Have an older home with 100 amp service; 2500 square feet in a U-shaped footprint. Need to replace ancient HVAC system and also plan for future splitting of home into a duplex/ mother-in-law apartment. City and fire marshall requires one meter when there is no firewall until zoned as duplex. Will need to run 3″ conduit from transformer to meter…which is about 200 feet if the service is upgraded from the existing 100 amp.
Eventually, all will be electric, two kitchens, 2 laundry, 2 heat-pumpd with strips.
Do I need a 300-400 amp service, or what size will eliminate having to do this again? If using a bigger amp service, can I set up two main breaker boxes with 200 amp for the expected three bedroom unit and 100 amp for 1 bedroom unit?
Trying to keep costs down and yet plan for future when 2 car garage would be converted into two bedrooms and a laundry room.
Other question is the HVAC system. Seems it is more economical to replace the old one now based on the existing square footage. Then when the additional square feet from the garage is added in, split off the systems and get a second unit.
Suggestions are appreciated.
Replies
Not sure of all the NEC specs but I think you will have to have a dedicated panel in EACH of the units no matter where the meter is. Each panel will have to be accessible by the folks in that unit and could not be sub panels or feed thru a non-accessible unit. In other words, you can't have the panels for both units locked up on one side of the duplexin-law suite.
I am guessing you already figured that out but that may change your electrical layout and meter schematic.
And just curious but what is the cost for an extra meter there? Here it is a $250 depo with the utility company but thats about it.
You would have the extra cost of a meter box and maybe weatherhead but splitting into two complete separate services may not be all that much???
Just my .02 of course,
Edited 11/6/2009 4:19 pm ET by Oak River Mike
Didn't ask about cost of second meter as the fire marshall will not approve. I've been here long before they asked for deposits....I think new service is about $100 or so.
It would have been in my best interest to have the second meter on the other side of the house...Much closer to the transformer and have a dedicated meter. Then add a smaller HVAC, rerun the ductwork and rewire that side of the house. This would give me a dedicated rental unit when not needed as mother-in-law unit.
Since the house is not zoned for a duplex and would have a lot of opposition to doing so...I have to anticipate future needs.
First issue is determining size of amps needed for upgrading HVAC. Inspector mentioned that replacing the breakers may eliminate the problem of blowing a breaker in the kitchen when 2 small appliances are used when the fridge is running. It seems fridge should have been on its own circuit...haven't figured that one out yet.
My thinking right now is to leave as is and spend the time and money upgrading the wiring in the existing kitchen from the subpanel. When zoned for multi-family then run new service, meter, etc, add panel. There is a lot that I can do to prep for that situation. Such as cutting doorways into the brick, setting exterior doors. creating entrance. Am most grateful that the sewer lines are already seperated!
Why all the bother...house is built to last. Too many steps up and around to keep through retirement years. Figuring out how to supplement income with rental units that will soon be paid for. Think it will pay off if Lowe's keeps having good clearance sales!
You really need to involve a desigh professional, such as a master electrician, with this plan. There's a lot that can be done today to prepare for future plans.
In electrical terms, converting a place into a duplex is no small matter; there are many additional circuits that will be required, even though the total calculated load will not change.
Ultimately, you're going to want not two, but three meters; one for each half, plus one for any 'common; loads that there might be.
Indeed, considering the various code changes in the past 15 years, I'd say it's just not practical to split this job up the way you intend. You really want to do this remodel just once.
"there are many additional circuits that will be required, even though the total calculated load will not change."Won't the calculated loads go up for coverting to a duplex of the same size.As you now have the base loads and minimum loads for 2 kitchens, 2 laundries, etc..
William the Geezer, the sequel to Billy the Kid - Shoe
Maybe, maybe not enough to matter .... no way to tell without a look at the place. As a duplex, you're talking 2- 100 amp services, with a PoCo feed of 150 amps (for starters), and that can cover a lot of loads.
Think of it as the electrical version of the 'alternative minimum tax."
I think the easiest fix is an outside meter main with 2 sets of jaws, only one meter installed at this time.
The more this all comes to light...no pun intended....I think that sticking with the original 100 amp service for now will be in my best interest. Appreciate all the input as more heads are better than one.
Just to have one more thing to mull over during the deep of winter...has anyone converted a bathroom into a kitchen? Drains are in place which makes it nice. How would you seal off the unneeded drains?
Also...one other question: when new service comes from transformer to house, it would need to cross over the sewer and water lines. Is that allowed?
There is nothing in the NEC that covers path of underground circuits, just the depth.However, this is outside the NEC.What you are going to run into to local requirements and practices by the different utilities.Because of frost depth and sewer depths you have have thread the needed up/down over and around the others.But baring some strange local requirements should not be a problem..
William the Geezer, the sequel to Billy the Kid - Shoe
Seems like these details all work themselves through once work begins. I like knowing what problems could erupt and head it off. Hate spending $ twice. Thanks!