Wiring for A/C

[jodil]

I have an appt on Sat and the buyers specifically told me that when I am there they want me to make sure the electrical system is sufficient enough for them to install central air this spring.

They said the home has a breaker box and a fuse box (common in my area.)

Just so you know, most homes here have 120/240 V service.. Homes in this area of town usually have the upstairs on main panel and stuff in basement (washer/dryer, furnace, water heater) on fuses...

How am I to know? What am I to look for?

Thank you for your responses!

[Richard Moore]

That's a can of worms with no simple answer, especially without knowing the service size, the size of the house, and what type of appliances are there.

Let's say it an average size house though.

First scenario is easy. If the furnace is electric, then should be no problem. The A/C will draw less than the furnace and both won't be on at the same time. Is there room in the panel for another double-pole breaker?

Beyond that you really are into doing load calculations for the definitive answer. Most of us don't do those.

But...let's say you have gas heat, but everything else is electric...range, water heater, dryer etc. Adding A/C would be pushing the limits of a 125-amp service but a 200-amp should be fine.

If the range and water heater are gas, then 125-amp may be fine.

BIG BUT: But that's only a very rough guideline and not something I suggest you actually use to determine future adequacy, something you'd be best staying away from declaring. Frankly, if you are not comfortable with this, and obviously you aren't, but have committed yourself, I can only suggest you pay a sparky for 1/2 hour of his time.

BTW...

"Just so you know, most homes here have 120/240 V service.."

A garden shed or detached shack might only have 120-volt, but I'm sure you'll find ALL homes have 120/240 service.

[jodil]

Understood, I will have my electrician stop by...The purpose of my comment for 120/240V is that alot of houses here ONLY have 120 V (two wires coming in off street.) Wasnt sure if that was necessary for you to know or not.

[hausdok]

Hi Jodi,

When you say "two wires" are you talking about two black wires twisted around a long steel cable that's anchored to another steel cable strung between poles and the weatherhead? If so, you're referring to a triplex cable and there are actually three conductors; two hots and the neutral - the neutral being the steel cable that's carrying the weight of the two cables twined around it.

Each of those heavy conductors carries 120 volts and each is connected to a different bus in the panel. The electric clothes dryers, water heaters, ovens, etc. run off of a two-pole breaker that connects to each bus simultaneously to get 240 volts.

OT - OF!!!

M.

[randynavarro]

Jodi:

Code Check Electrical has a fill-in chart to perform a basic load calculation of the home. Its pretty self-explanatory but not something to do if you're not comfortable with it.

[jodil]

Hi Randy,

No thats not what I mean. Theres just two cables coming into the masthead. I've seen this in the smaller rural areas (little towns with less than 50 homes) and some older areas (homes in the late 1800 age.)

Is this uncommon?

Originally posted by randynavarro

Jodi:

Code Check Electrical has a fill-in chart to perform a basic load calculation of the home. Its pretty self-explanatory but not something to do if you're not comfortable with it.

[hausdok]

Hi,

I'm not saying they don't exist, because I really don't know, but I've never seen an area that had strictly 120 volt service.

Here's what Hansen says on the subject:

Almost all residential services today provide both 120-volts and 240-volts. A few older 120-volt systems might still be in use, but these do not provide sufficient power for a normal number of modern appliances.

He also has a small chart of service sizes and lists "30-amps at 120-volts (Obsolete)."

Get online and order yourself a copy of Electrical Inspection of Existing Dwellings - 2001 Edition by Douglas Hansen. It will be the most valuable book in your library until you've gotten used to all of the electrical stuff that you need to know.

OT - OF!!!

M.

[Richard Moore]

I guess anything is possible, but 120 only sure seems unlikely, even in Noth Dakota. Jodi, next time you get a chance, snap a photo or two of the service drop, mast, etc on one of these.

[hausdok]

Here's a scanned picture from Electrical Inspection of Existing Dwellings - 2001 Edition by Douglas Hansen of a 120-volt service. I sure hope my friend Douglas doesn't chew me a new one over this, but I doubt if I'll ever get a chance to take a picture of one.

