CH working but no HW

[central1]

Hi there, I'd be grateful for some help if poss

7 day programmer with seperate CH and HW controls
glow worm 30 sxi boiler in the garage and a megaflo HE CL210 indirect cylinder.

System was installed in a new build two and a half years ago.

I drained the tank of hot water, switched both of the switches off in the airing cupboard next to the megaflow, and the gas boiler in the garage fires up in response to putting the CH on, but not in response to putting the HW on.

Any ideas?

 

[seco services]

what did you drain the tank for ?

 

[central1]

I only drained it out of the tap in the kitchen, just to make sure that there would be a request to the boiler to fire up to heat the water.

 

[seco services]

check your motorised valve next to the cylinder.

http://www.toolstation.com/images/library/stock/webbig/85125.jpg

 

[central1]

Ok will do is there anything I can look out for which would tell me it's not working properly? Thanks for your help btw.

 

[seco services]

do you have two of these valves

 

[central1]

yep, two

 

[seco services]

one will be heating one hw.
on the end is a lever so when their is no call the lever will have resistance.
when their is call the lever will be loose.
put the hw on calling and see is the lever is loose or tight if tight push it across by hand and see if the boiler fires up.
motor may have gone in the valve.
you can clip the lever in a slot when pushed to manual.

 

[ChrisR]

more here:
//www.diynot.com/forums/viewtopic.php?p=243656#243656

 

[central1]

Thanks guys, that is really helpful, I will try when I get home and let you know what I find, thanks again.

 

[central1]

There are indeed two valves, the one nearest the megaflow did have resistance when there was no call from either ch or hw, and the second valve furthest from the megaflow was in the manual open position.
I put the hw on, and ran the hot tap, and the resistance in the first (nearest) valve did disappear, but the boiler didn't fire up.
Am I also right in thinking that the motorised valves power supply is likely to be the top socket in the airing cupboard (the bottom socket is wired into the lower part of the megaflo)?

Just to add, 10 mins later, the resistance in the first (nearest) valve is still gone, and the top of the valve has just warmed up slightly, and I can feel a very gentle whirring from the valve. The pipes either side of the valve are still cool. The second furthest valve is still cold, and resistance present.

 

[seco services]

sounds like the motor is working as you have lost reistance on the lever.
but the motor shouldn't still be running after to mins.

you may have a faulty microswith in the top of the valve.
you need to find your wiring centre and check power on the orange wires from the valve to power up the boiler/pump

 

[central1]

Ok I just thought I would post an update.
My friend is a corgi heating engineer. I mentioned it to him and he had a look.

In short it was wired totally wrong.
There was no power to the CH motorised valve which was left in manual open
There was no permanent live to the boiler.
The permanent live was supplied by the froststat which was set at 20 degrees!

In short he has used his diagnostic skills and changed all the wiring connections in the wiring block in the airing cupboard, and turned the froststat down to 3!

I am totally shocked that it was wired from new with so many mistakes, and also that it functioned fine providing CH for 2 and a half years, with the immersion providng the hot water.