Heating system not switching on - Worcester 20/25 + megaflo

[broomradioman]

Dear All,
I have a heating system that wont switch on. No power to boiler but programmer powered up and lit up fine . Boiler is an oil fired Wrocester 20/25 Danesmoor and the tank is a Megaflo 210. I have two Honeywell motorised valves one is a V4043H1056 and the other at the bottom of the tank is a Honeywell 272848. The boiler wont switch on and there's no power or reset light. When I manually opne EITHER of the motorised valves the boiler fires up for a second or two then swtiches off as the arm moves back slightly even when recessed in the manual detent.

Is it the motorised valves or something else?

Thanks for any pointers and best wishes for 2011

Jim

 

[Tibbot]

You will need to eliminate each component in turn. Check power at motorized valves, they are fed by cylinder/roomstat which in turn are fed by programmer. A multimeter/voltage tester will be required to find where the fault is. On the Megaflo there is also a thermal cut out to the stat if it overheats. Are you sure neither CH or HW work?

 

[doitall]

You will need to eliminate each component in turn. Check power at motorized valves, they are fed by cylinder/roomstat which in turn are fed by programmer. A multimeter/voltage tester will be required to find where the fault is. On the Megaflo there is also a thermal cut out to the stat if it overheats. Are you sure neither CH or HW work?

The thermal cut-out is fine otherwise it would fire up in the manual mode.

I would suspect the heating actuator, programmer or room stat.

 

[broomradioman]

With no intervention from me there is no power to the boiler but there is power to the programmer. The boiler does not switch on and i've checked the reset switch and it has not fired. I have set the programmer to permanently on for both HW/CH (leds lit) and still no power to boiler. When I move the arm on EITHER of the motorised switches I hear the microswitch click and the system fires on for a second or so and then as the arm moves back slightly even in the manual detent, then switch is un pressed and the power goes off.

If I remove the cover on the top motorised valve and manually press the microswitch with a piece of plastic then the boiler is powered up and runs normally.

I suspect it may be a duff motorised valve and will need a plumber to fix

any other thoughts

Cheers and best again

Jim

 

[Tibbot]

I thought he was getting manual fire.

 

[doitall]

If there's a dimple on the silver case (top) take the actuator off and check the shaft is free in the valve.

With the actuator off it may go right over and fire the boiler up.

 

[doitall]

I thought he was getting manual fire.

Yes I worked that out before your post

 

[Tibbot]

You will still need to prove power is going from stat supply to the relative brown wires on each valve. Only because it's unlikely both have failed.

 

[broomradioman]

and the supply to the thermostat is where? On the motorised valve there are several wires going to the motor and two wires (grey and orange) going to the microswitch. With the microswitch jammed closed and the programmer on "always on" the system is running for now at least so we have hot water and heat. This will need professional help as I dont want to overpressurise the megaflo and blow/flood the house on new years day, that way divorce lies!!

system has run fine without a cough for 9 years so cant complain really!

let me know if there's any further suggestions in case it is something simple

I was thinking that maybe the prgrammer has had a wobble even though it looks ok? We had a power cut for 1 hour last night and maybe a surge has fried something. The programmer is a Siebe Lifestryle LP522

cheers again

Jim

 

[simond]

Not unlikely, it sounds like the MVs are OK.

Turn off the LX, remove the LP522 and you should be looking at a wallplate with NL1234 connections.

Run a wire from the L terminal to the 4,, mind your fingers and turn the juice back on. You don't need to replace the Prog 522 other than to cover the live connections.

If the heating fires up you have a duff programmer. You can temporarily replace the 522 to cover the backplate leaving the link in place, and run the CH on the thermostat.

NB: If you want the HW on as well, link L to the terminal 3 also.

Most programmers, such as the Honeywell ST9400, Drayton LP722, etc use the same backplate so it won't take long replacing it if you buy the right compatible unit.

 

[Tibbot]

Which valve have you jammed? What about the other? Are you saying both give same result? Have you tried the circuits individually. If you're unable to carry out these tests then, as you mention, you may need someone in. You shouldn't jam the Megaflo one as it acts as one of it's safety devices.

 

[broomradioman]

Its the one not near the megaflo inlet but up near the boiler and programmer that I've jammed. I'm going to swithc the boiler off manually overnite anyway so nothing should go awry and then trun it back on in the morning

 

[broomradioman]

One last question before I adjourn to the village hall for new years eve, how do I remove the Lp522 programmer? Does it pull of?, Snapp off? slide off? or screw off?

cheers

Jim

Happy new year to all and thanks to you all for the informative and useful replies!!

 

[simond]

two small screws on lower edge. Loosen screws to clear casing, and unhinge prog from backplate by pulling lower edge forwards

 

[broomradioman]

Programmer is fine so its looking like the top MV. Just checked this morning and it seems fine for now and is working normally so perhaps I've loosened up whatever was sticking, though I know it wont last so i will get another MV to be sure. I think the fault is in the microswitch that the arm on the rotor presses. The microswitch does look a little flimsy to say the least!

Thanks for all the tips and guidance and at least now I know a little more about how my system works!

Best wishes for 2011 to all

Jim