Heating Air for the Indoor Range

Ganderite

Ganderite

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Farm south of North Bay
My club is planning on installing a new air handling system. The current system is crude and we are getting too much lead in the air we breath.

I shot a match on another local range. They turned on the heat for the range air. They only do this if there are a lot of shooters on the range, because it costs $25 to $75 an hour for the propane, depending on the ambient temperature outside.

Can anyone provide any more insight into heating range air?
 
I built an eye surgery clinic a couple of years ago. Part of the contract was a gas fired heated Make-up Air Unit. The clinic was about 3000 sq. ft. The MUA was about 20' long and 10' wide. We reinforced the roof and added steel framing to carry the load. I don't remember the exact figure but
with everything in, it was up around 100k. That doesn't allow for lead filtration either. Operating costs are not cheap, at our indoor range I think it is around $40/hr.
 
25 to 75 an hour for fuel seems really high... our list price for a 33 lb bottle is 30 dollars for a Joe off the street .Not contract pricing. so full retail is about 10cents per cu ft. Ideally contract pricing would be half that.
 
Your range probably has a direct fired air handler that heats up fresh outside air and a large exhaust fan to remove the lead and gun smoke filled air. Because a system like this uses outside air and your location is Ontario there is a larger temperature rise for a direct fired unit using fresh air compared to a unit that reheats return air like your home durance. A hrv would be a good way to increase efficiency as it uses the heat in the exhausted air to preheat fresh air.
 
I think 98ssuck is suggesting a heat exchanger. But I'm not sure since it seems like his "hrv" mentioned in the last sentence is glossed over and I'm not sure what "hrv" stands for.

But in any event what you need is a heat exchanger that passes the heated exhaust air through one set of ducts with the fresh incoming air passing along these exhaust ducts to pull out some of the heat you'd otherwise be sending outside.

The problem is that you're moving a LOT of air in a system of this sort to keep the flow at the firing line adequate for pulling the gases forward. So any such exchanger needs to be a LOT larger or use a LOT more of them than a typical house size unit. The issue being that the warmed exhaust air has to stay in contact with the cool incoming air for long enough for a reasonable transfer to occur.

You'll want to have the fellow dealing with the upgrades talk to a few very big industrial HVAC outfits. No one in home heating would be dealing with such things. But factories where there's a need for high air movement would likely have a suitable size heat exchanger of this sort.

Talking to such outfits is likely the way to go anyway. Not understanding the size of the issue is why your club is in this situation already. Mere mortals can't begin to understand the size of the equipment needed to move the amount of air that needs to be moved.

One way to cut down on this is to install benches at the shooting line that limit the open cross section area. Closed in lowers and dropped upper skirts will reduce the area and greatly reduce the amount of air that needs to be moved. The safety rating is based on air flowing past the shooter at a given rate to draw the gases away from the shooter. So if framing and skirts can be used to reduce the cross section of the range to half then the amount of air flow needed to achieve the velocity across the reduced station ports is also halved. And that alone halves your heating issue at the same time it cuts down radically on the size and/or number of fans needed.
 
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98ssuck said:
Your range probably has a direct fired air handler that heats up fresh outside air and a large exhaust fan to remove the lead and gun smoke filled air. Because a system like this uses outside air and your location is Ontario there is a larger temperature rise for a direct fired unit using fresh air compared to a unit that reheats return air like your home durance. A hrv would be a good way to increase efficiency as it uses the heat in the exhausted air to preheat fresh air.
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However you increase lead exposure when recirculating any of the exhausted air that isn't filtered properly.
 
This is why chemistry labs have fume hoods. Trying to control and condition the air in the entire room doesn't seem practical. Why not look into turning each shooting stall (stall, is that right?) into it's own fume hood, with it's own ventilation? You'll be able to use a higher draw rate, and still only need to filter and "treat" a miniscule fraction of the air, rather than trying to 'turn over' the entire range.
The only thing you would need to prove, is that the ambient air remains sufficiently clean, over time. Relative to the alternative, anyways.
 
BCRider said:
One way to cut down on this is to install benches at the shooting line that limit the open cross section area. Closed in lowers and dropped upper skirts will reduce the area and greatly reduce the amount of air that needs to be moved. The safety rating is based on air flowing past the shooter at a given rate to draw the gases away from the shooter. So if framing and skirts can be used to reduce the cross section of the range to half then the amount of air flow needed to achieve the velocity across the reduced station ports is also halved. And that alone halves your heating issue at the same time it cuts down radically on the size and/or number of fans needed.
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This is what we have now, but it is creating problems. It causes a lot of turbulence as the air goes through those openings. Turbulence causes reverse eddies and lead on the shooter, and causes real problems when we are shooting PPC and IDPA forward of the stalls.

A big heat exchanger would cost real money. We can create good clean air at a reduced air flow by taking out the skirts and supply the air through an air wall behind the shooters. The next question is heat to take the edge off.

maybe the best we can do are electric radiant heaters aimed at the stalls.
 
Radiant/infrared heaters in the shooting area seem to work well. Same type of thing used in arenas, etc.

In my view there's no sense heating the entire range... that's a huge volume that's unoccupied 99% of the time.

For IPSC/IDPA I don't have a good suggestion. Would portable patio heaters behind the shooting area work?
 
###XX said:
Radiant/infrared heaters in the shooting area seem to work well. Same type of thing used in arenas, etc.

In my view there's no sense heating the entire range... that's a huge volume that's unoccupied 99% of the time.

For IPSC/IDPA I don't have a good suggestion. Would portable patio heaters behind the shooting area work?
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I agree. Radiant heaters behind the shooting line seem like the best option, you are wasting a lot if you are trying to heat the whole range.

