Trane classroom unit ventilator

[hvacsteve]

Hi

Has anyone else had the experience of the fan Trane UV’s running much slower than normal? I have never seen the problem when the fan switch is set to high but when switched low every once in a while I will open one up and the fan is obviously running much slower than normal low speed. Voltage from the auto transformer is 77 volts as is should be, amperage is normal. When I first saw this a few years ago I changed the motor and the new motor did the same thing. (That teacher was told her unit has to run on HI) I’m thinking maybe a breakdown of the transformer? I have seen this on units in 2 different schools, one school the units are about 10 years old the other 2 years old. I would love to get to the bottom of this rather that just having to run them on high speed (very Noisy)

Thanks

[richper]

Whats your voltage off the transformer? you wrote 77. Also does it only do it when you have the panel off? If so you may have a damper or air flow issue such as blocked coils.

[hvacsteve]

Yes 77 volts is correct for low speed. They use an auto transformer for speed control. As far as air flow goes that is not an issue, you can see the fan. I’m sure this is some sort of electrical problem.

Thanks for you reply

[jbg30]

Have a school with at least 75 trane units, when you take the front panel off the fan slows down every time from what I remember. I think the fan is off its curve when the cover is pulled.

I assumed the blowers were sized to depend on the airflow resistance through the return/oa grill to perform correctly and never gave it much thought.

I think the motor will overheat also if the cover is left off too long. Maybe take an amp reading with the cover off, then put the meter on min hold and put the door on for a minute and see if theres a change.

Come to think of it, I think I've noticed this with most manufacturers uv's. Maybe I'm wrong.

[hvacsteve]

okay thanks. i'll check that

[bruingtonbeagle]

i think your right jpg30 i think when you remove the cover,the air will cavitate and slow the blower down noticeably..i have several of these at the school system that i maintain.

[hvacsteve]

well I guess i'm not so sure its an electrical problem.

thanks