Have a problem with my central heating.
The bolier seems fine - pilot light comes on etc & propelor spins freely.
But the radiators don't heat up at all in the house.
If I turn up the setting on the boiler the pipes make a racket too - kinda clunking sound.

Do I need to bleed the radiators ? This was done about 6 months ago - though the heating hasn't been used much for a while due to the good weather in the uk recently.

Any help ?

Thanks

Ro.

 

Definately bleed the rads. Try the highest one to see if theres a lot of air in the system. Could be the pump or gate valve seized too, is the pump operating properly ?

 

Place a screwdriver onto the pump, and put your ear to the handle. You should be able to hear it whirring. It may just be stuck, so try turning themain pump using a large screwdriver - they have what looks like a big screw on the front.

DW

 

If your hot water is still heating up (assuming it is heated by your gas central heating) then you probably have a knackered diversion valve.

Look for a small silver box on top of a junction of three pipes, usually somewhere near the hot water tank. The middle pipe is the hot water feed from the boiler, and the other two are the legs for the hot water cylinder and the central heating loop.

There is usually a small lever on the box which allows you to manually control the solenoid valve. If when you move the lever one of the pipes suddenly gets hot then the solenoid motor is probably burnt out and needs to be replaced. You can usually swap the motor body without having to touch the pipework.

Good luck.

Cheers,

A.

 

Done that (I think) !!
I undid a screw on the front & inside was a propelor which turns freely using a screwdriver.

I think (I hope) that the pump & boiler are OK - so a bit puzzled as to why the radiators dont come on.......

Ro.

 

you may have air in the system rather than in the radiators. try turning off all the radiators bar 1 and see if that then heats up. then turn the radiators on one by one. i do this to get my rads to work when i drain he system.
Michael
edit to say - then drain any rad that is not fully heated up
another edit! should say bleed line above not drain!

[Edited by super slider - 4/11/2002 10:30:39 AM]

[Edited by super slider - 4/11/2002 10:33:18 AM]

 

As above - turn on the radiator upstairs which is closest to the boiler. Open the bleed valve and let it run. you might need to collect a bucketful of water, so be prepared. The boiler is obviously ok, so even gravity should allow thet rad to heat even without the pump if there is no airlock.

 

Ro,

The diversion valve isn't the same thing as the circulation pump - sorry if I misunderstood you.

The diversion valve is a pipe t-junction with a valve body in the middle, and a black or silver solenoid motor on top which moves the valve to control the flow of hot water from the boilder to either hot water only, central heating only, or both.

It is usually located somewhere near the hot water cylinder or boilder.

It is quite possible that the valve is diverting your hot water into the cylinder only because it is stuck in that position due to silt, rust and other crap in the valve - especially if you CH has been off for months.

In that case, the valve will have been sitting in one position for some time, and may have got stuck and burnt out the solenoid.

If you can locate it, set the control panel to HW ON with CH OFF, and turn the thermostat up to make the boilder run. If the valve is operating properly, two of the three legs at the valve will be hot, with one cooler (input and HW loop hot, CH loop cold-ish). Get someone to turn CH on, and listen for sound of the movement of the solenoid, and water. The cold pipe should then go hot. If not, the valve is stuck or knackered. If it does then you either have a problem with airlocks (bleed everything thouroghly) or the circulation pump (assuming the system isn't gravity fed).

Good luck.

Alex (amateur cental heating engineer!)

 

Alex m,
could be gravity hw though

Look in loft for c/heating tank,its probably bone dry!Refil with water

If its a combi boiler look at boiler pressure gauge,if its on 0bar refil with water upto 1bar on gauge.

unscrew silver screw on pump(i presume its a grundfos pump)check water comes out,rotate impellor with small screwdriver.

look in cylinder cuboard for silver box/boxes there is a lever on the side which moves according to room temp/water temp etc etc,move this across and lift up slightly and it shoud stay in the manual cutout(it wont spring back and close cos you have wedged it open).
put boiler on for heating and hot water,check rads again.

