Half the county lives over a belly duct: an if-then guide for manufactured-home owners

Why this guide is about the duct

Roughly 48 percent of the housing units in Suwannee County are mobile or manufactured homes. Almost all of them are cooled by a package unit sitting on a pad or roof, or by a small split system, feeding a duct that runs in the belly of the home between the floor joists and a fabric or board underlayment. That duct was thin when the home was delivered, and it has been soaked, chewed and sat on ever since. The wear differs by setting: on a homestead off US 90 around Wellborn it is usually rodents and sagging straps, while on an owned lot in Suwannee River Mobile Estates the river damp keeps the belly wet for months at a time.

So when a manufactured-home owner calls about the air conditioner, the air conditioner is the second thing we look at. Follow your symptom below and you will see why.

If the floor is wet, or the carpet is damp in one spot

Then cold air is escaping under the floor and condensing on the underside of the subfloor. The duct has a tear, a disconnected branch or a collapsed section near that spot. The package unit is doing its job; the air is going into the crawlspace and sweating against the floor. Fix: find the break, reconnect and seal it with mastic and mesh, and patch the belly board. If the subfloor has softened, that is a carpenter’s call before it is ours. On farm acreage below McAlpin, check too whether irrigation runoff or a low spot is ponding under that end of the home, because a duct repair will not survive standing water.

If one end of the home is cold and the other is warm

Then look at the crossover duct in a double-wide, or the main trunk in a single-wide. In a double-wide the two halves are joined under the floor by a flexible crossover that rodents, water and gravity attack first. When it fails, one half of the home takes all the air and the other takes none. In a single-wide the equivalent is a trunk that has separated at a joint, so the rooms past the break starve.

When the package unit never stops and the house still won’t drop below 80

Then either the duct is losing a large share of the air before it reaches a register, or the unit has lost capacity, or both. Check the duct first, because it is cheaper and it is usually the answer. Then the equipment: a dirty outdoor coil packed with hay dust and pollen, a charge that has drifted low, or a blower running slow.

If the electric bill jumped and nothing else changed

Then one of three things, in order of likelihood: the duct opened up and the system is cooling the crawlspace; the heat strips are running when they should not be, which on a heat pump package unit means a bad defrost control or a stuck reversing valve; or the compressor is drawing high current as it fails. The first is a duct repair, the second is a parts repair, the third is a conversation.

Call 866-266-5709

If the air from the vents smells musty or like the outside

Then the return side is pulling from under the home. Manufactured homes often have a single central return, and when the duct or the return plenum leaks, the system draws crawlspace air, with its moisture, dust and whatever lives down there, straight into the house. Sealing the return side and the belly ends the smell and usually lowers the humidity in the home noticeably.

What we do on a manufactured-home visit

Every call to a manufactured home follows the same path regardless of the complaint: open a skirting panel, inspect the belly and the crossover with a light, check the return plenum and the duct connection at the unit, and only then put gauges on the equipment. The repairs, in the order they usually pay back:

1. Reconnect and seal the crossover or trunk; patch the belly board.
2. Seal the return plenum and the connection between the unit and the duct.
3. Clean the outdoor coil and change the filter.
4. Correct the charge, replace a weak capacitor or contactor, fix a defrost control.
5. Only then, if the unit has fifteen-plus years on it and is failing, talk about replacement, sized for the home as it is, with the duct done right while it is open.

Replacing the unit, and what to do about the duct

When a package unit does reach its end, the replacement is an opportunity to fix the duct for good: a new, properly supported and insulated trunk under the floor, a sealed crossover, a real return. Setting a new unit on a torn belly duct buys a small improvement at the largest possible price, and we will say so before we quote one. The Cook’s trucks that reach Suwannee County’s manufactured homes start at 37 Fairmont Ln in Palm Coast, 144 miles east, carrying belly-board, mastic and package-unit parts; a person takes the call at any hour, and the clock has no say in the bill.