Noisy burner

[Burnerman]

I'd be grateful for any clues on this one - don't know where to go next.
The cooker is a double burner Raeburn that provides domestic hot water/heating combined with a cooking facility. The burners are by Nu-Way.
The problem is noise, which seems to be coming from the main burner pump. The noise is a fairly high pitched whine that can be heard throughout the house. The pump (Danfoss) is brand new, the fan impeller is tight and balanced, pump pressure is 125psi, flue gas fine at 12%. The system is gravity fed with a pipe length of around 25m, and is of 15mm copper pipe. I renewed the pump due to a different fault and I thought that the noise would stop too but it is exactly the same.
Both burners light up perfectly and give no trouble, there is no air in any of the lines and the burner unit isn't vibrating against anything. I've absolutely no idea how to stop this noise. Has anyone any clues? Cheers and thanks for looking! John

 

[Terrywookfit]

Check burner motor bearing!!

 

[oilman]

Then when you've checked one, check the other, then replace them both. 6206-2RS and 6206-ZZ

 

[Burnerman]

OK gents I'll do that...there wasn't any obvious play on the motor spindle when I replaced the pump but I realise that doesn't mean too much.
Thanks for your input - much appreciated! Cheers John

 

[oilman]

You'll probably need a bearing puller, and it might be advisable to have a press of some sort. DON'T hammer them in place, otherwise you'll be replacing the replacements.

 

[Burnerman]

Aha the famous zinc castings.....found that out the hard way!! Cheeers John