venting a dehumidifier

[oldjarhead100]

apparently I'm not the only one who is trying to figure this out lol I did that too Potted I have both now DH and AC and still it gives me issues

[Toripony]

Been going round and round on this subject... my main problem is humidity being in the PacNW and my 168 cu. ft. room is in my 800 sq. ft. (8800 cu ft.!) garage; temperature is borderline issue. So, after a few circles I settled for the DH in the grow room... adds heat but keeps the RH a couple of % lower than if I tried to DH the whole garage. Gradually the garage RH lowers as my DH air from the grow room is vented into the garage. The heat is also vented into garage so the whole place heats up slowly as the day goes on (starts out at 65 or so each morning). Had decided against a portable A/C due to cost and the fact that I already have cool air (in the garage) if I could just circulate it at the right volume. Without raising the RH. Right. Could vent the grow room out the window (25ft. away; need ducting and bigger exhaust fans) to get rid of the heat and there goes all of my RH conditioned air out the window. AND, adding the bigger fan then I need bigger A/C and DH! Someone said (@Hycheese?) portable A/C was very inefficient, so I thought about a window unit... $50 on Craigslist... but not for me... no, I need 18K BTU for the whole garage running at 10 amps, just to cool my 168 cu. ft. box. Wayyy expensive and wasteful. Mount the window A/C in the grow room wall?... now it's heating up the garage, the source of my intake air.
How to balance the A/C, the DH, and the ventilation flow for a small box inside a big room?!?!? Wish there is a magic formula to figure all this out. Lacking one, I gave up... keep the DH unit set higher than I wish... it reduces the RH some without adding too much heat... it's a constant balancing act requiring me to change settings every day depending on the weather outdoors. I think the portable A/C located in the box is probably my best hope but I can't justify $200-400 when I only need it for maybe 6 weeks a year whereas I need DH reduction 10+ months. Yea, I know most portable A/C does both functions but is not as practical at DH as a dedicated DH unit. Arrrrgh!

[DrPhoton]

Ah yes i know exactly what you mean. I have a friend who is a machatronics engineer who is in the same field. I was looking into getring into control engineering myself, but never ended up there.

[Potted]

U opened up a big can of worms OJH I just said f#@k it and got a portable ac unit

[Flockshot]

Run the dehumidifier outside the grow area and let the ventilation bring in the lower humidity air. Running the dehumidifier inside the grow area, and immediately pumping it out, is an expensive way to accomplish your goal

[hycheese]

40 years in industrial automation, all certs in refrigeration including large-scale ammonia R717 systems. My expertise is in PLC programming and instrumentation. I retired to a 3 hour/day part time job a few years ago because my brain was drying out.

[DrPhoton]

Good post, have you worked in the air conditioning field ?

[hycheese]

Chances are that the new 50 pint DH you bought has dual stacked coils and a single fan - the moist air is sucked through the cooler evaporator coil then immediately pulled through the warm condenser coil then the dehumidified warmer air is exhausted back into the room. Older units had separated coils and 2 individual fans and may have been possible to vent but even then the DH would slowly lower your room temperatures below what is needed or comfortable.

Recently I just pulled apart a 5000 btu window AC to see what was needed to split the coils to make a remote DH kinda like a mini-split heat pump. Even though I have all the equipment and HVAC tools to do it I decided to buy a second 30-pint dehumidifier for $100 instead.

One option you may have since it seems like you have quite a bit of ductwork is to make a bypass damper that can vent some of the DH to the outside and some of it to the inside. Basically, a wye connector pipe with a damper installed in the exhaust leg, when 100% open it should give a 50/50 blend and when closed it should send 100% back into the room. those dampers are common and cheap too. you could also try to force-feed the DH exhaust directly into the AC or as close to it as reasonable.

In the business, those dampers/vents are called enthalpy economizers which automatically adjusts the venting based on inside/outside conditions via remote sensors.

[DrPhoton]

No it doesnt need the hot air, it is a byproduct of the conditioning system required to create a cold radiator and condense moisture in the air. You may vent the heat if you wish.

[oldjarhead100]

I know the theory behind a DH but in a grow room scenario if you vent the hot air out of the room will it still dehumidify the room enough , or does it need that hot air in the room to work properly