How Does an RV Furnace Work?

One of many biggest perks to tenting in an RV as an alternative of a tent is dependable cooling and heating. It’s rather more snug to get up and prep your espresso in a heated leisure car than climbing out of a moist tent to gentle your camp range and attempt to get a hearth going. 

Identical to residential items, RV heating methods require common upkeep. However how will you service or restore an RV furnace for those who don’t know the way it works? To keep up an RV furnace, you’ll must know the way it works.

An RV furnace heats air after which circulates it by your RV utilizing a fan. Most RV furnaces function on DC energy even when your RV is plugged into shore energy, permitting them to work at a campground or when tenting off-grid.

However there’s rather more to it. So let’s dive into every little thing it’s good to learn about working, servicing, and troubleshooting RV furnaces.  

How Do RV Heating Techniques Work?

There are two principal varieties of RV heating methods: pressured air furnaces and hydronic heating methods. 

In pressured air furnaces, exterior air for combustion is force-fed by a sealed combustion chamber meeting and discharged to the outside, whereas inside air of the RV is moved throughout a warmth exchanger. This design ensures that no merchandise of combustion are combined with the inside air.

Hydronic heating methods use a heated floor to warmth water that’s distributed to radiators all through the RV. That floor will be heated by burning gasoline (i.e., propane or diesel), an electrical aspect, or utilizing main engine coolant to warmth that floor. Some hydronic heating methods warmth potable water and can be utilized for engine preheating. 

Technician Tip: All RV heating methods ought to have a knowledge plate containing the producer, make, mannequin, serial quantity, and enter and output (measured in BTUs/hour) of the equipment. This plate helps you determine your equipment for particular service and upkeep procedures. Your proprietor’s guide may also assist you perceive the kind of heating system you’re working with.

How Does an RV Furnace Work?

When you’re working with a pressured air RV furnace, warmth is distributed all through your RV utilizing a blower fan that’s powered by a small motor. Most pressured air furnaces burn propane to warmth air, however some make the most of diesel gasoline (extra frequent with hydronic heating methods). 

Earlier than we define the method, let’s outline just a few key phrases. 

A sail change is the primary security change in an RV furnace. It prevents your furnace from trying the ignition sequence if the blower motor isn’t operating at a minimal of 75% of its rated pace. 

A restrict change is the second security change. It opens at a preset temperature to stop overheating. The restrict change is mounted on the warmth exchanger or the burner meeting housing. It shuts off the burner however permits the combustion blower to proceed operating to decrease the tools temperature.

Security Tip: The restrict change does NOT act as a thermostat. In case your blower by no means shuts off, however your burner is biking on and off at common intervals, your RV must be inspected by a professional RV technician instantly. It is a symptom of an overheating restrict change, which may outcome from blockages, defective elements, or LP fuel adjustment points that create a really harmful state of affairs. 

Whenever you flip in your RV furnace, right here’s a normal overview of what occurs if it’s working correctly: 

1. The thermostat is turned on and indicators for warmth. 
2. {An electrical} present is shipped from the thermostat to the time delay relay constructed into the circuit board, which closes to energise the blower motor after a delay of 10-20 seconds. If the motor isn’t reaching 75% of its rated pace, potential points embrace low DC energy, a defective motor, a blocked return air inlet, or a blocked exhaust. 
3. When the motor comes in control, the sail change is moved by the airflow to shut a micro-switch and proceed the circuit. The micro-switch is about to require a minimal fan pace to shut. If the motor isn’t operating quick sufficient, you’ve got a sticky change, or there’s an airflow blockage that doesn’t permit the change to shut – the present will likely be interrupted. This circuit is impartial of the thermostat and motor circuit.
4. The sail change closes, sending energy to the restrict change, which then sends energy to the circuit board. Below regular operation, the restrict change is closed and opens at a preset temperature to stop overheating. 
5. The circuit board delays ignition for 10-20 seconds, permitting the blower motor to purge any fuel remaining within the combustion chamber.
6. The circuit board opens the fuel valve and sends a high-voltage present to the electrode.
7. If ignition happens, the electrode senses the flame and sends a present again to the management board, stopping the high-voltage spark and preserving the fuel valve open
8. If ignition doesn’t happen, the board will go into lockout mode and should be reset earlier than attempting once more. Most circuit boards will pause for 20 seconds, then strive for 7 seconds. They’ll repeat this 3 times earlier than going into lockout.