Then your air system only needs to exchange the lead filled air with fresh air. Maybe add a heat exchanger too? That way you can keep the air a bit warmer than without?
 
As others have suggested already, radiant heat (preferably natural gas fired) is the way to go. Heating the objects (people) is much cheaper than trying to heat all the air. Work on the air filtration problem separately.
 
I was at one in NS, the air is blown out on your backs on the line,, hence you freeze,, they put radient heaters above each firing point
 
Ganderite said:
Thanks guys. Just asked in case there was a perfect solution out there that we had not heard of.
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There is, but it's not cheap to build up front. Down the road, the operating costs are much better.

Heating a range entirely through the air handling system is stupid when you need 100% air exchange.

The ideal would be to use in floor heating directly under the booths and area behind the bench for primary heat. It can run 24/7 on a set back temperature and be boosted based on a motion or scheduled setting.

Using a heat recovery coil to scavenge heat from the exhaust to boost the make up air temperature with a separate booster coil completes the system. As the air handler for the range only runs during operating hours, your range maintains temperature for the cost of a glorified water/glycol heater and a 1/2HP pump most of the time.
 
Air walls behind the shooter is the best way to supply air, but still need to be tuned, otherwise you end up with dead zones and eddies as noted. Do you have natural gas at your range or propane only? being in Ontario you guys obviously need to seriously heat the air, and recovery may be cost effective. Just make sure you filter the air before sending it through any recovery systems as the lead will quickly coat the inside of the system and rob you of efficiency. Do not go the recycled air route, gun smoke is one of the products that really needs to be 100% exhausted due to the contaminants in it. You can pay for a system that will allow it, but man, they cost a ton. To simply take the edge of the bitter cold you guys face shouldn't cost more than $20 an hour, which should be recoverable through a drop in fee increase when people are there using it. Even at the worst here in BC when it's -20 outside it only costs us about $30/hr to run our entire system, with heat bringing the the room up to 20+ degrees. If I run it just to take the chill out it would be about $14/hr.
As for the above comment from MBJ, sorry, you're wrong, you have to heat the supply air, heated floors do nothing, infrared does not much better. You have 6-9 air changes an hour in a proper range, sometimes even more, that amount of air moving over you will freeze you if it's not conditioned. This science has been worked out and is known about in the industry. There is no point in keeping the room heated during off times either, unless it's used as a classroom space, in which case space heaters or wall mounted units (that don't mess with the airflow when it's a range) are all that are needed.
Just about no one recovers the heat from the exhaust air, although it is becoming more common as utilities go up. The new range in Chilliwack that the RCMP are building has a recovery system in place for both ranges. Huge huge money with a lot of upkeep required to maintain it properly.
 
I hadn't thought about turbulence off the skirts. That does change things up.

I like the idea of radiant heaters too. But unless the things are spewing lava I seriously doubt that they would be enough to take the chill off seriously sub 0 air coming off an air wall during a sharp evening in winter time Ontario. More than likely you'd be looking at a combination of radiant, heat exchanging and some modest air heating to make it so folks are comfy with a light jacket or sweat shirt.

The bottom line is that this is a serious HVAC engineering job that should involve a company that does up HVAC for local industrial plants that require serious air exchange. A company like that is the sort of folks that will be able to present options from barely tolerable to shirt sleeve use. Somewhere closer to barely tolerable is likely where your club will find it's acceptable price point.
 
talking to companies that have built ranges is the best bet because honestly the industrial guys have little clue on how ranges should be done either. Ask me how I know...
 
yeah I knew we were higher than recommended, but couldn't remember just how much higher we were.
 
I am an mechanical engineer that deals with ventilation & HVAC issues in research buildings from an owner's point of view (facilities operations). The attached photo is a copy from the American Conference of industrial Hygienists and show the suggested design for proper ventilation. The airflow is dependent on the cross sectional area of the length of the benches and height from the top of the bench to the top of the stall. This should be kept to a minimum.

RangeVentilation_zpsa44893a5.jpg
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This cross sectional area is multiplied by 50 to obtain the air quantity in CFM (cubic feet of air per minute). Here is an example :

Assume the height of the stall (H) is 4 feet and the width is 3 feet per stall and assume 10 stalls, W = 3 X 10 = 30 feet. The area would be 4 X 30 = 120 sq ft. Per the equation in the above reference, multiple this area by 50 to obtain the air flow, Q. In this example, 50 X 120 = 6,000 CFM. For comparison a typical bathroom exhaust fan in your home is 50 CFM, so this is equivalent to 120 bathroom exhaust fans. To heat this air, the following equation is used:

Heating required = 1.08 X ( Inside Air Temperature - Outdoor Air Temperature) X Air Flow ( in CFM)
Heating Required = 1. 08 X (70 F - 0F) X 6,000 CFM ( assume indoor temp is 70 F and outdoor temp is 0F) = 453,600 BTU/H -> round to 500,000 BTU/H
For comparison, typical high efficient gas furnace for your house is about 60,000 BTU/H (output heating of unit) or about 8 residential furnaces.

If a Make Up Air unit (MAU) is used to heat the ventilation air, it typically would be direct fired, meaning that the products of combustion are mixed with the supply air, passes through the range and is exhaust by the exhaust fan. The exhaust fan and MAU work in conjunction to each other and are interlocked. An energy recovery system would be difficult due to the lead particulate in the exhaust stream and would have to be filterer prior to any heat recovery equipment (very expensive to maintain).

At my range, we do not heat the make up air and relay on a radiant tube heater running the length of the stalls and is on a 30 minute timer. The exhaust fan is also on a 30 minute mechanical timer.

Hope this help to explain how the ventilation should be handled at an indoor range.
 
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