Doing a job that is having an underground aquarium installed in the downstairs walkout basement. The home has a 400a service using the 2 mains to feed 2 - 200 amp panels. I've added a 100a sub-panel from one of the 200a. I was going to add another probably 60a panel off the 100a to mount outside where the pumps will be. I believe its ok to run a sub-panel off another sub-panel. I ran 1-1/4" PVC underground where the tank will be and stubbed it up on the inside wall near the 100a and outside where the 60a will be mounted. Later I can can pull in 6/3 NM w/grd from the 100a sub-panel to the 60a. Half the run would be in the PVC and half in the inside wall and ceiling. Wouldn't make sense to have to run the PVC all the way to the 100a feeder panel just to run THHN. I believe they use THHN on the inside of NM wire now anyway. Also, just as a pool doesn't use a GFI, for the pump (only the light) I shouldn't need a GFI breaker for the aquarium pumps. Anything wrong with all this?
The Golden Rule - "The man with the gold makes the rule"
If you look at the specs for NM-B cable, you will find that the wires inside are described as meeting the requirements for THHN insulated wires. But the ampacity of NM-B cable is always limited to the 60C value for the conductors.
This probably won't make a difference in your case, but if all of the terminations had 75C temp ratings, then your 6/3 NM-B would have an ampacity of 55A, but 3 #6 THHN conductors in conduit would have a permitted ampacity of 65A.
#96220 - 11/10/0504:08 PMRe: Aquarium tank install
I would like to add something to this thread as an aquarium hobbyist, if the pumps or other equiptment do not require gfi protection and it is not considered a pond by the AHJ, I would not want a nuisance trip on a gfi to turn off my filters and other equiptment in turn killing livestock that could cost a pretty penny.
#96221 - 11/10/0506:50 PMRe: Aquarium tank install
You can't run NM in the pvc underground as NM is not rated for wet locations. Even though it may be THHN inside the insulation. You can run a 6/3 UF cable. You also may have a problem with the AHJ as they may want an insulated ground depending on how he classifies your installation. If your pumps are outside and plug in they will need to be GFI. Depending on the install you might need to do some bonding. I'd like to see pictures of this when it's finished. Sounds like a fun project and maybe some good fishing .
#96222 - 11/10/0509:01 PMRe: Aquarium tank install
To address this pond that is being installed on the outside.
The use of NM cable installed in a raceway on the outside of the house is addressed by 334.12 and 225.4. In short NM cable can not be installed outside.
Under the 2005 cycle of the NEC there are two articles that will need to be looked at. 680 part V (Fountain. Fountains, ornamental pools, display pools, and reflection pools.) And 682 (Artificially Made Bodies of Water. Bodies of water that have been constructed or modified to fit some decorative…..)
Under the 2002 cycle 680 part V was used for the ornamental ponds that I installed in the area that I work in. I haven’t installed one under the 2005 cycle.
As to protecting the pump with GFCI, I would strongly recommend this. I have a Koi fish pond at home. I lost the first couple of fish due to a bad pump motor. The fish died due to electrocution. Should the GFCI trip the fish can live for a few days without the water circulating but they won’t make it long with current flowing through the water.
#96224 - 11/11/0511:49 AMRe: Aquarium tank install
You just touched on a big difference with pool pumps. They are part of the equipotential bonding grid. Aslo the code is chipping away at the pumps that are not required to be GFCI. All 1p cord and plug pumps get GFCI now. I would not be surprised if all of them were GFCI in 2008.
(I also read this to be like a koi pond, which is under 680 V IMHO.)