[ktulu]

Hey guys I am working on an addition to my home and was hoping to get some advice on the sub panel I plan on installing in the new garage.

The existing house is 200 amp service and about 3500sq/ft. I will be adding an additional 1800 and will include the following:
2 half baths
2 full baths
2 bedrooms
800 sq/ft garage/workshop which will have several power tools including compressor and several large power tools.
10-15(more if I go crazy(er)) Arcade video games(250-350 watts each)
12 ton HVAC(heat will be gas)

Obviously these all won't be used at the same time but it is imaginable that all the video games could be on at the same time and definitely the AC, while the compressor kicks in and several lights are on.

I had planned on running a 100amp sub from my existing 200 amp panel but I think I should go to a 125amp 24 pole sub? I have a square-d panel currently and will be getting the same(homeline?) for the sub. There will be about 36 feet of wire between the main and the sub. I plan on using 3AWG or perhaps aluminum but not sure what gauge is correct for either. Looking at the scarcely available 125amp breakers I am unsure what size they will accept. Any tips there? I am not an electrician(DC job experience only) but am very comfortable around it having grown up around a master electrician and helping him in my developing years.

Any advice will be graciously received. Hopefully I have given enough info to get a decent response, if not let me know so I can provide it.

Thanks,
T

[bhayne]

I would say that #3 is too small. Since you are going to connect a compressor and the box is 36' away (plus the connection to the compressor), I would oversize the feed to 2/0 copper.
This will reduce voltage drop when the compressor starts.

By code:
100A: #2 copper, 1/0 aluminum
125A: 1/0 copper, 3/0 aluminum

Also, going aluminum has corrosion and strength issues. I'd stick with copper unless your house is wired with aluminum.

[ktulu]

Thanks for the reply! I figured I needed to go a little larger on the wire. I will go with 2/0.

I am having problems finding 125amp square-d homeline breakers. Thinking about going to G/E. Any thoughts? I am also thinking about using a 200amp panel and just service it with 125. Lowe's has a good price on the 200AMP combo. $99. Comes with a few breakers and has the right amount of spaces that I am looking for. If I am running the wire from my outside main panel... under the slab and into the new addition will I need a disconnect inside the garage? I will have a 125amp breaker at the main panel but was unsure if code required a disconnect inside the addition. I am also thinking about moving the panel closer to the main.. say within 15 feet total wire length and just eat the additional cost of running my romex the 24 ft to the new location.

Any suggestions.

[bhayne]

You can go with a 200A panel as long but if you use a 2/0 copper service conductor, you must supply the new panel with a 2 pole, 125A breaker from the main panel.

[tkrussell]

Your going to be thrilled with this answer, but calculating up the proposed connected load, to size a service for the sq ft, and applicable loads per NEC Calc Example D(b) Optional Calculation for One Family Air Conditioning Larger than Heating, the calculated Service Rating is a minimum of 242 Amps.

This is assuming gas water heater, and range, and no hot tub or spa, or any other large electric appliance. If any of these are electric, the amps go up from 242.

Also, assumes the garage shop is hobby or one man workshop.

Really should look into having these calcs checked to be sure your 200 Amp service can handle the load. If the 12 Ton AC is a high efficiency unit, it needs to be very good at getting the load below 200 Amps.

The code for #2 Copper with THHN insulation is 125 Amps for a residential feeder. At the high cost for copper nowadays, the code can be friendly. Any wire larger for a 36 foot run is wasteful of dollars.

Or Aluminum #1/0 XHHW is fine, just treat the terminations with wire brush and anti-oxidant compound, and torque properly (see manufacturers instructions) for a widely used economical substitute to copper. Al is popular with larger feeder wire in many applications.

Stick with the Homeline, it is fine, may need to order the 125 Amp breaker from a electrical supply house. I am sure you can find one on the Net to buy.

A typical 12 TON AC unit needs a 100 Amp breaker alone, and #4 Copper, I would bring the AC feeder back the 40 feet to the Main Panel, this will eliminate more connections, and reduce any voltage drop issue and increase reliability.

The next typical size service is 400 Amps. Can actually consider feeding the existing 200 Amp panel, and feeding a fully rated new 200 Amp panel. Then you can use #2/0 Copper THHN or $4/0 Al cable to feed the new panel.

Hope this helps.

