3 port keeping the heating on?

[spikewt]

Long story short. Changed a 3 port which is now sending 80v to the boiler switch live once the heating is turned on then off, so it fires all the time. Works as it should on the hot water. Valve Mi says that's what it should be doin.
Is there a valve out there that cuts the voltage off completely.
It's on a poxy biasi boiler but then it's actually workin as it should.
Thanks for reading.

 

[Ermintrude]

You've got a short somewhere mate. Or a very cheap and nasty valve

 

[spikewt]

Had my sparky there for 3 hours. Changed everything for new stuff. Triple checked the wiring, tried 2 brand new and different valves. Still does the same thing. If you look at the honey well valve, it says there will always be between 50 and 150 volt coming out when there's no demand.
We just don't get it.
Problem is I changed the valve 2 months ago and haven't gotta clue what it was I took out.

 

[spikewt]

http://www.honeywelluk.com/documents/All/pdf/975.pdf

This is where iv read about the voltage staying there. Last paragraph.

 

[doitmyself]

The low voltage on the valve's orange wire is a 'feature' of all mid-position valves and boiler manufacturers are aware of this. If the boiler is being turned on by this voltage, then the problem is more likely to be in the boiler.

 

[bigads28]

It shouldn't fire on 80v, what's the model of your boiler?

 

[Ermintrude]

Fit a relay?

 

[spikewt]

It shouldn't fire on 80v, what's the model of your boiler?

Biasi M96.28 SR / C2

G.C. 41-583-02

Problem iv got is I serviced it 2 months ago, switched the heating on, then the original valve starting letting water through the heating side while on hot water in the summer. So i changed the valve as the ball was damaged and now this is happening.

 

[bigads28]

Remove the switched live and see if the fault remains.

The three led's on the left hand side might indicate what the boiler thinks it should be doing.

ON OFF ON is CH operation
ON ON OFF is frost

I can imagine yer loosing your hair fast with this one!

 

[spikewt]

Switch live was one of the things i tried. boiler shuts down as it should.

Its just so annoying because everything is working exactly as it should and has been checked over and over. Its just this 89v on the switch live from the orange wire on the valve and a cylinder stat wire that makes the boiler fire.

89v should be there, just not activate the boiler. Im reluctant to replace the pcb as ill be paying for it but by the sounds of it, its becoming the last choice.

 

[bigads28]

Nightmare Spike, its starting to sound like that. You could give Biasi a call and just check there isn't anything else you've missed.

I wouldn't cover the board, its not your fault it's developed this fault. It'll be expensive too I'd imagine.

 

[spikewt]

going to get on the phone to them first thing in the morning.

All i keep telling myself is it just has to be something simple. Hopefully biasi will come back with something helpful.

just a simple service turns into this. gutted to say the least.

thanks for the suggestions, going to sink a rum and coke then bury my head in a pillow now!

 

[Ermintrude]

Biasi helpful? Dream on

 

[kay-jay]

Ive had this before and it was a faulty cylinder stat that was energising when it shouldnt. Might be worth throwing one on to check. They're only around a tenner.

 

[spikewt]

May have the answer now.

Biasi were really helpful. Turns out most 3 port valves have this problem. It's apparently the way they work.

Biasi said do one of 2 things. Either fit a Drayton as the residual voltage is below 60 so they say or fit a capasitor of 0.47 microfara across the switch live and neutral to take the voltage away.

Gonna go fit a Drayton later an see what happens.

 

[doitmyself]

Gonna go fit a Drayton later an see what happens.

Before you do that, check the voltage across the gas valve when the fault occurs. If it's low, i.e not 230V, the GV is faulty.

 

[spikewt]

Not sure how that would help as the fault occurs before the gas valve initiates. Its all down to the boiler being activated by switch live having 89v staying there once the heating is satisfied.
Next time you work on a three port, have a look. Switch it on on, call for heating but not hot water, then turn the room stat down. The valve will keep the switch live at 89 or so volts. Common thing so I here.
Reason why it don't show up often is due to boilers having high voltage side and low voltage side. On Biasi boilers, the same terminal is used for high or low voltage so it seems like the boiler gets confused.

Definalty one to remember now.

 

[bigads28]

May have the answer now.

Biasi were really helpful. Turns out most 3 port valves have this problem. It's apparently the way they work.

Biasi said do one of 2 things. Either fit a Drayton as the residual voltage is below 60 so they say or fit a capasitor of 0.47 microfara across the switch live and neutral to take the voltage away.

Gonna go fit a Drayton later an see what happens.

Great hope that sorts the problem out. The heads pop on and off those Draytons really easy too for future repairs.

 

[happyflyer]

I hate guessing on here, if you had the motor winding in series that might give you that low voltage, you need to check
that wiring 80VAC is an unusual voltage in anyone's book, start again with the wiring

 

[spikewt]

SOLVED!

the Drayton valve had a residual voltage of 12v so didn't activate the switch live once the heating was satisfied.

Love it when a problem like this is solved finally.

My sparky spoke to a big plumbing firm he works for and they came across this too. On Worcester boilers!

 

[Aquazone]

You can get a resistor/relay whatever you call it from Worcester (I think I have posted part no before) that goes between SL and N to counteract this, as I have has Worcester PCB's chattering due to this stray voltage

 

[solutions]

You can get a resistor/relay whatever you call it from Worcester (I think I have posted part no before) that goes between SL and N to counteract this, as I have has Worcester PCB's chattering due to this stray voltage

I have used a capacitor in the past to soak away the stray voltage. First time I came acriss it was when one was supplied wuth a new pcb for a glow worm micron which explained that its job was to deal with stray voltage from 3 ports. Not needed on s plan.