206danebmx
New User
- Location
- Seattle, WA
- Occupation
- Engineer
I am trying to evaluate whether we can add a hot tub to our existing split bus panel without having to change the breaker box, service lines etc. There is physical space in the panel for it but that doesn't give me the warm and fuzzy. It seems to be a 125 amp rated panel based on the markings on the inside of the panel and from what I can tell has 4 AWG service lines. There is no discernible marking but they appear to be the same size as the lower bus 60 amp 120V "main" wires which are labelled as 4 AWG TW.
I also have an electrician coming, but they are weeks out so trying to learn about this in the meantime while we source a hot tub.
I filled out the Residential load calc excel sheet and am getting this for our current house as is and also with the hot tub added. Also, I wasn't sure if I am allowed to to use the optional service calcs as allowed by section 220.82? I did the calcs without checking the box.
https://photos.app.goo.gl/jVUubA4ihwUr45AX6 (Hopefully this link works) not sure how to embed photos into the post. Theres also some photos of our panel in there too.
A couple things I wasn't sure of:
-We have a gas stove but the oven portion uses electricity and its marked as 25 amps @ 240V, so I applied this as 6,000 watts in step 5, is that correct?
-Most hot tubs I have seen use 50 amp 240V breakers, so I imagine the spa will consume no more than 40 amps, why does it say 57 amps in the calc sheet? Furthermore, I thought that the 50 amp 240V circuit would draw about 20 amps from each of the two hots (so 40 total), and it appears to be calculating double that?
Forgive me if I am missing this completely but this is kind of how I saw this being calculated in my head:
The other day I turned on almost everything I could in the house, especially the big items like oven and dryer and measured all 3 main lines for the house with a clamp meter. I was getting a pretty balanced load on the two hots and the difference was roughly showing up on the neutral. I got around a total of 93 amps (adding the two hots together). Now if I look up the 4 AWG TW stranded it seems to be rated at 70 amps. So, theoretically couldn't I be pulling 70 and 70 amps from each the hots (equals 140 amps total) without having to upgrade the service lines? I suppose the panel box would need to be updated since it is only rated for 125A? Or does the panel rating mean each hot line can take 125 amps? It describes it as "125 amp mains" which makes me think it means more than one (plural).
My thought was if I had a 240V 40 amps (actual draw) hot tub plus the 93 I measured that is 133 amps, so somewhat close to the max rating of the panel of 125 amps. But the calc sheet also says I would need 1 AWG wire I believe, is that number in AWG units?
Appreciate any help! Trying to learn here.
I also have an electrician coming, but they are weeks out so trying to learn about this in the meantime while we source a hot tub.
I filled out the Residential load calc excel sheet and am getting this for our current house as is and also with the hot tub added. Also, I wasn't sure if I am allowed to to use the optional service calcs as allowed by section 220.82? I did the calcs without checking the box.
https://photos.app.goo.gl/jVUubA4ihwUr45AX6 (Hopefully this link works) not sure how to embed photos into the post. Theres also some photos of our panel in there too.
A couple things I wasn't sure of:
-We have a gas stove but the oven portion uses electricity and its marked as 25 amps @ 240V, so I applied this as 6,000 watts in step 5, is that correct?
-Most hot tubs I have seen use 50 amp 240V breakers, so I imagine the spa will consume no more than 40 amps, why does it say 57 amps in the calc sheet? Furthermore, I thought that the 50 amp 240V circuit would draw about 20 amps from each of the two hots (so 40 total), and it appears to be calculating double that?
Forgive me if I am missing this completely but this is kind of how I saw this being calculated in my head:
The other day I turned on almost everything I could in the house, especially the big items like oven and dryer and measured all 3 main lines for the house with a clamp meter. I was getting a pretty balanced load on the two hots and the difference was roughly showing up on the neutral. I got around a total of 93 amps (adding the two hots together). Now if I look up the 4 AWG TW stranded it seems to be rated at 70 amps. So, theoretically couldn't I be pulling 70 and 70 amps from each the hots (equals 140 amps total) without having to upgrade the service lines? I suppose the panel box would need to be updated since it is only rated for 125A? Or does the panel rating mean each hot line can take 125 amps? It describes it as "125 amp mains" which makes me think it means more than one (plural).
My thought was if I had a 240V 40 amps (actual draw) hot tub plus the 93 I measured that is 133 amps, so somewhat close to the max rating of the panel of 125 amps. But the calc sheet also says I would need 1 AWG wire I believe, is that number in AWG units?
Appreciate any help! Trying to learn here.
