F&E Tank cold water outlet, WARM

[malooga]

Hi Happy New Year.

I seem to have a Problem with the flow on the central heating.
I've got a direct cold water system with a seperate f&e tank on open vented central heating. It's a dated system, about 25yrs old. Pumped but with one 2way port valve feeding eight rads. New grunfoss pump and 2 new gate valves. Pump running on 2nd speed setting.
The rad downstairs in the dinning room and now a bedroom rad has lost most of it's heat and are luke warm.
Bled them,alls good. opened up the TRV's fully and shut the loch shields down to 1/4 turn on all the upstairs. Went in the loft to have a check in the F&E and found the water quite warm. Checked the cold water feed pipe from the F&E and it is obviously feeding warm water back down, strange thing is the vent pipe is not very warm at all so not venting back into the tank,or doesn't seem to be.
Sorry it;s a bit long winded but if anyone has any ideas it'll be much appreciated.

 

[twgas]

what boiler make/model, how's your hot water. F&E tank does not feed out hot water, if its warm the heated water is going into it! either from the ventpipe or up the cold feed.

 

[malooga]

Hi Mick.
yep the hot waters fine. The worry is that hot water ifrom the rads is feeding back up the cold feed to the f/e because it is'nt going back up the vent.

 

[malooga]

Sorry forgot to tell you the make and model of the boiler. It's a Potterton Kingfisher, about 20+ yrs.

 

[swbjackson]

The hint is in the name feed and expansion cistern. The cold feed pipe is also the route for the expansion When the heating or hot water comes on the level in the f&e tank rises. This is due to expansion up the cold feed pipe which is actually a feed and expansion pipe. If it's only warm it's not an issue.

 

[malooga]

Thats great. Was a little worried that i had a bigger prob than i thought.
Any ideas about the luke warm rad in the bedroom and downstairs. Cheers

 

[swbjackson]

Do they get hot of you shut off the other rads? I wouldn't be surprised if you've got sludging problems on a boiler that age.

 

[malooga]

have'nt tried but i'll give it a go. try it tomorrow and post the results. Thanks for your help Mike.