Pumped CH Overflow

[sifu]

It sounds like you have a pretty old system so I would suggest cleaning the radiators individually. Adding something like Sentinel x400 to the system for a couple of weeks prior to this may help to loosen the sludge. If your rads are very old or are starting to look a bit ropey, then any cleansing may cause leaky rads, so be careful. There may also be sludge in the cylinder coil and/or pipes where the cold feed and expansion enter the system. If removing and cleaning the rads doesn't work then I would suggest getting someone in to look at your system design and to decide whether a chemical powerflush would be of use.

 

[DaveJ]

Thanks sifu

It is a pumped CH system only, separate HW supply from the boiler (it appears). As there are four pipes at the boiler, which I presume to be supply/return for the HW and CH, the pump (two speed) is set to the lowest setting and looks like it is on the return side of the CH.
?

Mmmm an interesting one, four pipes at the boiler, one has to be gas (I assume it is a gas fired boiler) the other cold feed from the header tank and the two remainding (22mm) flow return.

I would agree with the others, if it was pumped surplus going into the header tank then it would be drawn back into the system as it cools down.
It does sound as though "extra" water is being introduced to the system; the only logical place this can come from is the coil in the hot water cylinder.

Never done this before, but one way of being absolutely sure before you start ripping the tank out is to tie up the ball valve on the hot water header tank, open all hot water taps to drain down hot water circuit. Close taps and turn on central heating, if the coil is leaking you will get extra water out of the hot water taps which can only have come from the central heating circuit. via a leak in the coil.

As I say I’ve never done this before, perhaps some of the pro’s in the group could validate it?

Good luck.

 

[DaveJ]

Thanks sifu

It is a pumped CH system only, separate HW supply from the boiler (it appears). As there are four pipes at the boiler, which I presume to be supply/return for the HW and CH, the pump (two speed) is set to the lowest setting and looks like it is on the return side of the CH.
?

Mmmm an interesting one, four pipes at the boiler, one has to be gas (I assume it is a gas fired boiler) the other cold feed from the header tank and the two remainding (22mm) flow return.

I would agree with the others, if it was pumped surplus going into the header tank then it would be drawn back into the system as it cools down.
It does sound as though "extra" water is being introduced to the system; the only logical place this can come from is the coil in the hot water cylinder.

Never done this before, but one way of being absolutely sure before you start ripping the tank out is to tie up the ball valve on the hot water header tank, open all hot water taps to drain down hot water circuit. Close taps and turn on central heating, if the coil is leaking you will get extra water out of the hot water taps which can only have come from the central heating circuit. via a leak in the coil.

As I say I’ve never done this before, perhaps some of the pro’s in the group could validate it?

Good luck.

 

[sifu]

DaveJ, in a previous post leak said

Well the water level did not drop after it had cooled down, in all it rose about one inch. It seems that the water level only rises when the system is in operation, not when off. Any ideas?

My first thoughts were the coil until I read this. If the water level is not rising when cold then it is very unlikely that the coil has failed, although not impossible. Also, it hasn't been mentioned whether the F&E tank is higher than the cold storage tank, if so, then that alone eliminates the coil. I once encountered a system restricted with sludge so much that the pump sucked air down the cold feed whilst at the same time pumping over. The air moved to a rad and replaced the water that had risen up the expansion pipe. When the system was switched off the water in the expansion pipe and header tank levelled out causing a rise in the overall water level. When the system came on again more air replaced the water and the level rose even more. Leek, have you checked your system for air?

 

[LeeK]

Hi all,

Many thanks for the reply to my enquiry, lets see if I can provide answers to your questions.

DaveJ: There are four 22mm pipes used for the HW and CH, there is a separate 15mm pipe supplying the gas to the boiler, sorry for being little misleading.

sifu: Thanks for the advice I will see about getting some Sentinel this weekend. Both the cold water tank and expansion tank are located next to each other on the same level. As for the age of the system these are my estimates as some of this was before we moved here. The radiators and pipe work is from 76, the HW cylinder was moved into the loft in about 89 the boiler we had fitted in 91.

When the system first overflowed we had a registered corgi engineer round to check the system over. He checked the boiler and drained the system down (I was not in at the time, don't know what the water was like) and fully bled the system when it was refilled.