Technician Tip: A lockout may result from a defective circuit board, defective electrode, defective fuel valve, or any mixture of those points. If locked out, conduct a short inspection (LP fuel on, no airflow obstructions, correct voltage, and so on.) after which change the thermostat off and again on. The circuit board ought to present three extra tries. 

Obtain this RV furnace diagram for a visible instance of RV furnace design. The pictured furnace is the Dometic DFMD30 Mojave Propane Heater. Yours might differ relying on the make and mannequin. Seek the advice of your proprietor’s guide for the schematics of your RV’s furnace.

Methods to Reset an RV Furnace

To reset most RV furnaces, you’ll merely flip off the ability change, wait about 10 seconds, and switch it again on. In case your mannequin doesn’t have an influence change, flip off the principle breaker to the furnace, wait 10 seconds, and switch it again on. 

If no breaker exists, take away and reinstall the fuse comparable to your RV furnace. That’s why it’s necessary to have your RV’s circuit breaker panel correctly labeled. 

Study extra about troubleshooting RV circuit breakers.

The place is My RV Furnace Positioned?

Your furnace location is determined by the producer and the floorplan. For instance, the furnace in my Sundown Park Sunlite Traditional is positioned beneath the fridge and to the left of my circuit breaker panel. 

No matter your floorplan, perceive that the furnace itself received’t be seen. You will notice a return air vent (or vents) inside your RV and the air consumption/exhaust vent on the RV’s exterior. Right here’s an instance of what your return air and exhaust vents would possibly seem like: 

Technician Tip: It’s a good observe to find the exhaust vent on the RV’s exterior and confirm the exhaust is current and clear. We’ve seen too many campers lean a garden chair towards the vent, which may current a hearth hazard.

When you’re looking for an RV, it’s a good suggestion to search for a mannequin with an exterior entry panel to service the RV furnace. This panel isn’t included on all RVs, particularly entry-level journey trailers.

Methods to Activate an RV Furnace

Most RV furnaces are managed by a wall-mounted thermostat. Relying in your make and mannequin, you might have a digital management panel or an analog thermostat. 

Most analog thermostats have a small On/Off toggle change on prime, and RVs with a digital management panel may have a show for turning your furnace on and off. In both case, the next step is to show the thermostat as much as a setting above the present ambient temperature inside your RV. 

In case your furnace is functioning correctly, it’s best to hear the blower motor activate and really feel air blowing out of your inside vents. Inside 10-20 seconds, it’s best to hear the pilot gentle ignite and really feel sizzling air popping out of your vents shortly thereafter. 

When you go away your furnace on, it ought to proceed to cycle on and off to maintain the within of your RV on the desired temperature. 

How A lot Propane Does My RV Furnace Use?

To function your RV furnace, you’ll want an ample propane provide. When you’re not already acquainted, take the time to find out about connecting and turning on propane in your RV. 

The quantity of propane your furnace makes use of relies upon largely on its BTU ranking. BTU is brief for British Thermal Models, which is a unit of warmth measuring how a lot warmth it takes to lift the temperature of 1 pound of water by 1℉ at sea degree. 

A furnace with the next BTU ranking burns propane extra rapidly than one with a decrease ranking. So your first step will likely be figuring out your furnace’s BTU ranking, measured in BTUs per hour. 

Earlier than we get caught up within the numbers beneath, do not forget that your RV furnace received’t run constantly when you flip it on and regulate the thermostat. It would cycle on and off to manage the temperature inside your coach. That is vital to recollect when calculating how a lot propane your RV furnace makes use of. 

Let’s present an instance: 

RV and Furnace Specs (let’s use specs for the Keystone Cougar 30BHS)

• Propane Capability: 60 kilos
• Furnace BTU Ranking: 30,000 BTUs/hr
• Electrical Hearth BTU Ranking: 5,500 BTUs/hr

RV Furnace Propane Consumption Calculator

To begin, we should do not forget that propane containers can solely be crammed to 80% of their complete capability. So whereas the Cougar’s marketed propane capability is 60 kilos, its precise capability is 48 kilos (60 x 0.8 = 48). 

We will calculate the overall BTUs of 48 kilos of propane from there. 

1 pound of propane = 21,548 BTUs

48 kilos of propane = 1,034,304 BTUs

If our complete propane provide accounts for 1,034,304 BTUs, we are able to divide that by our furnace’s BTU ranking to estimate what number of hours our furnace would run earlier than that offer is exhausted. 

