Noisy heating system

[pricega1]

Hello,

This is my first post so I'll try and make it as undersatndable as possible.
I have a conventional heating system comprising of wall mountedd boiler in kitchen, thermostat in the hall, pump under the landing (yes I know but I didn't put it there!) hot water tank in airing cupboard in bedroom, expansion tank in loft. There are eight rads in total, all bled, little or no air in them.
When the boiler is on the pump runs continually. to put the rads on you tweak the thermostat in the hall. All is quiet when the rads are on but when they are off the system makes a noise like a plane going over, this wanes a bit and then returns and continues to cycle like that.
I thought it might be sludge in the system so drained it off (although couldn't do the full system as some of the rads were undrainable unless drained individually) and added some cleaning solution, ran the system, drained it off and refilled it. This seemed to work for a time even with the rads off, no noise. However the problem has returned and is as noisy as ever.
What do you think the problem is? Pump too fast? air? sludge? poor piping installation maybe?

Regards

Gary 🙂

 

[Mbear]

When this noise is occurring, have a look up in the loft to check if the system is pumping over(water firing out the open vent into the header tank).

Is the pump noisy or is it White hot? (not touchable with the hand)

Possibles,

choked cold feed,
Choked hw cylinder coil,
Tired pump,

These are where I'd be looking to start off

 

[pricega1]

By choked cold feed do you mean the cold feed from the expansion tank to the coil?
The pump is under the the landing, I'll have to have the flooring up and check it out.
Thanks for your help.

Gary🙂

 

[tamz]

The pump is cavitating. Look it up.

 

[pricega1]

"When this noise is occurring, have a look up in the loft to check if the system is pumping over(water firing out the open vent into the header tank)."

Forgot to mention mbear, that the system was pumping over. A plumber in our street said raise the level of the o/flow pipe. I did this and the pumping over stopped.

Gary

 

[Chrisgy]

" A plumber in our street said raise the level of the o/flow pipe. I did this and the pumping over stopped.

Gary

You mean vent pipe over the tank

 

[Mbear]

"When this noise is occurring, have a look up in the loft to check if the system is pumping over(water firing out the open vent into the header tank)."

Forgot to mention mbear, that the system was pumping over. A plumber in our street said raise the level of the o/flow pipe. I did this and the pumping over stopped.

Gary

U raised the o/flow pipe level? I don't think u did, I think ur gettin mixed up with what I was saying?

If it was pumping over and u raised the height of the U bend at the top of the OPEN VENT pipe then yes, making it taller may stop it pumping over however it does not cure ur fault. most likely causes of pumping over are, tired pump, choked cold feed or choked coil as I've said in a previous post. the additional cause can be this.... If a new pump has been fitted recently and it wasn't set to the correct speed(1-3/4) for that particular system then for talking sake... setting it at speed 3 when the old pump was set a speed 2 for example

 

[pricega1]

"If it was pumping over and u raised the height of the U bend at the top of the OPEN VENT pipe then yes, making it taller may stop it pumping over"

Yes, that's what I did.

"most likely causes of pumping over are, tired pump, choked cold feed or choked coil"

We've been in the house since '84 and the pump hasn't been replaced during that time.

Many thanks Mbear & Chrisgy. 🙂

Gary