PS- Be sure each bedroom has an AC-DC interconnected smoke detector, and one in the common area of the basement to interconnect with all others in the home.

[Dr D]

ktulu must have made a typo when he said that a 12 Ton AC unit would be needed to cool his 1800 sq ft addition. My home is 1800 sq ft and my garage addition is 1200 sq ft and use a 4 ton and 3.5 ton heat pump respectively. I live in AZ which in the summertime is a bit cooler than the surface of the sun.

[ktulu]

...Service Rating is a minimum of 242 Amps.

:eek:

The code for #2 Copper with THHN insulation is 125 Amps

I have decided to run the sub at the front of the addition. This will be about 15-20 feet total length. If I use 2/0 will that be good for 200Amp if I need that much service or should I go with 3/0? Or should I use Al?

The next typical size service is 400 Amps. Can actually consider feeding the existing 200 Amp panel, and feeding a fully rated new 200 Amp panel.

Am I hearing correctly that I may be able to come off the meter and split out to the two separate 200Amp panels? I have one of those meter/main panel combos. How would I need to come off the meter(assuming that's what you mean).

PS- Be sure each bedroom has an AC-DC interconnected smoke detector...

Definitely! I plan on connecting to the existing network and to the Alarm panel with separate detectors.

ktulu must have made a typo when he said that a 12 Ton....

:p Yeh should have been 4 ton. 12 seer is probably what I was thinking.


Thank you both for your continued input!:o

[tkrussell]

OK A 4 ton unit is a lot less load, probably only 30 amps, added to the 67 amps for the remaining load, 200 Amp for the entire home of 5300 sq ft is fine, which I thought the 12 ton AC was for.

Two breakers splitting a main service was for a 400 Amp service, a meter with disconnect can have two smaller breakers,like two 200 Amp breakers, or lugs, whichever is needed, to feed two panels. Not for feeding two panels off a 200 AMp meter.

Install the 125 Amp subpanel using either #2 copper or #1/0 Al as a feeder. Install the 125 Amp feeder breaker in the Main 200 Amp Panel.

I would still bring the feeder for the 4 Ton AC back to the Main panel. This probably only is #10 or maybe # 8 cable for this AC unit.

Again to arrive at 67 amps for the connected load, other than the AC unit, I had assumed gas appliances and no hot tub. If any of this is different, be sure to have the service calculations done, just to be sure. A 5300 sq ft home is getting close to needing a 400 service, depending on the electric appliances there are.

Will the quarters from the video games help pay the electric bill? Only kidding. Happy gaming!

[ktulu]

Will the quarters from the video games help pay the electric bill?

:D While they aren't enough to pay for jack I still find people putting quarters in even though they are all set for free play! I guess its just habit to them! Its like finding money in the folds of the couch!

Well based on your estimating and the fact that there are actually 3 AC units of about 8.5 tons total and there is a hot tub and pool(5 pumps between the two) I am investigating the 320Amp service. I am waiting on a call back now. Assuming I go that route should I run 2/0 to the 200Amp sub panel(<20 ft away)? I have a Homeline 200Amp meter/panel combo. Is it possible to upgrade the meter portion of the panel and have the POCO install a 320Amp meter with double lugs and come over to the built-in panel with 1 feed and then route the other feed out of the panel to a 200Amp disconnect and then on to the sub-panel? Or am I looking at having to replace the whole panel?

T

[tkrussell]

Ewww, you have a meter/combo panel? Not possible to use this and have another meter upstream.

You are on the right track with a 320 Amp meter, having double load lugs to feed two panels. But can't refeed the combo panel with the old meter socket in line. If the meter can be broken away somehow and removed, then you can use the old panel.

#2/0 copper is fine for a 200 amp panel.

[ktulu]

Well poop!

So its not possible to upgrade the meter housing in the combo or is it that I can't some out of the main panel and then to a sub panel?

I don't mind replacing the whole thing. I haven't asked if that is something the City will let me do or not. I would be comfortable doing the work just hate dealing with the City!:)

[tkrussell]

No can't upgrade the 200 amp meter section of a combo meter/panel. This is a longshot,ay be able remove that meter guts and just refeed the panel, but I would need to see the unit. Most likely not, or may not be able to rework the unit due to UL listing.

If you are referring to the city allowing you to do you own work, most states allow single family homeowners to do their own electrical work, with a local permit. Local inspectors can be more difficult to deal with when homeowners do their own work, but for good reasons. They just want the installation to be done correctly.

