Central heating alone doen not work, needs hot water to be o

[ashisdas]

I have a problem with my central heating system. When I only switch on the heating id does not work. I need to switch on the hot water & central heating together. Hot water alone does work. any idea, what is is wrong with the system.
Ashis

 

[xtrapnel]

but I have a little bit more information than the original poster.

Old fashioned CH system, i.e. hot water tank fed off boiler, not a combi.

Hot water kicks in fine, central heating not regardless of thermostat setting.

Have taken the motor of the HoneyWell motorised valve off, checked valve can move. Have managed by putting hot water control on to get some heat to rads, but boiler obviously turns off once tank is hot. Hot water hotter than would usually be.

Turned off at mains all central heating controls, switched off and restarted old boiler, no joy.

Suspect (hope) that the temperature thermostat on the wall (dial version) might have blown.

Had whole system checked out and lots of work done <3 years ago (would have been cheaper to get a new system the way it turned out). New heat exchange etc. fitted.

Now completely skint and need to try and fix this myself if at all possible. All help gratefully received.

Sorry OP for hi-jacking your thread, hopefully some info posted will be of use to you as well, think you'll need to describe what system you have for people to help you though.

 

[Agile]

Two people posting with problems.

But neither bothers to tell us what model of boiler they have!

Tony

 

[xtrapnel]

OK, sorry, will give details.

All controllers Honeywell.

Boiler is old-style (not Combi) Ideal Classic RS.

Have read the Wiki - currently getting some heat (not much !) to rads by turning up water thermostat, turning down boiler stat, and getting heat that way.

NB the valve having taken off the Honeywell motorised valve unit doesn't seem to move more than 10 degrees in either direction...doesn't feel stiff, that seems the limit of its travel. And also which way should it be turned - anti-clockwise or clockwise - to divert the heat to the rads not the boiler ?

MANY THANKS for any help you can give - I am trying to DIY by reading manuals and wikis etc.

 

[xtrapnel]

Another update: after having emptied the tank of hot water, and following the instructions in the Wiki to set hot water tank temp to 70C and the boiler stat down to 1, I set both the hot water and CH to be on constantly.

The rads are now hot (good), the hot water tank is still cold to the touch, and the boiler is no longer on (pilot light only).

Does this help with a diagnosis ?

Cheers.

 

[Armo74]

Sounds like the motor has gone and not moving the valve over to heating to fire up the boiler and pump. A new motor can be purchased. What you are doing with the hot water and boiler thermostats is only a temporary solution.

 

[xtrapnel]

Thanks for this - I wonder though, if I move the valve over manually - to either position - the CH doesn't "kick in" i.e. the boiler doesn't fire. Surely if it's the motor, moving the valve manually would achieve this.

Would that not indicate it might be the wall temp. thermostat that's faulty ?

Thanks for your reply.

 

[Armo74]

What it would indicate is that the microswitch has more than likely gone aswell, so it looks like it is going to be a new actuator.

 

[xtrapnel]

Dear Armo.

Thanks so much for your helpful replies.

OK, so as I'm obviously very ignorant about all of this:

- There is a Honeywell unit on the side of a three way pipe assembly - one pipe coming down (presume hot feed from the boiler) which has a pump on it (which appears to be working) , one going right into the tank, one going left and down into I presume the rads.

- This unit is the one I have taken off the assembly - behind it is a small valve that I can turn manually - like I've said, only about 15 degrees in either direction.

- I take it the assembly - i.e. the part containing the valve - is the actuator. So I would need something like this to replace it ?

http://www.plumbworld.co.uk/danfoss-2-port-motorised-valve-769-12718

If so, need to call a mate in I think !

MANY MANY MANY thanks for your help on this.[/url]

 

[Agile]

Another update: after having emptied the tank of hot water, and following the instructions in the Wiki to set hot water tank temp to 70C and the boiler stat down to 1, I set both the hot water and CH to be on constantly.

Cheers.

A cylinder should not be set to higher than 60° C.

I dont imaging the WICKI really says that ( its dangerous! ).

 

[Armo74]

The actuator in your picture is the plastic box, I assume yours is a silver box as it is a honeywell. The boxes contain the motor and the microswitches. Please do not attempt it if you are unsure, Also take note of what tony has posted.

 

[xtrapnel]

I was just following the advice on your wiki (see the section about what to do if the hot water's working the heat isn't). If that's not right, maybe it should be changed. Without sounding snotty - I'm just a poor layman (in every sense of the word) who's following advice - part of which (quite rightly) is READ THE WIKI before asking questions...

 

[xtrapnel]

Arno.

Sorry to keep plaguing you with questions ! What I can't understand is - if that silver unit (Honeywell, with the dimple on the box) has been taken off the assembly on which it sits (as I have done) and I'm operating the little valve it's meant to control manually, then surely the system should be working, if I've effectively by-passed the faulty part of the system by operating the valve myself.

If the CH controller is set to on, and the temp. thermostat (the round dial on the wall) is set to a higher temperature than the house is currently at, at the moment, the boiler is not kicking it. Regardless of where I'm moving the valve to - full anti-clockwise or full clockwise - on the housing that the Honeywell unit would normally sit on.

Really sorry if I'm being dense here. Obviously though with money at a premium, I want to make sure I buy the right part.

Many many thanks

 

[xtrapnel]

Another update: after having emptied the tank of hot water, and following the instructions in the Wiki to set hot water tank temp to 70C and the boiler stat down to 1, I set both the hot water and CH to be on constantly.

Cheers.

A cylinder should not be set to higher than 60° C.

I dont imaging the WICKI really says that ( its dangerous! ).

Here's what the Wiki on this site says (cut and pasted):

10) HOT WATER OK BUT RADS COLD (or vice versa) THANKS TO CHRISR

Usually down to motorised valve failure

This will work for fully pumped systems, for both a single 3 port valve or two x 2 port valves. Or a combination, come to that.

To get you warm, turn the cylinder thermostat right up to 70, and the boiler thermostat down to 1. Then put the CH valve lever (3 port valve lever) in the hooky place which holds it in the MAN position.

Read more: http://www.diynot.com/forums/plumbing/boiler-central-heating-faqs.175736/#ixzz2IpkMUTkT

 

[Armo74]

A temporary fix for hot water but no heating is to turn the cylinder stat up slightly and boiler stat down so the hot water thermostat doesn't become satisfied with just hot water on at the programmer. With the valve manually moved.