Y Plan / Mid Position Valve - Odd Boiler Behaviour

[steptoe]

For the right price I'll come and sort it out. I can do Y plans in my sleep!

you trying to steal work off me! :red card

bad day explode

 

[lilman]

You should check you have a "hot water off" signal correctly wired and working. You've been asked twice (above) about this and not answered, which leads me to suspect you don't understand the significance of this signal in a Y plan.

Do I really need to answer this!?

 

[steptoe]

yes, you do, cos you have left a system with an electrical fault and are not answering the simple questions put to you by people trying to help,

we're sparks, not Derek Acoiras mates.

 

[MikeShipp]

Mid position valves do not use a potential free contact for the demand signal and the diode and resistors in the valve head give rise to a potential that can cause the boiler to fire even though both thermostats are satisfied. I've changed a PCB on a Worcester and resolved this type of problem. The Y-plan is great in that you don't need a bypass as there is always a path for the water to flow (assuming TRVs not on every radiator) but the S-plan is much simpler to diagnose and, as building regs now require two zones, they ought to become the norm.

 

[Doc Hudson]

Hi all

Looked at a basic wiring set-up with programmer (dual channel), mid position valve, cylinder stat (no room stat) and Keston boiler. Heating engineer stumped so I had a look. If CH is selected at programmer the boiler fires as it should; when CH is set to off - the boiler remains on? Measured 89V at switched live. I know Honeywell valves 'leak' a bit of voltage - not normally enough for this to happen. Heating engineer had replaced the valve twice. What's occurring?

I understand how to wire a system - anyone else had this errant voltage on white wire when heating switches off. Its obviously enough to keep the boiler running!

Do I really need to answer this!?

yes, you do, cos you have left a system with an electrical fault and are not answering the simple questions put to you by people trying to help,

we're sparks, not Derek Acoiras mates.

It is very difficult for our forum members to answer anyones questions when the person asking the question fails to answer the simple logical questions being asked by those who are trying to help answer the problem in hand. The white wire is an input; to drive the valve either to the mid position (heat & Water) or the the fully driven position (heating only). The hot water electrical signal bypasses the valve completely going via the cylinder stat directly to the boiler, (commoned to the valve output orange on route). This voltage at the orange can back feed through the diode & resistors and micro switches inside the valve to give an "apparent input" voltage present on the White when the heating is off, due to the fact that the valve is in the home position with no switches operated. From the limited information you have give it sounds as though it is wired incorrectly, the big clue is the fact that 3 valves have been fitted with no success and you do not sound as though you have any awareness of how the 3-port valve operates, or stall's itself in the mid position by use of one or two 230v input signals. I can only suggests you actually answer some of the questions or it is pointless trying to continue this problem.

Quick update - visited premises again today. Heating engineer changed valve for another Honeywell 3 way. Same problem. All connections to boiler removed. Cylinder stat removed. No room stat. Hot water on 230V at sw live out. Hot water off 0V at sw live. Heating on 230V. Heating off 109V. Did notice that the valve seems to stop momentarlly at 109V on the way to 230V when the heating is switched. I'm stumped. Definately not the boiler. Wiring centre is all good. Tried replacement programmer. Only thing it could be is a duff batch of Honeywell valves? Engineer is gonna try it with a Drayton valve. I'll let you know the outcome.

What are you calling 230v sw live out? is this at the programmer or then orange valve wire? As has already been asked where is your 230v out signal for hot water off going. It is no good saying 'Heating off' or 'Heating on' without also saying the state of the water on/off relative to this. Water on+Heat on has to force the valve to stall mid-way, 109v is approx half 230v so sounds like a very typical stall voltage. To drive the valve fully for heating only the water off 230v is needed. From all the information you have give is does sound like a wiring fault. Have you got water off & heating off output connections crossed at the programmer? Some make of programmer have a non sequential water on/off heat on/off terminal arrangement.

Doc H.

 

[Doc Hudson]

I am not sure if it has been clarified. Is this a brand new system that has never worked correctly? or an existing system that has gone faulty? If it is new system then it is a wiring issue, if it is a fault, what was the last item that was replaced? as that will be the item that is wired incorrectly.

Doc H.

 

[steptoe]

its really not rocket science,

anyone that claims to be an electrician and cannot wire a heating system, be it Y plan, S plan or whatever is not only fooling themselves,

they are a liar.

 

[Doc Hudson]

its really not rocket science,

anyone that claims to be an electrician and cannot wire a heating system, be it Y plan, S plan or whatever is not only fooling themselves,

they are a liar.

Indeed as it is just a handful of series or parallel switches to operate a load. Which should be no more complex to fault find than two or three way light switching, to an electrically competent person.

Doc H..

