Dumbfounded - why wont the rads warm up !

[Malc C]

Ive been having issues with our central heating, mainly trying to get the downstairs rads hot (when the system worked you could hardly keep your hands on them !)

It has been suggested that the issue could be sludge or an airlock or a faulty pump. If you've read my previous posts then you'll know that most of the pipe runs to the rads is old, and so I've started to install new rads and pipework (in 22mm dropping to 15mm at the rads). However as its forcast to be -2 tonight I thought I would try and get at least the downstairs rads warm.

I drained the system. The water did have a slight tinge of blackness in it, but it drained down quite fast which would suggest that there was no blockage. I opened all rad vents to aid the drain down.

I then tightened up all vents and drain cocks and then turned on the water to the feed/expansion tank. When the tank stopped filling I went round and bled the rads allowing plenty of water to run into the bowl. I then turned on the electrics and set the heating running. After a short while the noise in the pump settle down and I used the bleed valve in the HW loop to bleed some more air out. I then went round each rad and opened the bleed valve again, venting a little more air out.

The pump works fine as I can feel the hot water progressing down the pipes right up to the tee that connects the rads (doubles) after the lockshield valve. Water is also squirted from the bleed vents so it must be flowing through the rad. However the rad still won't get hot, even though you can't keep your hand on the pipe the other side of the lockshield valve.

I've also noted that even though the thermostat is calling for heat (roomstat) and the rads are cold, the boiler sits there... then it might light anf run for a couple of mins and then switch off... even though the roomstat is still calling for heat.

Hopefully, when the new pipework is complete, which could be a few weeks away as I only have Saturdays to do it, the problems will go away, however I would like to hear what the more experienced guys have to say as to what needs to be looked at.

One thing I just thouht of, could the thermostat that sits on the pipe in the boiler (baxi solo pfl 60) be faulty and shutting off the boiler too soon ?

Malcolm

 

[sambotc]

Sounds like a lack of circulation. You will get water out of the vent as it could be coming from either the flow or return, and the other may have a blockage/lack of flow.

Do you have thermostatic radiator valves? If so take the heads off them.

The boiler is flicking off as it has no way of dissipating the heat, doesnt sound like a fault on the boiler.

Try turning all the radiators off at both ends except 1 and see if you can get it hot. If you can do it to all the others one by one.

What kind of system do you have, combi, vented tanks in loft? Make sure the pump valves are opened fully etc

 

[Malc C]

Thanks for the reply.

The system is a standard gravity fed (open vent I think the term is) one. In a nutshell the Boiler is less than 6 years old, the pump, 3 way zone valve, the HW cylindar and all electrics are less than a year old.

I don't have any TRV's - just simple lockshields. Some of which are hidden like the bathroom one by the bath panel (if you read the previous threads you'll see I had issues with some cowboy plumber !)

I can get the bathroom rad red hot, and have tried shutting it down by the feed valve (the return is hidden) - and one of the bedroom rads is luke warm. However the downstairs lounge rads are cold, but the feed pipe is red hot and when bled no air comes out of the vet, just water.

When I come to ripping out the old pipwork I might connect up a hose pipe and flush through the boiler feed and return pipes using mains pressure water just to make sure the blockage isn't there. Havig said that I guess if it was the bathroom rad and other pipes wouldn't be getting hot !

Malc

 

[sambotc]

Maybe air then, even though you dont get any out of the vent doesnt mean there isnt a pocket of air stuck in the return pipework to the rad.

Turn off all radiators and flick hot water off. Then open just the lounge radiator and flick heating on, see if you can move it that way.

If that fails then shut off both rad valves on lonuge rad. Drain radiator and remove. Get either a bucket under firstly the flow and open up the valve. Fill a buckets worth up and inspect for slow flow or debris etc. It helps if the boilers been on to so you know its hot water. Then do the same for the return. If you can't get a bucket under you may have to make something up to connect a hose on like a short piece of 15 pipe with a nut and olive on, then jam the hose on the end of the pipe and tighten the nut and olive up on the valve.

Worth a go if your cold for a minute!

Sam

 

[Malc C]

Sam, thanks for the help

I'll give it a try tomorrow. I have managed to get the rads in the lounge luke warm by shutting off other rads, but its late now and I need some sleep.

Malc

 

[bengasman]

if it is kind of blackish, it does not suggest sludge, it proves it

 

[ChrisR]

Standard metal screw-on end off a garden tap fits most old rad valves - makes hose connection easy.

 

[Malc C]

if it is kind of blackish, it does not suggest sludge, it proves it

Just as well I'm replacing the old pipework then !

 

[paulmago]

may i suggest when you fill up your system only allow cold feed pipe in tank to be 1/2 submerged long process but will allow any air to come out whilst being filled. once all rads have been bled give a day or two for them to settle

 

[Terrywookfit]

may i suggest when you fill up your system only allow cold feed pipe in tank to be 1/2 submerged long process but will allow any air to come out whilst being filled. once all rads have been bled give a day or two for them to settle

What a load of ballcocks!!

Stick to your filling loop thread!!

 

[sambotc]

may i suggest when you fill up your system only allow cold feed pipe in tank to be 1/2 submerged long process but will allow any air to come out whilst being filled. once all rads have been bled give a day or two for them to settle

So how do you vent the rad's if you're in the loft revving the ball valve?

 

[paulmago]

you dont have a dog and do the barking yourself. do you vent whilst refilling then?

 

[Terrywookfit]

Sure do!!

Especially if I have been out for an Indian!!

 

[Durgo]

IF the system is piped right it vents itsself hense the term open vented system - thats why you have a vent pipe going to the exspansion tank.
Some people used to put the return valve on the top of rads so they always bled themselves..throught the vent pipe (the one that points into the f/e)

 

[sambotc]

Yep can't rely on someone else to be there all the time.

No matter how you pipe the system or what method you use to fill it you will always have pockets of air which need removing.

How much and how easy is a differant matter!