Darkroom cooling/air conditioning options

[williaty]

I appreciate everyone’s input on this. I’m leaning towards the mini split for its efficiency, heating and cooling abilities, and ease of light proofing. After some research it looks like I can install it myself without too much difficulty.

You can do 90% of the work yourself, but I strongly encourage you get a professional to do the plumbing. The reason is that if you get anything into the system that shouldn't be there, it'll quickly destroy the whole thing. Too much humidity, too much ambient air, etc, and the whole thing is ruined. A professional will have the skills and tools to connect it without contamination or to pump it down and recharge it if they suspect something may have leaked. Definitely mount the compressor, mount the head, run the lines, etc yourself. Just leave the system sealed and let a pro make the connections.

[Drew Wiley]

An isolated outdoor conditioner pump connected by tubes to an indoor unit will be light proof, a window unit won't.

[jmdavis]

I used a portable unit for several years in Richmond VA. We have high humidity most of the year. The portable worked ok. But it only lasted 3 or 4 years, I think. When I redo my home darkroom (I am using membership community darkroom now). I will install a window type unit into the wall or go with a mini-split.

I have been considering a dedicated outbuilding instead of the outdoor entrance utility room I have set up now for replacement. 9x14 seems like a good size as does 12x12 or 8x16. Insulation is key. My ventilation is directly above the sink and below my head. Air comes in via a baffled and filtered 14x12 vent installed low in the wall. And the darkroom has a door that separates it from the space for the washer and water heater. My problem is that I can only get 5x7 feet. And that is a tight fit for anything more than 11x14 since my sink is only 5 feet .

[Jim Noel]

You can do 90% of the work yourself, but I strongly encourage you get a professional to do the plumbing. The reason is that if you get anything into the system that shouldn't be there, it'll quickly destroy the whole thing. Too much humidity, too much ambient air, etc, and the whole thing is ruined. A professional will have the skills and tools to connect it without contamination or to pump it down and recharge it if they suspect something may have leaked. Definitely mount the compressor, mount the head, run the lines, etc yourself. Just leave the system sealed and let a pro make the connections.

The systems are almost foolproof to install. Little or no danger of escaping gas. Only tool not found in most toolboxes is a 3'" hole saw. Be sure to get a tungsten carbide tipped one.

[brucetaylor]

I currently use a portable unit. It works pretty well until ambient gets over 95F, then it’s not very effective. It is reasonably quiet. It takes up precious floor space. I have one of the split units at work, it works great and requires no ducting. I’m going to get a split unit installed before the weather heats up next year. Whatever you do, don’t get a unit that is marginally adequate for your space, it will disappoint you.

[Tin Can]

Agree!

DIY

The systems are almost foolproof to install. Little or no danger of escaping gas. Only tool not found in most toolboxes is a 3'" hole saw. Be sure to get a tungsten carbide tipped one.

[brass.duet]

I built my 7'x10' darkroom in 2018 and acquired a Honeywell AC portable unit that is rated at 500 ft^2 and 229 CFM. Before I got this cooler, I had designed my ventilation to maintain a positive pressure in the room to avoid particulate ingress. At the max filtered air supply rate, with the AC on low, the balance skews to the "I can't keep up!", with the AC drawing more air out of the room than can be supplied (exhaust fan being off). As a compromise, I cool the room when I am not "dark", as needed. Additionally, it also disturbs the air flow pattern for sink exhaust to function correctly. Based on my experience, I think the standalone portables are not optimal for a darkroom.
Julie

[neil poulsen]

This all relates to a project that I'm just beginning. Please bear with me a bit, it's a little long winded.

Decades ago, probably the mid to late 90's, I purchased a "Photo Therm" device at a swap meet, thinking that I could use it for a temperature controlled water bath. It's been in a cabinet ever since. Last week, it occurred to me how I might use this device to control the temperature in my darkroom. (Keep it warm enough, without going overboard.) So I pulled it out, and turns out, that is likely it's original purpose. (I think?)

It's shown in the center of the photo. Just to the right of the device is a shiny metal thermocouple that detects temperature, and on the right side of the box itself, you can just barely see evidence of an AC (alternating current) receptacle . Look closely, and you'll see from the printing that it's wired for 500 watts. To test this unit, I plugged a lamp into to the receptacle, and heating the thermocouple above a threshold turned off the lamp. Letting the thermocouple cool below the threshold turned the lamp back on again. As you might assume, the dial in the center adjusts the level of this temperature threshold.

I heat my small darkroom with a small, ceramic heater. It works really well, except that the built in thermostat does a lousy job properly controlling the temperature at the interior of the room. My thought was to plug my heater into the Photo Therm's 500 watt receptacle, and place the thermocouple near my developer (?), but also towards the center of the darkroom. This will all work well, except that a 500 watt receptacle won't power my 1600 watt heater. So I will splice in a 2500 watt relay between the heater and the Photo Therm receptacle to provide the necessary wattage to the heater. (The relay is just to the left of the Photo Therm in the photo.)

The relay's function is to kick in the needed wattage to the heater, when it receives power from the Photo Therm. (The wattage needed to trigger the heater through the relay is far less than the 500 watts provided by the Photo Therm.) Working all this out, I was delighted when I noticed that the relay could also be wired in an alternative fashion. That is, it can be wired so that the relay turns on when the temperature increases above the threshold, and it will turn off the relay when the temperature falls below the threshold. (This is just the opposite of how the Photo Therm functions on it's own.) So through the relay, and with this alternative wiring, my Photo Therm unit can be used to cool the room by connecting an air conditioning unit to the relay. In fact, I can wire the relay to connect to both an air conditioning unit and a heater at the same time, so that it would turn on the air conditioning when it gets too warm, and turn on the heater when it gets too cool. While possible, I don't think that it would be practical to do this. Better to have only the heater turned on, or only the air conditioner turned on, but not both at the same time.

I will wire the relay in a project box that will have two receptacles in it and two plugs on two lengths of cords that extend from the box. One of the two plugs will go to the 500 watt Photo Therm receptacle, and the other will plug into an AC wall receptacle in the darkroom. As for the two receptacles installed in the project box, the air conditioner can plug into one of them, and my ceramic heater will plug into the other. (Of course, it matters which is plugged into which.) The Photo Therm will need it's own power source, so it will be plugged into it's own wall receptacle that's nearer to my developer.

One can see how this project of mine relates to the current thread. So, I thought that I would give this "brief" account of how it can all come together. The Photo Therm device is nothing but a portable thermostat; I'm wondering if something like this might be available on the internet?

When I get this all put together, I will post it with detail in the DIY forum on this site.

[Tin Can]

Neil,

I like hacks but always worry about old electrical devices, especially when daisy chaining high current

It is good the control device is in a metal can and has a grounding plug

Make sure the rest of the parts are also and well away from any water

There must be a better way

[CarolClark]

I also had many headaches with my old cooling system from my house at the beginning of June. I've tried many times to solve this problem with my own hands but with no choice. It was impossible to stay in the house during the day, especially if you live in Houston. Anyway, I've found some good experts from https://www.majorcooling.com/ that solved the problem in a few hours. I was delighted when I see that my cooling system is working and I don't have to be worried. Always is better to call experts to help you than trying solving all on your own.