sizing electrical service for new shop

[phred]

I'm in the planning (budgeting) stages of building a new shop. All of the structure and labor costs I have worked out but really need some help on panel size. Here a list of the large equipment going in the shop:
1) 5 hp compressor 1phase 240 volt 30amp
2) drill press 120 volt
3) tig/stick welder 230volt 52amp
4) mig welder 120v
5) 2 post lift 220v 20amp
6) miscellaneous small 110 & 120 volt tools.
7) Heat pump (36000 btu) 230v 60amp

Shop will be 36x32. Planning on receptacles @ 6' centers with a total count of about 20.
Planning on 18 - 8' fluorescent fixtures on the walls and ceiling (I hate dark shops)
The run from the shop to the current meter base is approximately 80'
Thanks in advance for the help

 

[veno]

200 amp service...

1) 5 hp compressor 1phase 240 volt 30amp+
2) drill press 120 volt
3) tig/stick welder 230volt 52amp+
4) mig welder 120v
5) 2 post lift 220v 20amp+
6) miscellaneous small 110 & 120 volt tools.
7) Heat pump (36000 btu) 230v 60amp+

total possible load 162amps + miscellaneous

 

[ArthurPE]

are those the circuit breaker sizes?
are those the output current for the welders?

compressor: 100% duty cycle 3.7 kva

drill press, tig, mig: I assume only 1 will be operating at a time...use largest welder I'm guessing input current 20 A ~4.6 kva

lift: momentary use, 50% duty cycle (probably not use with the press, etc., running) 3.7 kva

misc, figure 20 receptacles at 1800 va each ~ 3.6 kva

heat pump 11 kva

lighting ~3 kva

total kva ~ 30 kva, 125 A at 230 vac
150A would be good, but not really standard...200A

 

[phred]

The loads I listed are the ratings listed in the equipment I am moving into the shop.

 

[A_Pmech]

are those the circuit breaker sizes?
are those the output current for the welders?

compressor: 100% duty cycle 3.7 kva

drill press, tig, mig: I assume only 1 will be operating at a time...use largest welder I'm guessing input current 20 A ~4.6 kva

lift: momentary use, 50% duty cycle (probably not use with the press, etc., running) 3.7 kva

misc, figure 20 receptacles at 1800 va each ~ 3.6 kva

heat pump 11 kva

lighting ~3 kva

total kva ~ 30 kva, 125 A at 230 vac
150A would be good, but not really standard...200A

Arthur,

This is something that has been bugging me for a while. The trend in the past 15 years has been for larger and larger residential services. Yet, the power company never supplies a transformer capable of maxing the service. There are lots of big residential services out there that are "undertransformered". They work just fine because the biggest motor load is usually the washing machine, leading me to wonder what the point of the install was.

Owners here and elsewhere agonize about service size, only to be cut off at the knees by their power company. Or worse still, cut down by their neighbors who share the undersized transformer with them.

The problem as I see it with most garage shops isn't the wire out to the building, it's convincing the power company to hang a big enough pole pig to handle estimated and future load. My power co-op will hang anything I want, but most guys I've talked to say it's a major hassle to get anything larger than 25kva.

I've heard of installed 400A services with 15kva pots! That's a 60 Amp service with big wire. However, it looks good on paper to the owner, who doesn't understand transformer theory. The power company doesn't like paying to keep the field energized on a big transformer that, in their eyes, only sees a load on the weekends.

What are your thoughts?

 

[Stuart in MN]

I don't know the precise calculations they make when they figure this stuff out, but the power companies install transformers sized to handle what they figure will be a typical load. They assume it will at times be overloaded, but the transformers are built to withstand it as long as the overload doesn't last too long.

 

[hidollartoys]

total kva ~ 30 kva, 125 A at 230 vac
150A would be good, but not really standard...200A

This is only true if ALL devices are being used at max power requirement.

I believe that service size is sometimes equated to "**** inches".

"My service is bigger than your service" or "I have the biggest service in the neighborhood".

Be realistic. Does a basic home shop really need more than a 100 amp service?

If you are approaching a full 200 amp continious requirement, I believe you need to consider biting the bullet and installing a 3 phase service.

