Radiators hot upstairs, but cold downstairs!!!

lambo28

How do you bled the pump?

crazy_girl_2

I have this problem, you need the system draining by a plumber. You will have sludge in them. are they lukewarm at top of rad and cold at bottom of rad? Apparently, this means build up of sludge. If cold at top and warm at bottom need bleeding for future reference. Crazy Girl.

lambo28 wrote: »

Hi

I drain my central heating system to put in some Fernox MB-1 and it all went well. However, after switching on the system, my radiators are hot upstairs but stone cold downstairs.

What is wrong with it?

I am willing to work through this fault by a process of elimination! Please help

lambo28

The pump is a Grundfos UPS 15-50, if that helps

Darkroom

Check the diverter valve (either 2 port or 3 port) is working properly. It might only be partially opening and the small amount of water getting through is only getting to the upstairs rads, esp ones closest to the pump.

EliteHeat

lambo28 wrote: »

How do you bled the pump?

Unscrew the big screw. Water and air comes out. Close it.

bookduck

lambo28 wrote: »

I can hear the pump work away!

And gravity fed too? I'm no expert but I do not think you should hear the pump working at all as it should be off. Fairly sure the system should be completely switched off when bleeding the system otherwise you may suck air back in.

Once bled, switch it on again and let it run for a few mins, Then go through the procedure of bleeding it again.

lambo28

What is the diverter valve? What does it look like?

lexie55_2

Elite Heat right, do as he says...

Darkroom

lambo28 wrote: »

What is the diverter valve? What does it look like?

That's a 2 port one and you'll have 2 of these - one for heating, 1 for hot water. Undo the 2 screws & lift off the control box part. On the brass part you'll see a valve. Check it rotates freely and then align it back to the initial position so it can mate with the control box when putting it back.

Also check the bottom of the control box and see if the motor is turning the actuator (which normally moves the valve when the box is mated) when the heating is switched on.

If you've got a 3 port one then it's pretty similar except it has 3 pipes going to it and they'll only be one of them in your system.

bookduck

This is probably your set up.


If ALL your radiators upstairs are HOT - not warm, then I can't see how it can be the valve or pump. If some upstairs are warm while others hot then it could be the pump.

If I'm correct, hopefully you have a airlock somewhere in your downstairs radiators/pipes. If you don't have an airlock, then you have a blockage . I'd guess on saying you partially drained the system so the stuff from the header tank go into your system and the gunk has now blocked it up - but i'm no expert, it is just what happened to me.

You need to go to the pipes on the ground floor and trace them back to the boiler. Turn your heating on for 5 mins. The pipes should feel hot. If they feel warm, keep tracing it back. You are trying to find a point where there is a marked reduction/increase in heat over a few feet of pipe and this is most likely where the problem lies.

My crystal ball guess is that the water comes out of the valve and goes into a T-piece with one end feeding the radiators upstairs and the other feeding the ones downstairs. The particles being heavier will take the downstairs route. If ALL the radiators downstairs are cold-ish, then I'd start looking/feeling just after this t-piece and your will probably find the problem and the bottom point most likely near a bend somewhere.

Again, if I am correct (big IF), you probably would be better off replacing the pipe, rather than unblocking it as that may cause the gunk to spread.

If the gunk is is ferrous, then you may be able to detect it with a magnet and also may want to fit a Magnaclean