1,034,304 BTUs / 30,000 BTUs/hr = ~34.48 hours

If we run our furnace and electrical fire concurrently, you possibly can really scale back your fee of propane consumption since you’re additionally counting on electrical warmth: 

30,000 BTUs – 5,500 BTUs = 24,500 BTUs

1,034,304 BTUs / 24,500 BTUs/hr = ~42.22 hours

You’ll be able to insert the suitable figures out of your RV into the instance above to calculate how a lot propane your RV furnace makes use of. However do not forget that these calculations are based mostly on 100% run time operation. 

Different variables, equivalent to chilly climate and your required temperature setting, impression your furnace’s potential working hours on a full LP provide. As an example, you possibly can roughly double the variety of hours your furnace will function for those who estimate a 50% responsibility cycle (i.e., your furnace will run for half the time you’re tenting). 

Listed here are some tips about conserving propane in your RV.

Technician Tip: Keep in mind there are different propane home equipment in your RV. The calculations above characterize solely the obtainable working hours on your RV furnace, however they can be utilized if you realize the BTU rankings of your RV’s different home equipment, equivalent to your water heater, fridge, range, oven, and out of doors grill. 

Methods to Clear an RV Furnace

Pet hair could be a drawback for sure RV furnaces. For starters, cleansing and disinfecting your RV after each journey retains it in the very best form attainable, and it’ll assist your RV furnace run extra effectively. 

Inside your RV, use an RV vacuum to maintain mud and dander to a minimal. You’ll be able to take away the return air vent to hoover mud and pet hair round your furnace unit on some floorplans. Simply flip the furnace off earlier than doing so. 

Outdoors your RV, use a transportable air compressor to take away mud, particles, pet hair, and bug nests out of your furnace’s exhaust tube. It is a good factor so as to add to your seasonal upkeep checklist when winterizing your RV within the fall and dewinterizing it to prep for spring tenting.  

Technician Tip: Please observe that pressured air furnaces (not hydronic heating methods) are designed to function with out filters. When you had been to accumulate and discover a approach to set up a filter in your pressured air furnace, it might void any current warranties and create a probably harmful state of affairs.

Troubleshooting RV Furnaces

Troubleshooting your RV furnace will be advanced, however we now have just a few downloadable sources to assist. You too can schedule a service appointment at your native Tenting World Service Heart for knowledgeable furnace inspection. 

Right here’s a call tree for troubleshooting RV furnaces. 

And right here’s one other particularly for thermostat-related points. 

Past that, you are able to do some fundamental troubleshooting with the suitable instruments. 

Measuring Line Voltage Utilizing a Digital Multimeter

1. Measure incoming voltage on the wire connections on the facet of the furnace. The nominal voltage must be 10.5 to 13.5 volts DC beneath an unloaded situation. If lower than 10.5 VDC, the blower motor received’t spin quick sufficient to activate the sail change.
2. Flip the furnace on and confirm the ignition. 
3. Measure the voltage on the wire connections on the facet of the furnace. The nominal voltage must be 10.5 to 13.5 volts DC beneath a loaded situation. 

If measurements discovered are exterior the suitable vary, you might have a problem along with your RV’s DC energy provide (i.e., your battery). Seek the advice of your service guide for additional furnace diagnostic suggestions. 

Evaluating Correct Airflow

1. Open all discharge registers and any closeable registers inside your RV and confirm air discharge by really feel (or utilizing an airspeed indicator). 
2. Be certain that airflow isn’t hindered by throw rugs or different ground coverings. Hindering your furnace’s airflow could cause the restrict change to open. 
3. Confirm that the discharge is heat and test that no carbon monoxide is current utilizing a carbon monoxide check. 
4. Test the opening measurement for the furnace’s return airflow, guaranteeing it matches your unit’s working guide specs. 

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Different checks are required to confirm the right operation of your RV’s propane system – to not point out the added complexity of hydronic heating methods. If and once you’re feeling overwhelmed and caught, please don’t hesitate to contact your native Tenting World Service Heart. 

Do you’ve got every other questions on furnaces and RV heating methods? Ask away within the feedback beneath.

Tucker Ballister is our Technical Content material Author. He’s a lover of the open street and the proud proprietor of a 2021 Sunlite Traditional journey trailer (his third RV to this point). Take a look at extra of his RV adventures, gear opinions, and out of doors recommendation at thebackpackguide.com.