Outdoor disconnect for multiple mini splits
After doing the manual J, it’s pointing to having four individual single zone mini splits for our 1.5 story cape in CT (front runners are two Mitsubishi FH06’s for the 2 upstairs bedrooms and two FH12’s downstairs for the kitchen and living room) to get the low BTU modulating for the bedrooms. For aesthetics, I’m thinking of having the four outdoor units wall mounted in a row on one end of the house, away from the prevailing wind.
The FH06/09/12’s require 230V 15 amp circuits, and installation manual states “1-3-1, Power should be taken from an exclusive branched circuit”, so I’m looking at replacing my load center with a larger one with 8 open slots, or adding another sub panel, then running 14g wire to the disconnect.
Simplest solution seems to use an outdoor load center enclosure, and then it can do double duty as a sub panel and disconnect. It’s not best practice to use breakers as switches, but they should rarely be switched.
Any reason not to?
(ex: Siemens W0816ML1125CU – https://w3.usa.siemens.com/powerdistribution/us/en/speedfax-product-catalog/Documents/2017/SF-17-Sect-01-ALL-web.pdf)
Thanks.
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Replies
Generally I only see outdoor load centers in desert location. The one I deled with did not seem like it was designed to handle water.
Walta
Circuit breakers can be used as service disconnects are are used this way all the time. I have actually designed systems at work where the circuit breaker is intended to be used as a switch and not an over current protection device (OCPD) and is marked as such (I have to put a sticker on it) which allows me to use a lower interrupting rated breaker since it’s not expected to actually interrupt an overload condition.
If you have several outdoor units grouped closely together, what I would do is to install a small subpanel near the units and run one feeder to the subpanel from your main panel. The subpanel would then feed appropriately sized feeders to each of the units you need to serve. If you have two 15A units to feed, I’d feed the subpanel with a 30A circuit (10 gauge wire), and then put two 15A breakers in the subpanel. Make sure to label them to do it right. Siemens makes a nice little 3R (raintight) rated 4 space subpanel that would be perfect for this. I’ve used it before for small greenhouses.
Remember that your subpanel needs separate neutral and ground busbars, so you might need to get an optional ground bar kit. If your outdoor units need 240V power ONLY (no neutral), then you don’t need to run a neutral to the subpanel at all. Even though it may not be required, it’s nice to have a convenience outlet near the outdoor equipment to run tools. If you have a neutral in your subpanel, you can tap the outlet off of that using a separate single pole breaker. With only two units to serve, you can’t use demand factors to reduce the supply to the subpanel so it has to be sized for the total current of both units running.
Bill
Walter - Thanks for your reply. Our outdoor meter is in a Nema Type 3R rated box, which seems to be what most of my neighbors have too. It's been raining nearly every day here, too... I'd be happier with Type 4, though, but according to NEMA, seems like 3R would be adequate:
NEMA 250-2003: Type 3 Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); and that will be undamaged by the external formation of ice on the enclosure.
Zephyr7 - Thank you. That make a lot of sense. I'll check it out. Cheap enough to include a neutral 10g cable to the sub panel, and nice to have an extra outlet (perfect for the Christmas lights!).
The outdoor units require 11A min circuit ampacity, and I believe I'd feed the indoor unit from here too (1A), so 24A for both... I'd probably do a 50A sub panel to have extra capacity for extra circuits...
Thanks for the help!