LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 25)

15
Service Manual - NeoTherm 500
Troubleshooting the 24V AC Power Supply
B2
24V AC
between TB3
and TB4?
Yes
No
24V AC supply is OK
120V AC
to NT unit?
No
Yes
Troubleshoot the 120V AC
incoming voltage.
120V AC at
main power switch
(3-7 on SW1)?
No
Disconnect power.
Check for continuity through power switch SW1.
Replace if necessary.
Disconnect power.
Check transformer - see Section B34.
Replace if necessary.
Reset
circuit bkr. on
transformer
24V OK now?
Yes
24V AC supply is OK
Why did breaker trip?
Loose or damaged wire?
No
Check
for bad
transformer -
Trans. OK?
Yes