Small AC plus Small Dehumidifier on 15A

Can I run a 5-8000 BTU window AC which normally operates at less than 600watts plus a 35 pint per day humidifier than normally operated at less than 400watts. The constant draw when both are running should be around 8-9 amps. But can the circuit handle both compressors? If hot and humid and both compressors kick on at the same time, will it trip the breaker???

They might trip the breaker if they come on at the same time, check the start up amps of each one.

Rurumo said:

They might trip the breaker if they come on at the same time, check the start up amps of each one.

Click to expand...

50-70 pint DH’s usually say 6.7-7.8 amps on the label even though they only pull about half of that long term. They can pull 33 amps at startup. Not sure how to find start up amperage for an individual model, but I’m assuming EACH will be over 15 amps by itself. But the start up current doesn’t last long, does it? If a 70 pint DH doesn’t trip the circuit pulling 33 amps for a few seconds, what will trip the circuit??

GlueSniffer said:

50-70 pint DH’s usually say 6.7-7.8 amps on the label even though they only pull about half of that long term. They can pull 33 amps at startup. Not sure how to find start up amperage for an individual model, but I’m assuming EACH will be over 15 amps by itself. But the start up current doesn’t last long, does it? If a 70 pint DH doesn’t trip the circuit pulling 33 amps for a few seconds, what will trip the circuit??

Click to expand...

I had a similar conundrum recently and managed to find the startup amps for each, either in the manual or just searching online. Neither was more than 15 amps. Worst case scenario you just need to stagger their starts somehow.

A 15 amp DEDICATED circuit on a 110 volt system would allow 1650 watts. For safety sake it's a good idea not to exceed 80 % of capacity and to check connections for excessive heat etc.

Rurumo said:

I had a similar conundrum recently and managed to find the startup amps for each, either in the manual or just searching online. Neither was more than 15 amps. Worst case scenario you just need to stagger their starts somehow.

Click to expand...

I was hoping to have both set to a desired temp and humidity and leave it automated. I’m trying to design a grow room using only two 15 amp circuits. I have one circuit loaded up to 1200 watts (lights and fans) with intermittent power up to 1350 watts (other fans, humidifiers, ... stuff that only runs for a minute or two at a time). That circuit is ok, afaik, but that only leaves one circuit for the window AC and the dehumidifier.
I will look for more specs online and try to find options that work best. I’m thinking about trying to set up (2) 2x4 tents (one for mother/clone and one for veg) and a 4x4 flower tent. Want to put all 3 tents inside a 8x8 tent. 8x8 will have Window unit AC, dehumidifier, scrubber with carbon filter, and three oscillating fans. Each tent will have a light, an exhaust fan, a small humidifier, and clip on pole fans. Want to keep the 8x8 at 65-70 degrees and 45-50% humidity and will use humidifiers and exhaust fans to keep each tent below 85 degrees and in an acceptable RH range.

Rob Roy said:

A 15 amp DEDICATED circuit on a 110 volt system would allow 1650 watts. For safety sake it's a good idea not to exceed 80 % of capacity and to check connections for excessive heat etc.



View attachment 4733164

Click to expand...

I understand that. My question is about whether or not small appliances with compressors really do need a dedicated circuit for each compressor and what it takes to trip a circuit breaker. How long the start up current lasts? And how long can a 15 amp circuit exceed 15 amps before it trips?

Will the tag on the back of the unit give the start up current? “Rated Current” on my 50 pint says 7.8 Amps which is about 1000 watts. However I think it operates at less than 500 watts most of the time.

From what I remember about circuit breakers, they operate using thermal overload protection that will interrupt the circuit when it has a continuous load exceeding the current rating of the breaker. They also incorporate a magnetic interrupter that reacts instantly to large overloads(short circuits).
The challenge is using a breaker that has a high enough magnetic trip to allow the momentary current draw during startup.

TBH the only way you will know if it will work is to try it. Worst case, you trip a breaker, no biggie. If both compressors kick on at the same time you will know pretty quick if the circuit can hold the load.

Im dumb. I just realized that if I split the other loads (lighs, fans,...) between the two circuits, I can put about 750 watts and a DeHu on one circuit and the other 750 watts and the AC on the other circuit. I think the breaker (and wires) would like it better if I was pulling 750watts and then had ONE compressor kick on. Compared to pulling 50-100watts (fans only) and then having two compressors kick on at the same time.

I just discovered time vs current trip characteristic curves for breakers. The one I looked at had me believing I could run 75 amps through a 15 amp breaker for about 10 seconds before it trips. 135 amps might trip after 1 second. 150 amps might cause a delay, then trip. 300 amps might trip right away. Not sure if this is even reasonable, but seems to be - at least on an order of magnitude. I'm still researching starting current, but it sent me down a rabbit hole of hvac stuff. kVA/HP, NEC code letters, FLA, RLA, LRA, MOC, MCC, NUGZ,....

GlueSniffer said:

I just discovered time vs current trip characteristic curves for breakers.

Click to expand...

Temperature can really effect these curves on most residential breakers. If your panel is in a really hot garage then breakers trip much easier under startup draw.