SWUD help!

[jemawalton]

I have a SWUD 058 / T96H00976 that is going off on supply fan overload failure immediatly upon start-up. The fan has no VFD, voltage good, contactor good, CTs ohm out perfect, fan runs fine when contactor pushed in manually. The controller goes into pre-fan mode for about 2 seconds, and then faults on overload. Trying to cover all my bases before condeming the controller but I am running out of things to check. Customer mentioned they had a smoke alarm in the area yesterday that might have shut the unit down but I can't see anything that would cause an overload fault. Help!

[maxster]

if you push the contactor in manually the 1U1 module will fault out on an overload diagnostic even if the fan runs....you have to clear the active fault,and go for a normal start in auto/local on the rocker.repin all the 3 CTs from the 3 phase feed on the fan contactor back at the 1U1.before restart make sure you have no active diagnostic in the B ...C is stored faults that are NON-Latching your fan fault is Latching will lock up the unit on start no matter how many times try if you don't clear B.to Quick Start the unit hold the advance button down(with thumb) and move the rocker from off to auto/remote then to auto?local and let off the advance button.unit will start up and compressos will run for five minutes fan will stay on and unit will go back to setpoints.that forcing the fan to run is OK to do but your forcing the CT to send a run signal to the 1U1 when it isn't looking for it.same goes with the compressors if you do a push test they will OL trip a diagnostic calling also for a Latching reset.two ways to clear B diagnostics are.....disconnect off/on with rocker in the off mode....hold advance button down and move the rocker from OFF to auto/remote back to OFF then scroll to see it is clear

[txhvac]

You said the fan runs good when push in on the contactor, what kind of amps are you pulling? Are you close to trip point? You said there was a fire alarm the other day...did a fire damper close on the discharge side of your fan? There is also a possibility your 1u1 board may be going out. Maxster has some good info. hope this can help.

[jayguy]

from SCWD-IOM-3...

Check the ribbon cable from the A3 to the 1U2. J4, pin 17 to pin 2. This is for the supply fan.

0.7 to 1.0 VDC while the fan is ON. 12.0 VDC when the fan is OFF.


Also, "Loss of Line Current" definition: < 8.0% CT rating.

Check out your 1T2 transformer (I hate this transformer!!)
1T2 @ board A6, VAC,
1-2 (Y-Y): 7.85-11.7
4-5 (BR/Y-Y): 45-55% of pins 4-6
5-6 (BR/Y-Y): 45-55% of pins 4-6
4-6 (BR-BR): 4.25-6.5
7-8 (BL-BK): 14.4-21.8
9-10 (R-R): 13.1-19.5
11 (G): Ground

[jemawalton]

Thanks for the info. I ended up powering the unit down for about 20 minutes and cleaning years of dust out of the controller to inspect the ribbon cables. I found no smoking gun there but when I powered it back up, it ran like a champ. I checked the 1T2 transformer and found all voltages good. I am suspecting a ribbon cable or the controller itself. I will be back doing running inspections soon so we will find out.

P.S. The fan was running well under full load when the contactor was pushed in manually.

Thanks again guys.

[maxster]

another thing to check on maint.is all the philips screws that hold the boards in place they are the grounding paths back to the TRs

[maxster]

sorry we hijacked your thread,whats they results on that fan problem on that SWUD

[hvac_lady]

I was given the opportunity to inspect two Trane SWUD052A units prior to building management turning over the floor to a new tenant. We checked everything and the systems were functioning normally. We were called a few months later when the tenant had new ductwork installed. Upon arrival I saw that hthe tenant removed all VAVs, pneumatic controls and the new ductwork was very small and I was told by the architect that hje designed the supply ductwork at .08"/100' static. I was told by a trane rep that the static pressure should be at 1.6" for the system. Does any one know if the .08 static pressure is too low.