Double check load calc math

[Hcooperrn]

Hi everybody, background user here, hoping to borrow some of the collective wisdom though.

I'll probably reach out to an electrician at some point, however, I really want to have as good an understanding as a layman can have. Not a stranger to electrical -- my dad and grandfather were both lineman, and I've done a full basement successfully.

Here's my story -- I'm worried I'm getting close to the max on my 200amp service. I live outside Dallas, and here are the specs I've plugged into a couple of load calc spreadsheets: 3200sq ft, 3 small appliance circuits, 1 laundry circuit, 1-5.4kw dryer, 1-5.1kw oven, 1-7.1kw range, 2-4 ton ACs, 2-2.4kw central furnace, dishwasher, 2-refrigerator, 1-1.58kw microwave, 1 range hood, 5 vent fans, 1 disposal, 1 garage door opener, 1 Xmas light circuit, 1 exterior light circuit.

What I'm hoping to add -- 1-50amp RV hookup, 1-60amp hot tub (negotiable), 1-20amp swimming pool filter (above ground, only pulls ~400w), 1-30amp shed/workshop circuit.

Depending on the calculator spreadsheet, it looks like I'm coming out to somewhere around 213 amps if I add 9600w in as an appliance load for the RV hookup and 2 small appliance circuits for the shed and pool (I'm guessing that's not the right way to do it?).

Am I in the ballpark? Or do I need to up my service if I add all that? I've confirmed with the POCO that I can move up to 400amp if I swap the meter, just don't want to go through all that if it's overkill.

What do you think?

 

[RegeSullivan]

I have a lot of practical experience with residential electric but I am not an expert so take this for what it is worth... Even if you turned everything on at the same time it is unlikely you would max out 200 amp service. Keep in mind most circuits are designed to generally not exceed 80% and it is unlikely you will have every possible circuit at full (80%capacity) at any one time. Your two biggest amp draws listed are the 50 amp RV outlet and the 60 amp spa. While the spa might run close to capacity the RV is unlikely to use even half the capacity at any one time. Two future items that could require upgrading to 400 amp upgrade are electric on demand water heaters and fast charger(s) for electric cars. These are items that tend to be very high draw and be in use at times when other high draw items are in use. (Think along the lines of coming home from work, plug in the electric car or two, start dinner, take a hot shower, with both A/C units cooling house down on a summer day - could easily be 48 kw or 200ish amps on each leg of your service.)

I would not be concerned but if I were, I would add the circuits and monitor the main panel with some sort of watt minder type device. Those things are becoming cheaper all the time. Or, better yet... stress test it, turn most everything on while monitoring the panel with a couple of clamp on meters turning on more items until you are maxed out. I'd be surprised if you got anywhere close to 160 amps on either leg unless you needed to balance the load better which is a pretty easy thing to do.

 

[alfredeneuman]

You won't use the AC and heat at the same time

 

[RegeSullivan]

You won't use the AC and heat at the same time

I thought about mentioning that but I am not familiar with his HVAC system or the winter temperatures in Dallas. I know some HVAC systems with heat pumps supplement with resistive heating when the heat pump cant keep up. I could be wrong but I assume heat mode or cool mode the compressors energy use will be about the same.

 

[Hcooperrn]

Thanks for the replies and thoughts, keep them coming!

Furnaces are gas, I guess I was assuming that was the blower rating? They are big Trane units. To my knowledge, I've never heard the outside compressor running when the furnace does. In the summer, its not uncommon for both ACs to run 80% of the day.

Good call on the water heaters -- I have 2 gas currently, and was anticipating changing one of them to a tankless; however, I guess I was assuming that it would be gas as well (easy to vent, it's in the attic). The cost difference to upgrade electric vs keep gas will be a factor at some point I guess.

I've had my eye on a Tesla for a while as well, not in the immediate future though.

I can definitely take another look at the circuits to make sure they are balanced -- right now, the two external lighting circuits are on the same side, putting them opposite of each other would make more sense, right? Since they are usually on at the same time? That's the idea behind balancing, trying to find things that likely cancel the neutral load, right?

 

[RegeSullivan]

Thanks for the replies and thoughts, keep them coming!

I can definitely take another look at the circuits to make sure they are balanced -- right now, the two external lighting circuits are on the same side, putting them opposite of each other would make more sense, right? Since they are usually on at the same time? That's the idea behind balancing, trying to find things that likely cancel the neutral load, right?

I wouldn't change anything unless you know of or have evidence of a problem. On every panel I've seen in the USA the bus bars are stacked so every other breaker is on the same leg. If the two circuits are one on top of they other they are on different legs. As evidence of this look at your 240 breakers. They should have handle ties and so are situated one on top of the other.

 

[Hcooperrn]

Got it, makes sense.

If I stick with 200, I was planning on moving up to a 40 spot panel. It's getting pretty crowded (almost every 120 would be a double to make room for the new 240 breakers), and nothing is on an AFCI yet (2002 build, and no building dept jurisdication where I live).

I guess worst-case, I'm not going to burn down the house (as long as I do the new circuits correctly), I would just start getting nuisance trips at the highest demand, telling me I need to upgrade?

 

[sberry]

I am sure it has happened and other guys seen it but I have never came across an overloaded residential 200 and I been at this a while.
Really the only one was in a bar on hot August etc and they had 2x, maybe more the connected equipment even if you add a tub and a car. 5 50A fryers , AC, the rest of the place, 2 coolers, couple micro, lights, coffee,,, wayyyyyyy more than any house could ever put on.

