Dometic DF Series Service Manual

26
EN
Furnaces
6 HEATING ISSUES
A furnace is a vital part of any heating system, but it is only one part. A majority of furnace problems are caused
by issues outside the product itself. When diagnosing/troubleshooting a furnace problem, always check the
following items before replacing components, as the problem may stem from one of these heating issues and not
the furnace:
6.1 Identifying Heating Issues
Operational Issue Potential System Issue Page
• Visible buildup of soot
• Burner ignites, then locks out
• Furnace over-fires or under-fires
Gas Pressure 26
• Motor vibrates or is noisy
• Furnace is limiting
Ducting 27
• Motor runs, but no spark
• Furnace is limiting
Return Air 28
• Motor runs, but no spark
• Fan runs too fast
Voltage 29
Check the Gas Pressure
➤ Check that the gas pressure is set at a minimum of 11" W.C.(at the furnace), with a minimum of 50% (ideally
100%) of other gas-fired appliances operating while the furnace is in operation. The pressure should be tested
using a U-tube manometer. If using a digital-type manometer, calibrate it oen with a U-tube manometer.
➤ Check the outside air temperature. As the air gets colder, it reduces the BTU capacity of liquid propane (LP).
The gas pressure is affected by a combination of the fill level of the LP tanks, the ambient temperature outside,
and the number of BTUs the furnace requires. Use the following example chart to understand the impact of
these three factors on whether there is enough gas pressure to sustain ignition in the furnace:
20 lb. Bottle (*30 lb. bottle: multiply x 1.40) for 40,000 BTU Furnace
Tank fill-level 20 °F 0 °F -5 °F -10 °F -15 °F
60%
Tank Capacity
36,000 18,000 12,750 8,500 4,250
50% 32,400 16,200 12,150 8,100 4,050
40% 28,800 14,400 11,400 7,600 3,800
30% 25,200 12,600 10,450 7,300 3,150
20% 21,600 10,800 8,100 5,400 2,700
10% 16,200 8,100 6,075 4,050 2,025
65 lb. Bottle under Mtd. for 40,000 BTU Furnace
Tank fill-level 20 °F 0 °F -5 °F -10 °F -15 °F
60%
Tank Capacity
95,600 47,800 36,000 23,900 12,100
50% 86,000 43,000 32,250 21,500 11,750
40% 77,000 38,500 29,250 19,250 9,625
30% 68,000 34,000 25,500 17,000 8,500
20% 58,000 29,000 21,750 14,500 7,250
10% 43,200 21,600 16,200 10,800 5,400
Example: 40,000 BTU furnace, 65 lb. LP bottle, 40% full, 0 °F outside: tank capacity is 38,500 BTUs.

Dometic DF Series Specifications

General

Brand	Dometic
Model	DF Series
Category	Furnace
Language	English