Author Topic: Heating/boiler operating even when set off at control box...  (Read 903 times)

Heating/boiler operating even when set off at control box...
« on: January 02, 2019, 09:15:09 am »
It's a conventional vented system with two year old boiler, hot water tank and honeywell 3 port valve. 

Last night I noticed that the rads were still hot, even though the heating timer on the Drayton LP522 control box (airing cupboard) had long since turned off.  I found I could turn the boiler on and off using the wall thermostat, even with the heating set to OFF at the control box.  We have hot water, and this morning with the rads cold, and wall stat turned down, I used hot water from tap, and the boiler hot water kicked in - so I think hot water is fine.  With HW on, the control box HW button does turn the boiler on/off.    I wondered about a frost stat operating, but AFAIA there is none.

Any ideas why the heating now appears not to be controlled by the CH/HW control box at all, and only by the wall stat? Where do you reckon the fault may be?  What can I check?
"an inordinate fondness for beetles"

Re: Heating/boiler operating even when set off at control box...
« Reply #1 on: January 02, 2019, 10:33:59 am »
I *think* that the timer usually controls the three port valve, which then turns on the heating.

As such, if the 'synchronous' motor in the three port valve has failed and the valve is stuck in the heating on position, the heating will remain on.

Try manually moving the valve - if it is the same honeywell valves as in our system, there is a lever on the side that you can move. If this is the problem, you can buy the motors from ebay for pennies.

Re: Heating/boiler operating even when set off at control box...
« Reply #2 on: January 02, 2019, 11:08:10 am »
I'd concur with faster. AIUI any frost stat would be associated with the boiler, and for protection of same, so would kick in and just heat up the primary loop to prevent boiler freezing.
We are making a New World (Paul Nash, 1918)

Re: Heating/boiler operating even when set off at control box...
« Reply #3 on: January 02, 2019, 12:36:03 pm »
Thanks both.   I checked the user manual, and under 'frost protection' it says a Frost stat can be fitted to protect garages / storage rooms, so there doesn't appear to be anything built in.

Re. Honeywell 3 way valve, we do have CH & HW atm.  AIUI  if valve was stuck in CH posn we'd have CH/hot rads, but no HW.   If the 3w-valve was stuck in mid posn,  I think the rads would get warm when the HW was on.  From this am, it appeared that the HW works fine,  with the CH wall stat turned down and with the rads staying cold.   ???
"an inordinate fondness for beetles"

Re: Heating/boiler operating even when set off at control box...
« Reply #4 on: January 02, 2019, 01:17:27 pm »
It sounds like it might be miswired and the CH side of the controller isn’t in circuit, or at least not in the right place. AIUI it’ll normally be in series with the room stat, so if the controller is off the thermostat shouldn’t do anything.

Re: Heating/boiler operating even when set off at control box...
« Reply #5 on: January 02, 2019, 01:29:15 pm »
It sounds like it might be miswired and the CH side of the controller isn’t in circuit, or at least not in the right place. AIUI it’ll normally be in series with the room stat, so if the controller is off the thermostat shouldn’t do anything.

Thanks, I wondered about this, particularly since different firm once wired our CH pump incorrectly.  The thing is I reckon we'd have noticed if it had been miswired two years ago, and the CH couldn't be operated by the Drayton controller, as I'm pretty sure we've used the CH advance button etc on the controller box sucessfully.  HW appears to operate and be controlled Ok, so could it be a microswitch thingy, somewhere in the CH circuit that has gone I wonder...   

edit.  I have powered everything off, and back on, so doesn't appear to be fixed by 'rebooting'.
"an inordinate fondness for beetles"

robgul

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Re: Heating/boiler operating even when set off at control box...
« Reply #6 on: January 02, 2019, 05:22:54 pm »
The diverter valve could just be intermittently sticky - it happened a couple of times on our old boiler and we just replaced the motorised bit.

Rob

Re: Heating/boiler operating even when set off at control box...
« Reply #7 on: January 02, 2019, 06:04:58 pm »
Thanks both.   I checked the user manual, and under 'frost protection' it says a Frost stat can be fitted to protect garages / storage rooms, so there doesn't appear to be anything built in.

Re. Honeywell 3 way valve, we do have CH & HW atm.  AIUI  if valve was stuck in CH posn we'd have CH/hot rads, but no HW.   If the 3w-valve was stuck in mid posn,  I think the rads would get warm when the HW was on.  From this am, it appeared that the HW works fine,  with the CH wall stat turned down and with the rads staying cold.   ???