 

[ard]

Hmmm. You are going to pay an electrician to upgrade your main panel?

That might change my calculus on upgrading to a 320.

Not saying you NEED it, but the added cost is likely low(er)

 

[Hcooperrn]

Thanks sberry, I'm getting more confident based on all of this input. When we were looking at homes here, only a few in our size range had 400a service already, and they had two 5ton ACs, inground pools, hot tub, the works.

And no, if just upgrading the main panel, that I can handle -- have it all staged and ready, label all the lines ahead of time, call the POCO for a temporary disconnect, and replace.

 

[RegeSullivan]

You can add a subpanel. Its likely less than changing out the old one if you have room for one.

 

[Hcooperrn]

That's a good thought. If I add a 125a subpanel, that would run all the new circuits plus the AFCIs I want to add (6 total for all of the plugs in the house).

I was thinking that the new circuits would be another subpanel, just because I need to get them all the way to the other side of the house (~90') and I can use aluminum for that run. That seems to make more sense than running individual lines for the RV, shed, and pool circuits all the way through the attic and then outisde. For that run in the attic, if I were to follow rules and derate for bundled and high attic temps, I need 1-1-1-3 aluminum I think?

I guess I need to price out the options...

 

[sberry]

Another panel really relieves congestion. It also lowers V drop on long runs. Can save a lot of labor in some cases, a once and done deal too. My preference if I can make it work is number 2 with only 1 major appliance and most of the time a 60.
In my own home, wouldn't have a problem with a couple if it was practical. In my shop the distance is enough it was easier and cheaper and let it be tapped for welder. ! got 5 additional. If I detail planned could have reduced 1 elbow and a couple more things I plumbed in the floor could have been done internal just as well. Its irrelevant in the end but cable is a little easier. Nothing is as good as local breakers.

 

[sberry]

I got 400. I could do it all 2 and I got a lot of ****. Maybe 75A automatic loads, air comp, cooler, well plus a couple fridge and freezers. Additional is like welding, mostly 1 machine at a time, 20 to 40A very intermittent. 24 intermit pressure wash. The object is to have what you need not to see how much you can use. If you ever want aux power its a lot simpler. I done it all but the cooler on 100, not all that much sure I wouldn't trip up a 100, only a 15K ****** on the pole. Having 2 panels un congested a lot of stuff. I had one with feed thru, I hooked a 100 to the lugs for my Synchro but its so rare I use I that its irrelevant.

 

[sberry]

I plumbed it so fast that could have saved a few fittings and made a couple straight runs thru the walls. Shops are a bit different due to door heights, ceilings too, making hi long runs cost, going over doors is a problem so floor pour is a big saver.

 

[sberry]

Most panels are 100. They make some in 125, I think the major brand is a MLO in that size. The biggest 100 is 24 spaces. I think they use 3 boxes, maybe 4. Maybe 5 if you consider 150. But,,, 100 is so common, fits 1/0 I believe. The neighbor brought some wire to his barn, 1/0 but had planned on 2 and had to change a breaker and some lugs in **** way too small for it. They make 6 space and 8 in the same box designed for additional work in the same structure and now it seems one of them added a 12to the line or stocks it in the store. Box store doesn't always carry every model in the lineup.

 

[sberry]

With all the larger conductors need to get a ground bar adapter for larger wires. The load calc of this is the most interesting part. A neat option would be a set of meters, hook it to the phone to read the demand.
What would make some sense in the grand scheme and make use so much cheaper is to use off peak, I think they figured out that the credit went away for demand killers they don't even bother anymore. If they gave off peak rates investment could pay back fast compared to long term solar/wind.

 

[Hcooperrn]

Appreciate all the advice, I'll do some more homework, make some more space, and go from there, thanks!

 

[RegeSullivan]

That's a good thought. If I add a 125a subpanel, that would run all the new circuits plus the AFCIs I want to add (6 total for all of the plugs in the house).

I was thinking that the new circuits would be another subpanel, just because I need to get them all the way to the other side of the house (~90') and I can use aluminum for that run. That seems to make more sense than running individual lines for the RV, shed, and pool circuits all the way through the attic and then outisde. For that run in the attic, if I were to follow rules and derate for bundled and high attic temps, I need 1-1-1-3 aluminum I think?

I guess I need to price out the options...

With all your new circuits being on the other side of the house it only makes sense to set up a subpanel there or as close as is reasonable to where they will be used. It should reduce the cost of wire overall and give you room for lots of expansion.

Something to consider, the cost of a 125 amp subpanel vs a 200 amp 40 slot main isn't much when you consider most come with the 200 amp main breaker and usually a handful of 15 and 20 amp circuit breakers. You can use the 200 amp main breaker as a disconnect because the overcurrent protection is provided by the breaker in the main panel. To make a main panel a sub remove the bond between the neutral and ground (EGC). A 40 slot panel gives you a lot of room to add all those high draw electric fast chargers and what ever else you add when you upgrade the house to 400 amp service.

 

[Hcooperrn]

Thanks for all the advice, going through my current circuits now to come up with the most economical plan.

Pretty sure I want to run a 100amp subpanel across the house though -- this would have the 60amp hot tub, 50amp RV, pool filter, and shed circuits coming out of it.

I'll need to go up and across the attic, dropping out the eaves, to an exterior subpanel. I've seen the attic get as hot as 135* in the summer. Total run will be somewhere close to 100'.

Knowing I need to derate for the attic heat, can I still get away with 1-1-1-3 aluminum, or should I step up to 1/0 or 2/0?