Reverse Polarity blow PCB? Worcester boiler with overun

[Robinson]

Ok guys had a day and half today....Y plan Honeywell room stat, 7 day prog 2 channel.
Worcester boiler with over run......

Some how the mains L/N got cross and had few 3 amp fuses blow in spur before we established issue...boiler fuse was ok though and once established that a donkey had connected wrong way around we continued with setup.....Seemed to have all wiring correct. But Cyl/Stat and Room will not turn Heating or water Off ......pump runs but no switching off...tryed turning cyl stat right down and room stat but boiler still fires...

I have heard that because the over run is controlled by pcb it could be this causing prob....ie. pcb been damged by reverse polarity thus now keeping overrun on....

I dont have all details on boiler model or actuator etc at mo...But wondered if you knew of any other maybe cause's or if any of you got links to diagrams of Y plan with pump over run......got one on honey prog and seemed all good but maybe we have got something wrong regarding the over run cables.....as that was not on the diagram, only on boiler elec diagrams which were alittle confusing...

 

[Big n Daft]

Go back to basics, clear the mind.
1, Check the wiring is correct with no faults. Point to point ,buzz it out.
2, Check components of the heating system for electrical integrity. Valves, pumps, stats and stuff are switching and free of earth faults etc with an multimeter.
3, If you feel confident then force feed the components from the controller/boiler and confirm operation.
4, If everything works then the pcb is duff. But you must satisfry yourself it all works first.

Only done one heating system and had similar trouble me'self due to a dodgy plumber.

 

[nickblake]

Agree with big and daft ..............top answer......................see your not as daft as you made out in other thread lol

 

[Robinson]

clear the mind..

Yes this is defiantly the hard bit. Yeah tomo gonna start buzzing out it has new prog, new valve, new stat, so shouldnt be them....was concerned and the L/N error tho...last thing we need is new PCB....

 

[diditrain]

There was a reverse polarity issue on worcester boilers not so long ago if i remember correctly. Recieved an email from the manufacturer

 

[truckster]

Not got the boiler details but just as an obvious thought have you got the live/sw live(if there is one) in the right way?

Another thought, don't know if it's applicable but some boiles will fire on around 150V, there can be enough leakage onto the orange sw at the valve to give this. If thats the case you have to install a 230V relay into the boiler sw wire. Don't get a manufacturers one they wll cost about £65, go to the w/salers and get one for a fiver.

 

[PC Electrics]

Have you removed the link between Lr and Ls?

 

[Robinson]

Have you removed the link between Lr and Ls?

Yeah link was removed......but wasnt too sure on the terminals for over run. another little terminal block on two pins with LS NS only, its says you need this
direct to pump which is cool, but was confused as to whether we need neutral there too as well as over on ST10 terminal block where the link was... thought this might of affected it too

 

[diditrain]

what model is the boiler. Not 100% certain but i seem to remember one i done and i think the connections for the pump were iz and nz

 

[sparky3366]

the pump over run is just a case of wiring the pump to the boiler (pl &pn) or lp np..., switched live and then normal l,n,e.

 

[Robinson]

what model is the boiler. Not 100% certain but i seem to remember one i done and i think the connections for the pump were iz and nz

Yes i seem to think this was the case. The model no 30CDI conventional

It was wired as too the honeywell Y PLAN diagrams but pump being connected to the terminals IZ NZ ( i think diditrain is correct) to boiler directly.....

 

[diditrain]

Just looked at the manual, the connections for the external pump is LZ and NZ.
This boiler had the reverse polarity issue for the pump connections. I always check with my tester now before i connect the pump.

To begin with, what i usually do is disconnect the call from the room and cylinder stat from the wiring centre then make sure that they are making and breaking when you turn the stats up and down.

 

[Dunc]

Just to clarify, is it just the pump that won't switch off or is the boiler itself still firing even when the stats are turned down? If the boiler is still running then forget belling out all the cabling initially. All you need to do first is disconnected the switch live to the boiler. If the boiler still fires with the switch live disconnected then the problem is internal with the boiler. If the boiler shuts down then test to see what voltage you have on the orange wire from the MV. If the voltage on the orange wire is still 230V when all the stats are turned down then the problem is either a faulty MV or a connection problem on the cylinder stat. However, if the voltage is between 50-150V (which is normal on a Y-plan valve) then the issue is with the boiler being too sensitive. To fix the problem you'll need a Y-Plan Capacitor Kit which will absorb the voltage.

Capacitor Kit Link

The other option is to fit a S-Plan instead seeing as how Y-Plans are such rubbish!

 

[nikmet]

It is possible to plug the pump connector on the wrong way round, it will plug onto the pins both ways!! check its correct for live to live neutral to neutral

 

[Robinson]

It is possible to plug the pump connector on the wrong way round, it will plug onto the pins both ways!! check its correct for live to live neutral to neutral

REALLY thats interesting didnt consider this. !

 

[Robinson]

Pump seems ok its the boiler is firing with cyll stat and room stat turned down. I had a feeling the boiler was firing still with switch live removed....Which worries me as you say could be internal....(could this be to do with the reverse polarity diditrain mention.?)

Diditrain was this a boiler fault or just something you managed to cause?

I get back there friday..

I staY optomistic and believe its simple wiring issue...

 

[Robinson]

SO if its wired ok as to Y plan am i right in saying all that should be different as what NOT shown on Y plan is that the LZ (over pump) from boiler now just connects directly to PUMP LIVE as too the NZ to the Neut of pump. Neither are no longer connceted to Terminal 8......But then what about switch...Where come from and go?

sorry guys ....for the hassle...

thanks

 

[diditrain]

Hi Robinson, this was a manufacturer fault not one that i created.
A batch of boilers was released into the market with this issue not sure how many in total as i cannot find the info anymore.

Can you just clarify wether it is an existing fault that you have been called in to rectify or is it a new installation

 

[Robinson]

Hi Robinson, this was a manufacturer fault not one that i created.
A batch of boilers was released into the market with this issue not sure how many in total as i cannot find the info anymore.

Can you just clarify wether it is an existing fault that you have been called in to rectify or is it a new installation

New Installation. !

 

[diditrain]

Ok
The boiler requires a permanent live, neutral, cpc, switched live and a pump over-run.
inside the honeywell wiring centre you generally have a link between terminals 12 and 13 and another between 13 and 14
This is before you put any of your cables into the wiring centre. Did you remove these links and then just put one between 14 and 12?
If you have not then with your pump still running once the boiler has fired initially it will cause the boiler to carry on firing.
Hope i am making sense as i tend to waffle a bit