January 2020 - B.I.M.S. Air Conditioning, Heating, Ventilation, Refrigeration, Dallas, TX

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warehouse unit heater

Unit Heaters for Commercial & Industrial Heating: a Definitive Guide

Trane Unit Heater

Since approximately 1916,  unit heaters made have their way into the lives of people, warming up all kinds of spaces from homes and classrooms up to warehouses and entire factories.

Unit heaters for commercial & industrial heating are stand-alone appliances specifically created to provide heat while using different sources of energy to accomplish this task. The sources of energy used can range from hot water and steam all the way to number 2 fuel oil, natural gas and propane.

As simple as they seem on the surface, these appliances have different components and accessories depending on where they are to be used and what energy source will power them.

Read on to learn more about the ranging type of unit heaters, sizing requirements, along with placements, all designed to warm up your business and keep production buzzing along.

Types of Unit Heaters

Because of the wide and varying environments that unit heaters operate in, they come in a wide range of shapes and sizes and types. Some are versatile and can be used in a variety of ways while others are designed specifically for niche applications.

Most unit heaters use a fan to produce a flow of air that is high-volume in order to be strong enough to distribute the generated heat evenly and efficiently in the environment in which it's installed.

Each type of unit heater comes with it's own limitations, disadvantages and advantages. A common component however is an integrated fan used to produce the high-volume flow of hot air while the variable lies in the way the heat is generated.

There is a grand total of ten types of unit heaters that are primarily used for commercial and industrial heating which we will go through in this article.


1st Unit Heater Type - Circulating Hot Water Systems 

In this system the hot water is generated by a main boiler. Depending on the area that needs to be heated, hot water is circulated to one or more Low Pressure Hot Water Unit Heaters (LPHW).

This type of unit heater can be seen in places such as warehouses, shop entrances, industrial businesses, sports halls and workshops. They are usually very reliable and keep a low sound level while in use.

Commonly, these types of unit heaters are controlled by devices such as an electronic thermostat to control the fan and/or water flow. One such thermostat has the capability to handle multiple Circulating Hot Water Systems.

A benefit of this system comes when coupled up with drip pans and drains, which are also be used to cool spaces or processes. Once the main boiler is shut off, the ventilator can be left functioning for this system to provide ventilation and cooling as well.

2nd Unit Heater Type - Standard Electric Heater

For medium sized commercial and industrial facilities, these basic units start from 3kW (3,000 Watt) and upwards with support for both three phase or single phase electrical applications.

The size range of such a unit heater begins at just over 12 inches wide and extends all the way up to 3 feet and sometimes beyond. Some are quite square in shape, while others are more pancaked in nature. The way they operate is quite simple, they convert electrical current into heat.

This is achieved by circulating an air current through a set of electrical resistors that heat up. The resistors heat up the air and this results in radiant heat for the space it's installed in.

These types of unit heaters are for smaller spaces in commercial and industrial buildings, such as offices or test rooms.

Standard Electric Heater
Steam Fed Heater

3rd Unit Heater Type - Steam Fed Heater

While some boilers are designed to produce hot water, others take it up a notch and heat the water up to the point it becomes steam. Besides the LPHW unit heaters from above, steam fed heaters use a fan and a coil to push the air throughout the desired area.

However a coil setup is a far, far heavier construction. The role of the coil besides making the fluid transfer heat into the air, is to make the fluid change state.

This change in state plus steam condensing in the coil, generates more heat versus an LPHW unit heater. The output of a steam unit heater requires a connection to a steam pipe that can withstand up to 10 bar or more.

These types of unit heaters are generally found in larger commercial and industrial operations with larger requirements and budgets.

4th Unit Heater Type - Specialized Application Electric Heater

This type of unit heater can be customized to fit any particular business or use case.

For example, some unit heaters are created to function in damp and corrosive environments such as car washes and sewage works or to withstand vibrations on an offshore platform.

Others are created to function in low element temperatures such as agricultural buildings and heat at high temperatures of up to 158°F.

