RDB1 Faulty Motor or capacitor or fuel pump?

[NigelGiddings]

Hi,

I have an oil fired boiler that uses an RBD1.

Over the last few weeks it has begun to 'Lock Out' from time to time.

If the boiler is reset everything was fine for a number of days.

More recently the 'Lock Out' has occurred more often.

The fault has now developed such that the Fan does not rotate during the start up phase. By removing the air baffle it is possible to access the Fan and asses how difficult it is to turn the Fan/Motor/Oil Pump. The effort required to turn the Fan varies as it goes through a revolution, I assume this is the action of the Oil Pump? While it is fairly hard to turn, using a finger tip, it doesn't seem too excessive considering the size of the motor?

I have removed the oil pump, the Motor / Fan rotates freely. The pump also rotates quite freely off of the shaft (it had no oil in it at the time).

Having looked at the potential points of failure I see that it could be:

The Oil Pump, but this is pumping OK when the motor turns and seems OK when spun off the Motor Shaft.

The Motor, runs fine and will even start 3 out of 4 times, it seems to depend where it stops on the oil pumping cycle. Rotating the Fan 180 degrees when it does stall means the motor will start next time.

The Capacitor, I have removed and tested with an analogue meter and it shows a 'Kick' but I haven't been able to verify it is within tolerance.

The Motor Brushes, I was not able to fully remove the motor as the Fan fixing has stuck on (I did remove the grub screw). Should I try inspecting the brushes for wear (7 or 8 years old?)

The Motor bearings, with the Oil Pump removed all seems to spin fine.

The Motor itself?

Any guidance on what to expect in terms of load on the shaft with the pump connected and primed would be very useful. Alternatively more info on brush wear/replacement and any more ideas about the Capacitor?

Thanks in advance

Nigel

 

[Best]

No offence, but you really shouldn't be doing too much to your oil burner as you are not qualified & out of your depth a little. The motor does not have brushes - it has a capacitor because it is an induction motor. You likely just need a new capacitor as the RDBs often go.

 

[Roger Welton]

I'd get some one who knows what they're doing, will be fixed within in the hour, most oil tech keep all the above parts on van. Do you have means to set fuel pressure and fuel air mix if you replace any of the parts?

 

[Best]

As above ^^^, if the motor is spinning free, then it is possible to have a worn oil pump causing lockout intermittently, but you need the burner set with an engineer then. I would go with a new capacitor ( even if oil pump is faulty so could capacitor be) & if any more bother get an engineer.

 

[NigelGiddings]

Thanks for the replies...

I realise the burner will need to be set up properly and will be arranging for a service call to do just that once the fault has been cleared. It makes economic sense to have the boiler tuned in the same way as you would tune a carburettor on a car....Plus all the safety issues as well.

While I realise not all 'oil techs' are the same my experience of professionals in all fields leaves a lot to be desired and I don't want to end up with the Pump, Motor and Capacitor changed at £200 plus time if it only requires a £10 part. I am not complaining about call-out charges, people need to make a living and the amount charged has to cover costs, training, certification, insurances vehicle etc. etc and all plus VAT!

Having read the various manuals I am confident that I can repair the fault, what I am missing is the 'experience' of what feels right and what feels wrong.

Thanks for the heads up on the Motor Best, I had read elsewhere on this board that the brushes can be an issue... You shouldn't beleive everything you see on the internet...

Thanks again.

Nigel

 

[lame plumber]

pump £50, motor£70, capacitor£10 long way short of £200, you cant repair and set up a boiler by feel despite what you think!!! I am always astounded when someone posts a question then proceeds to tell the forum that they have no faith in oil or gas engineers but expects them to provide answers free of charge!

 

[NigelGiddings]

Dear Lame Plumber what I said was 'While I realise not all 'oil techs' are the same' trying very hard to point out that there are good guys and bad guys. The problem is identifying them...

I have used Forums on the internet to help me with all sorts of technical problems, just recently how to replace the seals on my Diesel engine, parts £6 and my time, local diesel specialist quoted £250. I also used a Forum to help me build my Home Cinema using second hand equipment, cost to me £1,000 plus time, local AV specialist would have charge £4K to £5K for the design with another £20K for the parts if I had bought new.

You may think I'm a cheap skate, I like understanding how things around me work and getting my hands dirty.

Obviously dabbling with boilers can be lethal and appreciate the words of warning but I see one of the great attributes of the internet and Forums in particular is the free exchange of information.

 

[Roger Welton]

I realise the burner will need to be set up properly and will be arranging for a service call to do just that once the fault has been cleared. It makes economic sense to have the boiler tuned in the same way as you would tune a carburettor on a car....Plus all the safety issues as well.

I wouldn't advise running the boiler if you repair it yourself until this is done, you would be gambling with the lives of your family

 

[Best]

To be honest, a lot of "engineers" are not really doing a good job & often are expensive to add to that! But you have to find someone decent & stick with them.
If you want to try a capacitor, then it won't cost you much. No point in you changing an oil pump & then getting an engineer out to set it all up. A decent guy should do it all for 2hrs labour max if rest of job is in good nick.

 

[Dotty]

Not when you put the lives of your family at risk!