I'm in process of setting up a tropic fish hatchery in my garage. Totaling up the Loads I'll have with various heaters, pumps etc., and it looks like I'm headed for some issues with my current 20A service. Currently have SIX 20A GFCIs in parallel, pig-tailed from two junction boxes above my garage, all with 12/2. I installed that circuit last year.

If everything happens to be on, which there's a good chance of that in colder months with all the aquarium heaters cycling on, then my two existing 20A duplex GFCIs will be drawing a combined 30A, with one of the GFCIs alone hitting 24A (over its 20A rating). So something's going to trip - plug strips, GFCIs, or the Breaker. Not to mention should I fire up my 3.5HP router or chop saw on the other outlets at some point for a project.

Thought about running a new stand-alone 10/2 30A service to power the two 15A Tripp-Lite strips, but then that seems like a new beast, with new 30A receptacles, and then converting the Tripp-Lite plugs to 30A plugs, which seems sketchy and far from Code.

SO, what to do? Do I have an issue, or am reading this wrong? Do I run TWO NEW stand-alone 20A circuits from the Service Box; one for each of the Tripp-Lite plug strips, dividing up that 24A load, and call it good? Or is the 30A circuit a better way? Whatever the is the correct/best way is what I'm down for. Aquarium stores run 75 to 100 heaters, granted they are lower wattages (75W ea) since they have ambient room temperature to help maintain water temps.

Drawing attached of my existing electrical and planned potential Loads. I'm getting 119-120V at my outlets, as measured.

 

Welcome to the forums! You only need one GFCI receptacle per circuit to protect itself and others downstream. Having more than one will cause nuisance trips. WHat you need to do is run a dedicated 60 amp circuit from your house panel to a sub panel in the garage where there is also a 60 amp main breaker with several breakers that can control several circuits. You can't run 15 amp circuitry on a 30 amp protected circuit. THe wiring will burn up before the OCPD trips.

 

Each 20A circuit should have no more than 1920W of heaters connected continuously. If you need more heaters than that, then you need more circuits.

General-purpose circuits should not have breakers larger than 20A.

If this is an attached garage, the correct procedure would be to run new circuits from your service panel, or perhaps feed a new subpanel in the garage from the service panel. If this is a detached garage, then you will need to run a new feeder underground or overhead from the main building with larger wires to support the additional loads.

 

Yes, this is an attached garage. House panel is on the outside of the garage wall. Seems like running two new dedicated 20A circuits; one for each plug strip with heaters, is the simplest way. And not exceeding the 1920W for each circuit. Thanks

 

House panel is on outside of attached garage, so it's easy to run new circuits. For my existing 20A service to my garage outlets, I had put GFCIs at the end of each parallel run from a junction box so if one outlet trips, I don't loose power at any other. Is that acceptable, or did I make a newbie mistake with that train of thought? Seemed cheaper than running 12/2 up and down the walls, doing all the outlets in series, with one upstream GFCI.

 

I did something like that for a customer. Every receptacle was a GFI type as the customer didn't want everything on the one circuit to be shut off in case of a trip. The line side of the receptacles are tied together and the load sides are unused.

 

Correct, I left Load sides unused, with the factory warning label tape still over the connectors. I was hoping my thought process was ok on that application. Possible wet environment near a lot of my garage receptacles, with various fish hatchery and water filtration units.

 

All garage 120 volt 15 and 20 amp receptacles are required to be GFCI protected anyway regardless of any wet environment.

 

Good to know. Learn something new with every wiring project I post here. Thanks.

 

So, I'm going the route of two new 20A circuits to achieve adequate power for the aquarium heater load, but don't want to eat up more space in my home panel than needed.

Do I go with a tandem 20A single-pole, or two separate standard 20A single-pole breakers? Is the tandem truly two independent 20A legs on the same pole, or will tripping one trip both legs? The goal here is to at least keep power to one plug strip of heaters, even if something faults and I lose power on the other plug strip of heaters.

 

Yes they are separate. There is no common trip. Maybe I missed the answer but to verify this is an attached garage isn't it?

 

Tandems provide two independent circuits. Not all panels allow tandem breakers, and some allow them only in certain slots -- check the panel label for approved breaker types. A hint is to look at the number of allowed circuits vs. the number of slots. If circuits is larger than slots, then some tandems are allowed.

 

Yes, attached garage with house panel on exterior garage wall.

 

Currently, I believe I only have the one tandem 20A in there, with 3 tandem 15A for house lights and outlets, with 4 slots remaining open. But I'll check the panel and make sure what I've installed to date matches my panel requirements (and fix if not).