Depending on the type of system,y-plan,fully pumped,gravity hot water,Combi boiler,sealed system etc etc,there are a lot of things to go wrong.

please supply more info,e.g is it a combi?make of boiler?do you have 2 water tanks in loft?sort of pump?any mid-position,zone valves?


Duncan
Corgi registed professional installer

 

I am no expert - so here goes

All central heating controls & hot water controls are in the garage with the boiler (the thing with the pilot light?)
From here you can set either HW or CH to come on once/twice or 24hr - or off.
There is also a dial on the boiler going from 1-5 which I assume is related to the hot water ?
In the house on the wall in the hallway is a thermostat that controls the radiators.
Upstairs in the airing cupboard is a hot water tank with an on/off switch (not investigated further in this cupboard so cant tell you what else is in there)There is a radiator in the bathroom which seems to have a life of its own & comes on differently to the others.

Hope that helps !!

Ro.

 

Ro,
Main thing is, are you still getting hot water??(without using immersion heater)?...Anyway...
switch boiler on using timer/clock.
does boiler fire up?(not just pilot,the main burner)
have a look where the boiler is.Is the pump near it?
If it is ,see if there are any silver boxes on the pipework near to the pump.
Also have a rummage around the cylinder(hot water tank)its common practice to put the pump and divertor valve near the cylinder(well, it is up north!)
So you have a room stat in the hallway,turn up to full.
Check rads again.
if nothings happening, look at cylinder,is there a small thermostat stuck to the side of cylinder??..If so,its a fully pumped system with divertor/mid-position/zone control,valves.
There must be a siver boxed thing on a pipe somewhere!

Before the technical stuff, have a look in your loft at the central heating water tank(the samller of the two).It should have water in it.sometimes the water evaporates and the ballcock gets stuck,so it doesnt refil the system.(usually only the downstairs rads work because they still have water in)

also the pump may be on its last legs,causing the circulation to be very poor.

check simple things first.Tank full,water in rads(open vent a little on rads,check for water),boiler firing,pump running and not stuck,room stat set to full,are we getting hot water like normal?......Got to get back to work now,but i will check back here after 6pm.....have fun....


Duncan.

 

Also is the thermo switch in the hallway firing the boiler. It should make a clicking noise, then the boiler should fire.

You have the same setup as I have here, and my bathroom rad also seems to be funny at certain times.

DW

 

nope - the thermostat "clicks" & the boiler doesn't fire - does that mean a new thermostat ?

Ro.

 

Bathroom rads are sometimes tapped off the hot water flow and return,instead of central heating pipes.these will only work when the hot water is on.

Ro,you havnt said if the boiler fires for hot water??
Do you get your hot water from the boiler or is it electrically heated,eg imersion heater!!???

please check what i have said in previous reply's.
if tank is full with water and your getting hotwater in the cyliner using boiler its probably a syncron motor,that goes in a divertor valve,only about £10 and easy to fit.

 

This happened to us the other day. Turned out to be a combination of a bit of air in the system and a stuck valve - well it was the valve but the air once bled made the rads hotter

Didn't cost a lot and had it serviced at the same time.

 

Many thanks to everyone who offered advice.

Scooby Nutter your advice in particular was really really great.

Turned out to be the syncron motor as you thought as hot water in tank was always OK.

The whole system is getting old now (20plus years) so I have taken out a maitenance contract with British Gas for £15 per month which I think is good value considering I anticipate lots of work being needed on the central heating in the near future.
Speaking to neighbours with similar aged houses & same central heating set up it seems that I am nearly the only one who hasn't had boilers/pipes/valves replaced yet - so best take out some insurance.

To call out an engineer would have been £80 call out for the firat hour plus £17 per 15 mins afterwards plus any parts !!

Think I am in the wrong business !!

Thanks again all

Ro.

 

Ro,
no problem for helping you out.
glad its sorted.

I would have charged £40 all in,to diagnose,and replace syncron,that Includes new motor!

theres a hell of a difference in price around the country



Duncan.

 

Blimey - wish i lived nearer blackpool now !

Thanks again

Ro.

 

[Edited by bros2 - 7/2/2003 1:12:55 PM]