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Author: Subject: Heating engineers - Help please!
russbost

posted on 14/10/20 at 08:24 AM Reply With Quote
Heating engineers - Help please!

Our CH is a Worcester Bosch boiler (7 years old) with hot tank, fairly old (20 years?) Honeywell programmer & modern generic programmable thermostat.

Recently the heating has sometimes been coming on on it's own, ie when the thermostat is telling it it's already hot enough & to shut down. We leave the programmer on constant for the CH & the hot water is timed to come on morning & evening, but sometimes, in the middle of the day or night the heating will be on even tho' the stat is saying it's off - there is a small symbol on the stat which says when it's asking the boiler for heat, so you can tell when on or off.

Even if I go & turn both CH & HW off at the programmer, & wait a couple of minutes for the boiler to shut down, it's still going & the main pump is still running - the only way I seem to be able to stop it is to unclip the 2 way valve motor from the valve, use the little lever on the side to drive the motor to the HW position - this is sometimes VERY stiff to push across (whenever the heating is jammed on, it's always in the CH position) reset the valve to match the HW position & refit the drive motor. If I then turn heating on constant & HW on timed as normal with the stat not asking for heat everything seems to then work normally for a couple of days.

I can't see it can be the programmer as switching that to off doesn't stop it, I guess it could be the internal control of the boiler as I know that always hangs on for a couple of minutes or so after everything is turned off, but if that's the case why would messing with the 2 way valve affect
it ?- it would seem to point at a fault with the 2 way valve or motor, but I still don't understand where the boiler is getting it's feed from with the programmer turned off unless there is a feed from within the drive motor on the valve - is that the case?

The valve itself seems quite free, easily turned with small pliers, when pump is running & you go from one position to the other it goes across with a distinct "thunk" - the motor is obviously working ok some of the time as after a reset as I describe above everything may work fine for a couple of days, do these things go intermittent - do I just need a new drive motor or do I need to get a plumber in?

If the answer is "don't be a tight git & get someone who knows what they are doing to sort it" please just say so - I won't be offended!





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russbost

posted on 14/10/20 at 08:26 AM Reply With Quote
Just to add, when I'm saying 2 way valve not sure that's correct description, it's a 3 port valve so I'm assuming can only go one of 2 ways?





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gremlin1234

posted on 14/10/20 at 09:03 AM Reply With Quote
I have seen cases before where the motorized switch causes the CH to be on continuously.

I would replace the drive motor unit, and test it like that

then call a plumber if that doesn't work

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russbost

posted on 14/10/20 at 09:13 AM Reply With Quote
That was my initial thinking, are all 3 port valve motors the same? Most seem to come with the valve, which I don't think I need & don't want to get into breaking into the water system unnecessarily - I take it the colour coding will be the same on any 5 wire unit ?(I think mines 5 wire, but will confirm b4 ordering anything). Many seem to be metal bodied, mines plastic, does that matter?

So I take it that one of those wires from the valve sends a feed to the boiler when it's in the CH position even if programmer is turned off? As otherwise I can't see where the boiler is getting it's "request for heat" from?





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HowardB

posted on 14/10/20 at 09:15 AM Reply With Quote
check that the CH/HW valve is moving, it can normally be adjusted by hand.
The other easy check is if either the controller or the programmer are battery powered,. new batteries is a simple low cost action

hth





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russbost

posted on 14/10/20 at 09:24 AM Reply With Quote
It seems extremely stiff, I haven't attempted to force it across when the pump is on & water flowing, as I said the valve goes across with a fair old "clonk" when adjusted by hand with the motor unclipped.

Sometimes the motor seems more resistant than others, it's obviously quite low geared as when driving the motor by pushing the valve across you can hear the motor being driven quite quickly

Both programmer & programmable thermostat are mains powered





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HowardB

posted on 14/10/20 at 09:42 AM Reply With Quote
Does you motor drive in both directions - my last one was driven 1 way and a spring return.
Driven for CH spring return for DHW





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gremlin1234

posted on 14/10/20 at 09:53 AM Reply With Quote
there are several manufacturers/models of actuator, - replace like for like.
https://www.toolstation.com/central-heating/motorised-valves/c458

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russbost

posted on 14/10/20 at 10:06 AM Reply With Quote
I'd say it's driven both ways, how can you tell? tho' if I physically push the lever over to the CH side, it is then locked there unless I make a physical request for HW, at which point it moves back to the HW position as it should, if I pull it back to CH whilst requesting just HW it goes back to the HW position, but if, when there's no demand for HW or CH I pull it across to CH position, it won't allow me to push it back, it appears locked there?





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Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours. http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

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peter030371

posted on 14/10/20 at 10:28 AM Reply With Quote
I had exactly the same problem. Turns out the frost stat fitted in the loft next to the boiler had packed up and randomly turned the boiler on because it thought it was too cold (even in the middle of summer). I had tried everything else but as the system was new I didn't think this would be the problem! 15 later and all fixed, been fine ever since and not doesn't wake me up in the middle of the night by coming on at random times.

If you haven't got a separate frost thermostat the boiler might have one built in?

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russbost

posted on 15/10/20 at 12:26 PM Reply With Quote
New actuator ordered, took me a while to track down exact type as it has no manufacturers name on it, apparently both British & Scottish gas ones are like this, but are in fact a Drayton part MA1

The heating is, of course, working perfectly at present!! but will get new actuator fitted at w/e & report back in a week or so to confirm if fixed.

Thanks for help & suggestions guys!





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Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours. http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

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chris

posted on 16/10/20 at 06:10 PM Reply With Quote
yes sounds like you need a complete valve not just actuator if you are saying it is hard to move it should be easy if there are three pipes going to it then yes it is a three port valve and also sometimes called a mid position valve and yes this valve will turn the boiler on even if stat and programmer say no
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russbost

posted on 17/10/20 at 09:40 AM Reply With Quote
It's not the valve that's hard to move it's the actuator unless I've cut power to the whole system. I've got another actuator, arrived yesterday & fitted, all working fine at present, but given that it was an intermittent fault won't know for certain for a few days yet





Furore Formula Car - the only two seater modern Formula Car lookalike. I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours. http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

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