Furnace

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Furnace:

The Rialta furnace is supplied by Suburban Manufacturing Company of Dayton, Tennessee.

The standard Rialta furnace model is the Suburban NT-20SE which interestingly enough is only rated at 18,000 BTUH. All other models within the product line have the two digits to indicate the actual BTUH so the model number on the Rialta incorrectly suggests that the NT-20SE would be rated at 20,000 BTUH. It requires 12V DC power to operate the controls and only burns Propane. There are no 110V AC power requirements for either the furnace, fan, or thermostat controls.

Model Number BTUH Input Height Width Depth Voltage Amp. Draw Ship Wt. Unit Wt. Min. Depth Max. Depth
NT-20SE 18,000 9 1/2" 9 3/8" 21 1/8" 12V DC 2.8 27 lbs. 22 lbs. 21" 27 3/4

Problem Areas:

Please note that the controls and fan on the furnace only run on 12V DC. If you are "dry camped" and allow the furnace to run frequently all night long, in very cold areas you will likely find your coach auxiliary batteries almost dead by the morning. You'll notice the furnace fan slowing down and starting to make unusual noises. Running the engine or generator will quickly recharge them and no harm is done.

The furnace uses an electric igniter to start the combustion process and no "pilot light" is used. It also incorporates a "sail switch" which means the gas is not turned on until the fans blow air into the combustion box and exhausts any possibility of a previous gas build-up. If you listen closely when you turn on the furnace you'll first hear the fan operate for a few seconds and then the ignition of the gas begins. If the fan does not come on to expel any accumulated gases in the combustion area, then the electric ignition is prevented from occurring.

Also note the two furnace vents that are required to be in the exterior skin of the Rialta. One is a "fresh air intake" and the other is the "exhaust vent". If you live in an area that frequently has "mud wasps" or other such insects that have a habit of building a nest in little confined areas such as in these tubes, then you should consider covering these vents with a suitable metal screen material. Suburban does not recommend covering these vents but you have to be the judge if the problem warrants such coverings.

If your furnace is blowing nothing but cold air, then it probably is in lock-out mode or the limit switch has opened and not reset, or the sail-switch has detected that the fan failed to come on first. Lock-out occurs when a problem exists during the trial for ignition. Your dealer or a Suburban service center should be consulted to diagnose this condition.

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Furnace FAQs

Questions & Answers

If you've got questions about your Suburban RV furnace, check out this list of questions frequently asked by customers.

Question 1

 

Can I repair my furnace myself?

 

Question 2

 

If I have a product problem, how do I get service?
Question 3

 

Where can I get parts for my furnace?
Question 4

 

My service company/dealer has generic parts for my furnace that cost less. Are these parts OK?
Question 5

 

Can I use my furnace while driving?
Question 6

 

Is it safe to install a bug screen over my furnace vent?
Question 7

 

My current furnace needs to be replaced. What BTUH size should I buy to replace it?
Question 8

 

Is there any preventative maintenance required on furnaces?
Question 9

 

Can I close off a register so more heat goes to another part of the vehicle?
Question 10

 

What causes the majority of furnace problems?
Question 11

 

My furnace runs, but it's just blowing cold air. What's wrong?

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Question 1
Can I repair my furnace myself?
 

Answer:
No. Never attempt repairs yourself. The unit must be serviced by a qualified installer, service agency or gas supplier. Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life.

Question 2
If I have a product problem, how do I get service?
 

Answer:
First, if your RV has its original furnace and is still under the RV manufacturer's warranty, follow the steps described in your RV owners manual. Second, contact a conveniently located Suburban Recommended Service Center. A list of such service centers is located in this section of the web site. Describe to them the nature of your problem and make an appointment to have the problem corrected. Third, you and the service center can contact Suburban's Customer Service Department at P.O. Box 399, Dayton, Tenn., 37321, or call us at 423-775-2131 if more assistance is needed.
 

Question 3
Where can I get parts for my furnace?
 

Answer:
Genuine Suburban replacement parts are available from Suburban service centers. If the service agency does not have the merchandise you need in stock, they can order for you. If there is no Recommended Service Center in your area, you may contact any local RV dealer or service agency for assistance. Suburban sells through most RV wholesalers, so the local agency should be able to order parts for you through their normal source.

Question 4
My service company/dealer has generic parts for my furnace that cost less. Are these parts OK?
 

