Choosing the Perfect Natural Gas Or Propane Unit Heater For Your Garage Or Workshop

Fan forced natural gas and propane garage heaters burn fuel in a heat exchanger to produce heat. Natural gas unit heaters are very common in populated areas that have natural gas piped throughout neighborhoods. Propane unit heaters are typically used in rural areas where natural gas is not available.

Operating Principle

When there is a need for heating, the fuel from your natural gas line or propane tank flows through a gas valve inside the unit heater. A spark or pilot flame ignites the fuel and a flame is produced inside a heat exchanger. When the heat exchanger reaches a pre-set temperature, a fan turns on which blows space air through the warm heat exchanger. The air entering the heat exchanger absorbs the heat from the heat exchanger, resulting in a warmer discharge air temperature. As the fuel is burned, by-products of combustion leave the unit heater through a vent pipe also called a chimney.

Benefits of fan forced gas or propane unit heaters in garages or workshops:


oPowerful, fast self contained heat producers. They don’t rely on a centralized boiler to supply heat.

oLow clearance requirements on low profile units.

oMost units have adjustable louvers to help direct warm air where you need it most.

oDurable. All unit casings are treated for corrosion resistance and finished with a baked-on, high solids paint.

oHuge range of sizes and styles to match the heater to your heating load. If selected properly, you don’t have to worry about under or over sizing.

oThe fan can run in the summer without heat to help circulate air.

oNatural gas units are always ready to run. You don’t need to worry about replenishing your fuel supply.

Drawbacks of fan forced gas or propane unit heaters in garages or workshops:

oGas fired units require more maintenance and service then other types of heaters.

oBy-products of combustion require special attention. If the heater is not vented properly, dangerous fumes can enter your garage or workshop.

oClearance requirements must be met. A flame is present. You must be sure combustible materials (fixed or airborne) stay away from the unit heater.

oDirty, dusty or corrosive atmospheres require special attention.

oFan forced units move large volumes of air which can kick up dust in your garage or workshop.

Unit Configurations:

Gas and propane unit heaters for garages and workshops blow air horizontally into the space. Adjustable louvers allow for vertical adjustment of airflow. Most major manufacturers also offer horizontal louvers that allow for side-to-side adjustment of airflow. Gas and propane unit heaters for garages and workshops can be broken down into several categories based on the venting type and heat exchanger design:

Venting Types:

Good: Gravity Vented

Due to its low cost and compact design, gravity vented propeller unit heaters are a good choice for some garages and workshops. The term gravity vented refers to a unit heater that vents naturally, without the assistance of a fan. A gravity vented unit uses the air in the garage or workshop for combustion. The warm by-products of combustion rise out of the unit heater through a flue pipe to the outdoors. A gravity vented unit is the least expensive style; however, you must be sure the following conditions exist:

1) Your garage or workshop can not be under a negative pressure. If your space is negative, the by-products of combustion will not vent properly and you will experience nuisance tripping from a safety switch that senses a blocked flue vent. Negative pressures occur when air is being exhausted from a space without any source of make-up air. Gravity vented units can be very sensitive to pressure changes. Sometimes a bathroom exhaust fan turning on can be enough to trip off a unit. If you have a gravity vented unit that is experiencing nuisance trip outs, you may want to install an aftermarket power venter that gets installed in the flue vent pipe to help push the by-products of combustion in the right direction.

2) Specific vent pipe routing is required. Gravity vented units operate on the principle that hot air rises. Vertical venting through the roof of your garage or workshop is preferred. Sidewall venting is more difficult. Venting through a roof can become more expensive since you need to completely weatherproof the hole in the roof. The manufacturer’s detailed installation instructions must be followed closely.

3) Since the air inside the heated space is being used for combustion, it is important that the atmosphere is clean. If you are comfortable lighting a match in your garage or workshop, then you should feel comfortable about running a gravity vented unit in your space. If there are any combustible dusts (woodworking shops) or fumes in your garage or workshop, choose a separated combustion design which is explained below.

