Can't control central heating on its own

[wilro15]

On our heating we can't seem to turn on the central heating on when we want to. We have a back boiler, mid-position honeywell 4000-3916-003 valve, room thermostat, cylinder thermostat and a Siemens RWB9 programmer.

The only way we can get the heating to come on is to turn up the temperature on the cylinder stat and force the valve open by pushing down the lever. This means as soon as the hot water tank reaches its temperature the heating goes off.

Can anyone help and suggest what the problem might be?

Thanks in advance for your help.

 

[Youllneverguess]

Dead valve/valve motor. Replace valve/valve motor.

 

[45yearsagasman]

Honeywell synchron motors are readily available.
View media item 37352

 

[wilro15]

Really? This will be the 4th time in 9 years that its been replaced. What causes them to fail?

Why do I also have to turn up the temperature on the cylinder stat?

 

[ChrisOxford]

Honeywell synchron motors are readily available.

...even from Wickes (at a price): http://www.wickes.co.uk/invt/443039

 

[45yearsagasman]

With a dead synchron the only stat that has control is the cyl stat and the water temp in the cyl will increase, hence the need to turn the stat up.
Curious as to why, if this has happened 4 times before, you didn't suspect the motor this time?

 

[wilro15]

Because I'm new to all of this, and I was thinking that it shouldn't really fail this often.

Is it normal for these to last only 2 years or so?

 

[Agile]

Its not normal, they often last at least 10 years.

Perhaps you keep your valve hot by covering it with clothes?

Perhaps the replacements were cheap ones and not genuine "Syncron" ?

Tony Glazier

 

[wilro15]

It gets hot, but only because hot water goes through it. Otherwise its not covered up. Not sure if it was replaced with a genuine Synchron before - it was always done by a plumber so I was never sure what they were doing.

Thanks for your help, everyone.

I will look at getting a new one, am I right in thinking I have to drain the system to do this?

 

[45yearsagasman]

No, the motor can be replaced without draining. Isolate electrics and remove silver cover from valve and all will be revealed.
They are not polarity concious.

 

[wilro15]

Awesome, I'll go ahead and order one.

Wish me luck!

 

[wilro15]

The broken valve says "Synchronous Motor 230V 50HZ Z5 RPM". Does that mean its a cheap one?

 

[45yearsagasman]

Get a genuine Honeywell part if you can, it will be packaged as a genuine part. Your present one may not be.

 

[wilro15]

For what its worth, it wasn't the Synchron motor. I replaced it last night and nothing has changed.

I hit "CH ON", the red light comes on the controller but no activity anywhere else. I hit "HW ON" and everything comes to life but the radiators stay cold. If I then manually push the lever on the valve the radiators heat up.

Interestingly if I then turn off CH, the valve lever will move itself back. So the programmer can talk to the valve ok.

I will be trying a new room thermostat tonight. It has to be that the stat isn't calling for heat even though it is turned up full.

 

[BlueMoonMole]

Insead of forking out for a Room Stat, link it out temporarily...

Isolate the electrics, place a cable between the wiring in the Room Stat and away you go!