Answer:
Use of generic replacement parts is not recommended or approved by Suburban. Our first concern is your safety. Second is our concern over product performance and customer satisfaction. When you install a non-Suburban part, we can guarantee neither. Be aware that use of non-Suburban parts will void the warranty and you will assume liability consequences. It also violates the intent of the UL, CUL, AGA or CGA certifications.

Question 5
Can I use my furnace while driving?
 

Answer:
No. Suburban does not feel this is a safe practice. Some states have laws forbidding the use of propane while driving. You should be sure all gas appliances are off and their ignition systems are off while the vehicle is in motion or being towed.

Question 6
Is it safe to install a bug screen over my furnace vent?
 

Answer:
No. Suburban does not approve - nor do we recommend - using the aftermarket screens being sold to cover the outside vent cap. This restricts the exhaust and intake air, resulting in improper burner operation and a potentially unsafe condition.

Question 7
My current furnace needs to be replaced. What BTUH size should I buy to replace it?
 

Answer:
Check your furnace data plate for BTUH input. The replacement should be the same BTUH size or a close equivalent. Do not oversize your furnace. Too much heating capacity leads to rapid cycling and reduced comfort levels. If you do choose a larger BTUH furnace, your installer must make sure the installation requirements meet or exceed Suburban's installation requirements for ducting, return air, clearances and gas pipe size.

Question 8
Is there any preventative maintenance required on furnaces?
 

Answer:
Yes. We recommend an annual inspection by a qualified service technician. Also, you as the owner/user should inspect the furnace monthly during the heating season for the presence of soot on the vent. Operating the furnace in this condition could lead to serious property damage, personal injury or loss of life. If soot is observed on the vent, immediately shut down the furnace and contact a qualified service agency.

Question 9
Can I close off a register so more heat goes to another part of the vehicle?
 

Answer:
No, this is not recommended. Doing so will cause improper furnace operation and possible overheating of the furnace.

Question 10
What causes the majority of furnace problems?
 

Answer:
Conditions that can affect the performance of your furnace can include:

  • Low gas pressure caused by a number of factors, including a malfunctioning regulator or low gas levels in the tank. This can only be tested by a qualified service technician.

  • Low voltage, which again can only be checked by a certified service technician.

  • Inadequate ducting. Have your dealer make sure the furnace has at least the minimum number of ducts and required duct area (min. sq. inches), excluding closeable outlets. Check for proper duct connections at the furnace or collapsed ducts. Make sure ducts are clean and clear of obstructions, and are as straight and tight as possible.

  • Restricted or insufficient air return: the return air passage should meet the minimum open square inches as specified for the particular model of furnace installed. It must not be blocked or restricted. Keep the furnace compartment clean of any materials that can block the air flow around the furnace.

  • Unauthorized alterations and improper reinstallations.

  • Failure to adhere to the preventative maintenance measures outlined in the users manual.

  • Question 11
    My furnace runs, but it's just blowing cold air. What's wrong?
     

    Answer:
    Your furnace is in lock-out or the limit switch has opened and not reset. Lock-out occurs when a problem exists during the trial for ignition. Your dealer or a Suburban service center should be consulted to diagnose this condition.

     

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    Thermostat:

    The wall mounted thermostat is made either by Robertshaw Controls Company or beginning in the 2003 model year also by Suburban Manufacturing. Both types are typical of most inexpensive thermostats used in RVs. Its only function is to determine the surrounding air temperature and signal the furnace to turn on or off depending upon your desired temperature selection. In the Rialta, it operates only on 12V DC and there are no 120V AC wires involved in its operation.

    There are two minor  problems with the Robertshaw thermostat. First, the thermometer is not only very difficult to read but is known to be somewhat inaccurate. There is a thermometer calibration procedure outlined in the "Installation Instructions" sheet included with the new Rialta papers, but most people end up moving the selector lever to wherever they "feel" is the most comfortable without actually looking at the temperature read-out.

    The second problem is that the on-off lever located on the bottom moves very stiffly over its limited total travel of approximately 1/4". You may think that the furnace is off when it really is not, or vice-versa. The letters indicating on-off are very hard to read so sometimes you must physically move the lever to make sure it is in the desired position.

    The thermostat does NOT have to be installed perfectly level and will operate in all positions when wired correctly. The only user service possible concerns the contacts where the temperature control makes or breaks the circuit. Robertshaw recommends the use of any unglazed paper sandwiched between the contacts and moved back and forth to polish the contacts and remove any tarnish buildup. Most "back-yard" mechanics will use a small piece of fine emery cloth or even extra-fine sandpaper to clean the contacts.

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    Page Updated: 30 March 2013