Better: Power VentedA power vented unit is very similar to a gravity vented unit with the addition of an integral flue vent booster fan. On a call for heat, the booster fan turns on to ensure the by-products of combustion will be vented properly. Power vented units are the most popular type of gas and propane unit heater for garages and workshops. The booster fan allows for greater flexibility with flue pipe routing. Horizontal venting is very easy. In a garage or workshop, most venting is done through a sidewall to avoid costly roof modifications. Many of the major manufacturers are phasing out gravity vented units and are replacing them with power vented units as their entry level product.

Best: Separated CombustionSeparated combustion units are rapidly gaining in popularity. While traditional gravity and power vented units utilize space air for combustion, separated combustion units are sealed from the space. Separated combustion units for garages and workshops have 2 flue vent pipes. 1 flue vent pipe draws in air from the outdoors and 1 flue vent pipe exhausts the by-products of combustion back outside. This sealed combustion design eliminates you concerns about burning the air in your space. Separated combustion units are a must in your woodworking shop where fine dusts can ignite with an open flame. Separated combustion units are usually slightly more efficient since they do not use the heated air in your space for combustion.

The only drawback to a separated combustion unit in your garage or workshop is the 2nd vent pipe. A 2nd vent pipe requires a 2nd hole in your wall or roof. Most manufacturers offer concentric vent kits that allow the 2 vent pipes to join at a galvanized metal box on the interior of your garage or workshop. The box combines the 2 vent pipes on 1 end and diverts them into a pipe within a pipe on the discharge end. This allows you to only penetrate your wall or roof once. This also can make your unit more efficient as the warm flue exhaust warms the cold outside intake air.

Heat Exchanger Designs:

Traditional natural gas and propane garage and workshop heaters are tall and narrow. Most manufacturers are transitioning towards the newer tubular heat exchanger design. Tubular heat exchanges are more flexible and resist cracking over time. This design also allows the unit to be wider and shorter which is necessary for most garages and workshops that do not have ample overhead clearance.

Standard natural gas and propane garage and workshop heaters come with aluminized steel heat exchangers. Aluminized steel is more then adequate for typical garage and workshop installations. The life expectancy for a natural gas or propane unit heater in a clean environment is 20+ years. If your application involves high humidity levels or mildly corrosive atmospheres, your natural gas or propane garage heater will last a lot longer if you upgrade to a stainless steel heat exchanger.

Options and Accessories:

Natural gas and propane garage and workshop heaters have several options and accessories to help meet your specific requirements. High CFM blowers, 2 stage units, wall mounted thermostats, air deflectors and vent caps are very common accessories used in garages and workshops. If you’re not sure what to order, call us and we will recommend a unit to meet your specific needs.

Installation Overview:

1) Suspend the unit heater using threaded rods or angle iron. Some of the low profile units include angle iron for mounting your unit directly to the ceiling.

2) Install natural gas or propane piping.

3) Install vent pipe.

4) Wire a low voltage wall thermostat to the heaters terminal strip.

5) Wire the high voltage power required to operate the heater. This is usually 120 volt power in garages and workshops.

Commonly Asked Questions:

1) How do I calculate the heating load for my garage or workshop?

ANSWER: There are many free heat load calculator tools available on the internet. Do NOT fall for equipment that is advertised as “will heat up to 400 square feet”. Heating a 400 square foot insulated garage in Florida is a lot different then heating a 400 square foot un-insulated metal garage in Maine. 1 heater can not magically service both 400 square foot spaces. You do not want to undersize, and you do not want to oversize.

2) How do I control my natural gas or propane unit heater in my garage or workshop?

ANSWER: A wall mounted 24 volt thermostat is required. When there is a call for heat, the thermostat sends a signal to the natural gas or propane heater to turn on. Upgraded thermostats include a “fan” switch which allows you to operate the fan with no heat in the summer.

3) How do I determine how much heat a natural gas or propane unit heater will generate?

ANSWER: Natural gas and propane unit heaters for garages and workshops are listed by their fuel inputs. For example, a 100,000 BTUH unit will consume 100,000 BTU’s of fuel per hour. The actual heating output depends on the unit’s efficiency rating. If the unit is 80% efficient, the actual heat output will be 80,000 BTU’s per hour. Do not pick a heater based on the nominal size. Many people think this is the actual heat generated by the unit. They end up with a unit that is undersized.

4) What is the best location in my garage or workshop to install my natural gas or propane unit heater?

ANSWER: The natural gas or propane unit heater in your garage or workshop should be located in the coldest area, and it should be angled slightly so it blankets warm air across the coldest wall.

5) What is the best location to install a wall mounted thermostat in my garage or workshop?

ANSWER: The thermostat should be mounted in a location that represents a good average temperature in your garage or workshop. If it is located in a cold spot, it will falsely run the unit heater more then it should. If it is located in an area that receives direct sunlight, it will falsely run the unit heater less then it should. A well insulated interior wall is the best spot for the thermostat.

6) I have a natural gas unit heater that is 30 years old and in perfect condition. How do I convert this to propane?

ANSWER: Most manufacturers will only produce parts for equipment that is 20 years old. After 20 years, it is assumed the unit will be replaced with newer, more efficient technology. In some situations, you may be able to contact the manufacturer of the gas valve directly for an aftermarket conversion kit.

7) How can I compare the cost to operate natural gas, propane, oil and electric unit heaters?

ANSWER: There are manyh energy cost calculators available on the web. Pull out your latest utility bill and use this information to run an analysis.

8) What is included in a natural gas to propane conversion kit?

ANSWER: Different fuel types operate at different flow rates and pressures. The springs and orifices inside the gas valve needs to modified to match the fuel type. On some equipment, the igniter also requires an upgrade.

9) How do I decide if a separated combustion natural gas or propane garage or workshop heater is required?

ANSWER: If you’re not comfortable lighting a match in your space, then you need a separated combustion unit so that there is no open flame being exposed to the heated space.

10) How do I vent my natural gas or propane garage or workshop heater?

ANSWER: You must carefully read the installation instructions for your specific heater. Manufacturers do a good job outlining common practices. Local codes may dictate venting requirements and override the manufacturer’s recommendations. It is not a good idea to buy your vent pipe in a “kit”. There are several types of vent pipe, and the inexpensive kits that are designed to fit all installations don’t always form a perfect seal. A kit that offers “flexibility” means there are a lot of expandable pieces and joints that need sealing. The fewer joints you have, the safer your system will be. Hang your heater in the best possible spot for comfortable heating. Draw a sketch of the venting required and bring it to you local plumbing or home goods store. They will know your local codes, and they will select the pieces in the longest lengths available. This saves a lot of extra joints that can be very dangerous if they are not sealed properly.

Best Whole Room Space Heaters

Many space heaters are advertised as “whole room heaters” – but exactly how big is a whole room? One possible answer can be found in the Vornado heater manual which describes a whole room, relative to the heater’s capacity, as 16′ x 16′ with an 8′ ceiling. These dimensions work out to 256 sq. ft. and 2048 cu. ft. respectively – easily the size of most family rooms, kitchens, or living/dining spaces.

Over the last year a major shift in space heater technology has re-shaped consumers’ taste in whole room space heaters. Among the winners are those that employ ceramic or quartz infrared heating elements.

Among whole room heater manufacturers, Lasko holds the number two spot for bestselling heaters with its model 755320 tower heater with digital display ($45). (Number one is Lasko’s 754200 compact heater $20).

Ceramic heaters have gained wide spread popularity for a number of good reasons. One is reliability. Speaking from personal experience, our Lasko 5141, no longer available, refuses to give up the ghost after 6 or 7 birthdays – or approximately 52.4 space heater years.

A few more reasons behind the popularity of ceramics for heating are quick heat-up and safe operation. Ceramic heaters are also relatively quiet and produce an even heat which is often described as “soft.”

Radiator Space Heaters
A radiator will always be a radiator so there isn’t much you can do with it. Despite the lack of any game changing technology, the radiator type heater remains one of the safest. Among radiator heater makers, Delonghi dominates the market with its model D0715T Safe Heat Oil-Filled Radiator ($55).

