Mobile Home Heating Guide: Furnaces and Heat Pumps

In this exhaustive mobile home heating guide, we cover the basics of both electric and gas furnaces as well as mobile home heat pumps.

If you’re having an issue with your mobile home heating system this is a must-read.

It’s a good idea to read this guide if you’re having an issue with your cooling system too. That’s because the heating and cooling systems are considered to as a single system referred to as HVAC.

HVAC stand for Heating, Ventilation, and Air Conditioning.

Mobile Home Heating: 3 Main Parts of Every Heating and Cooling System

A mobile home HVAC system is composed of 3 major components:

• 1. The heating or cooling source (the furnace that heats and the AC that cools)
• 2. A single control system usually known as the thermostat
• 3. The distribution system or duct system that carries the modified air throughout the home

Mobile Home Heating and Cooling Control Systems

In most cases, your mobile home heating and cooling system will share a single control device most commonly known as a thermostat.

The thermostat is a small box that tells the rest of the system what to do. You can usually find it located on a wall in the middle of the your mobile home.

Control System

Simply put, a control system thermostat or control panel on your wall that tells the furnace, AC, or heat pump to kick on.

There are digital and mechanical thermostats.

What is a Mechanical Thermostat?

Mechanical mobile home thermostats are also called snap discs or snap action mechanical thermostats. They use a small bimetal strip that expands and contracts with temperature changes. When the metal strip expands it disconnects from the contact to switch the system off. If the metal strip constricts it makes contact with the wiring to kick the system on.

Mercury-bulb thermostats were also popular. Mercury, an element that conducts electricity but acts like water, is inside a small glass tube. Whenever it tilts, it will make or break contact with 2 wires on each side to tell the system to kick on or off.

Mechanical thermostats are very cheap ($10) but they are not very precise. That’s why digital thermostats are recommended by HVAC experts.

What is a Digital Thermostat?

Digital thermostats can be programmed to automatically cut mobile home heating systems on or off anytime you need them. If everyone works or goes to school from 8-5 you can keep the system from turning on and off as much. There are some thermostats with wifi capabilities that work with your smartphone.

Air Care Heating and Cooling states that digital thermostats should be used in all homes now. Installing a digital thermostat can save between 5-20% of your heating and cooling costs right off the top. You can get smart thermostats that can save even more based on your family’s schedule.

Mobile Home Heating (or Cooling) Source

The most popular mobile home heating sources are furnaces and heat pumps. Wood stoves, fireplaces, and space heaters are also popular.

There are different furnace designs such as up-flow and downflow or sealed combustion. And there are different fuels that power mobile home heating systems but electricity and gas are the most common. We’ll cover them below.

All heating and cooling sources must be designed and rated specifically for mobile homes.

Sometimes they are labeled ‘HUD-Approved’ or even ‘high static approved.’

Distribution System – Ductwork and Vents

Your mobile home heating system uses insulated duct work to move the warmed air throughout the home.

The ductwork is comprised of the main trunk ducts and crossover ducts, or flexible tubing, is used to connect the two main trunks of a double wide.

The main trunk duct carries the heated air to each register to warm a room. The plenum is usually the part of the ductwork that is directly around the heat exchanger or furnace.

The distribution system of a mobile home heating system is mostly made with sheet metal ductwork. These ducts run right down the middle of a mobile home. For double wides, the main truck ducts run down the middle of both sides. These ducts need to be maintained and updated whenever possible. Learn how one reader insulated under their mobile home with foam board and saved a ton on heating costs.

What is Improper Static Pressure?

Mobile home-approved heating and cooling systems are also called HUD-approved systems or high static approved. High static is an issue that occurs in heating systems when the ductwork is too small for the amount and force of the warm air traveling through them. These small ducts are an issue when trying to calculate the proper sizing for a furnace or air conditioning unit.

In mobile homes, the supply ductwork is considered to be too small for effective operation but so is the return supply. It’s recommended that you always upgrade your ductwork when you install a new heating or cooling unit.

If the resistance to the air circulating through the ducts of any heating and cooling system is too great the unit will have to work harder to push the air through the ductwork. This will compromise the efficiency of the unit and leave parts of the home too hot or too cold depending on the season. If the resistance gets too strong no air may flow through the system at all.
DSCR.com

What is a Forced-Air Heating System?

Most mobile homes use a forced-air heating system. This just means that the air is driven through the ducts with a motorized blower. The warm air is pushed out of the furnace and into the ductwork to escape through the registers, or vents, and into the rooms. 

The warmed air in the home is then sucked back into the furnace via a return duct and the cycle repeats. It’s a closed system and without the blower pushing the air through the ducts and acting as a suction for the return air the home wouldn’t get or stay heated. 

While the blowers are always powered by electricity, the heat itself can be produced by different methods. Natural gas and electric furnaces are the most common but oil-burning furnaces are still around.

What Is a Downflow Furnace? 

Furnaces are designed to blow the heated air it creates in one of 3 directions or orientations: up-flow, downflow, and horizontal flow. Up-flow means the blower pushes the heated air up because the furnace is lower than the ductwork. Horizontal flow is used for furnaces that are located on the same level as the ductwork.

Mobile homes will always use the downflow orientation because the furnace is sitting in a small closet in the middle of the home and the ductwork is below it. The blower needs to push the heated air down into those ducts.

Downflow furnaces are designed to pull the air in from the top of the furnace, heat the air, and then blow it down through the ducts under the furnace floor to heat the home. The blower pulls the warm return air back into the unit through vents via a suction created by the blower fans. Mobile homes may have a large vent in the floor or wall close to the furnace that will allow the return air to reach the furnace again.

How to Find the Right Size Electric Furnaces for your Mobile Home

AFUE stands for Annual Fuel Utilization Efficiency. It’s the grading scale of efficiency used by the Dept. of Energy and measures how well the furnace converts fuel to heat. For example, the minimum efficiency allowed is 80% now which means the furnace converts 80% of the fuel to heat and the other 20% is lost.

BTU stands for British Thermal Unit and is a measurement of the amount of heat that is required to raise the temperature of one pound of water by one degree. All HVAC systems use BTU as a standard measurement.

The Cool Calc has a free plan that can help you determine the right heating and cooling equipment for your home using the Manual J method. Trane shares the following list of variables that must be considered to calculate the right heating and cooling systems:

Factors in Mobile Home Furnace Sizing

• Square Footage
• Climate Zone (see image below)
• Ductwork Size
• Number and style of windows
• Natural shade or sunlight
• Quality and amount of insulation
• Number of people using the space
• Heat-generating appliances

Square Footage and BTUs

Trane also shares the following chart to find the right BTUs needed for the square footage of your home. The left column is the square footage of your home and on the right are the BTUs needed to heat it:

Rule of Thumb — The maximum size unit you should buy would be 15% over the BTUs you need for cooling and 40% of the BTUs for heating. The max for heat pumps is 25% since it handles both cooling and heating. (Source)

Trane

You can use HVACDirect’s Sizing Guide here to find the right-sized furnace and AC for your mobile home.

Furnace Stages, Motor Speeds, and Dual Fuel

Mobile home furnaces are available with many options. The most important is furnace stages, motor speeds, and fuel type.

A one-stage furnace is either on or off. It has a fixed gas valve that releases gas at one speed and a single-speed blower. On a two-stage mobile home furnace, both the gas valve and the blower motor have a fast and slow setting. This can save energy costs because milder days won’t require a wide-open running speed. On most furnaces, the slower setting is the one that is used most often.

The third option is the type of fuel the furnace uses. Electric furnaces will run only on electricity but gas-powered furnaces can be modified to accept oil or propane. This is called dual fuel.

How Does an Electric Furnace Work?

Electric or electric resistance furnaces are basically big toasters. The red coils that toast your bread are used on a much bigger scale to heat your home.

An electric furnace has a cluster of elements, or resistance coils, that get very hot one by one. This staggered heat keeps the system from overloading the mobile home’s electrical system. A fan, or blower, pushes the hot air through the ductwork to heat the home. In a site-built home, the furnace would use supply ducts to send the heated air back into the unit to get heated again but mobile homes don’t have these supply ducts.

Electric furnaces use multiple safety features to keep the unit from getting too hot. Since there isn’t a lot to electric furnaces, and there’s no combustion gas to vent, they usually last longer than their gas or oil counterparts.

Natural Gas and Propane Furnaces for Mobile Homes

What are Sealed-Combustion Furnaces?

