Sigarms, I have to say that a lot of what you say about tube heaters, is contrary to all the literature I have read, all my discussions with the sales people I have bought them from, and all the considerable experience I have had using them in the 4100 sq ft shop I built 25 years ago, and several other buildings I have worked in and installed them in.
I do not want to have a running argument over this so, I will state my case, and if you interested enough to check with Sun Tube or CoRayVac, etc, I am confident they will be willing to back up the statements I am going to make, If you do not agree, no problem, I will agree to disagree.
Tube heaters heat with radiant heat, exactly like the sun does. The burner, or burners mix air with the combustion gases from the burner and exhost the gas on the end of the tube opposite the burner. As the heat radiates from the tube it starts out hottest at the burner and cools sometimes substantially if the run is long enough. But, if the system is designed properly and working properly, heat will radiate the entire length of the tube. Radiant heat does not heat air directly. It heats objects, then, as the heat dissipates from those objects it warms the air. This is why they say the floor is an important part of the heater, the heat radiates, with the help of the reflectors above the tube and warms the objects in the building, the biggest thing being the floor, it is the main object. This is not to say the floor gets
hot, but it does absorb, and radiate heat. Homes are being built with the same concept, where the sun porch has a stone or brick floor to absorb the heat from the sun during the day and radiate it back into the room at night. The tube heater will also warm cars, airplanes, etc. anything that absorbs heat fast like people or sheet metal will feel it first. We felt warm, even though the air temperature was only 62 degrees F. This is one of the ways it saves you money, you feel warm because of the radiational effect even though the air temp is cool, so you can keep the thermostat set lower. The other way it saves you money is if you have to open overhead doors in cold weather, like a repair shop. Open the door of a gas station bay in the winter with regular forced air heat, and in 30 seconds most or all of the heat in the shop is lost. With a tube system because of the radiant effects, the air is not the primary source of heat, the objects in the building, the floor the cars etc, are. So, opening the door, even for a few minutes, does not remove all the heat from these objects. That means your recovery from having the door is much faster because all these objects are radiating heat back into the air. And then, the temperature returns to the 62 degrees or so you may have had it set at, rather than the 70 or 72 you would have had to be comfortable with forced air your saving money again.
I know there are systems installed out there that do not work like this, systems that were not installed properly, are not sized properly, or maintained properly, or as I have seen sometimes just junk. This often causes a lot of confusion about these systems. If your shop was only comfortable under the burners or in "spots" then it certainly did not work as well as it should have. A properly designed and installed system will be warmer directly under the tubes, but, it should be comfortable in the
entire building. I have had may conversations with people who have decided these systems are no good based on a system or systems they have had a negative experience with. Then it becomes very difficult to convince them otherwise. One example was a series of airplane hangars, each had 4 tubes in them and though they were big enough they never were able to warm the hangars much when it was cold.
We replaced 2 of the heaters with Sun Tubes of the same size, and they produced so much heat they drove you out of there. All the other heaters soon were replaced.
There is no doubt that I like a forced air system for all out comfort. But, If you want to warm up a shop fast and economically there is no doubt a tube system is the way to go.
When I finish the new Garagemahol it will have both.
