I just recently bought a house that was made in the 1950's. I would
like to add a hot tub to the house (220V). Protection to the house's
electrical system is provided by a fuse box - which is full. My
question is, how do I add a sub panel to the fuse box assuming that the
electrical system can handle the load? I am assuming that I branch the
wire directly off (in parallel) of where it comes into the fuse box.
So are you telling me to replace the fuse panel? I really would rather
not... seems like alot of work. I am checking to see if I have adequate
service to the house. Assuming I do, I would just like to know how to
add a subpanel for the additional load of a hot tub.
If the fuse box is the original to the house and it was built in th
50's and is now full you will need to up grade. Think about how man
more appliances we now use compared to back then,-large ref.,ele
dryer, multiple tv's, computers, microwaves etc. It may be a lot o
work to upgrade but if you overload and cause a fire can you live i
your new hot tub
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You have to disconnect an existing 220v circuit, connect up the subpanel
to where this circuit was, and then reconnect the existing circuit(s) up
to the new sub-panel.
By the time one does this much fiddling around, replacing the fuse box
with a new service is usually not that much more expensive, since your
already doing most of the work anyway.
You could hook up an A/B switch to your fuse panel, and if it is in the
A position it would feed your fuse box, and if in the B position it
would feed your new panel. You could probably even install 220v outlets
throughout your house and just plug everything into them.
- Jeff Wisnia
Call several licensed electrical contractors in your area and get estimates.
Then you will know if you can add in another subpanel.
Your concept of ".....assuming that I branch the wire directly off (in
parallel) of where it comes into the fuse box." Is not a acceptable method.
If I understand correctly what your doing.
Others have stated, get a new service. which considering the era of the
equipment you have is good advice.
What size main fuses are in your existing fuse box? This should tell
you what size service wires you have. (I will assume a standard 60A
Square D fuse box.)
Do you have an electric range? If not, the cartridge fuse pullout
labelled "RANGE" can be used to power your hot tub (with proper GFCI
protection, etc.) or used to power a small subpanel. If the RANGE
connections are already being used by a water heater, dryer, etc., you
are kind of out of luck unless your fuse box has feed thru lugs (lets
you tap in after the MAIN fuses).
A better solution is to replace the fuse box with a breaker panel -- it
doesn't have to be 200A. You need to run a load analysis to see how
much you need (I only needed about 85A when I ran the calculations, but
opted for a 150A panel instead of a 100A or 125A so I would have enough
capacity to add a big subpanel later for a workshop.)
But a 150A can be run (with great difficulty) in a 1 1/4 conduit if
that's what he's got already. (Use 1 1/2 or 2" if you gotta run new
service conduit anyway)
And the wire is a lot cheaper for 150A. And the panel is a little bit
smaller and might be easier to fit in the existing space.
He needs to do the load calculations and see what size he really needs
though, then probably go one size larger.
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