Tunnel Heaters

[Earl Weiss]

I'm in the midwest.

Typical tunnel heaters are ceiling hung "Unit heaters." Gas / forced air.

Have had several brands - Reznor, Modine. ADP, Lennox.

Heater corrosion in Damp areas is an issue with moisture laden with soaps etc. Misting in the air and laying on the Units 24/7.

Have tried several things to reduce corrosion:

Cover units with tarps in non heating season.

Position so that they suck air from a drier part of the tunnel.

Now trying Stainless heat exchanger option. Adds about $200 (From $1500 to $1700) to the cost of a 300K BTU unit.

This won't stop rust on other parts like burners etc.

Anyone have better ideas / solutions?

 

[Ric]

Rather than electronic ignition I prefer the old fashioned standing pilot light. It keeps the unit just warm enough to prevent condensation year around. However, it won't work in all locations of your tunnel...for instance, the blowers may blow out the pilot.

 

[Washmee]

I've got one of these. It's basically a large Natural gas fired turbo heater. It's mounted next to my blowers and heats the entire tunnel.

http://www.frost-fighter.com/directfiredheaters.html

 

[Earl Weiss]

I would think air flow CFM would be important.
They are rated 400K BTU 2500 CFM and 800K BTU 1.5 Million BTU at 7700 CFM
http://frost-fighter.com/wp-content/uploads/2013/08/DF-400-DF-1500-Brochure.pdf

A ceiling Hung Lennox by Contrast 390000BTU is 4400CFM
http://ecomfort.com/lf24-400a-horiz...zed-steel-heat-exchanger-390000-btu-3948.html

So, it seems you move a lot more air with the Unit heater, and I don't think we could get away with a non vented unit. We had the stainless jet engine type and they had to point toward the door. We tried to turn it around. Kep tunnel warm but you really could not stay in the tunnel with it on this way.

 

[Washmee]

My tunnel is quite long(160'). This unit only runs when all the doors are open or after hours when no one is in the tunnel. My blowers move a lot of air so CO doesn't stay in the building. I also operate with well water which is 55* and tends to warm things up too. What areas are you trying to keep from freezing?

 

[Earl Weiss]

Trying to keep equipment from Freezing. Tunnels range from 90 - 190 feet. Up to about 120 feet a 300K BTU at each end does the job. After that I need a 3rd heater in the center.

The biggest issues are at about 15 degrees and colder. At those temps I have used torpdo heaters to supplement.

 

[Washmee]

I must be lucky because I've never really had problems with equipment freezing. My wash sits north/south and the prevailing wind is from the west. My conveyor ends about 25 feet from the exit door. On really cold busy days I do get a little ice build up near the blowers but that is about it. I also use a kero torpedo heater at the entrance end when we first open up on cold days. But after about an hour or so if we are busy it is turned off. In my area if it's below 10*'s business really drops off so we kepp our doors at the exit end closed between cars. That big jobsite heater does the job for me.

 

[pgrzes]

Why has nobody mentioned using a radiant tube? if you added a radiant tube heater at the dryer end of the tunnel and run the tube down the middle if that runs at night it will keep the equipment and concrete warm for the following day. Just protect any wiring or hoses that run directly under the tube.

 

[Earl Weiss]

if you added a radiant tube heater at the dryer end of the tunnel and run the tube down the middle if that runs at night it will keep the equipment and concrete warm for the following day..

Heating when we are closed is not an issue. I know the concrete retains heat, but I am skeptical how long it would last after 7:00 am with all the water running across it.

 

[Washmee]

Earl, I would be interested in knowing what the temperature of the water you use in the tunnel is. As I said in my earlier post mine is 55* for the functions that use cold water and about 100* for functions that use hot water. In the past I used radiant tube heaters, but after they stopped working due to age I bought the jobsite heater. It works so well that my loader has the warmest spot in the wash. BTW, I have the 800k-1mil BTU unit. Its mounted right at the blowers and they push the hot air all the way through the tunnel. I'll take a video and post it for you to see it in action.

 

[Earl Weiss]

Earl, I would be interested in knowing what the temperature of the water you use in the tunnel is. .