They can be designed to stand on their own, be wall mounted or attached to the ceiling. This type of unit heater is one of the most sought after by business owners because of their portability. However, these types of unit heaters can quickly become an inefficient use of electricity if not kept in check.

Specialized Application Electric Heater
ATEX Heater

5th Unit heater type - ATEX Rated Heater

Created to be used specifically in hazardous areas where explosive gases may be present or where regulations are very tight due to the chemicals that are being used in the space to be heated.
 
These areas represent a challenge when it comes to heating as using a wrong technology to produce heat can end up becoming a very serious safety issue or even cause a catastrophe if the system produces even one spark or an electric arc.

ATEX rated heaters are widely used in oil and gas refineries, gas generation plants, paint storage areas and other locations that work with highly inflammable liquids or vapors.

6th Unit heater type - Propane, LPG, Oil and Diesel Fired Heater

As the name implies, this type of unit heater produces heat by burning any of the above mentioned fuels.  

These systems are mainly used in construction, concerts, festivals, large weddings, agriculture, horticulture and similar applications where permanent electrical connections might not be present.

Heat is transported from the burning chamber by a fan and multiple ducts to the targeted areas. Check your indoors air quality requirements before employing these types of unit heaters for commercial or industrial use.

Propane Heater
Solid fuel heater

7th Unit heater type - Solid Fuel Heater

Usually found in industrial business setups that produce good amounts of combustible waste such as wood, logs or any other combustible waste.

These types of unit heaters generally come equipped with a high power centrifugal fan and a heat exchanger that once connected to a duct, is ready to distribute heat to multiple locations.

By far the most cost efficient type of heater for your business, provided that combustible waste is a bi-product of your production. As always with any unit heater, you should check to assure you are not emitting harmful exhaust smoke or chemicals to indoor or confined spaces. 

8th Unit heater type - Biomass Heater

Very similar to conventional gas boilers but 100% specialized for burning biomass fuels which are renewable in nature and a lot less polluting than a regular gas heater.

Range of heat output from this type of unit heater begins around 43 kW and goes to 300 kW or larger. The units are totally self-contained and ideal for industrial environments.

Biomass Heater
cabinet heater

9th Unit heater type - Cabinet Heater

Perfect for small enclosures and situations where a minimum temperature has to be maintained.

Usually used in applications that are sensitive to low temperatures or extreme variations of temperature such as electronic equipment , traffic signals, control panes or outdoor electric power houses.

Generally more efficient than just using an incandescent light bulb or similar apparatus.

10th Unit heater type - Forced Air Heater

Perfect for many different small, medium and ever larger commercial and industrial installations. This system is very similar to the Standard Electric Heater system but has a fuel source such as natural gas or propane and employs a fan.

Fans are used to speed up the airflow through the system and also to help carry the heat with air.

To distribute heat better and farther, the forced air heaters are usually linked up to a system of duct work, but not always. Often times they are used stand alone and hang overhead with minimal electrical  and gas requirements.

If a duct work is used, it facilitates the transportation and pointing of the heat in the desired area. This provides heating for larger spaces without taking up any floor space.

Forced air unit heaters are quite common and make up the bulk of many heating requirements for warehouses, garages, stores, shops, etc. They have only one drawback and that is many of these are louder in character and aren't good for conversations near by. 

forced air heater

Sizing unit heaters

When it comes to calculating your unit heater sizing, there are a few components to take into consideration. This is just a basic guide as you must always take in other environment variables to make a final determination as to proper sizing.

1. Figure out the cubic feet of the desired areas to be heated
Measure the height, length and width of each area you want to heat. Now take and multiply these numbers to obtain the cubic feet.

2. Calculate the temperature increase that you need
Write down the temperature you want to maintain. Check and see what the lowest area temperature is. Subtract the lowest area temperature from the desired temperature to be maintained . The result is the desired temperature increase.

3. Determine the BTU you need
Get your total cubic feet number and multiply by .133. The result is then again multiplied by the temperature increase result from the calculation at step 2. Round the result to the nearest thousand to have a clear image of the total BTU requirements or heater size you may need.

4. Make sure the calculations take everything into consideration
Your heater size needs might need  to increase if you have large windows, light insulation or drafty doorways. It's always better to oversize the system than to install one that doesn't cover the entire need.

