Baxi Solo HE cutting out after 15 minutes

[T0NY]

Hello, I have the affor named boiler which is not working correctly. The hot water seems to work o.k. but when the central heating is switched on the rads warm up and the boiler fires but after approx 15 minutes the indicator lights on the boiler go out and do not come back on. I have noticed that when it does this I can bring the boiler back on by running the hot water and this also re-heats the rads but again fails after the 15 minute period.
I have checked the timer and this seems to be working fine although I have noticed that when the fault occurs the indicator light for CH on the timer will not extinguish even when switching it to the off position. It's as though there is a back feed of power coming from somewhere. I have turned the room thermostat right up so as to eliminate this too.
Any advice on where to start with this now would be greatly appreciated, I am an Electrical engineer so I'm not wanting to call out an engineer to fix what seems to be an electrical issue, although I may be wrong...

 

[BLOD]

It sounds to me like an external control problem and not the boiler.
Get the wiring diagram for your heating system and when it does it again check what is & isn't getting current, at the wiring centre if you have one would be a good place to do this

 

[GrahamM]

Has been working ok in past?
Any work done to tie in with problem?

In my opinion you should have an experienced engineer look at it. Not doubting your capabilities, but I have in past encountered a number of electricians that can't get their head round how a heating system is wired.

 

[T0NY]

The installation is 13 months old, originally owned by my mother she had the system done just before she past away and unfortunately I have no record of the fitter, I wish i did, as to be honest the whole thing looks a bit of a bodge job to me so i'd like to get him back just to give him a smack in the face. I have no problem getting my head around the switches etc, I work with thermostats and electrical heating through my position at work. I think I'm just going to remove the stats and timer for a start, check the wiring through and replace them.

 

[BLOD]

tony, if you can describe your system we might be able to help more - do you have 2 x two port valves or a 3 port valve etc.

 

[T0NY]

As far as i can see there is just one valve and this has three large pipes connected to it. I have just been looking at this by coincidence, I've taken the cover off it and as far as i can see it doesnt seem to be moving at all. How is this supposed to opperate? I have noticed a little leaver underneath it, what is this for? I will take a photo.
Sorry if i'm a little indescript its the first time i've done anything with central heating.

 

[T0NY]

I've attached a couple of images of the tank room, ignore the garish wall paper.

 

[BLOD]

open up the wiring ctr and use a multimeter on the end of the wire from the valve
With just heating selected (and when it's working) you should get 240v on grey, white and orange.
When it stops working if youve got 240v just on grey & white then replace the valve head.

 

[BLOD]

it'd also be worth removing the valve head and checking the spindle moves freely & isn't jammed.

 

[RoryD]

if I'm reading you correctly, the CHB will not reset after lockout? pcb mate

 

[jtsplumbing]

Try checking the flow thermistor or overheat stat, what are the lights on boiler showing when boiler go's off ?

 

[T0NY]

o.k. bit of an update. After further investigation the valve seems to be oporating I can hear a squeek from it when the room thermostat is switching on and off. The boiler is cutting off on the ho****er thermostat, obviously the boiler knows the water is hot enough and is therefor shutting down. Next I checked the ch pump and have noticed the pump is being turned off by the hw thermostat on the tank, surely this is not right and it should be controlled by the room thermostat?
I am going to replace the broken wc box tomorrow which will mean I'll have to disconnect the wiring in there anyway, could one of you confirm for me that I am right in thinking both the valve and the pump should be controlled by the room thermostat?

 

[BLOD]

Tony, have you tested with a multimeter on the wires from the valve ?
if you don't it could be a cold Christmas

 

[Millsy 82]

If you are not sure what you are doing call in a heating engineer. A decent one will pinpoint the fault very quickly and could save you wasting money on not needed parts.

 

[T0NY]

Found a wiring diagram for the system, I didn't realise the valve when powered by the room thermostat switches a live feed to the pump (or its supposed to!) I'm off to get my multimeter this morning to test it through but I suspect the switched live output on the orange wire isn't getting through either because the electronics in the valve have failed or the valve is sticking slightly. Either way looks like a new valve is required. Is it usual for these valves to fail after just a short time, its a Honeywell 3 way valve, are there any better, more reliable ones you could suggest?
Thanks for your help everyone it's been a learning curve but at least i have a better understanding of the system now!

 

[tamz]

Check the wiring on the timer and cylinder stat before you buy a valve

 

[T0NY]

I've checked the output from the valve and as expected i'm not getting 230V feed to the pump once the cylinder stat kicks out. The room stat is supplying the feed o.k. so there's obviously some breakdown within the valve itself. I've temporarily taken the feed from the room thermostat to run the pump and bingo, no shutdown and the system is cutting in and out nicely.
As asked before, I'm after a reliable valve, what would you guys suggest?

 

[BLOD]

I'd stick with Honeywell, if the spindle moves freely just replace the actuator.

 

[vern]

I'd stick with Honeywell, if the spindle moves freely just replace the actuator.

Yep agree...10 min job with wiring and no draining down!

 

[T0NY]

So I can remove the motor assembly without taking off the whole valve?

 

[vern]

So I can remove the motor assembly without taking off the whole valve?

Yep dry pocket, 2 brass screws under cover, undo screws ,isolate electrics change wires one by one like for like.....job done.
You can buy the actuator without the valve, but stupidly it ain't a lot cheaper, it will be a V4073

 

[T0NY]

Brilliant thx for the info :yesnod: