hello all I am demoing a 150 amp AHU with electric heat everything is on same 150 amp circuit. This unit is existing and is in an attic. I am installing two new AHus which are smaller and they are part of a VRV system. These two new units will have electric heat packs per unit at 30 A apiece. The AHUMOP will be 15A per. My question is could I get rid of the existing 200 amp disconnect and do taps off the existing feeder?. Everything is within maybe 5 foot. I will be installing disconnects for the AHUs but contractor has yet to show me how their electric heat will be installed. I would install a load center in the ceiling, but the ceiling gets up to 120° maybe even more and I do not want to have nuisance tripping. Would it be feasible to do this?
Tap question for new ceiling mount AHUs
- Thread starter Cursitti
- Start date
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
You would need to meet the tap rules of 240.21(B).
Also, do not forget to account for 250.122(G).
Also, do not forget to account for 250.122(G).
So it would be safe to say I can use a 30 amp fuse able disco for all these. And use 10Awg with a #6 equipment ground to each disco and unit? Im sometimes unsure about tap requirements. Even though this is not getting inspected I want to do my due diligence. Thank you for the reply
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Seems fusible disconnects would have similar risk of nuisance tripping to me.
Another thought though, if the bulk of the load is for heating, attic shouldn't be at such a high temp when heating demand is there and that likely reduces that nuisance tripping risk?
Technically you’re right on that. But I’ve just recently taken out 70 year-old fusible starters out of another attic and they have not had any problems since 1956. Of course, I will label all the equipment fans in the ceiling below at the ductwork of the supply side. But there’s also another electrical contractor that is on site and will do anything to make a dime. I would just hate for him to come in there and overload a panel and then I get blamed for it. He’s ripped work out of my hands twice now.
Yes I will use #10 for everything thank you