Still worth having a poke around in the valve in my opinion, as iirc it contains micro switches which turn the boiler on and off. The control bit on top separates quite easily from the water/valve part underneath and it would be worth testing the switches and checking if they are activated or not.

arabella

  • no se porque yo no lo se
Re: Heating/boiler operating even when set off at control box...
« Reply #8 on: January 02, 2019, 07:37:14 pm »
I had a related problem where my hot water was always on.  This was after plumbers and electricians had been and gone and checked the motorised valve, thermostat etc due to <not quite sure really, but the heating wasn't working before and was after>.

I changed the controller having left everything off for a weekend with no reduction in HW temperature.  I knew it wasn't the heating as it was summer by then and satisfactorily off.
This solved it, I think. Well, no noise in the night when it should all be off so I assume success.
In the dark, all views are the same.

Kim

  • 2nd in the world
Re: Heating/boiler operating even when set off at control box...
« Reply #9 on: January 02, 2019, 07:46:43 pm »
PSA for *combi* boiler users: Heating always on means the diverter valve or the microswitch connected to it (both inside the boiler) is b0rked, fooling the boiler into thinking that hot water is being drawn when it's actually heating the radiators.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Heating/boiler operating even when set off at control box...
« Reply #10 on: January 02, 2019, 08:23:43 pm »
Thanks.  The boiler's being serviced soon, so will get the engineer to take a look.  If it's the boiler, that's under warranty.  IME if it's the 3 way valve, the whole lot normally gets replaced, as they say 'the valve, was probably sticking and stressing the motorised bits'; system drain down etc... 
"an inordinate fondness for beetles"

Re: Heating/boiler operating even when set off at control box...
« Reply #11 on: January 02, 2019, 11:19:26 pm »
PSA for *combi* boiler users: Heating always on means the diverter valve or the microswitch connected to it (both inside the boiler) is b0rked, fooling the boiler into thinking that hot water is being drawn when it's actually heating the radiators.

Not in this case though - in the first post the OP confirms that with the thermostat turned down (boiler off), the boiler kicks in when hot water is drawn, which makes me believe both the diverter valve and associated microswitch are likely to be fine.

Gattopardo

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Re: Heating/boiler operating even when set off at control box...
« Reply #12 on: January 02, 2019, 11:22:48 pm »
What is the boiler, make and model.

Kim

  • 2nd in the world
Re: Heating/boiler operating even when set off at control box...
« Reply #13 on: January 03, 2019, 12:06:04 am »
PSA for *combi* boiler users: Heating always on means the diverter valve or the microswitch connected to it (both inside the boiler) is b0rked, fooling the boiler into thinking that hot water is being drawn when it's actually heating the radiators.

Not in this case though - in the first post the OP confirms that with the thermostat turned down (boiler off), the boiler kicks in when hot water is drawn, which makes me believe both the diverter valve and associated microswitch are likely to be fine.

The OP's boiler isn't a combi.
To ride the Windcheetah, first, you must embrace the cantilever...

Feanor

  • It's mostly downhill from here.
Re: Heating/boiler operating even when set off at control box...
« Reply #14 on: January 03, 2019, 12:21:00 am »
It's time to get a meter out and follow the call for heat signal from the timer, through the stat and any zone valves into the boiler.
Otherwise we are just guessing.

Re: Heating/boiler operating even when set off at control box...
« Reply #15 on: January 03, 2019, 04:34:41 pm »
It's worth watching John Ward's excellent series on central heating wiring;

https://www.youtube.com/channel/UC2uFFhnMKyF82UY2TbXRaNg

I was able to diagnose a faulty switch within the 3 port valve using his guides.

Re: Heating/boiler operating even when set off at control box...
« Reply #16 on: January 07, 2019, 09:58:25 am »
Apparently it's the controller, probably a faulty microswitch creating an on circuit in the box.    :-\   240v wall thermostat checked out OK.
"an inordinate fondness for beetles"

hulver

  • I am a mole and I live in a hole.
Re: Heating/boiler operating even when set off at control box...
« Reply #17 on: January 07, 2019, 10:30:07 am »
Apparently it's the controller, probably a faulty microswitch creating an on circuit in the box.    :-\   240v wall thermostat checked out OK.
I had something similar when we moved into our current house. Heating and How water running at weird times. I looked for a replacement and found it had been replaced by one that had identical wiring and back plate. Swapping it over was super easy.