Y Plan Heating System is on all the time

[Connor Williams]

Hello guys I am having problems with a Y Plan Heating system that has been a long running issue.

The boiler and pump is on all the time even with the programmer turned off.

The actuator & programmer have been renewed and its made no difference but I did notice when I was doing the electrical checks on the wiring junction box that the cylinder stat circuit is always live even when the programmer is off or set for heating only.

That is the common live is always providing electric to the stat which is then sending power to the water off circuit where the grey 'water off' wire is connected from the 3 port zone valve.

Even when the programmer is turned off and all the other terminals are dead these two circuits are always live, common live going in to the stat and the wire coming out of the stat to the hot water off terminal which is always live and sending a signal to the boiler and pump.

The only way to switch off the boiler & pump is by turning down the cylinder or wall stat. I have renewed the stat but its made no difference. I am thinking it may have been incorrectly wired.

I am a qualified plumber and before I call in my electrician any thoughts would be greatly appreciated!

All the best,
Connor

 

[diamondgas]

with programmer removed from its back plate does the boiler still fire and pump run? What make boiler do you have?

 

[midlands based]

Id say 1 of 2 things. Faulty programmer not switching the switched live off. Or bad wiring. As diamond says, disconnect the programmer and see what happens.

 

[Ollieg]

The hot water off connection shouldnt go to the pump or boiler.
The hot water off from the cyl stat should go to gray on the 3 port and hot water off from the programer.

 

[Connor Williams]

Thanks for the replies, yes apologies the wiring does seem correct with the stat wire going to the grey hot water off which goes to the third terminal of the programmer.
when I tested the wiring at the junction box the grey hot water off was sending a constant on/off signal to the zone valve causing a constant clicking noise on the actuator, even when the programmer is turned off.

when I remove the programmer facia this does shut everything off.

i wondered if the live on the programmer is somehow sending a constant signal up the hot water off wire on the programmer to the zone valve whenever the programmer facia is fitted.

I will check the make of boiler, the boiler is in the garage I wondered if it was a faulty frost stat but then these are wired to bypass the programmer anyway so am baffled at the moment. Thanks for your help

 

[Carlos_UK]

Hi,

If everything switched off when you removed the programmer, this would suggest that its faulty and so needs replacing.

 

[diamondgas]

when I tested the wiring at the junction box the grey hot water off was sending a constant on/off signal to the zone valve

With the programmer off you should get a constant 240v on the 'grey' and 'h/w off' junction connection. If it's switching on/off with the programmer is off then you have a wiring issue as it should be constant! I'd guess that the on/off supply is coming FROM the actuator down the grey?

I wondered if the live on the programmer is somehow sending a constant signal up the hot water off wire on the programmer to the zone valve whenever the programmer facia is fitted.

It should be constant with the programmer off!!

Basically these actuators are moved to mid by the room stat and beyond by the cylinder off and/or hot water off from the programmer.

 

[Connor Williams]

Well many thanks for all your help guys sorry its taken me so long to reply, this job was a huge learning curve.
After renewing the zone valve & actuator and the cylinder stat, to no effect and checking all the wiring which was all correct, I was stumped.

The fault was eventually traced to the capacitor on the new central heating pump, it was faulty and was sending very strong back signals to the programmer which was bypassing the programmer (burning it out) keeping the system running constantly.

Ever heard of that before?! The previous plumber had renewed the pump and the customer had had the problem of the boiler constantly running ever since he changed it.

I didn't check the pump as I never thought the capacitor could cause a fault like this, especially a new one.

The pump was changed again and that cured it. A new pump with a faulty capacitor caused all these warped electrical signals that were too strong for the programmer to control or handle.

We live and learn and hope thats of use for future fault finding, all the best and thanks for your help, Connor

 

[Ollieg]

Bet it was a grundfos that was ment to have a suppresser fitted on ot.

 

[Connor Williams]

It was indeed a Grundfos pump, apparently a faulty batch were sold with dodgy capacitors, the customer rang them and complained about the costs incurred with this difficult to find fault and they have said they will refund the money.

This could cost them a lot if many of these pumps with faulty capacitors were sold.

 

[Ollieg]

I had this problem and took out 5 3 port actuator heads before my boss asked me to spend as long as it took to get it fixed.

It took me 4.5 hours. The pump pulled just a bit more than 3 amps which didn't blow the fuse but melted the contacts inside the microswitch of the 3 port.
I rewired the whole system and damaged another 2 actuators
Until I found it!!!

 

[Ermintrude]

I did one and there was no live to wiring center - 6 year old BG install!