Just my "bigger" opinion.

 

[ArthurPE]

This is only true if ALL devices are being used at max power requirement.

I believe that service size is sometimes equated to "**** inches".

"My service is bigger than your service" or "I have the biggest service in the neighborhood".

Be realistic. Does a basic home shop really need more than a 100 amp service?

If you are approaching a full 200 amp continious requirement, I believe you need to consider biting the bullet and installing a 3 phase service.

Just my "bigger" opinion.

if he's got a heat pump that actually draws 60A and a welder that draws 52A, he's >100 right there, nothing else considered...you did note that I derated/duty factored the equipment...he's bgot no large motors so I see no need for the expense of 3 phase...

honestly: I doubt the ratings for both...I suspect the 52A is the DC output and the 60A is the circuit rating...

I would go 100 or 150 in this case...

I have no opinion on 'dicks'

 

[ArthurPE]

Arthur,

This is something that has been bugging me for a while. The trend in the past 15 years has been for larger and larger residential services. Yet, the power company never supplies a transformer capable of maxing the service. There are lots of big residential services out there that are "undertransformered". They work just fine because the biggest motor load is usually the washing machine, leading me to wonder what the point of the install was.

Owners here and elsewhere agonize about service size, only to be cut off at the knees by their power company. Or worse still, cut down by their neighbors who share the undersized transformer with them.

The problem as I see it with most garage shops isn't the wire out to the building, it's convincing the power company to hang a big enough pole pig to handle estimated and future load. My power co-op will hang anything I want, but most guys I've talked to say it's a major hassle to get anything larger than 25kva.

I've heard of installed 400A services with 15kva pots! That's a 60 Amp service with big wire. However, it looks good on paper to the owner, who doesn't understand transformer theory. The power company doesn't like paying to keep the field energized on a big transformer that, in their eyes, only sees a load on the weekends.

What are your thoughts?

utilities can do as they please, they are not subject to the NEC, but only the NESC...they undersize equipment to save cost, so if it blows, you are inconvenienced and they replace it...you make a good point about minimizing inductive load...also, more than 1 customer is usually fed off of a xfmr, so they apply a duty cycle to derate it, ie, not everybody washes or cooks at the same time, etc.

power transformers are robust devices and can take a coninuous overload, iirc, of 15% miniumum, and short term >150%

for a 200A 240/1 service (48 kva) they'ld probably use a 25 kva, as long as there are no large continuously running motors...or multiple motors starting and stopping...

 

[malodin]

I would like to just chime in a little bit, though i know nothing about 48kva or that side of things on the the transformer.

What i do know is this, the difference in cost between a 320/400 amp meter panel and that of a 200 amp is less than $200. along with the cost between power wire being neglagible as well.

What i did not see is what the original posters current power meter is rated at. if its a 200 amp service he will be hard pressed to squeeze 100 amps out to the garage if the house has electric heat/ac etc..especially if he is not single and has a family as they will be using stuff when he is in his shop.

With that being said if phred has a 320amp meter/panel service he can easily branch off and run 200 amps to the garage and leave the house with its current 200 amp panel.

But i am from the school of thought on electrical needs that there is no such thing as to much, especially when the difference is small change compared to overloading and burning something up.

Why would you want to "just slide by with what could work or is just barely over the requirements?"

when figuring out the best way to do my shop electrical(which i have just finished) i have full electric appliances in my mobile home, it was and is fed with a 200 amp service. The problem for me was getting another 200 amps to the garage, i could have installed a 100 amp service to the garage and probably been ok with the amount of work i would be doing, but again why go small when there is a chance it might not be good enough. i.e. running a welder and my a/c compressor kicks on while all the lights are on etc? so for me it was easier to add a 320 amp meter/panel, branch 200 amps to the original mobile home meter panel and a 200 amp service to the garage.

I think the primary concern for Phred should be where is he getting the power from? sub panneled off the main meter panel if so what is the meter/panel rated at? if 200 and he has mostly electrical appliances, he might want to think about changing it up, all it takes is a phone call to the local power company to find out what his place can handle.