Central Heating tripping out the Electric

[Pauli11]

Hi all.

I'm hoping someone can help with advice with this particular problem.

I have an oil fired central heating system and a pressurised mains fed water supply.

Tonight, after being away for a few days, I pressed the water heater button on the programmer, and after about 20 seconds the mains tripped.

I then reset the electric, turned off the water heat button, and all was well. So I pressed zone 1 heating, and again, 20 secs later the electric tripped. I repeated for zone 2 (bedrooms) and the same thing.

After some research, I cheked the 3 motorised valves, and all seemed to be functioning ok, sounding smooth and starting the valve opening procedure for about 20 seconds before the power tripped.
That made me rule out the valves on the basis that one could be faulty and causing the problem, but its unlikely all three would be faulty and all at the same time.

So, out to the garage, where the oil fired burner boiler and pump are located. I was confident that I had narrowed the problem down to the pump. With the power off, I opened the centre screw, and turned the pump manually, all seemed smooth. I opened the power box at the side of the box expecting to see water in the compartment, but it was bone dry, clean and no sight or smell of any problem. I disconnected and reseated all cabling.

With all 3 zones on the kitchen based programmer all switched on, and the isolated switches to the pump and boiler switched off, I then turned the power to the pump on (it has its own switched supply beside the pump). The pump started normally and run without any difficulty.

So, the only switch left to turn on was the isolated supply to the burner. Switched it on, and it started its "warmup, pre burn " period. Then after 20 seconds, when usually the burner bursts into life, the whole lot stopped and the power went off again.

So I'm presuming its the burner unit thats causing the problem. Thats a pain, because the pump or valves, I can get my head round. The burner unit is big and complicated and scares me!!
I would really appreciate any advice as to what in the burner could be the problem, or most likely problem. Or if Im barking up the wrong tree. As I said though, by a process of elimination, I am fairly sure valves and pump are not to blame.

The other possibilty (doubtful) is a faulty programmer. I can't even get this opened, and its the discontinued model (Horstmann channelplusXL). The replacement model opens differently.

Please help!!!

 

[dcawkwell]

Burner transformer or ignition leads in the burner
or possibly the solenoid coil. My guess would be the ignition leads
perhaps worn and arcing to the body of the burner.

I have discounted a fault in the motor as I would expect that to occur
as soon as the motor starts.

 

[Jezclayton]

You've not said what make/model the burner is but the problem is most likely caused by failure of the solenoid valve which is located on the pump. Soleniod coil normally activates after about 7-12 seconds depending on burner. Try unplugging this and trying again. If no trip you have found the problem. Otherwise it is likley to be the ignition transformer at fault.

 

[Agile]

Lets assume its tripping an RCD which only needs 30 mA to trip.

It seems that the tripping occurs when its time to ignite the boiler.

That could be be a fault associated with the ignition electrodes and I would add particularly the earthing between the ignition circuit and the electrodes.

Some use ignition electrodes which are balanced to earth and if one of these is badly sooted up or a wire thata has come adrift then it could be causing an unbalanced current to earth.

Or as suggested if the trippling is shortly after sparking starts then a faulty solenoid coil perhaps leaking to earth.

Tony

 

[Jezclayton]

Sudden rise in activity here. Must be witching hour.

 

[Agile]

Isn't that the BEwitching hour?

Perhaps its because the Queen has finally gone to bed after watching all those ships and planes?

 

[Pauli11]

Thanks. Thats very helpful.

I'll try and check both. The ignition leads at fault would make sense, given that the burner seems to go through its preburn bit. It seems to trip the electric right at the point the unit would usually fire up. Would that be when the ignition leads would fire?

If its not too much to ask, could you tell me briefly how to recognse and change both e leads and solenoid?

I'm pretty handy and logical with most jobs, so a pointer in the right direction would notmally get me started

Burner is a Riello RDB2 90/120

 

[Pauli11]

WOw,

All these replies came in as I was typing that last post

I ran out to the garage just to check the brand and it is as above. Seems to be a concensus on 2 possible culprits?

The power is tripping at the RCB.

Really appreciate your replies, thankyou. Anyone like to advise me on how to recognise swap the solenoid or ignition leads?

 

[Jezclayton]

Isn't that the BEwitching hour?

