Horizontal installation support and drain

What is going on

When you lay a furnace on its side, the coil and the furnace both need real support and a way to get rid of water. People forget the coil drain, and the first summer there is a ceiling stain. The rules below are for the UH1 upflow converted to horizontal and the DH1 downflow in horizontal. Take your time on support, because a sagging cabinet can bind the doors and put stress on the drain connections.

Likely causes

• Upflow UH1 being converted to a horizontal install
• DH1 downflow furnace set in the horizontal position
• A horizontal evaporator coil or 95% furnace sitting over a finished space
• New install where the cased coil needs stabilizing

Check in this order

1. Install an auxiliary drain pan under a horizontal evaporator coil or 95% furnace. Run the auxiliary drain to a separate line (no trap needed)
2. Fit the three brackets included with downflow furnaces to stabilise the furnace and TXC cased coil, using the rear coil case screws and four bracket screws
3. Place the 2/4TXC coil downstream of the furnace. The coil apex may point toward or away from the furnace
4. Support the furnace at both ends and in the middle
5. Raise the furnace at least 6 in so the condensate drain can exit the cabinet
6. Check that the unit has the slope required by the installer's guide so condensate runs the right way

More furnace guides

• Abnormal conditions and protection
• Adjust gas valve manifold pressure
• Air for combustion and ventilation in non-direct vent installs
• Airflow adjustment check
• Airflow and temperature rise check
• Bottom return filter rack installation (upflow)