4- Return Air; Trouble Shooting Guides; Mechanical Thermostat - Atwood AFS Series Training Manual

CAUTION – Ducting Installation
4" Flexible Hose

Each 90° bend adds the equivalent of 10 feet of ducting hose

Ducting should be securely attached to the furnace

Each run should be a short and straight as possible and pulled tight
2" Flexible Hose

2- 2" duct runs do not equal one 4" duct a 2" duct is only 3 sq. inches of open area.

2" duct adapters are available

2" ducts are ideally suited for bathroom and holding tank compartments.

2" ducts are option in addition to what ducting requirements are needed.
Closeable Outlets

A closeable outlet does not contribute to the minimum of total outlet recommended for a furnace.
Bottom Discharge

Furnace must be completely sealed t floor and plenum with a bottom discharge gasket, with no air gaps

If furnace is installed in middle of run, the main duct run must be a minimum of 24 sq. inches on both sides

If furnace is installed at the end of the run, the main duct must be 48 sq. inches

#4- Return Air

Trouble Shooting Guides

Guides are only intended for use on Atwood® products by service technicians who have successfully completed Atwood® training. This guide
should be used in conjunction with the appropriate Instruction Manual provided with the product and any applicable Industry Standards. This is
not intended to be a complete list. Please direct questions concerning service of Atwood® products to
proceeding.

Mechanical Thermostat

* NOT COVERED UNDER WARRANTY
CAUSE
BLOWER DOES NOT RUN
Temperature selector out of place
Thermostat wires broken or disconnected
Heat anticipator burned out
No continuity through thermostat with contacts closed and
switch on.
Continuity through thermostat with contacts closed and
switch on.
FURNACE DOES NOT CYCLE PROPERLY
Furnace cycles too quickly
High temperature variance
Note: When the anticipator is set properly and the heating system has operated for a few hours, the furnace should cycle 5-6 time per hour.
This return air requirement can be met in a couple of ways.

The return air grille mounted on an inside wall of the trailer, exposed to the
cabinet area of the furnaces is the most common mounting used on the 85, 89 and 2-
Stage series furnaces.

Another option is to provide openings at various locations in the furnace
cabinet area capable of drawing air from inside the trailer (i.e., routed holes at bases of
sofas or walls, etc.)
The total square inches of openings must meet minimum requirements.
Do not place any types of air filter in front of or behind the return air door. Blocking this
area will substantially decrease the return air causing – less air delivery to the heat
registers – short cycle of the furnace – limiting of the furnace.
We recommend electrical air filters that can be placed anywhere in the open living area
of the recreation vehicle. They can be purchase in most stores.
Remember the better the return air supply to the furnace the better the furnace will
function and give better heating circulation to the RV.
Re-set to desired position
Repair or replace *
Dead short. Repair short and then replace thermostat. *
Faulty relay drawing more than 1 amp. Replace relay and thermostat.
Replace thermostat.

Check and reestablish power to thermostat

Reset tripped circuit breaker

Correct poor ground

Correct any loose wires

Replace defective relay

Replace defective motor.
Move anticipator to a higher amp setting to lengthen cycle. NOT covered
under warranty
Thermostat located too close to a heat duct. Move thermostat or duct outlet. *
Move anticipator to a lower anticipator setting to shorten cycle. *
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1-866-869-3118
option 5 before
SOLUTION