 

[steptoe]

exactly doc, Im sure Ive said that before,

its only an on/off switch with perhaps a 2way or intermediate thrown in for good measure.

 

[Sharpend]

Forgive me here but would it not be prudent of the OP to have researched the Y plan wiring diagram to familiarise himself with what he should be looking for/at when he goes to the job? I'm pretty see that the Honeywell site has the said diagram easily available for perusal. Particularly if he is not familiar with heating system wiring.

Isn't this a case of 'Fail to plan, plan to fail' syndrome.

We can not be expected to know everything but there is information in abundance freely available on the interweb, so no excuses not to research before hand in my opinion. Only recently I had to do the same thing with network issues as I admit to not knowing much about them.

The OP stated that it is 'basic wiring', so I initially bought hat he was more use to complex system wiring? Which now appears incorrect. So if it is basic wiring should it not follow that basic fault finding would be appropriate?

 

[steptoe]

I.did.offer a.wiring diagram, but was dismissed as it was basic electrics.

 

[Sharpend]

I.did.offer a.wiring diagram, but was dismissed as it was basic electrics.

Had noted this Steps, which is why I don't understand the OP's difficulty with this, a simple admission that he needed a drawing as reference then surely he'd had the information hat he need to diagnose the fault?

 

[steptoe]

I do loads of Y plans, (and other systems) and would say Im pretty confident with any of them,

but I keep a copy of honeywells [very easy to follow] wiring diagram in the van all the time so if I do have an issue I can get it out and double check what I thought I knew anyway.

always good sometimes to trace it back in black and white rather than whats in your head.

 

[lilman]

I do loads of Y plans, (and other systems) and would say Im pretty confident with any of them,

but I keep a copy of honeywells [very easy to follow] wiring diagram in the van all the time so if I do have an issue I can get it out and double check what I thought I knew anyway.

always good sometimes to trace it back in black and white rather than whats in your head.

Firstly - apologies if I was a tad rude earlier in the thread; been a long few weeks. As you know I've been a member of the forum a long time and always appreciate all your help.

Like Steps I always have a bunch of manuals to hand; even trained on a Honeywell course. Usually install wiring for Veissmann boilers. This problem just had me stumped. Basically the original Keston service bloke turned up to service the boiler - bit later on the fault occured. He then changed the valve a couple of times. Then I had a look. All the wiring is good at the wiring centre, the programmer, the cylinder stat - I re-terminated all connections.

 

[SPECIAL LOCATION]

So are you saying it is now solved ?

Not clear from that post? opcorn

 

[lilman]

So are you saying it is now solved ?

Not clear from that post? opcorn

Not yet - it's being looked at next week by someone else. I will post the outcome.

 

[SPECIAL LOCATION]

Not yet - it's being looked at next week by someone else. I will post the outcome.

:shakehead

even trained on a Honeywell course

So the Honeywell course is not that good then?

As steps said earlier...

its not rocket science to isolate individual components out of the system to verify what or where voltages are going or appearing from!

You can even isolate the 3port valve out of the wiring for testing purposes...

Diss all the 5 wires from the valve, use wagos to stuff relevant voltages on the Grey & White,

stuff a lamp off the Orange by another wago, watch for the valve moving..

easily proved...

As has been said earlier stick a bit more of a load, (lamp) across the boiler feed....

(again wagos are the dogs danglers for this)

to see more clearly what voltages are going where..

All the other bits are just 1-way or 2-way switches operated by time, heat or manually..

So not too difficult to trace the paths for Heat on / Water on / Water off.

Sounds like a crossed wire somewhere,

either mix up of two cables with same colour (e.g. red & red)

Or programmer or thermostat wiring crossed on wrong terminals...

{or actually the two statements are variants of the same problem!!!!}

:huh:

 

[steptoe]

Firstly - apologies if I was a tad rude earlier in the thread; been a long few weeks. As you know I've been a member of the forum a long time and always appreciate all your help.

Like Steps I always have a bunch of manuals to hand; even trained on a Honeywell course. Usually install wiring for Veissmann boilers. This problem just had me stumped. Basically the original Keston service bloke turned up to service the boiler - bit later on the fault occured. He then changed the valve a couple of times. Then I had a look. All the wiring is good at the wiring centre, the programmer, the cylinder stat - I re-terminated all connections.

not being funny,

but that is a world away from checking all the cables are actually in the correct terminals to start with.

 

[Nicky Tesla]

"You've put in over 700 of them over the years"

Putting them in and fully understanding them are two different things

 

[Nicky Tesla]

This is good info for fault finding http://www.electriciansblog.co.uk/2011/11/how-does-a-y-plan-central-heating-3-port-mid-position-motorised-valve-work/