Micathermic Heaters
Micathermic heaters are basically radiator heaters enclosed by mica panels for enhanced heat distribution. Since they depend on convection for heat distribution they are fan-less and noise-free. Designed for versatility, they can be mounted on casters or hung on a wall, and are said to be a good bathroom heater – which I don’t recommend for any portable electric heater.

Once all the rage, micathermic heaters have all but fallen by the wayside. Maybe it had something to do with a customer complaining about sparks shooting from his DeLonghi HHP1500 Mica Panel Radiator. So it’s interesting to note that the Kenwood HHP 1500, also made by Delonghi and strongly resembling the original, is one of Consumer Reports’ highest rated heaters.

However, all is not lost. The Bionaire BH3950-U micathermic heater ($85) rates 4 out of 5 stars from its users for silent operation, portability, and whole room, non-drying heat.

Convection Heaters With Fans
Fan-forced convection heat is the M.O. of most whole room space heaters. The top rated heater makers in this category are Lasko and Delonghi, mentioned previously, along with Holmes, Honeywell, and Vornado.

New from Vornado this heating season is the PVH, or Panel Vortex Heater ($60). This heater is a departure both in price and design from Vornado’s most popular heater, the round cornered EH1-0034-06 AVH2 Vortex Full-Room Electric Heater ($97). The new, easy to operate flat panel design houses the same technology used in their more expensive models.

The secret to harnessing Vornado’s vortex of heat is to locate the heater at one end of the room with a clear path to the opposite wall. When the air hits the opposing wall it splits and is deflected back around the perimeter of the room to heat every square inch of space.

From Holmes, sold under the Patton brand name, is the new PQH307-UM Tower Quartz Heater with Adjustable Thermostat ($45). This fan equipped unit is on the smaller end (150 sq. ft.) of whole room heaters and offers two heat settings corresponding to the number of quartz tubes turned on.

This year Honeywell has the distinction of a recommendation from Consumer Reports for its model HZ-817 Electric Convection Heater ($70). The 30″ long, baseboard type heater has no fan and relies solely on convection for heat distribution.

Unfortunately, this heater is a victim of its own success and is either unavailable, back ordered, or sold at highly inflated prices resulting from scarce supply. Kaz USA Inc., the manufacturer of Honeywell, is aware of the problem and suggests the HZ-617 Whole Room 2-in-1 Heater ($70) as an alternative. The main difference is the addition of a fan to the HZ-617 which can be turned on or off at your pleasure.

Without a doubt, the biggest shift in consumer preferences for electric space heaters has been to furniture style quartz infrared heaters. The introduction of EdenPure a few years ago was followed by an onslaught of competing makes and models.

Infrared Quartz Heaters
The newest of these is the Dr Heater infrared heater. Dr Heater features a dual quartz/ceramic heating system, gets food reviews, and costs $150 – $200 less than its competitors.

Finding the best whole room space heater is easy once you know the size of the space you want to heat, how fast you want it heated (heaters w/fans are 3x faster), and your budget.

Do It Yourself-Tankless Water Heater Installation With Recirculating Pump


For years, I wanted to have the efficiency of a tankless water heater, but I never knew how to get a heater installed in our house since it contained a recirculating pump connected to the existing tank heater. I didn’t find any information on the Internet on how to deal with both a tankless water heater and a recirculating pump. The challenge with this configuration is that in order for the tankless water heater to turn on the burner it requires flowing water. The recirculating pump doesn’t draw enough water to ensure that the burners turn on so therefore another solution needs to be created to have a hot water configuration that includes a tankless water heater and a recirculating pump. This article will describe the hot water topology to use for creating a hot water system in a domestic house that contains both a tankless heater and a recirculating pump.


Designing a water heater system for a domestic house that contains both a tankless water heater and a recirculating pump requires thought and consideration. This article will describe how to design a tankless hot water installation, what you need to purchase, how to prepare for the installation, installing the heater itself and expectations with a tankless water heater.

Design a Tankless Hot Water Installation

When designing a tankless water heater system, you need to consider: water hardness, gas flow, exhaust and venting, drains, and the dreaded recirculating pump.

Water Hardness

Hard water will destroy a tankless water heater. The calcium build-up destroys the efficiency of the heater and will eventually prevent water from moving. Testing your water before you install the heater is critical, and you want water that is less than 50 ppm. If your water isn’t soft, you must install a water softener.