OT - OF!!!

M.

[Les]

I can't count how many two wire drops we have seen. Thousands. There was a 4-5 sq block section of Lansing Mich that was 120vac until 10-15yrs ago. So it is possible, but not likely.

There are still houses here that have 30amp entrances. And houses that had split entrances: one for you and one for neighbor.

Jodi's question is one that I've seen avoided by new inspectors for decades - she had the gumption to ask it!

[Richard Moore]

That looks exactly like the old, original KT feed from my house to my garage.

[jodil]

Yes that picture is exactly what Im talking about.

Well, neither electrician I know can stop by during this inspection, so I am going to have to wing it...any advice?

I tried to find the Code check electrical fill in chart Randy suggested but could not find it. Any one know where I can go to get that? No I am not prepared to figure it out, and I will let the buyer know that. But I would like to give it my best shot for my own experience.

Thanks

Jodi

[Neal Lewis]

Originally posted by jodil

Well, neither electrician I know can stop by during this inspection, so I am going to have to wing it...any advice?

Here's my advice- don't wing it. Find the size of the service and any other major items w/2 pole breakers in the panel and then get back here.

An A/C condenser unit for a smaller house will only need maybe a 30 amp circuit. Could the service handle that? Is there enough physical room for a couple of 2 pole beakers?

[hausdok]

Hi,

You can see the Code Check worksheet online at: http://www.codecheck.com/service_calc.htm

Has anyone visited the Code Check site lately? If not, you should. Scroll down the home page to see who's featured there. Then go to the top menu bar and click the tab, "Ask Code Man." I've got to give him credit, Doug's got stones!

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

There's no good reason why a home inspector shouldn't know how to do a rough load calc. Go to the code check website and print the load calc table. Practice a few times.

This calc involves adding, subtracting, multiplying and dividing. It ain't rocket science. It's Jeff Foxworthy stuff.

- Jim Katen, Oregon

[Richard Moore]

Originally posted by Jim Katen

There's no good reason why a home inspector shouldn't know how to do a rough load calc.

Jim, I agree in principle but, the few times I've tried the calculations, I've never been real comfortable with the results.

Take my house for instance. I'm just under 3000sf if you include the basement. Gas heat for main floor, about 5000 watts total of electric heat on the 2nd, electric water heater, dual fuel range, etc, etc (no A/C) and allowing for a couple of my bigger workshop motors, I come in at just under 115-amps. Maybe that is all I actually need, especially as it's just the wife and me here, but my gut tells me the 200-amp is better. If I were doing this home for a buyer, I'd be very hesitant about predicting his family's future use and saying it was OK if it had a 125-amp service.

The bit about the load calc that has always bugged me the most is the first section...everything above "Special Appliance Loads" in the code check table. A 3000sf house (lets say 4br/3½ba/1 kitchen) allows 27.81 amps for that section. Make that 30 amps on each 120 volt leg. Probably fine most of the year, but I can see a crowded house over the holiday season easily exceeding that as everyone gets up in the morning, some drying their hair while others make coffee and toast with all the interior and Xmas lights on.

Fortunately, the housing stock around here is generally in good condition with almost all older homes having newer service and panels and it's been a long time since I "sensed" an undersize service. Probably the opposite is the norm here with even small 1200sf ramblers, with gas heat, water and range, often having 200-amp service.

So yes, I agree that an HI should be able to do the math to determine a suspected undersized service. I would be OK reporting inadequate current adequacy if the "official" figures didn't add up. Future adequacy needs a crystal ball IMO and I think your average HI is best leaving that to the buyer and the electrician of his choice.

Jodi's "they want me to make sure the electrical system is sufficient enough for them to install central air this spring." is one of those cases where I'd be very wary if the figures came out "OK" but were anywhere close.

[kurt]

I don't think it's too much of a stretch to say the service can't handle central AC.

Jodi says Mike's pic is exactly what it looks like. That's 120v, no?

If it's a 2 wire feed, it's a near sure bet that the panels are inadequate, and the distribution wiring is a rats nest of various issues. I rarely see them anymore, but the 120v systems I've looked at always needed mega-upgrades throughout.

