In this second segment of a multi-part series on RV inspection and maintenance, we will discuss the RV furnace. These articles provide tips on performing annual inspection and simple maintenance only. These pro-active steps should help mitigate unexpected component failures.
RV forced-air furnaces are available in a range of BTU values and consist primarily of a blower, combustion chamber, control board, and wall thermostat. However, another key component is the time delay relay (TDR). This device delays the furnace flame ignition to allow the blower to purge the combustion chamber of residual gas. Similarly, it forces the blower to continue operating after the flame is extinguished. It is important to remember this when using the furnace. When you turn up your thermostat to demand heat, the blower should come on immediately, while it may take up to two minutes for the burner to ignite. Similarly, when the set temperature is reached or the furnace is turned off, the blower will continue to run for a while even though the burner should turn off immediately.
Make yourself aware of where the furnace fuse is located. In most cases, it is in the 12V fuse block with the other fuses.
RV furnaces are usually located behind a cabinet or under the fridge. They are generally accessible via a removable panel, so it is a good idea to remove this panel and inspect the furnace and surrounding area. Clean any dust and debris from around the furnace housing. Since the furnace gets very hot during operation, it is very important to make sure there are no combustible materials or items located in the furnace area. It is recommended to not store anything around the furnace.
While you are inspecting the furnace, check the ducting for damage, cuts, or tears. If any of the ductwork has collapsed or become kinked, straighten it out. If there are any rips or tears, repair them using duct tape. Any flow restrictions in the ducts will not only limit the heating capacity in your RV but could also cause the furnace to overheat and short-cycle. Similarly, damage to the ducts can cause ancillary areas of the coach to overheat, possibly resulting in a fire hazard.
Locate the combustion chamber exhaust and intake tubes on the outside of the RV as shown in the photo. These can be identified as the familiar chrome double-tube fixture. On some furnaces, the tubes are integrated into an external furnace access panel and on others, the tube assembly is directly mounted to the RV sidewall. For the former configuration, the furnace components can be easily accessed by removing this exterior panel. For the latter, the components must be accessed from inside the RV by removing a panel from the furnace itself. Fortunately, there is no reason to access the furnace internals unless there is a component failure. If the combustion chamber develops a crack or hole, Carbon Monoxide (CO) can escape into the living areas of the coach instead of being vented to the outside through the exhaust port, which is an extremely dangerous situation. This is why it’s important to have a working CO detector in the coach.
Inspect the intake and exhaust tubes and remove debris, insects, webs, or nests. Insects like to hang out or nest in these tubes. If this is a chronic problem on your coach, you may choose to purchase vent screens, which are available online or at RV supply stores.
About the Author:
Steve Froese, an avid RV owner, traveler, and Coach-Net member since 2013, is the principal of “A Word to the Wise Technical Communications”, a published RV author, certified RV technician, and licensed Professional Engineer. He frequently collaborates with the “RV Doctor”, Gary Bunzer, and has worked with the RVIA/RVDA as a technical and training writer and consultant. Professionally, he works as a quality engineer and musician. Watch for more of Steve’s work in upcoming Coach-Net publications.
Ray M. ~ “We’ve had a service plan with Coach-Net with 2 different RVs and we’re so glad we do. Twice in less than a month we’ve called with tire issues. Both times your representative helped us to get back on the road in a short amount of time. Thank you from two happy campers.”