Gas Flow

Tankless water heaters need a lot of gas to the heater when it is running. If the heater cannot get the necessary flow of gas, the onboard computer will generate a fault and the heater will not function correctly. Most heater manufacturers specify that you need a 3/4″ gas line to the heater. Some manufacturers suggest that you test that you have enough pressure from the gas meter and to install a larger gas meter from the gas company. For my installation, I didn’t perform any modifications to the gas line since it was already 3/4″ from the meter. I was definitely nervous the first time the heater fired up awaiting a fault from the computer, but gas pressure has never been an issue with my installation.

Exhaust and Venting

Exhaust and venting is the biggest source of issues with tankless hot water systems. Many installers connect the heater directly to existing duct work which will most certainly lead to system failures. You have to make sure that you use the venting that is specified by the heater manufacturer. If you do not use the correct venting the heater will absolutely fail. The venting manufacturers have worked directly with the heater manufacturer to make sure that the vent pipe is sized correctly and that the heater operates at peak efficiency. Also, make sure that you follow all of the recommendations for connecting the vent to the heater and venting it to the outside. Expect to pay 20% of the heater cost in vent pipe. Vent pipe for a tankless water heater is not galvanized and not something that you can pick up at the big box home improvement stores.

The heater not only uses the vent pipe for exhaust, it also uses it for fresh air intake. Using the correct vent pipe is critical to the success of your installation. There is so much caustic molecules on the exhaust of the heater that you will destroy the heater if you don’t use the correct venting.


Many homeowners choose to install a condensing heater. A condensing heater is more efficient, but it does have two drains on it. The first drain is a pop-off valve in case of a over-pressure situation like a regular tank water heater and the second drain is for the condensing liquid. My heater came with a plug installed on the condensing drain. If you forget to remove this plug, or you don’t correctly install a drain to remove the condensing fluids your water heater will rust out.

The combustion byproducts of natural gas are water and other petroleum byproducts. The water that is produced from the combustion needs to be drained. I chose to drain the liquids into an outside area that is full of vegetation. You should consult your city and or county code on the proper disposal of the condensing liquid. Water heater manufactures provide mechanisms for treating the condensing liquid.

Recirculating Pump

Challenges with a tankless water heater is that they need a flow of water to turn the burner on. I honestly wasn’t sure that the recirculating pump that was installed on the existing tank heater in the house could generate enough flow to trigger the burner to ignite. Not wanting to take a chance with this installation, I chose to install a buffer tank that would keep a small amount of hot water always hot. Installing a buffer tank also eliminates the phenomena known as a “cold-water sandwich” when the heater takes time to respond to new demands on the hot water flow as faucets are turned on and off throughout the system.

I calculated that my house had over 6 gallons of water stored between the location of the water heater and the furthest faucet. You can calculate how much water is stored in your pipes with this formula:

Gallons = [1/2 * pi * [radius of pipe (in)]^2 * length (in)]/231

1 Gallon = 231 cubic inches

pi = 3.14159

Since I had to move 6 gallons of water from the furthest faucet to the heater, I felt that a 7 gallon water heater would be big enough for the demand. I purchased a 7 gallons point of use water heater from Bosch.

I connected the recirculating pump to draw water directly from the tank instead of the tankless water heater. The cold water from the point of use water heater is fed directly from the tankless water heater.

System Expectations

With this hot water system, you will never run out of hot water and you will gain the efficiency of a tankless heater. There is one design flaw with this system, and that is if you run the recirculating pump without drawing any hot water from any of the faucets the hot water coming out of the faucet will be luke warm. This is due to the fact that the water is constantly heating the pipes and slab if the pipes are in the slab. This heat exchange is a lot for the small point of use water heater to keep up with. In my house, I manually control when the recirculating pump is turned on and wait about 30 seconds for the hot water to reach the furthest faucet. I can then turn on the hot water and not notice any cooling of the water because the tankless water heater is mixing water into the recirculating loop.

I would recommend this system to anyone that wants unlimited hot water.