Gas furnaces create heat using combustion. A sealed-combustion furnace uses combustion air or fresh air that comes down through the roof jack. Once the combustion has occurred the spent air goes out the bottom. The firebox and flue are closed off to the inside of the home.

New manufactured home gas furnaces must be approved for manufactured homes by HUD and they must be sealed combustion.

Sealed combustion furnaces bring outside air directly into the burner and exhaust flue gases (combustion products) directly to the outside, without the need for a draft hood or damper. Furnaces that are not sealed-combustion units draw heated air into the unit for combustion and then send that air up the chimney, wasting the energy that was used to heat the air. Sealed-combustion units avoid that problem and also pose no risk of introducing dangerous combustion gases into your house.Energy.gov

Natural gas furnaces are more efficient than electric furnaces and are rated by the AFUE or Annual Fuel Utilization Efficiency.

In older gas furnaces with less than an 80% efficiency rating, combustion is created by constant pilot light. When the gas valve is opened, the gas flows over the pilot light to ignite it and create heat in a combustion chamber. Then the heat moves into a container called a heat exchanger where a blower blows it through the ductwork under the mobile home.

The older gas-powered furnaces need a special venting system to pull in the combustion air or air used to create the combustion and to release the spent gases that were created by the combustion. To do this with just one hole in the roof a special chimney or pipe called a roof jack is used.

Related Reading: Consumer Reports Gas Furniture Buying Guide here.

What is a Roof Jack?

A roof jack is simply a metal pipe inside another metal pipe. The outer pipe pulls in the fresh air and the inner pipe releases the spent air/gas.

Newer gas furnaces with an 80% or higher efficiency rating will not have a constant pilot light. Instead, an electrical control board or ignitor creates a spark on demand. The gas then flows through the burner to create combustion in the heat exchanger. The blower still pushes the heated air through the home.

Gas furnaces still need electricity to power control boards, valves, thermocouples, and blower that forces the warm air through the ductwork and into each room in the home.

Gas furnaces still need electricity to power control boards, valves, thermocouples, and blower that forces the warm air through the ductwork and into each room in the home.

Order this roof jack here.

Atmospheric Sealed-Combustion Downflow Gas Furnace

Atmospheric gas furnaces use the weight difference between hot and cold air to create a warm home. It’s a cyclical system where the combustion air enters and exits in the same double-pipe flue. Cold combustion air goes down the outer ring of the flue and into the furnace to the heat exchanger. That air is mixed with the gas at the flame, the warmed air is forced through the ducts and the flue gases go out the roof. The cycle produces a vacuum that pulls more fresh air from the flue into the firebox. 

Natural gas, or atmospheric sealed-combustion downflow gas furnace, has a specially designed flue that pulls fresh air into the furnace from the crawl space of a mobile home and into a heat exchanger to get warmed, and then the blower pushes that warm air through the ducts to heat the home.

Forced Draft Gas Furnaces

Forced draft gas furnaces have a small fan called a draft booster that pulls combustion air from the outside via a chimney or pipe. It pulls the air into the firebox and pushes the exhaust gases out.

Related Reading: Heat Pump vs Furnace – The Pros and Cons of Each Heating Type

How to Size a Mobile Home Heat Pump

HSPF is the Heating Seasonal Performance Factor. It’s the most used measure of a heat pump’s heating efficiency.  SEER is the cooling efficiency of a heat pump.

SEER stands for Seasonal Energy Efficiency Ratio and it measures the cooling efficiency of an air conditioner or heat pump. Trane states the formula to calculate the SEER taking “the cooling output for a typical cooling season divided by the total electric energy input during the same time frame.” Think of SEER like gas mileage – the higher the number the better. An air conditioner rated at 13 SEER uses 30% less electricity than a unit that has a 10 SEER.

Ton or Tonnage describes the cooling capacity of an air conditioning system in relation to melting one ton of ice in a 24-hour time frame. One ton of air conditioning cooling is equal to 12,000 Btu per hour. For example, it takes 288,000 Btu to melt one ton of ice in 24 hours.

Choosing the right size of heating system is tricky with mobile homes that have the original ductwork. As mentioned above, mobile home ductwork is thin and small compared to site-built home ducts. Many ducts in mobile homes are only 4″x 10″ and when they are that small they will interfere with the heat pump’s efficiency and SEER ratio. See above for the mobile home furnace sizing guide.

