Glow Worm 18 hxi Condensing Boiler fan

[Terran]

Need some help from someone who is familiar with these boilers. The fan in this developed out-of-balance problems resulting in very noisy operation and vibration.

This was replaced with a new fan which lasted for about 5 hours and then stopped.

The voltage from the fan transformer on blue and red wires is supposed to be 24V dc according to the manual, it actually measured around 35V when I checked it. (The fan is a dc speed controlled job which blows the gas/air into the burner.)

We put the old fan back in and this works perfectly (apart from the vibration problems mentioned)and seems happy on the 35 or so volts. We are now awaiting an exchange for the faulty new fan but I wonder if the apparent over-voltage from the transformer might have caused the fault.

So before we chance plugging in the new unit does anyone have any advice?

Many thanks.

 

[andsam]

Is the vibration noise intermittant or is it constant.

 

[Terran]

The vibration is not constant, (looking at the impeller and spinning it by hand it is quite obvious that a balance wieght or something has dropped off at some time). At low speed is more pronounced than when running at high speed but there is still some there, I guess it is the frequency of the vibration changing with speed.

That is why a new fan was fitted, that did not vibrate it worked fine until it just stopped working with what appears to be an electrical fault.

 

[andsam]

If the air gas ratio is not set correctly at the gas valve you can gat a vibration noise comming from the burner/fan area. This is set up using a telegan and an adjustment to the gas valve.


But this dosent explain the probs you have had with the new fan. Swap the fan and see how you go.

 

[Terran]

If the air gas ratio is not set correctly at the gas valve you can gat a vibration noise comming from the burner/fan area. This is set up using a telegan and an adjustment to the gas valve.But this dosent explain the probs you have had with the new fan. Swap the fan and see how you go.

Yes thanks for that - it all makes sense to my gas fitting oppo, I don't mess with the gas side of things my area is electrical - and why I got involved here.

It is quite definitely a mechanical / balance problem on the old unit we are not bothered about that. The service call was to fix a noisy boiler which the new fan did, just that it failed after about 5 hours and then things got really quiet!

The fear is that the new fan failed because of an over-voltage situation although that seems less likely as the old unit is still working (noisily) after almost a day.

 

[Agile]

I am surprised that you have not checked with the manufacturers to advise on the supply voltage.

Most of these have a DC supply of about 35vdc and a speed signal to control the speed. Usually they have a Hall effect sensor to indicate the rotational speed and the controller adjusts the speed to the correct value required.

Its difficult to imagine how the balance could go out of adjustment unless the shaft has become bent.

Tony

 

[croydoncorgi]

Some impellers have balance weights that can fall off.....

 

[Terran]

Some impellers have balance weights that can fall off.....

Yes there were / are small clips on the impellor blades and a mark where one had fell off.

 

[Terran]

I am surprised that you have not checked with the manufacturers to advise on the supply voltage.

Most of these have a DC supply of about 35vdc and a speed signal to control the speed. Usually they have a Hall effect sensor to indicate the rotational speed and the controller adjusts the speed to the correct value required.


Tony

Yes looks like brushless dc motor, the voltage is applied to it all the time. Then Hall effect ic on the motor board will pulse probably twice per revolution and the speed controlled by PWM from the panel in the boiler - similar principle to bigger machines I am more used to.

Will give them a call as you suggest to confirm that the voltage. The 35 Vdc you mention would seem reasonable to me after looking at the supply which appears to be a simple transformer with a bridge rectifier and smoothing caps.

Thanks

 

[Terran]

For anyone who might be interested I got this reply after contacting the manufacturers tech support.
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Thank you for your enquiry.
The correct nominal voltage reading is 36V dc red to blue.

Martyn D Buckley
Technical Support Manager
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