High Limit And/Or Safety Limit Maintenance; Seasonal Maintenance; Filters - Trane GXAA Installation, Operation And Maintenance Manual

M M a a i i n n t t e e n n a a n n c c e e

High Limit and/or Safety Limit Maintenance

Single furnace units are equipped with a primary high limit on the upstream side of the heat
exchanger and a secondary high limit on the downstream side of the heat exchanger. Multiple
furnace units are equipped with a primary high limit on each furnace section and a secondary
high limit on the downstream unit. The primary high limit is a disk type switch while the
secondary high limit is a capillary switch. To service or replace high limit or safety limit:
1. Turn off the manual gas valve and electrical power to the MS unit.
2. To access the high limits, remove the four screws from the top of the raceway on each
3. To remove the secondary high limit, remove the wires from the limit switch, remove the
4. Complete appropriate start-up procedure as given in the "Start-Up" section of this manual.
5. Check Burner Adjustment.
6. Check gas control valves and pipe connection for leaks.
7. Check operation of auto gas valve.
8. Check operation of safety devices.
9. Inspect and service blower section of system.

Seasonal Maintenance

The unit should be thoroughly checked before the start and at the end of each heating and
cooling season.
1. Motors and belts should be inspected.
2. Tighten belts if loose.
3. Check and clean DX or Chilled Water coil twice yearly, if unit is so equipped per
4. Check air throughput at beginning of heating season to confirm unit operation is within the
5. At beginning of heating season clear Condensate Drain Pan and P-trap of water if unit is
6. Evaporative cooler must be cleaned and maintained per manufacturer's instruction
7. Inspect Control Dampers during periodic maintenance. Damper pivot points should be
8. Blower wheels should be checked periodically for dirt build-up on blades. Clean as required.

Filters

The filter section has been designed to incorporate (as standard) one-inch washable filters. Other
optional filter types are also available: two-inch washable throwaways; or one or two inch hi-
efficiency 30% pleated filters.
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furnace section and swing the raceway down. The primary limit can be removed by removing
the two screws holding the high limit bracket to the heat exchanger and removing the bracket
and limit assembly from the heat exchanger. Note location of and remove wires from limit
switch, then remove push nuts and springs holding limit switch to bracket. Re-assemble in
reverse order making sure that parts are assembled so that spring pressure holds limit switch
securely against bottom header plate of heat exchanger.
screws and stand-off sleeves holding the limit switch body to the mounting plate. D D o o n n o o t t
r r e e m m o o v v e e t t h h e e s s c c r r e e w w s s h h o o l l d d i i n n g g t t h h e e m m o o u u n n t t i i n n g g p p l l a a t t e e t t o o t t h h e e h h e e a a t t e e x x c c h h a a n n g g e e r r . . Slowly pull the
switch and capillary assembly out of the retaining tube, taking care to prevent kinking the
capillary tube. Re-assemble in reverse order, carefully pushing the capillary tube into the
retaining tube to prevent kinking the capillary tube.
manufacturer's service manual. Chilled Water coil must be winterized at beginning of heating
season (i.e. drain water from coil per manufacturer's instructions).
specified temperature rise range.
equipped with DX or Chilled water coil. Clean out drain pan and fill P-trap with a non-toxic
glycol solution.
frequently during the operating season.
cleaned to ensure free damper operation.
MUA-SVX006B-EN