radiators luke warm

[newbie33]

hi,

I have been having problems with my central heating, the radiators are only getting luke warm.
I have a thorn apollo boiler, fitted with a 3-port valve (honeywell)
When i turn on central heating only I can feel the pipework going into and coming out of the cylinder is getting warm.
This results in scalding water at the taps, which i would assume is the valve letting by?

I have downloaded the wiring diagram for my system from the honeywell site.

I am quite competent with electrics and have checked a few things with my multimeter, But the confusing thing is i am getting 240v at the common on the cylinder thermostat, when only central heating is switched on?
So I assumed that the honeywell timer was faulty, I replaced this but I am still having the same problem?
Heeeeeellpppppp....... somebody please

 

[D_Hailsham]

The FAQ on How the mid position valve works has detailed instructions on checking the valve.

 

[MANDATE]

When 'only CH is on' HW must be off. The wire from the HW OFF terminal of the programmer supplies power to the satisfied terminal of the cylinder stat either directly or via the valves grey wire.
If HW was in a satisfied condition when you checked it, the common of the stat would be linked to the satisfied terminal and you would get backfeed showing 240v, but its not connected to the 'not satisfied terminal' or the programmer (HW is not on)so it's not taking any active role.
Does that make sense

 

[newbie33]

Thanks D_hailsham... I have had a look at that post.
I think that I can understand the operation of the 3-port valve, and i have checked throught the wiring.

I just can`t understand why I am getting 240v at the Common to the cylinder thermostat, when only the central heating is switched ON on the programmer.

I have removed the 2 wires from the wiring centre at the terminal strip ( Hot water on & C on the room stat) and the 240v is actually coming from the Common on the cylinder thermostat.
I also was seeing 240v from pin 1 on the cylinder t/stat.
This voltage disappears when central heating on the programmer is turned off.
I am a little bit confused??

 

[D_Hailsham]

Just a thought. Which model Honeywell valve do you have - V4073 or V4044? They are physically identical.

 

[newbie33]

its a mid position valve V4073, it has 5 wires

 

[D_Hailsham]

its a mid position valve V4073, it has 5 wires

That's shot down my thought that it might be a W plan (hot water priority system).

It is obvious that something is wired incorrectly. It's just a case of checking and double checking everything.

The FAQ tells you how to carry out the checks. Do them and report back what you found.