Gurgle! Rattle! Clang!!! (Central Heating)

[Thejudge]

(Sorry if this contains a lot of info - better too much than too little!)

I have the following CH: Icos Ideal HE-18 boiler, 7 rads (6 with Honeywell TRVs, 1 - in hall - controlled by wall stat), Grundfos Alpha+ pump, Drayton cylinder stat and 3-port actuator. System is in three-bed council house and was installed 18 months ago.

Back in mid-January, I had a problem with what appeared to be a stuck actuator on the 3-port (no HW). Council's contractor came out and sorted it.

Since then, though, I'm regularly getting the following problem: once the system has been on for an hour or more, when the boiler burner kicks in, there's a distinct sort-of 'choking' sound from within the boiler. The boiler can also rattle a bit.

This seems to then travel within about 20-30 seconds through the pipes to the area around the pump/3-port/HW cylinder. There is then a series of loud noises from this area (worrying, as I sit in the living room right underneath it!). These noises vary from sounding as if someone is dragging a heavy bit of furniture around, to a sound which is like someone physically wrestling and wrenching the pipes at that point. It can even cause the HW cylinder to shake, and I'm sure this is not doing any of it any good at all (not to mention my nerves!).

From listening to the sounds coming through the pipes in the living room when it's doing this, it sounds to my untutored ear as if not enough water is going through the system, hence the 'choking' (see point 3 below, though) - but then, what do I know?

At other times, instead of or as well as this, there's a machine-gun-like rat-tat-tat in the TRVs on some of the rads. Also, turning the TRVs up and then back down to the previous setting (whatever it is) can produce the same gunfire) Then, at other times, the whole system seems to run fine.

These are the things I've tried so far:

1) Bled the radiators - no indication of air in any of them
2) Bled the pump (you know, that vertical pipe with the screw-cap on it) - no air there either
3) Changed the pump speed. Whichever it seems to be set to, it either doesn't cure it at all, or seems to cure it for a few hours to a day or two, then it's back in full Radiophonic Workshop mode.

Also (I don't know if this is relevant, but I'll ask anyway), how far around should the spindle on the 3-port be able to turn? Mine will only turn from about 10 o'clock to about 12 o'clock. The guy who came last week to do the annual gas safety check said that this was normal.

I'd be grateful for any advice on this, as it's shaking the s**t out of the system (and my nerves). As it's a council house, I would only be willing to do things like minor adjustments myself, but if I needed to call the Council's contractors in, I'd like to have some ideas as to possible causes.

Thanks in advance.

 

[hellomum]

the trv's that are making the noise could be on the return instead of the flow (if they are one-directional). Just change them anyway.

 

[chrishutt]

The system sounds dangerous. Overheating in the boiler , probably due to poor circulation. Your landlord is responsible for the CH system so get them to get a Corgi registered heating engineer in.

 

[ACOperson]

Yes, circulation or maybe AAV inside the boiler is not venting air from heat exchanger. If its a council house they should have contractors with a max 24 hour response time.

You're not having to constantly re-pressurise the system are you?

 

[Thejudge]

Now I am worried!

It was pretty bad on Thursday night, but no problems at all so far tonight (system on for 4+ hours).

It's not a pressurised system, ACOP, so at least I don't have to fret about that as well.

BTW, pardon the ignorance, but what's an AAV?

 

[ACOperson]

Does the tank in the loft have any water in it?

An AAV is an automatic air vent BTW.

 

[Thejudge]

Yep, it's an Icos Ideal HE-18.

From what little I know (mostly from reading this forum!), it's not a pressurised one. Expansion tank in loft, open vent pipe to it from cylinder, that sort of thing. Am I right in this?

 

[Thejudge]

(That's weird! ACOperson, did you just edit your last post? I'm sure you asked whether I was sure it was an open system!)

How much water should there be in the expansion tank? Last I looked (about 2-3 weeks ago), it was I would guess about 2-3 inches deep. I'll check again on Saturday though, if you think it's significant.

All I do know is that what's in it could only be described as "water" by a politician . When I first went up there, it looked as if half a dozen poorly hyenas had chucked in it. The smell followed me downstairs and I had to burn a joss-stick in the bedroom to exorcise it!

I've checked the ballcock, and that seems to move freely, and I held it down for a few moments to raise the liquid level a bit.

 

[ACOperson]

Yes you are right. Is there water in the tank though?

