HVACopediaTrane · Furnace troubleshooting
Downflow furnace on combustible floor (subbase)
What is going on
DH1 downflow on a combustible floor. Can't sit it right on carpet, tile or any combustible flooring. Wood flooring is the exception. Use the subbase.
Likely causes
- Not a fault. Floor protection requirement for a downflow install.
Check in this order
- Put subbase BAYBASE-205 between the furnace and combustible flooring on vertical downflow installs.
- Downflow vertical with a cased coil? No subbase needed.
- Cut the floor opening to the dimensions in Table 1.
- Check the opening is square and clear of joists or wiring.
- Seat the furnace on the subbase and confirm no gaps around it.
- Check clearances to combustibles on the rating plate before leaving.
Applies to: DH1 downflow furnaces
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Source: Trane installer's guide 18-CD29D1-11, p. 8. Written in our own words; check the manual for your exact model.
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