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Thread: AC, Venting, ideas for a Darkroom Shed?

  1. #31
    Resident Heretic Bruce Watson's Avatar
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    Re: AC, Venting, ideas for a Darkroom Shed?

    Quote Originally Posted by Tin Can View Post
    I still have the big hole saw i will need.

    Bruce Watson

  2. #32

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    Re: AC, Venting, ideas for a Darkroom Shed?

    Quote Originally Posted by Bruce Watson View Post
    Air is compressible. You can pull it, but you can't push it effectively. If you try to push air down a duct with a turn in it, what usually happens at the turn is a drop in airflow. Because what the fan is doing now is raising the static pressure between the fan and the turn in the duct. How much static pressure a fan can produce is a typical fan specification -- it's usually right there on the name plate around the model number. After that level is reached, air flow down the duct is essentially zero. You can't push a rope. You can't push air.

    I don't expect many people to actually understand this because most people haven't been through mechanical engineering school. For those that have, this is simple fluid flow. For those that haven't, it's like magic. I get that it's not intuitively obvious, but that doesn't mean that I'm not telling you the truth.

    So, put the fan on the outside of the building so it can exhaust into the entire outside atmosphere. It's not possible for an individual fan, no matter how big, to effectively increase atmospheric pressure. So the fan won't generate any increase in static pressure, and therefore will maximize it's airflow.
    Oh I get you now. Yes, I deal with this with PC watercooling. Typically it's high static pressure fans in front of the radiators (though in my next build I may swap one of the radiators and put it in a pull). Those are fans specifically designed to push air through a small radiator so it's a pretty simple problem to solve.

    But back to the darkroom, right so if I make a light trap/baffle I need to makes sure the fan is at the end of it so it pulls from inside the room and not pushes. That's probably easy enough, though I'd have to figure out how to protect the fan from the weather.

  3. #33

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    Re: AC, Venting, ideas for a Darkroom Shed?

    HOA's or not you need to insulate heat and cool your darkroom. Otherwise you can have mold. a friend of mine did not heat his darkroom and it is all full of mold. I would expect the enlargers bellows at least are ruined as well as anything else that will hold mold - like negatives and lenses. As far as venting goes - Delta made or makes electric fans and air intakes that are baffled to not allow any light in. I had one of the Delta fans in my last darkroom and was very happy with in. My current darkroom has a ceiling fan over the sink which seems to work OK. As far as heating and cooling a ductless heat pump would be ideal but expensive. Window air conditioners work well and portable heaters or wall heaters work well - you just can't let photographic material be exposed by the electrical elements.

  4. #34

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    Re: AC, Venting, ideas for a Darkroom Shed?

    Dawg.... Home Depot sells heat/AC window type units. I bought one when I was planning to build my darkroom inside a semi trailer I owned. Gave up on that idea! The unit I bought will heat/cool a fairly big room( will check box tomorrow for specs). That might be the way to go.

    On the wiring-I'd have a trench dug and use the grey PVC conduit. You might want to oversize it a bit to allow for more service in the future as needed. It'd be way cheaper to pull more wire thru a large pipe than to dig and run more conduit and wire.


    Oversize the wire....a safety factor is a lovely thing. Overloading your wiring is one of the fastest ways to burn your house down... When I had this house rewired in 2009, I had bought 750' of 12 gauge Romex before hand-the electrician was told I didn't even wanna hear the words " 14 gauge"!

    If your outside box is out of room, your electrician should be able to upgrade you to a larger box. However, I'd call the local electric company and see what the amperage rating is on your service line from the pole. That might need to be upgraded.

  5. #35

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    Re: AC, Venting, ideas for a Darkroom Shed?

    Thanks for the info everyone! Sounds like while the shed itself isn't that expensive, probably everything else will be haha. I'll have to come up with a price list of sorts I think. Also going to evaluate the price difference in having a prefab shed versus building my own. The bummer is it would be nice if I could iterate things. I don't need to install AC if I build the thing in the fall so I could save some money on that (until the summer) but will still need venting of course, electrical (though in a pinch maybe a battery and an inverter if I don't need an AC for the fall and don't store any chemicals in the shed during the day - meaning I won't need a fridge). But I'll still need a lot of stuff to get going.

