© 2011 Trane All rights reserved 1

General Service Bulletin Nuisance Rollout Switch Trips Modulating Furnaces Models: *UHMB060, *UHMB080, *UHMB100, *UHMB120 *DHMB060, *DHMB080, *DHMB100, *DHMB120 *may be A or T

Serial Numbers: 09322XXXXX through 11073XXXXX

ORDER No: FURN-SVB42A-EN DATE: February 25, 2011

Introduction This is a “fix on fail action” to address reports of the manual reset roll out limit (also referred to as the direct vent box limit) switch tripping without apparent cause. This has been reported on Natural and LP gas installations. The action described in this bulletin is not being taken to address any safety concerns.

Discussion When the roll out switch opens, in the communicating system mode an “ERR 87” will be indicated, in the 24 volt mode “Roll Out Open” will be displayed on the user interface display. This is most often due to the heat generated from normal operation of the heat exchanger and not flame rollout. Under certain op-erating conditions, some models have demonstrated a sufficient amount of heat build up to raise the tem-perature in the burner box above the trip point of the 180° or 190° limit. Another cause for a rise of the burner box temperature is the result of incorrect location of the hose connections at the “H” fitting. (see Fig. 2) Units with serial numbers 10513XXXXX through 11072XXXXX were produced with an automatic reset 180° limit and units with serial numbers 11073XXXXX and after were produced with a 200° automatic reset limit. Through previous instructions, some units were field modi-fied to eliminate the nuisance tripping either by changing to a 180° automatic reset limit or having the setup changed to operate on a single stage. The Cor-rective Actions described below should be performed on all units modified with

Fig. 1 Roll Out Limit

“H” Fitting Connections

SSA-SVB42A-EN 2

the 180° limit change or the setup change.

Corrective Action This is a “fix on fail” action. Should a unit within the af-fected model and serial num-ber display an “ERR 87” or “Roll Out Open”, the follow-ing steps should be taken:

1. Verify the correct position of the “H” fitting in relation-ship to vacuum tubes per Fig. 2.

2. Ensure the condensate trap is filled with water.

3. Verify the correct manifold pressure for both Low and High fire operation. Refer to Installer Guide Installer Guide 18-CD3D1-7.

4. Replace the original manual switch or the 180° w ith the automatic switch.

5. If set up steps were previously modified for single stage operation, return the setting in the comfort control to “modulating” performance. Refer to Installer Guide 18-CD3D1-7.

Parts Ordering Information Order the replacement 200° automatic reset switch SWT03525 from the local Trane/American Standard parts office.

Material Authorization This bulletin authorizes one SWT03525 switch as a retrofit material compo-nent.

Material Disposition Parts replaced per this bulletin action should be disposed of according to the direction of the local Trane or American Standard Field Service Representative in accordance with state or federal environmental law.

Questions Dealer and distributor associates contact the local Field Service Representa-tive (FSR). FSR should contact Residential Systems Field Operations Excellence. Indoor products team.

Fig. 1 PS1

Fig. 2

Brass Fit-ting in this connection.

© 2011 Trane All rights reserved 3

Literature Order Number FURN-SVB42A-EN

File Number SV-FURN-SVB42A-EN 02/25/2011

Supersedes New

Stocking Location Electronic Only

Trane has a policy of continuous product data and product improvement and reserves the right to change design and specifications without notice. Only qualified technicians should perform the installation and servicing of equipment referred to in this bulletin.

Models: TUHMB060ACV3VA TUHMB080ACV3VA TUHMC100ACV4VA TUHMD120ACV5VA TDHMB060BCV3VA TDHMB080ACV3VA TDHMC100ACV4VA TDHMD120BCV5VA AUHMB060ACV3VA AUHMB080ACV3VA AUHMC100ACV4VA AUHMD120ACV5VA ADHMB060BCV3VA ADHMB080ACV3VA ADHMC100ACV4VA ADHMD120BCV5VA