I agree w/doing the load calc. It isn't complicated. Jodi should do a couple simply to get comfortable w/the idea. You run a simple formula, you come up w/a number.

If the house has a 120v feed, you know the panels should be updated. Not updating would be a ridiculous false economy.

Jodi, get pics and post after the gig; the answer will probably be very apparent.

[Jim Katen]

Originally posted by Richard Moore

Originally posted by Jim Katen

Jim, I agree in principle but, the few times I've tried the calculations, I've never been real comfortable with the results.

Take my house for instance. I'm just under 3000sf if you include the basement. Gas heat for main floor, about 5000 watts total of electric heat on the 2nd, electric water heater, dual fuel range, etc, etc (no A/C) and allowing for a couple of my bigger workshop motors, I come in at just under 115-amps. . .

Try snapping a clamp-on meter at your service conductors and they start firing stuff up. Create a realistic Thanksgiving morning. What do you get?

- Jim Katen, Oregon

[Richard Moore]

"Create a realistic Thanksgiving morning. What do you get?"

The wife's family yelling at each other! How does that help?

[]

[jodil]

Im going to call the seller and see if I can stop by a day or two early and take pics of what I need for this "special request." It may be more complicated than you all are thinking, according to the agent it has two subpanels (one breaker one fuses) and a kitchenette in the basement.... And they have 12 cats....yay

[Jesse]

If it's really just a 2-wire service, no load calc necessary. It's an inadequate service, regardless of AC. New service drop, new service panel, probably new sub-panels. With all that, and other details that are sure to come up, they should be set to run central air.

[jodil]

I dont know if it is only 120V service. I just mentioned in the beginning of this post that we have that type of service here. The topic got exploited because many members I guess had not heard or seen of such inadequacies! Ill find out and post soon...

[Brandon Chew]

Back to the original topic before the thread drift.

I have an appt on Sat and the buyers specifically told me that when I am there they want me to make sure the electrical system is sufficient enough for them to install central air this spring.

How am I to know? What am I to look for?

• You need 240 volts.
• You need space in the panel for the breaker since the A/C needs to be on its own circuit (there are many ways this could be accomplished).
• You need to make an estimate of the power needs of the A/C unit.
• You need to do a load calc on the house.
• You need to determine if the existing service provides at least the number of amps that are required by the load calc.

If you were an experienced and competent electrician, you could look at the panel and in just a few minutes make a pretty good educated guess at the answer. Mentally, the electrician would be going through those same steps as he/she formed an opinion.

You are being asked to provide a service that is beyond the scope of a typical home inspection, and one that requires skills beyond that of a typical home inspector. It is not difficult to learn them. Perhaps your electrician friends could walk you through it.

If it was me, I would not:

• "wing it" or bluff my way through
• do it if I did not feel qualified to do it
• try to hide my lack of qualifications to do the task from my client
• do it for free (if I was qualified)

When you do the inspection you are likely to find issues with the electrical system that need repair by a qualified electrician. I see no shame in saying "Determining whether the electrical system has adequate capacity to add central air conditioning is outside the scope of a home inspection and I am not qualified to do it. Have the electrician do this task for you when at the home making estimates for the repairs that I noted during my inspection. If this is an important issue for you, then have an electrician come out and do this for you separately from the repairs."

If you learn what you need to know and feel confident doing it, then go for it! (and charge for the extra time, knowledge, and liability for providing this additional service).

I hope this helps and good luck!

Brandon

[jodil]

Well, the big day has arrived and I am quite sure without even doing the load calculation worksheet that it is not possible on this current system for an AC unit. There were three panels, but I was able to identify the main fuse as just 60 amps.... This house has two kitchens (all electric appliances) electric dryer, about five million recessed lights, and three pronged outlets all non grounded of course...

That worksheet that someone posted in the topic is really hard to under stand... In fact I dont have a clue what its talking about. I have a different one that my wonderful friend George Wells (bestinspectors.net) sent me... I'll ask him if I may share it.. Its alot more user friendly and simple for people like me