[ktulu]

...ay be able remove that meter guts and just refeed the panel...

That is what I was hoping. I was reading that 320Amp meter sockets have the same connection as a 200A where a true 400A is different.

I assume by "seeing the unit" you mean the meter side? I could take a pic but obviously can't pull the meter to open that side.


BTW! You ROCK!:D

[ktulu]

Just talked to the POCO and they told me that I will need to run new 3" sch40 conduit to the raiser and it has to be 30" deep. They charge $30+$2.11 a ft for the pull and the connection. She said I have to have it inspected before they will connect it.

The only hard part is having to go under my driveway with the conduit. And once I bring the conduit to the existing panel I won't be able to go all the way up to the house until I can remove the existing conduit so I won't be able to get it inspected.:confused:

What is typically done in a situation like this? I can go without power for the day but going all night without it would suck! I can get a firm time when the inspector would be here but the POCO is a whole other game. It would seem I would need them to disconnect the power in the AM. Allow me to finish the run and upgrade the meter socket(assuming/hoping I can) and disconnect for my sub panel then have the inspector come and then the POCO pull the cable.

:cool:

[tkrussell]

As much prep work that can be done should be done. May take a couple of inspections , install the UG conduit up to the service first, then the service change itself.

The inspector should be able to inspect the conduit only, then schedule a day to actually change the service and connect to the new UG conduit.

Getting under the pavement can be done by directional boring, which can be expensive, or a backhoe can push a conduit under if the driveway is not too wide.

Make sense?

[ktulu]

Sure does! I really appreciate all the help. I am going to run 2/0 into the new addition. Purchase a 200Amp Main panel for the addition and run it in 2.5" PVC(is that enough or shoul dI go 3")? I will worry about the service upgrade after the addition is complete. Or at least in the dry.

Since I may need more wire to work with when I upgrade my service can I loop the feed going to the sub around the inside of the main panel. For instance coming up at the bottom and going to the left up and over the main feed and back down the right side and into the 125Amp breaker? I hope that made sense? That would give me 2ft or so to play with when I upgrade the main panel.

[tkrussell]

2 " PVC is fine for three #2/0 and one #4 for the equipment ground. Loop as much wire as you can for now in the panel, but be sure you have enough. This will be real tough to splice if not long enough later.

Plus you will need to splice # 2 wire onto the #2/0 at the main panel to get the wire into the terminal. Trimming the strands to fit into the terminals not really a good idea.

[ktulu]

Cool. So by looping as much as I can does that mean I can go all the way around a loop and a half say and still be OK. As long as I can get the faceplate on!:D

So if I can not upgrade my meter socket and Square-D doesn't seem to offer a larger panel in their homeline range should I go with QO? Or should I look at using GE or another panel? If so I should get that same brand for the sub I reckon. I have searched the net and Squared.com and cannot figure out if I can upgrade it. I found it on their site. It is a SC3040M200S Homeline ALL-IN-ONE RING TYPE OH/UG 200A SURFACE.
(http://ecatalog.squared.com/fulldeta...er=SC3040M200S)
They have it priced at $1300+:eek:

I had no idea!

Would be nice if I could just upgrade it but if I can't I want to make sure I go the best/most economical route. Quality being the higher priority.

[tkrussell]

OK I looked at the picture of your unit. Thoese are not popular in this area, very popular out west. I think it is worth asking the local inspector if you could gut the meter jaws, and bring in your new 200 Amp feeder onto the main lugs of the panel.

The round hole will need to be covered, here is the problem. Inspector will not let just any cover be used. He may not allow the unit to be modified due to UL restricitions, or any mods, like a cover, would need to be same metal thickness, and painted with same paint, (touch up paint is always available from the manuf.)

If you do get a new panel, stuck with Sq D Hom line, the quality is fine. Will be able to reuse your breakers, as long as they did not get wet. Any breaker that gets wet must be discarded.

[ktulu]

OK. I have been following you until that thing about the hole. Are you saying that I should ask the inspector if I can remove the meter socket and cover it up with a plate and then install a new service entrance/meter box and just feed that panel and the sub panel from the new meter box? That would opposed to upgrading the meter jaws/socket and feeding the 2 panels.

I'm not out west... about half way.

Thanks!