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Service Bulletin Index - Johnstone Supply

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Goodman Manufacturing Company, L.P.<br />

1810 Wilson Parkway / Fayetteville, TN 37334<br />

(888) 593-9988<br />

FAX (931) 438-2273<br />

DATE: August 6, 2003<br />

TO: All Goodman Distributors<br />

FROM: Technical <strong>Service</strong>s Department<br />

SUBJECT: Nuisance Primary Limit Trips on GMT & GMTH Revision “A” Model<br />

Furnaces<br />

Goodman has received field complaints regarding nuisance tripping of the primary limit<br />

on GMT and GMTH Revision “A” model furnaces. Not every Rev. “A” furnace exhibits<br />

this condition which seems to be a function of the duct static and its effect on airflow<br />

across the heat exchanger.<br />

Our investigation into this matter confirmed inconsistent airflow patterns within the heat<br />

exchanger under varying duct pressures. At certain conditions, the airflow shifted<br />

enough to bypass the primary limit causing it to trip prematurely. To correct this<br />

situation, a filler plate is installed in the blower deck behind the indoor blower assembly.<br />

This repositions the blower assembly directly beneath the heat exchanger and closer to<br />

the primary limit. The new position ensures even air distribution over the heat exchanger<br />

and primary limit at all airflows within the recommended temperature rise for the furnace.<br />

It will be necessary to replace the primary limit with one furnished in the kit.<br />

Filler Plate Kits have been released<br />

and are available from the <strong>Service</strong><br />

Parts Department for installation on<br />

GMT Rev. “A” and GMTH Rev. “A”<br />

furnaces that have been determined to<br />

be experiencing nuisance primary limit<br />

trips. The kits are selected based on<br />

the furnace cabinet width and are listed<br />

in the chart on the right:<br />

MODEL FILLER PLATE NEW LIMIT<br />

GMT045-3 (A) B13701-89<br />

GMT070-3 (A) 4016000 B13701-98<br />

GMTH045-3 (A) B13701-99<br />

MODEL<br />

GMT070-4 (A)<br />

FILLER PLATE NEW LIMIT<br />

GMT090-3 (A)<br />

GMT090-4 (A)<br />

GMTH070-4 (A)<br />

4016001 B13701-98<br />

MODEL FILLER PLATE NEW LIMIT<br />

GMT090-5 (A) B13701-89<br />

GMT115-5 (A)<br />

GMT140-5 (A)<br />

4016002<br />

B13701-87<br />

B13701-98<br />

GMTH090-5 (A) B13701-89<br />

Page 1 of 2<br />

SERVICE<br />

BULLETIN<br />

S-172<br />

4016000S 14” MODELS<br />

4016001S 17.5” MODELS<br />

4016002S 21.5” AND 24” MODELS

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