Related Reading: The EnergyStar Guide Sizing Guide

How Does a Heat Pump Work?

Heat pump seems to be a terrible name for a unit that cools but once you understand how a heat pump works you’ll see how it got its name. Refrigerators and air conditioners work by removing hot air, or extracting it, and putting it somewhere else, usually coils. So, it pumps heat away. Get it?

A heat pump has a refrigeration system with two two copper coils, one inside and one outside, and a compressor. When heating, the liquid refrigerant pulls the heat from the air. Energy.gov explains the process well:

A heat pump’s refrigeration system consists of a compressor and two coils made of copper tubing (one indoors and one outside), which are surrounded by aluminum fins to aid heat transfer. In heating mode, liquid refrigerant in the outside coils extracts heat from the air and evaporates into a gas. The indoor coils release heat from the refrigerant as it condenses back into a liquid. A reversing valve, near the compressor, can change the direction of the refrigerant flow for cooling as well as for defrosting the outdoor coils in winter.

Energy.gov

A heat pump can heat a home but they aren’t so efficient when the temperatures get below freezing. A common complaint is that the air is warm but it isn’t warm enough. They are better paired with a furnace that has a 4-speed blower. They do fine cooling homes in the summer, especially in mild climates.

The air handler in the existing furnace would be used by the new heat pump and the furnace’s coils can be used as a backup heating source. Supply ducts on heat pumps should be insulated to prevent sweating and critter damage. 

Heat pumps can be added to an existing mobile home furnace. However, the components must be properly sized for efficiency. It’s always better to buy and install everything for your mobile home heating and cooling system at one time. That includes ductwork.

How Much are Mobile Home Heat Pumps?

Mobile home heat pumps are more expensive because they produce both cool and warm air. A popular brand of mobile home heat pumps is StyleCrest’s ReVolve. They come in several different sizes, from 2 tons to 4.

The 2 Ton 14 SEER Revolv AccuCharge Mobile Home Heat Pump with 24,000 Btu is $1,545.95 at HVACDirect.

Packaged Heat Pump Units

A packaged unit contains all the heating and cooling elements in one large outside unit. Packaged units are easier to install than split systems, but if you have the room, we recommend a split system since it is more energy-efficient. Heat pumps aren’t the greatest at heating homes below 35-40 degrees.

When choosing a new unit be considerate of the company you buy from. Make sure there is a sound warranty and 24 hour furnace repair.

Split Unit Heat Pump Systems

A split system has the heat pump or AC condenser sitting outside of the home while the furnace, evaporator coils, and air handler are inside. Split systems are great if your home’s furnace is working fine and you just want to add air conditioning to your home. However, many homeowners tend to overestimate how big of a system they need and buy a unit that’s too big. This causes dehumidification within the system and higher energy costs. 

Matching Your Split Unit Components

You will need to make sure your new mobile home system is compatible with your old one. StyleCrest, the nation’s biggest supplier to manufactured housing builders has a properly cross-reference matching guide that will help you choose the right parts. Technically, this is for their distributors but it’s not difficult to use. You can find the mobile home heat pump matching chart here.

Coleman is another top furnace company and apparently, they have a confusing serial number system. I found the following images online:

How Much are Split Systems?

Currently, at HVAC the 2.5 ton 14 SEER 20KW Revolve Accucharge mobile home heat pump and electric furnace system run $2,838.85.

The conclusion to Mobile Home Heating Guide

Hopefully, you understand a bit more about mobile home furnaces, heat pumps, and heating systems in general.

Any new mobile home heating system must be approved for your manufactured home. You cannot use a unit designed for a site-built home. With the new technologies and EnergyStar guidelines, we have some really amazing mobile home heating systems on the market. Unfortunately, they aren’t cheap but with the high-efficiency rating, you can recoup your investment in a few short years.

Thank you for reading Mobile Home Living®

Please note, that if I don’t fully understand a subject I will reach out to experts to make sure I’m sharing accurate information (I’m just a plumber’s helper so HVAC is a bit out of my league). In this case, the experts at HVAC Direct helped me with this article and also allowed me to become an affiliate. That means I will get a small percentage of the sale at no cost to you if you buy anything using the affiliate links in the article. It was a win-win for me and I appreciate their kindness very much.