Central Heating Problems....... Fixored

[GingerMagic]

Hello everybody, I have a problem with my central heating and thought I would ask all you knowledgeable people first, as I'm too tight to phone a plumber......

Right, my boiler works fine on the hot water functions, but it won't cut in when I turn the room stat so it clicks. I know there is power going to the stat as it clicks, but then this signal doesn't seem to reach the boiler. The programmer is working fine, and the display on the boiler shows the demand for heating, but still won't fire up. I've increased the water temperature on the boiler to try to encourage the boiler to fire but still no joy.

I replaced the room stat with a new one earlier as its a cheap fix - still not working..

Is there something that goes between the room stat and the boiler, that may be at fault? There are no faults on the boiler display.....

I'm getting a bit stumped, and my family are getting cold ( luckily the wood burner is in use.... )

Any pointers will be much appreciated, but please bear in mind I am not very good with electricalicity stuff.....

Kelv.

[PeterN]

Hi Kelv

Do you have a meter, a cheap multimeter will do. When you set the programmer to 'heating' check for voltage on the room stat and also on the appropriate connection on the timer. It could be that the system is working OK but the two way valve is not operating thust not switching the hot water through to the radiators.

Look for a motorised valve, it will probably have three 3/4" pipes connected to it (or 22mm if you are young) one from the boiler, one to the radiators and the other to the hot water tank if you have one. I assume its a gas boiler, if so and its a combi, you wont have this arrangement so it could be a fault with the boiler itself.

Peter

[grasmere59]

Have you got a combi boiler or a conventional boiler and a hot water cylinder?

[GingerMagic]

Hi, well - I've always had a dodgy motorized valve where 2 or 3 rads get hot when you put the hot water on. This was replaced but didn't change anything so I just learned to accept that the hallway rad being warm is a way of letting me know the hot water is still on...

I should have mentioned earlier that my boiler is a Gloworm 18, its was fitted in 2009 and has been serviced a couple of times. Its a standard condensing boiler ( I don't like combis ) and it is good on gas - even with this and a new gas range-cooker I use less gas now than I did with my old boiler on its own..

From what I have figured out so far, the boiler will not fire up at all if you want the heating on. The wiring from the room stat goes up to a white box with 4 inputs mounted by the hot water tank. 1 is labelled with 'stat' and 1 is labelled 'pump' , the other 2 have no labelling. The output wire goes directly to the central heating pump, which I guess won't cut in if the boiler doesn't ask it to....

The white box of wires has a cover on it, so maybe if I look under this cover there may be a broken wire or fuse inside?

Power to stat is fine as it clicks ( no power-no click ) and the boiler is working as it should as far as ignition and pumping when putting on the hot water.

[GingerMagic]

Just a thought - does the motorized valve control the boiler, or does the boiler control the motorized valve? It could be a bit sticky but I'm not sure how this will affect the boiler.

I guess I'm buying a multimeter tomorrow..

[grasmere59]

In a normal "y" plan system the 3 port diverter valve has a "hot water priority" unless the room thermostat calls for heat then a small motor inside the valve head (synchronous motor) powers the valve open and at the end of it's stroke hits a microswitch which turns on the pump and boiler,if the hot water tank thermostat and the room thermostat are both calling for heat the 3 port diverter valve will power open to it's mid position microswitch and hold in the mid position giving heat to both heating and hot water.It sounds like the motor within the motorised valve has failed and the valve is stuck in it's "hot water priority" position.There is sometimes a little lever on the side of the motorised with which you can manually override the motor.If you can get the lid off the valve you may be able to replace the motor,there will be 2 wires going to it and check you have 240v to it,if you have when the room thermostat is turned up and it doesn't power open I would suspect it has burnt out.I hope this makes some sort of sense.

[PeterN]

We don't have any gas here unfortunately, have an oil fired Rayburn but at least I don't have to be registered to repair that. We do have a cottage with gas and recently had a fault the opposite to yours, central heating but no hot water, that was a fault in the boiler, a thermostat I think but that is a combi boiler.

If its permanantly on hot water it could be the valve motor either faulty or just stuck, if you take the cover off you should be able to move it manually, or there may be a lever sticking out of the side, you will hear the motor spinning when you move it.

Peter

[lozz]

Not sure on this boiler,
but some have there own built in temp controls on them so you can over ride the room stat,by taking out a link wire on the board. (wiring diagram?)

Tbh you might be best asking a plumber, try here http://www.ukplumbersforums.co.uk/

if you post on there..just add a side note that your not intending on working on the gas side of thing's.
you might get the odd one that will ankle bite

[GingerMagic]

Thank you everyone for your input.

Brett, your explanation of how things work is great - I now understand how the system works ( I thought the boiler/programmer controlled the motorized valve....pffft ) so I will take a sneaky peek at the valve tomorrow. If it turns out to be stuck then I will try to free it.

3/4" or 22mm is fine with me Peter - I was born in '74, so learned metric at school and imperial by my Dad ( miss you Dad ).....

Lozz - I hope no-one takes offence to my post, but its true - I have no intention on facking around with gas and/or electrickery - I just about trust myself with a paper plate...

Cheers, Kelv.

[lozz]

I'know what its like mate,
last winter the boiler in our house decided its time to feck up, (always winter aint it )

ihad about 3 plumbers out 1 after the other all said its this and that, (parts roullete)

after afew hours on the web ..iworked it out and managed to get the thing to work,


As long as you dont touch any gas valve's or anything todo with gas side of it ibelieve its legal,


ours as been torn out now replaced with a high rated combi,

[Welly]

Sounds like you need a new head for the mid-position valve, it's likely to be a Honeywell valve and there's 5 colour-coded wires running to the wiring station within 0.5mtrs. It's an easy DIY job, just turn the power off first. I did mine about 5 years ago I think it cost about £45.00 from memory.

Just check that whichever make it is that you can change the head without draining down. The Honeywell head has a little 'nipple' pressed into the metal casing to indicate it can be changed 'live' as it were.

[GingerMagic]

Thanks Welly. I'm not sure if this valve has a part I can replace - its a MSM plumbing own brand.

I decided to take a look in the airing cupboard earlier, I removed a board which had some switches on it, the top one is the immersion heater and the bottom one is disconnected.

IMAG0794.jpg

As you can see, the valve is annoyingly placed so the wiring is at the back and the motor is facing the cylinder.....

I took the cover off the Motorized valve earlier ( I turned down the room stat and turned off the programmer, just in case ) and here is what I saw...

IMAG0795.jpg

There is a manual control lever at the rear of the unit ( I looked at a new valve at work to compare ) which sits in the middle of the slider. I can push this lever down and hear the motor or something moving, which then slowly returns to the centre of the slider when I let go - there is no place to 'lock' the lever this way. If I lift the lever then there is no resistance at all, the lever simply flops around, which I guess is an issue.

Inside the unit is the motor ( I think ) and a couple of springs. The spring nearest the front moves when I push the manual lever down, but the longer spring nearer the back doesn't move when I lift the lever up to the floppy part of the slider

IMAG0796.jpg

I tried to gently tap the big silver bit and around the springs but nothing happened - I guess its a new Motorized valve for me then....
About £40 for a Boss 3 way valve from work.

[Welly]

Not sure if you can replace the head on those but its very close to the cylinder for screwdriver access

[GingerMagic]

Yes, not very forward thinking was it......

At least I have a stack of firewood to tide me over.

[PeterN]

http://www.ebay.co.uk/itm/MOTORISED-ZON ... 4adac9b6b1