If there is water, if the pump is turning and if there is no air in the system it could be a couple of things:

Intermittent pump fault, pump not turning sometimes (usually when very hot)
causing boiler to occasionally overheat.
or

Boiler overheating due to faulty protection mechanisms (eg NTC, gas valve etc).

 

[croydoncorgi]

What about pump connected back-to-front? Well - anything's possible!

Perhaps you can describe where the pump is located relative to the 3-port valve and boiler, and in which direction the embossed arrow on the pump casing points.

 

[Thejudge]

Is there water in the tank though?

There was a couple of weeks ago. The problem pre-dates my last check (which I described before).

Boiler overheating due to faulty protection mechanisms (eg NTC, gas valve etc).

Boiler was given gas safety check last week. Engineer didn't say there was a problem.

Perhaps you can describe where the pump is located relative to the 3-port valve and boiler, and in which direction the embossed arrow on the pump casing points.

Boiler is on the ground floor, in the kitchen at the back of the house. 3-port, pump and cylinder are in a former airing cupboard in the front bedroom.

In that cupboard, imagine three pipes coming up through the floor.

Pipe (A) goes straight up into a Pegler Ventair, and from there into the roofspace.

Pipe (B) comes up into the 3-port. From the 3-port, one pipe goes up to the 'bleed valve', one goes off this one into the cylinder (HW), and one pipe comes from the 3-port into Pipe (C)

Pipe (C) has one pipe leading off it to the cylinder (CH?), then is joined by the pipe from the 3-port. It then goes to the pump (which is a few inches higher up than the 3-port). The pipe then goes up from the pump into the Ventair.

(If this isn't clear enough, I could try and do a schematic and provide a link)

The pump appears to be upside-down, that is that the label is upside-down and the control which in the manual pictures is on the left as you look is on the right. I can't see an embossed arrow on the casing, though.

 

[ACOperson]

When boilers are making the kind of noises you are describing it is usually due to overheating of the heat exchanger due to either :

1. water in the heat exchanger not moving, or not moving quickly enough.

or

2. Air in the heat exchanger and pipes.

or

3. Protection mechanisms failing, causing gas rate too high (not usual).


It is possible that even if there is water in the tank, that the cold feed is blocked, and perhaps not enough water in the primary circuit. The only way to check this is to turn off the feed to the F&E tank, drain some water out of the system and then see if the water level in the tank drops. If it does not drop then the cold feed pipe is blocked. If this is the case, then it is likely your problems are due to air in the pipes not being replaced by water from the tank.

If the pump is not turning, scenario 1 above will happen. Ensure pump is turning,

I'm not familiar with the Pegler Ventair, if it is a cylindrical unit with a cap on the top then its an AAV. Try loosening the cap to see if any air comes out when the system is full.

Please also remind us why you have not called the council contractor out for this problem. they will be able to check if the pump is turning, check for air and check for blocked cold feed if they feel it is neccessary.

 

[chrishutt]

Boiler was given gas safety check last week. Engineer didn't say there was a problem

Gas "engineers" working on local authority gas safety checks will be under pressure to carry out checks in an unrealistically short time and are unlikely to be able to do the job properly, even if capable of doing so.

 

[ACOperson]

Yes, I do CP12's for LA contracts. they expect us to service & issue safety certs on 8-12 room sealed boilers a day or up to 10 back boilers.

Due to the unrealistic workload placed upon them, guys at the company I work for frequently leave faults on boilers because they are rushing.

 

[Thejudge]

Quoth ACOperson:

Ensure pump is turning,

I'm pretty sure it is. When I change the control setting on it, the pitch of the motor changes. As I said, I've tried the pump at just about every setting (variable and constant), and the problem either doesn't go away at all, or goes away for a short period and then returns, especially the longer the system has been on.

and again:

I'm not familiar with the Pegler Ventair,

It's a short length of the pipework which is about twice the bore of the rest of the pipes. Judging by the name, I suppose it's to help vent the air out of the system.

and once more, even:

Please also remind us why you have not called the council contractor out for this problem.

Two reasons, really: firstly, the difficulty of describing the fault to the air-headed girl on the other end of the Council's Repairs Line; and secondly, the problem of trying to get time off work just at the moment.

As your advice now goes way beyond what I'm able to handle, I'll bite the bullet and call the Council early in the week.

Thanks to all for your help. I'll try to get back to you with the solution once they've found it.