Honeywell ST6400A programmer

[cbasson]

I have had the programmer up and runnning perfectly for the last 12 months or so.

However this morning we wake to find all the electricity spurs have tripped, caused it seems by the ST6400A. The remainder of the sockets can be turned back on and used with the programmer set to off, so the clock on the programmer is working but hot water and heating are both off.

Not sure what had changed overnight but here we are.

Just spoke to Honeywell who helpfully informed me "I've no idea, get an electrician in."

Now I've probably missed off some useful information here, so let me know.

But does anyone have any pointers.

Many thanks.

 

[cbasson]

So with hot water and heating set to off, the rest of the spur works fine.

When either the hot water or heating is turned on, via the override button, extra hour buttion or slide switch, it appears that the main switch for the heating trips first knocking out the programmer and the remainder of the downstairs spur.

 

[stem]

You don't say in your OP, but I assume this programmer is operating your central heating system.

What do you mean by "all the electricity spurs have tripped"? What has tripped exactly? MCB? RCD? what does it say above the device(s) that have tripped.

You assume it's the programmer. How do you arrive at this conclusion? It could be anything connected to the same circuit. fridges/freezers are connected 24/7 and can cause tripping.

If it is associated with the programmer, my experience is that is is far more likely to be something connected to it such as the boiler, pump, motorised valve, wiring etc.,

If it is an RCD that's tripped, My first examination would be for a water leak into an electrical device.

 

[stem]

OK your second post was sent whilst I was typing, It appears it is the programmer or something attached to it.

Please clarify what is tripping, I think you may be using the term "Spur" incorrectly

 

[cbasson]

You don't say in your OP, but I assume this programmer is operating your central heating system.

Sorry yes, the programmer operates the heating and water and sits in the kitchen

What do you mean by "all the electricity spurs have tripped"? What has tripped exactly? MCB? RCD? what does it say above the device(s) that have tripped.

Apolgies about my terminology, I am probably/definitely mis-using terms. The programmer trips the RCCB on the main circuit board.

You assume it's the programmer. How do you arrive at this conclusion? It could be anything connected to the same circuit. fridges/freezers are connected 24/7 and can cause tripping.

I arrived at the programmer after turning off all electrical units and turning one device on at a time, until the system tripped - giving me the programmer. Then with all on (inc the heating wall switch) but the programmer set to its off position, the circuit fails when heating/hot water is set to "on"

If it is associated with the programmer, my experience is that is is far more likely to be something connected to it such as the boiler, pump, motorised valve, wiring etc.,.. If it is an RCD that's tripped, My first examination would be for a water leak into an electrical device.

As the RCCB is tripping, where would one start looking for leaks (sounds like a stupid question...)

 

[gas4you]

As we don't know what your system consists of I will try to generally answer.

Does it do it on HW only, CH only or either?

The most common things to check first will be the pump or the fan in the boiler if it has one.

Try isolating the pump from the heating system then try again.

Could look for any leaks dripping onto the 3 way valve (or 2 port valves)

 

[stem]

An RCD (RCCB) trips when there is an earth fault it will normally turn off several circuits, usually the socket outlets, and will probably be rated at 30mA

An MCB trips an individual circuit when the circuit is overloaded. These are marked according to the circuit they protect eg 6A for lights, 32A for power etc.,

If the RCD is tripping when the programmer turns on there is probably an earth fault with part of your central heating. It often is a leak.

Look at the pump, are there any signs of water leaking from the pump into its terminal box? If you have any motorised valves check these for leaks too, also have a look at the boiler, but don't strip is down unless you're competent to do so.

After that without proper testing equipment, it comes down to disconnecting items to see if you can find the cause.

Pah! gas4you beat me to it. Must learn to type more quickly

 

[cbasson]

As we don't know what your system consists of I will try to generally answer.

Does it do it on HW only, CH only or either?

The most common things to check first will be the pump or the fan in the boiler if it has one.

Try isolating the pump from the heating system then try again.

Could look for any leaks dripping onto the 3 way valve (or 2 port valves)

New type closed system, does it when either water or heating is set to on

and thanks will investigate further

 

[gas4you]

At least the same advice from 2 different trades

If it is a system boiler then could be leaking in the boiler onto electrics.

Quite often could be the auto air vent leaking.

 

[cbasson]

Thanks for the adivce guys.

Doesnt look like valves, pump given the amount of dust everywhere..

Looks like I'm shelling out for a profoessional tomorrow

 

[cbasson]

As an afterthought, the boiler is a Potterton Suprima 60 and I had the PCB replaced/upgraded 3 months ago due to the PCB generic problems.

What chance this one is rubbish also?

 

[gas4you]

The new pcb kit and wiring loom that you have to fit with this kit, are usually pretty reliable.

However, saying that, rule 1, never assume anything new is working.

I would still try disconnecting the pump, obviously not a system boiler with it built in. The pcb controls the pump on this boiler. Safest way is to disconnect the pump live at the boiler terminal block, but then as it is the RCCD tripping could be a neutral to earth fault.

I've also had to replace numerous gas valves on these as well