?).

So, does the above make sense?, is this a likely scenario?

My thoughts to remedy this, bearing in mind the boiler is enclosed in a kitchen unit and the access to the pipework is, at best, minimal, is to drain the CH system down (via lowest radiator), probably leave the cold-feed on (F&E tank in loft) to do sort-of a low-pressure flush of the system.

I might also be tempted to fit one of those magnetic sludge removal devices (e.g. Fernox boiler buddy) to try to remove the suspended matter from the system

Does the above solution sound practical?, or is it (metaphorically speaking) pissing in the wind? If so, barring reaching for the yellow pages and my flexible friend, is there anything else I should be trying?

Regards

Mike

[Andy Hall]

It's possible. Have you tried bleeding the radiators?

That would be one way but have very limited results. If the system is full of sludge, telltale signs are if there is a gas released from the radiators when opening the vents and it can be lit. This is hydrogen from corrosion. Another is if the centre areas of the radiators at the bottom feel cool when the system is hot.

A better method of cleaning is to flush at each radiator position. Leave the water supply to the header tanks or filling loop on. Use Plastic sheet and old towels and newspaper on the floor. Close the radiator valves noting the lockshield position. Position vessels to collect the water. Cat trays are good for this. Bear in mind that water from a sludged heating system and the sludge are indellible dyes. Undo the union nuts on the valve slowly and allow the radiator water to drain into the vessels. Tip to let remainder out. Fit small plastic bags to the valve tails with rubber bands and take the radiator outside. Flush through with mains hose or pressure washer. At the radiator position, open each valve in turn to flush water from the pipes together with crud. Refit the radiator.

This procedure should be started upstairs on each radiator and then downstairs. Finally flush at the boiler if you can.

After this add a flushing agent to the system, refill and run it for the recommended time - usually a week. The hot water helps to dissolve other material. It is not a substitute for flushing properly.

Finally flush through with plain water and add corrosion inhibitor.

While doing this exercise, check that there is neither pumping over or sucking down of air if you have a header tank. If there is, post again for comments on that. The problem is that these introduce oxygen into the system and promote corrosion.

An alternative approach is to rent a power flushing machine from a hire place. These are generally attached at the pump and water forced round opening one radiator at a time.

Another is to pay a heating engineer to do this. Expect to pay several hundred for this.

Finally you could ask BG to do it. They will subcontract to a local engineer and mark up the deal. A second mortgage for this one.

This is the wrong approach. These things are like sticking a band aid on a major wound. You can remove some sludge from the system. In the meantime, the radiators will continue to corrode and eventually expensively fail. It is much better to prevent corrosion in the first place and it is very easy and much cheaper to do that.

[Roger Mills]

It's not clear from your post whether or not the system is actually working - or whether it runs for a very short time, accompanied by the banging, and then stops?

If it's *not* running, it sounds to me as if the pump has failed. If the pump isn't working, the water in the boiler will boil - sending lots of steam into the pipework - which may account for the noise.

If it *is* working, it could just be that there's air in the radiators, which is getting circulated now that the heating has come on. Have you checked that there is water in the F&E tank? This could have dried up if the ball-valve is stuck shut - causing air to be drawn into the system.

So make sure the ball valve is working, and then bleed all the radiators and see whether that makes any difference.

[Mike Dodd]

It seems to run for a short time, with banging, then stops. After it stops there's continued rumbling and moaning in the pipework, which supports your boiling idea.

Pump failed?, hmmm, a fairly new pump, and it *sounds* like it's turning, and it vibrates like it's turning... any chance the impellor could have fallen off? :)

(also speed control does have the appropriate effect on the sound)

Water in F&E - albiet luke warm, well, bearly tepid, tbh(hmmm, why?), and very, very sludgy (ok, water level maybe 3 inches, and hand dipped in - sludge feels 5-10mm deep on the base of the tank).

Radiators - bleed them all - no air/gas - just water.

[Mike Dodd]

Yes - no gas from any (immediate spurt of water)

Actually, can't get any heat to the rads (sorry, the story is developing from 6am this morning when I was getting ready for work)

Hmmm, that's an idea.

That's a less attractive idea.

Hmmm.

My plan was to use this to mop up the sludge that'd remain in the system

- although I agree this would be better done via a proper flush.

[Mike Dodd]

Stupid question time - any way to test the pump, or do I have to drain the system (looking like I'm gonna have to do this anyway), remove and place carefully in a bucket of water?

[Mike Dodd]

Actually, I could believe that it is the pump...

The boiler, from cold, will burn for quite some time - couple of minutes. Bangs, stops, waits a while, tries again - burns for a few seconds (overheating?)

Then, upstairs, having turned off the HW and CH demand the pipework under the pump (boiler side) is distinctly warmer from the output from the pump - which I think is being heated by conduction, only.

So...

Tomorrow, drain, remove pump, quick test and off to a plumbers centre for a replacement, if necessary.

Thanks for help, will report back.

[Roger Mills]

Most pumps have a removeable end cap (on the end of the motor, furthest from the water connections). If you remove that, you can see whether the shaft is rotating. If it isn't, it may be jammed by a bit of crud. there should be a screwdriver slot in the end of the shaft, enabling you to rotate it. You may be able to free it if it *is* jammed.

If the shaft *is* rotating, it's still possible (as you suggested earlier) that the impellor has become detached fom the shaft. You can't check that without removing the pump.

Does your pump have service valves or gate valves either side? If so - provided they work(!) - you can turn them off and remove the pump without needing to drain the system. Fit new rubber washers when you put it back together. [If you have to replace the pump, it should come with new washers anyway].