'Chuffing' Boiler

[psychoangus]

Hi there,

I have a Potterton Suprima and a Boilermate II. Recently the central heating pump located near the BM II seized. I shut both gate valves, replaced the pump for like, bled the air out of the front screw (Grundfos 15/50) and opened the bottom valve. Central heating back on.

Now the boiler is making a very strange 'chuffing' noise intermittently - For about 10 minutes it will chuff along, about 4 'chuffs' a second, as if it were a steam engine. The noise and vibration seems to be coming from the large flue pipe coming out of the top, and not the copper pipes.

Just had British Gas round for an annual boiler service and of course it failed to make the sound and ran smooth as you like. He said it could be scaling or a bit of air going round and round the system, but I can't see how that much air got in, and it's only started doing it after I changed the pump.

Any ideas? Not funny when it wakes me at 3am when the BM II demands hot tap water......

Cheers,

Dave

 

[wetshoes]

Are both valves open on pump you changed ?

 

[plumbnuts]

Have you checked what speed the new pump is on?

 

[psychoangus]

Both valves are open, yes! The pump works fine and the house heats and there is no coldness to the tops of any of the radiators.

However, the pump is on speed one out of three. The old pump was on the highest speed - three. Someone said that this was unnecessary and probably was the reason it seized up so quickly (i live in quite a new house) so my new one I set on speed one. Could this make a difference? I thought it would just govern how quickly the house heated up??

 

[wetshoes]

Has the boiler pump setting been changed ?

I think it needs to be on as fast a setting as possible, while giving a certain temperature difference between boiler flow & return.

I have a manual somewhere and will look it up.

rgds

 

[psychoangus]

Hey thanks mate, much obliged.

Well I can only whack it up to speed three and see if it makes a difference. Anything for a full nights sleep.....

 

[wetshoes]

Just out of interest, what setting was boiler (lower) pump on ?

 

[psychoangus]

As in, the 2nd of the two pumps near the boilermate II? It's on mid-speed, two. Haven't touched that.

 

[plumbnuts]

Just what I was going to say, I must learn to be quicker.

Turn the pump speed up to II and see if it stops, if not max it.

 

[wetshoes]

Why not go the whole hog and turn both pumps up to 3 - if problem stops try turning each one down bit by bit.

 

[psychoangus]

I'll try that tonight and let you know.

Why would the pump speeds make the boiler chuff though, if you pardon the expression?

 

[wetshoes]

If noises are being caused by boiler getting too hot,turning the boiler pump to a higher speed should increase the flow through the boiler, and it should help to cool it a bit.

 

[psychoangus]

Gotcha, and it just started doing it again before I went to bed, so I changed the speed to speed-3, the chuffing evened out and it stopped. Put it down to one and I thought the boiler was going to vibrate off the wall, so there we have it.

Thanks for all your help, I might put some de-scaler through it all anyway, just to be sure.

A happy customer, thanks guys!