Once all the above steps above are done, all that remains is to search for the unit heater capable of producing the required BTU's. Once again, there are other variables that come into play with air quality, electrical demands, and/or fuel resources available and cost metrics to be considered.

Heater placement

Location, location, location... is crucial when it comes to unit heater placement for commercial and industrial heating. Efficiency is easily diminished with a bad placement and ends up costing you more money, fuel and/or electricity.

Best place to install a unit heater is near doors or windows. The simple reasoning behind this is that unit heaters in general will heat up cold air that manages to get in through these doors or windows and avoid the propagation of cold along the floor. These spots are known as heat loss sources. Just as a reminder, we're not talking about central heating installations in these cases.

Placement in heat loss sources will significantly improve efficiency and can save you money from the very beginning. Efficient heater placement eliminates the need for extra heating equipment such as door heaters or infrared tubes.

Another important tip is to place the heaters near the perimeter of your space and direct them to blow inwards, to the center of the space. However always keep in mind that the heater should not blow directly into obstructions as these reduce the effective range of the heater.

It's best to position a unit heater in such a way that it has the most amount of open space in front of it and clear of any obstructions.

Depending on the type of space you have and the total size of it, unit heaters can be placed on the ground, suspended on walls or suspended from the ceiling to fit any building structure or other requirements. However, not all types of unit heaters support installation on walls or from the ceiling.

Tube-type vs. others

tube type heater

When looking into deciding which type of unit heater to go with for commercial and industrial heating, you have to take into consideration the activity that is happening in the area you wish to heat up and the space you actually have available for heating equipment.

If you don't have a lot of space and don't need a lot of clearance in the day to day activity you might want to look into tube-type unit heaters.  These generally employ one single source of heat production and tubes that will drive the heat to the desired areas.

Tube heaters are not 100% efficient. This means you have to take into consideration the heater's AFUE (Annual Fuel Utilization Efficiency) percentage. For example if the AFUE is 80% and you have a total cubic feet requirement of 500,000 BTU, then you divide the number by 0.80. The result will be 625,000 BTU.

Therefore to make up for the inefficiency, you need a 625,000 BTU tube heater to be sure you get at least 500,000 BTU generated.

Another important factor to take into consideration is height of installation. Tube heat is radiative heat and this means that height impacts the heat. For example doubling the standard installation height you get 1/4 of the heat to the areas where you need it. There is a sensitive balance between maintaining minimum clearance and keeping heat effective.

Besides actual installation height you must also keep in mind that some capacities and tube lengths require 7-8' clearance for combustibles.

Is Tube Type Unit Heating a Viable Option For You?
You can go with forced air unit heaters. These are more efficient than the tube-type unit heaters and generally cost less upfront as it requires less electrical work, less gas piping and other works.

Perfect if your space does not have a lot of air infiltration. If your only issue is a tall ceiling, this can be mitigated by installing ceiling fans to push and keep the heat down.

Forced air unit heaters average about double the heat per each dollar spent on the equipment vs the tube-type. Sometimes one forced air unit heater might make up for two tube-type unit heaters for many commercial and industrial applications.

The most important aspect to figure out is what the desired space is better suited with. If the space is better suited for tube heaters, the forced air unit heater will surely cost more in utilities and not provide the same level of comfort.

This is not a simple calculation nor decision. That's why we are here you help you make the best decision to squeeze out the most out of each dollar invested. Give us a call today at 833-TRY-B.I.M.S., Inc. for a free consultation.


Maintenance Repair & When to Call for Service


Regular preventive maintenance helps maintain operational time.  A combination of good operational practice and maintenance limits downtime. An annual or more often inspection prevents damage of most types of unit heaters. 

Need troubleshooting help with your unit heater or heating system? Can't decide if it needs repairs or a full replacement? Give us a call today for a consultation. For urgent repair requests, telephone our 24-hour staffed emergency helpline.  We are factory trained and preferred warranty service providers for many of the top brands in North America. We service all of the Dallas and Ft. Worth areas of our great state of Texas.