    I'll let folks know if/when I do it! I'll probably make a build log of sorts to document the progress.

  6. #36

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    Re: AC, Venting, ideas for a Darkroom Shed?

    Okay, the smallest AC/heat unit Home Depot has is a 7500 BTU cooling-3850 BTU/hour heating unit. They claim it will cool 320 square feet. It's 110 volt. $469

  7. #37

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    Re: AC, Venting, ideas for a Darkroom Shed?

    Quote Originally Posted by MrFujicaman View Post
    Okay, the smallest AC/heat unit Home Depot has is a 7500 BTU cooling-3850 BTU/hour heating unit. They claim it will cool 320 square feet. It's 110 volt. $469
    Yep this is true! Thing is, the amount of power I need for my darkroom, without AC, is maybe 150W? Enlarger is a cold light, the safelights can be LEDs, maybe a few white LED bulbs. If I converted my enlarger head to LED, pretty much everything in the room could be run on 5-12V DC were it not for the AC. Means I can directly power almost everything with a deep cycle lead acid battery or a large mult-cell lipo even (perhaps a very large one).

    With AC though now it's enough power to need to consider conduit. Even that small AC unit at Home Depot, while I could run it with a heavy duty extension cable, I probably shouldn't as noted previously. So now I need a conduit, perhaps some breaker boxes, etc. I'm going to need AC - for sure. But if I save my pennies and look at building this in the fall, I don't have to worry about AC until late spring which gives me a lot of time to save and plan for a more proper solution. I guess the catch is, if I opted for a window/wall unit, I'd have to make sure I framed that out ahead of time.

    I dunno I might go full tilt with everything but I need to put my costs together and were where things land. One thing the above isn't accounting for is the few times I'd need heat. In Texas it's not _that_ often, particularly if the shed gets warmed by the sun during the day, but a heater also uses enough energy I'd have to be careful just dragging an everyday extension cord out there. Maybe I can get some hot stones and water and make a sauna :P

  8. #38

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    Re: AC, Venting, ideas for a Darkroom Shed?

    You want to run conduit feed for the electric with a GFI breaker anyway. Three circuits if possible. One for the enlarger, one for the A/C and one for the rest.

  9. #39

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    Re: AC, Venting, ideas for a Darkroom Shed?

    Quote Originally Posted by Luis-F-S View Post
    You want to run conduit feed for the electric with a GFI breaker anyway. Three circuits if possible. One for the enlarger, one for the A/C and one for the rest.
    I think Luis is right. Plan on 60 amps of service for the darkroom.

  10. #40

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    Re: AC, Venting, ideas for a Darkroom Shed?

    Any reason for something so high that I'm missing? If the shed was for carpentry work, I could see the need for power for saws and other woodworking stuff, but I calculated my power needs so far and it's less than half that:

    Enlarger: 100W
    Lighting: 2-20W
    Fridge: 250W
    Fan: 10W
    Split-AC: 1200-2750W (2750W looks to be start up power, 1200W continual)
    Rotary: 10W

    That's 3140W which is around 28A. Using an in-wall AC, it drops down to 2390W / 21A.

    Definitely more than just running a Romex 12 gauge cable out there but less than half of 60A. The AC, unsurprisingly, uses the most amount of power by far. I'm actually more worried about voltage sag with it than the actual power requirements, since that could change my exposure times without a line conditioner since I use a ColdLight. Hadn't bothered with messing with that since my next timer may have a lux compensation and I plan to switch to LEDs eventually anyway. I'd have room for two enlargers though so I put 100W since my other enlarger still uses an incandescent.

    Without the AC and fridge, I'm only at about 140W - easily enough to run an extension cable out (with a GFCI end) to get started for fall/winter darkrooming or to power from a 12V battery with an inverter probably for an entire darkroom session. Doing so could give me several months to save for the AC and electrical costs.

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