Perhaps its because the Queen has finally gone to bed after watching all those ships and planes?

Oh Tony. I think the phrase you refer to is be-witching. I mean witching hour. Look it up, it even has a Wikipedia entry.

 

[Jezclayton]

WOw,

Really appreciate your replies, thankyou. Anyone like to advise me on how to recognise swap the solenoid or ignition leads?

Google RDB solenoid so you know what it looks like and then remove the plug from it. The burner won't fire but if the RCD doesn't trip order a replacement coil and problem is solved.

If RCD still trips post again.

 

[Pauli11]

OK, now I'm really getting concerned.

I took off the burner cover, and removed the solenoid. The burner fan came on, and the unit ran no problem for several minutes before I turned it off.

Great, it must be the Solenoid. I checked the Solenoid, and it looked like new. Pulled the power plugs off (two) checked and reseated, and done the same at the power supply box.
I reinstalled the Solenoid, fired it up and off she went. No RCD flick, and a big healthy flame.

By this time, I had unbolted the black HT box, so I went about connecting everything the way it was.

Tried the unit again, and it went through the 6-8 second startup, fired for about 6 seconds and cut out. It did not trip this time.

After 4 or 5 instances of this, I pulled the soenoid, and the ignition unit (I think thats what its called, and went out for replacement parts.
Was lucky enough to get the exact parts at my local plumbers.
Fitted them, and got the burner igniting for 6-8 seconds on a strong flame, then cutout. No RCD flick at this stage.

After another check of the parts, I pwered the boiler up, and the RCD tripped again. It is now tripping as soon as I apply power,, even with the Solenoid unplugged.

Any ideas? I thought I had this isolated. What would cause the unit to stop after 6 seconds of flame (strong arc from the ignition unit). And why is it now flicking the RCD again even with new parts? Can the solenoid or Ignition be fitted incorrectly?

 

[Pauli11]

Problem solved.

Being the inquisitive bugger I am, I pulled the burner off and virtually stipped it down on the worktop. Oil pump was a little gunged up, so that got a good cleaning. Apart from that, eveything was like new even though the unit is 10 years old. This was baffling, as the electrode wires were in as new condition, as was all the wiring.

So I connected it up and it fired first time. I run it for about 5 minutes, no issues.

I then realised I hadnt got the pump on. Switched the power to it, and bang, RCD trip.

On closer inspection, the water pump was corroded around the joint. I pulled it off and took off the junction electrical control box. There was water in one of the connector blocks, and blackening on some of the terminals. Obviously this was causing the issue.

The problem stems from a little plastic red screw cap, that sits at the top of a vertical pipe which is a foot above the pump. This vavle cap is leaking a small drip of water which was running down the foam insulation, straight onto the pump, and right at the joint.

What is that little cap for, seems like some sort of pressure release or overflow?

 

[dcawkwell]

Problem solved.

Being the inquisitive b*****r I am, I pulled the burner off and virtually stipped it down on the worktop. Oil pump was a little gunged up, so that got a good cleaning. Apart from that, eveything was like new even though the unit is 10 years old. This was baffling, as the electrode wires were in as new condition, as was all the wiring.

So I connected it up and it fired first time. I run it for about 5 minutes, no issues.

I then realised I hadnt got the pump on. Switched the power to it, and bang, RCD trip.

On closer inspection, the water pump was corroded around the joint. I pulled it off and took off the junction electrical control box. There was water in one of the connector blocks, and blackening on some of the terminals. Obviously this was causing the issue.

The problem stems from a little plastic red screw cap, that sits at the top of a vertical pipe which is a foot above the pump. This vavle cap is leaking a small drip of water which was running down the foam insulation, straight onto the pump, and right at the joint.

What is that little cap for, seems like some sort of pressure release or overflow?

Auto air vent.
If there is no air left in the system simply screw it down. It will be ok.
Needs replacing but next time you drain down and refill will do.

 

[oilboffin]

It just goes to show what a great university life is I'll certainly remember this one,but the problem is now solved so all is right with the world

 

[Agile]

In most cases a boiler turns on the pump as soon as there is a demand for heat.

It seems yours is only turning on when the flame would ignite. Thats rather unusual.

Faulty pumps are very common!

Tony