Good question and the answer is I have no frickin idea and I think it varies greatly depending on various factors.

Starts out at whatever the City of Chicago delivers it at. Then it may travel along 100' or more of piping in the tunnel and gain or lose heat. Then I have hot and cold lines T'd together to supply mixing stations that supply just about every function except first and final rinse. Depending on business volume the mixing station temperature will be higher or lower and I tend to make the mixture warmer to fight ssnow and / or icing issues. Basicaly a seat of the pants thing.

 

[robert roman]

Raising ambient temperature from 15 to 35 degrees F. (20 degrees) in 120’ tunnel requires 576,000 BTU and 190’ tunnel needs 884,000 BTU.

Raising temperature by 25 degrees, 120’ is 720,000 BTU and 190’ is 1.1 million. By 30 degrees, 120’ is 864,000 BTU and 190’ is 1.3 million.

Insulation could reduce this by almost half as much. However, big problem with tunnel is end walls. Open doors and combination of positive displacement and temperature difference (cold outside and warm inside) causes evacuation of heat. Wind only makes it worse.

Creating an air chamber inside tunnel and installing automatic air curtains (plastic) can cut this loss significantly. Strategically placed air vents (louvers) in roof can help prevent condensation on ceiling and heater corrosion.

In long tunnel, radiant is effective at keeping water from freezing on mitter baskets, wraps, cloth, arches and overhead plumbing but not good for heating ambient air or floors/walls.

In warmer climates, I’ve gotten by winter with a torpedo heater without many issues. Above Mason Dixon Line, tunnel design is more complicated because cold affects wash quality, mostly drying.

Industrial furnaces face same issues, displacement of heat with open hearth. Plus, furnace is loaded with cold steel which absorbs heat energy. Same applies to wash where temperature of the car entering the tunnel may be as cold as outside ambient air.

So, an air chamber can have good ROI at low temperatures and high volume.

 

[TEEBOX]

Earl,

I'm in Detroit and use ceiling Radiant Heaters. One is placed in the loading area, one in the middle of the wash and the other is before drying area. I also use a Windstar door at exit to retain the heat. My tunnel is 130 feet long. I have replaced the igniter on all 3 at least once in last 8 years. The heater closest to dryers has the most corrosion. I can't seem to get it clean. Our prevailing wind is from the west however, my wash sits North/South. That North wind is brutal. In between cars I usually close the entrance door halfway to help retain heat. Today is a sunny 20 degrees with real feel of 8 degrees. Customers in stores because we are dead.

 

[Earl Weiss]

Have Plastic Doors at exit and they help. At buildings with oversize entrances I narrow the opening in the winter to accomodate the largest vehicle using Plastic strips i remove in Spring. Cuts down on the wind somewhat.

Thanks for the input. Seems no magic bullet vis a vis corrosion issues.

 

[mjwalsh]

Thanks for the input. Seems no magic bullet vis a vis corrosion issues.

Earl,

We don't have a tunnel but one of the best things we did 22 years ago was get rid of our gas fired air to air unit heaters that are the same as what you describe. They specifically say "no chlorinated vapors". I have a very unpleasant memory (happened during a severe below zero cold spell) of calling after hours our gas company's service department to take care of one of them because of a no pilot issue. The guy said he could get it going easily except after inspection he found a tiny pin hole in the heat exchanger from corrosion. He said that it can no longer be used ... period ... it's the law ... until a whole brand new unit was put in place.

I am not sure if you have a closed loop boiler or have considered one ... but we use that approach with circulating glycol through a Spirec heat exchanger to avoid glycol being in the boiler heat chamber for better efficiency. Steam - Hot Water style Trane unit heaters but any corrosion now is limited to strictly cosmetic ... proven for more than 22 years.

We hope this helps.

Mike Walsh King Koin Car Wash in North Dakota

 

[Washmee]

Here is a video of my heater. It looks like it is going to get a real workout next week with predicted high temperatures in the single digits on Monday and Tuesday.

[video=youtube;MibIS2QFkkE]http://www.youtube.com/watch?v=MibIS2QFkkE[/video]

 

[JMMUSTANG]

What type heater, BTU's?
Natural gas?