CH/HW problem.....

[Golotus]

Hi guys - my first post here so be gentle with me

I've had a bit of a look through things and I can't fine anything relating to the problem here, so apologies if its been asked before

We have have a Potterton 40e boiler with a Potterton 2001 control/programmer unit. No real idea of age, though the house is around 15 years old and have no reason so suspect that the water system isn't original.

The problem is that the central heating doesn't come on when asked, but it does seem to run just fine with the hot water is on. Now thats OK when the hot water is actually being heated, but once up to temp, the radiators being to cool, continuing to do so until the hot water is heated again.

I'm guessing the problem is within the control/programmer box? Any thoughts guys?

 

[seco services]

im saying its the motorised valve.

have you a 3 port mot valve ?

 

[MANDATE]

Guess what? I agree with seco. Better get searching, there's plenty on this forum about this problem.

 

[Golotus]

im saying its the motorised valve.

have you a 3 port mot valve ?

erm.............. wouldn't have a clue I'm afraid - any suggestions as to where I'd find it and how to test?

 

[MANDATE]

The pump supplies water to it, which then goes to either HW or CH or both HW/CH. So you'll find it just after the pump.

 

[seco services]

after the pump.
what make is it ? will say on side or top ?

 

[Golotus]

thanks for that

this is a pic of the set up we've got

Bedged up as a Myson Power Extra, a 3 port I think - and it looks like its been a bit warm at some point as the case appears to be a little mishapen (melted). How do I work out if thats where the problem lies?

Thats the main pump just above it is it?

 

[seco services]

wheres the cylinder stat gone ?

 

[Golotus]

wheres the cylinder stat gone ?

not sure what you're asking here - everything you see there is what we inherited when we moved in nearly 5 years ago

Apart from the boost button getting stuck on for days at a time, everything has work just fine up until a few weeks ago

 

[MANDATE]

Your valve responds to the condition of the HW and CH.
It closes the relative port when in a satisfied condition leaving the other port open. unless both HW and CH are both in demand. In which case it takes the mid position and both ports are half open.
The room stat controls the room temperture and the cylinder stat controls the HW temperture, which decides what position the valve should be at and whether or not the boiler should be on or off.
Your cylinder stat should be in the rectangular cut out on the cylinder. It's a integral part of the 'Y' plan. (looks as though the wire is there)
Can't understand why its not there or how it has operated, is it possible it's been moved to another position on the cylinder which can't be seen on the photo.
Regarding the 'valve' you need to remove the actuator head off the spindle then. (a) test spindle for stiffness (b) try the head while off the spindle, ie
first try HW only (valve should drop back if not already back)
Next put CH on, both are on,(valve should move to mid position)
Now turn the HW off. (valve should move from mid position to the CH position) You'll hear boiler stop and restart within a second or so.
You'll find either valve moves to CH only but boiler does not light.
Or it may not move to CH only position.
The problem can be due to 'stiff spindle' or ' faulty motor' or one of the 'two microswitches'
1st microswitch relates to power on grey wire to drive motor over last half of range.
2nd microswitch relates to power coming from valves 'orange wire' to fire boiler.
These microswitches are soldered in and not easy to replace and a replacement actuator head is around £45 and easy to fit. You must remove power and fuse to ensure the 'grey' wire is not live'

 

[Golotus]

many thanks for that - will give it a try

 

[Golotus]

BTW, the cylinder stat.....

Your cylinder stat should be in the rectangular cut out on the cylinder. It's a integral part of the 'Y' plan. (looks as though the wire is there)
Can't understand why its not there or how it has operated, is it possible it's been moved to another position on the cylinder which can't be seen on the photo.

there is a little block on the end of the wire - its not particularly clear in the pic as its quite small. Its kinda wedged in a section of cut out insulation, but it isn't actually against the copper of the cylinder, just near it

 

[nickso]

the cylinder stat is on the wall. the thermistor is on the cylinder on the end of the wire.

 

[Agile]

I dont think the stat has mains isolation so coudn't that sensor potentially be at mains voltage ?

Tony

 

[Golotus]

I dont think the stat has mains isolation so coudn't that sensor potentially be at mains voltage ?

Tony

could that be a problem?


another question if I may...... the side of this motorised valve has a slider switch on it, labled auto and manual overide - what does this do? and how should it operate? On the auto side its almost as if the slider isn't actually connected to anything, on the manual overide it appears to be sprung loaded, and pushes the slider straight back, about half way along its available travel. It doesn't keep itself in the overide position, its only action appears to be to try and shut down the HW side of things, but only while you stand there and hold it down. Is this right?