central heating system problems..? pump or control , help pl

[mike2008]

Hi Can anyone help. I have a back boiler system which rans perfectly the last 2.5 years that I have been in the house. Then since the winter started although hot water is ok,as it had been used during the summer the heating is on and off..

Sometimes, when the timer comes on the heating is ok, then only upstairs is ok..downstairs no.. then another time if I switch off the rads upstairs the downstairs gets hot..and other times all rads on are ok..and then now..only the upstairs get hot and the downstairs are cold. They were even occasion when all rads were cold..and even though the heating switches are on.

I can hear the pump moving water..but, although it may sound like a dying pump..I also find that the control switch are sometime to be blame..esp the heating ones..where the switch move from off to on..

can somone please help me solve this problem and get my heating working again..

thanks

mike

 

[gas4you]

You've answered most of it yourself.

It is either the pump very tired or sometimes sticking, sludge in the system, or the controls, but I would go for the first 2 first, as the controls would not really distinguish between the up and down rads.

 

[mike2008]

Hi Dave

Thanks for the reply..I checked and bled the rads until clear water ran out without any sludge.. When I turn the speed select buttons it sound s like from 3 to 2 it slows down(fan) than into 1 in slow to a near halt and then I turn it back up again trying 2 than 3 ..and it sounded like it gathers speed but still the heat will go as far as the upstairs rads..when I used to turn them off the heat goes downstairs..not now though..

Do you think I should try and bleed the rads again before I call someone in to change the pump. Or, is it easy to remove the pump and then try to see if there are sludge that may be clotting there?

In the long long..if I have to replace the pump..what would it cost me?

btw could it not be the room thermostat..as I can only hear the click to 10-15 deg.. and I tried to remove it but it would not give. a couple of days ago when the heating was running I turned the room thermo down and that started the whole problem..again...is that an area I need to look first..?

Thanks for the advise so far..I am still loking for more ...
cheers

 

[MANDATE]

I take it that there is no motorised valve then and the room stat just switches the pump on and off.
If power is present at the pump when you turn the room stat up then that proves the programmer and stat works even if the pump is the problem.
When I had a pump problem I didn't remove the whole pump. Just the 4 allen screws and the wiring. then remove the pump motor leaving the pump body in situ. Then wired it up again in the workshop to find it was faulty. Replaced the pump motor only because of access problems.
Don't forget pumps need bleeding of air as well as radiators.
If the stat and pump are ok then I think your looking for either a blockage or air lock in pipe work.
Has the system been drained?
It seems to me gas4you has got it spot on.

 

[twgas]

another thing to check (if gravity hw, pumped ch) is there an anti-gravity valve that could be blocked/sticking.

 

[mike2008]

Hi Guys

Thanks for the quick replies..

I will have another look and try again with all those advises and let you guys know what happens..

Cheers for now..

 

[bengasman]

I have yet to encounter the first bbu that was not full of sludge
this often also wears out the pump much faster