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Worcester Bosch CH Problem

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GrahamF

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We spend half or more of the year away from home so, when leaving in winter, leave CH programmed to fire up for 1/2 hour, 3 times per day as we have a radiator in conservatory which could freeze before boiler (in airing cupboard) frost stat kicks in. 15 year old oversized (inherited with house) Greenstar 35cdi controlled by MT10RF wireless time clock/thermostat.

Left home early Dec and part way through February, house checker reported house like an oven, very unusual. She turned stat down but nothing changed £80 gas used in one month. When it warmed up a bit, I asked her to turn boiler off. Came home a couple of weeks ago and decided most likely a faulty controller so, new transmitter and receiver installed, no difference. Local Bosch guy thought most likely circuit board not talking to receiver and we decided rather than spend money on old boiler, replace with new, slightly smaller Greenstar Compact 32cdi. Transferred new controller off old boiler. Fault is still there with heating coming on during night, outside programmed times.

Everything in the house was disconnected while we were away, no smart meter and wi-fi, phone, TV, etc., all unplugged. Only wireless gadget being wireless doorbell. We have a sub-station next door and elec board deny any alterations to it.

Assuming the new and old programmers aren't/weren't faulty, what are the likely sources for outside RF interference and how to trace? Worcester Bosch say the range of controller rules out interference from a neighbour's CH. Something has changed, that's for certain! One solution I suppose may be to install hard wired controller/stat but that would entail redecorating etc.
 

Adam W.

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"Transferred new controller off old boiler. Fault is still there with heating coming on during night, outside programmed times."

Hmmm, could it be the controller thingy ?
 

GrahamF

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"Transferred new controller off old boiler. Fault is still there with heating coming on during night, outside programmed times."

Hmmm, could it be the controller thingy ?
Although I think unlikely that old one went faulty and new one was also faulty, I have Worcester Bosch coming out on Monday so that will be checked. problem is, I'm expecting the same reply as elec board (SP Energy Networks) "not our fault sir" attitude so, trying to find if anyone else has had similar fault and cure.
 

GrahamF

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Can you disconnect the controller and see if it still comes on?
It's a possibility, could take the batteries out of it to disable and see if the boiler is receiving signal from elsewhere, will try that tonight. They do also have different control systems where time clock would be boiler mounted and just room stat by radio control which may be an alternative but, we need to find what's causing the problem.
 

GrahamF

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Making some progress I think, it appears the new stat/controller is faulty. I let the heating shut down last night on time clock then as HappyHacker suggested, disconnected by removing the batteries. Heating stayed off all night as it should do but I'll do it again tonight just to confirm not a coincidence.

No home network here for gizmos, don't even have or want a smart phone. I prefer hard wired but having decorated right through when we moved in, don't fancy embedding or capping a cable so W Bosch can replace with new RF unit under guarantee - if my diagnosis is correct:).
 

Chrispy

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Do you know if you have a y plan system with a three port valve to control heating and hot water, if so look up three port valve problems I think you may fine your answer there.
 

GrahamF

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Do you know if you have a y plan system with a three port valve to control heating and hot water, if so look up three port valve problems I think you may fine your answer there.
I did wonder about that but radiators didn't heat up when drawing domestic water so valve didn't appear to be sticking. To rule it out, I put boiler on "eco" setting to stop pre-heat, which made no difference to fault. Remember, the fault was on the old boiler and the new, which points to the timer/programmer which is the only common component.
 

Terry - Somerset

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Recently had a similar problem which I tracked down to a faulty Danfoss valve. This should only open to allow hot water from the boiler to pass when the controller tells it.

But time and corrosion meant that the valve sometimes did not return to "closed" when the heating controller said "off". Just needed some lubrication, not replacement.

Issue made worse in our house as heating relies upon thermostatic radiator valves, not a central thermostat.
 

Chrispy

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There is or at least there was a known problem with some boilers when used with three port valves it is because of the way they work electricaly. They can work fine most of the time then won't turn off, which seems to be your problem.
 

Stevekane

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I dont know about your boiler but if its a “combi” boiler I doubt it will have a 3 port valve, anyway to get back to your original thoughts on it, I installed a Horstmann RF wireless thermostat, all working fine untill one morning I notice our heating is running,,after much head scratching I realised its being controlled by next doors RF thermostat,,I changed the operating frequency and had no more issues, we have a detached house and there are several brick walls and an allyway between us,,,is it worth changeing your frequency just to see if it helps?
Steve.
 

GrahamF

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I dont know about your boiler but if its a “combi” boiler I doubt it will have a 3 port valve, anyway to get back to your original thoughts on it, I installed a Horstmann RF wireless thermostat, all working fine untill one morning I notice our heating is running,,after much head scratching I realised its being controlled by next doors RF thermostat,,I changed the operating frequency and had no more issues, we have a detached house and there are several brick walls and an allyway between us,,,is it worth changeing your frequency just to see if it helps?
Steve.
It is a combi boiler. No way to change frequency, it's factory set and transmitter and receiver are paired. I put the clock 12 hours out today to test and at 4.30 this afternoon the boiler came on as it has been doing at night, which rules out an external RF signal overruling it at the same time but in the morning.
 

HappyHacker

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If the timer is turning it on at a set time is there a timing program that is set for 4:30? I have a wired thermostat controller but it is one of these "intelligent" ones and making sure all the programs are correctly set is a pain. Every time program is always on, it is the temperature setting against the program that controls whether or not it calls for heat.
 

Stevekane

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Its very difficult for me to fully understand your actual set up but re reading your posts am I right in thinking that you are still using the old “programmer” with the segmented dial? Youve changed the boiler complete with stat and reciever so these parts should be okay, but,,and Im no expert, the segmented programmer sounds like a very old bit of kit,,?
 

GrahamF

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pe2dave

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I dont know about your boiler but if its a “combi” boiler I doubt it will have a 3 port valve, anyway to get back to your original thoughts on it, I installed a Horstmann RF wireless thermostat, all working fine untill one morning I notice our heating is running,,after much head scratching I realised its being controlled by next doors RF thermostat,,I changed the operating frequency and had no more issues, we have a detached house and there are several brick walls and an allyway between us,,,is it worth changeing your frequency just to see if it helps?
Steve.
Are you able to change the frequency? From one fixed channel to another? Presumably at both ends?

If it is interference, you might reduce sensitivity by shielding the receive end, hoping your tx gets through, the interfering one doesn'tJ?
 

GrahamF

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Worcester Bosch engineer due in an hour or two, will see what he has to say. Can't change frequency and pretty certain I've ruled out external RF interference because if I put the controller clock time wrong for time of day, the boiler still fires up at the same clock time, around 4.30.
 
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