Riello burner motor not starting

[Justin_]

Hi everyone,

I have a Grant Vortex external combi about ten years old which has caused no end of problems since installation.

I've replaced quite a few parts myself over the years but I'm currently facing a problem that I'm hoping somebody will have faced and know what is causing it.

The Riello burner motor won't run and this is what I've done so far:

1. Removed the burner so its in front of the boiler but still connected to electricity and oil.
2. Taken the end cap off the oil pump to check it spins. It spins fine.
3. With the oil pump off, turned the shaft on the motor which also spins freely.

I've tried switching it on with the oil pump off and watched the motor shaft that the oil pump slots onto. It slowly turns maybe 1/8 of a turn then stops. It'll do this most times if I turn it off, wait, then turn it on again.

I thought maybe the capacitor wasn't working so replaced it with a new one but exactly the same thing happens.

Has anyone faced this problem and can please help pinpoint what is causing it?

 

[Exedon]

Probably motor bearings on pump side as you have ruled out capacitor
Simple answer new motor.

 

[Moss5]

To fire -up my burner (outside of the boiler)I have to cover the flame tube outlet with a plastic bucket. This fools the sensor to believe that no light is visible. On ignition, the bucket is removed and burner continues to fire.

 

[Justin_]

New motor received today and still no luck unfortunately.

I didn't "install" it.
I kept the old motor in place on the burner and just connected the new motor wires up to the control box and capacitor and when I switch it on exactly the same thing happens with the new motor. The shaft turns just a little and stops.

This should narrow down the problem, but I don't know what I should be looking at next. Can anyone offer any suggestions please?

 

[oilhead]

What model burner is this? On a Vortex, I would expect an RDB burner and there are only live, neutral and earth connections as the capacitor is connected to the motor. A new motor should come with a new capacitor. Did you use this? Without a pump connected, if the capacitor is OK, the fault must lie with the control box or the connections. Have you checked the voltage from the control box to the motor?

 

[Justin_]

Thanks for all your help so far guys!

Oilhead, the burner is a Riello RDB 2.2 and I tried the new motor and capacitor together.

I called an engineer who (mis)diagnosed the fault as being the control box sitting on top of the burner. I thanked him and ordered a new control box to fit myself.
The new control box arrived and I excitedly fitted it looking forward to heat, but nothing changed and it was exactly the same.

Having no faith in the previous engineer I was then able to get another engineer to look at it who said it must be the fan, as the fan not spinning would prevent the motor from running and everything from firing up. I questioned this as I thought the fan was connected to one side of the motor and the oil pump the other side of the motor and he insisted the fan is a separate electric unit and not powered by the main motor.

I thanked him and sent him on his way and checked the parts diagram which shows what I thought - the motor has the fan impeller attached one side and the oil pump the other side unless I'm missing something.

I'm able to spin the impeller freely but I still have exactly the same fault - when I switch the boiler on via the switch in the top panel, the motor shaft turns just a little and stops. The old motor (still connected) does this, and so does the new motor if I just connect the wires without installing it in the housing.

I have a new capacitor
I have a new control box
I have a new motor

When I turn it on and the motor shaft turns a little, there is no resistance and I can turn the shaft in both directions while still switched on. Its as if it turned by some residual power stored somewhere and isn't getting power to properly turn it.

Both the pumps run when I switch it on - its just the burner which does not appear to be functioning. The wires that plug into the capacitor seem to have a strong current running through them as I zapped my finger quite well while testing without the cap over the wires.

The power lead to the burner control box has all the connections tight, following them back behind the top control panel the earth is solid and goes to a point with the other earths, the live appears to go to a clear relay which clicks and lights red when switched on, and the blue appears to go to the main switch.

I've swapped the wires from the main switch to the test switch to see if the switch itself is faulty but the symptoms are still exactly the same.

I'm completely baffled and don't know what to try next.

All the wires and connections seem good.

 

[Exedon]

Have you actually used a multimeter to check voltage at motor?

 

[oilhead]

As I asked, and also Exedon, have you checked the voltage at the motor connections? Also, you could try spinning the motor manually when it locks up.

 

[Terrywookfit]

If you do not have a multi meter, you could wire a fly lead direct to burner to test.

If you have tried the motor and control box the fault is on the controls.
The easy solution is a voltmeter as pointed out already.

 

[Justin_]

Thanks everyone, I've tested with a multimeter and the results are very inconsistent.

On the wire which runs down from the top panel down the the burner control box, I've seen anywhere between 190 to 225 volts. Sometimes its zero.

Following that wire up to the connector block on the left of the top panel and probing the wires in the connector block, again sometimes I get zero and sometimes I get around 216v.

In the first image, I unplugged the live and neutral and tested the voltage there.
When I get a reading there if I unplug the motor and test the prongs on the control box I also get voltage there.

The second and third images are both taken with the boiler switched on. If I get no reading I switch it on and off multiple times and may sometimes get a reading but when I do get a reading there, the motor still doesn't run.

The live seems to go to the left of the two the clear relays (I've swapped them over with no change), the neutral goes to the on/off switch and the earth is well connected with other earths.

 

[Exedon]

Have you checked voltage each side off main boiler on off switch?

 

[oilhead]

It would seem that you have identified a connection fault somewhere. Follow it through logically from the fused spur.

 

[Justin_]

Thanks everyone for your help.

I've been testing more today and have uploaded a few pictures showing the voltage at certain points.

Should the clear relays give a reading with the boiler switched on but burner not running? The red light is on each of them, but I may not be checking the correct connections?

Boiler end of the 5 pin plug: 233v
Female socket on boiler: 233v
Main on/off switch: 233v
Highlighted connectors on left hand PCB: 233v
Relays and wires at top/left of boiler which go down to burner: 0

 

[martyndc88]

Does the burner lockout?

 

[Justin_]

Burner lockout light is never illuminated.
It appears than no power is getting to the burner but I don't know why