Allied Furnace: Replacing a furnace that shared a common vent
Replacing a furnace that shared a common vent on a Allied furnace: When the new Allied furnace is vented on its own and the old furnace used to share a common vent, the remaining appliance is left on a vent that is now too large. Without the heat of the old furnace, the flue gas cools and may not draft properly. Verify draft on the remaining appliance before you leave, and do not assume the old vent is fine.
Applies to: Common vent replacement
Common causes of replacing a furnace that shared a common vent
- Vent was sized for both appliances together
- Cooled flue gases in an oversized vent giving weak draft
- Condensation or spillage at the remaining appliance's draft hood
How to fix replacing a furnace that shared a common vent: step by step
- Check the size of the existing vent for the remaining appliance.
- Check draft with the remaining appliance running on the existing vent.
- Correct the vent size if the draft is not proper.
- Look for signs of spillage, rust or staining at the draft hood.
- If you are unsure of the vent sizing, have a licensed technician check it, since this is a carbon monoxide matter.
If the unit shows an error code, look it up: Allied Furnace codes
Models
92G1UH92G1UH0450892G1UH0451292G1UH0700892G1UH0701292G1UH0901292G1UH0901692G1UH1101692G1UH1102092G1UH1352095G1UHA93UHA95UH
Source: Allied 92G1UH installation manual, p. 20 (PDF p. 20). Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.