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I moved into this home few months ago in California (U.S.), and want to understand how much electric load I can use in each room. The house doesn't have HVAC and I am using floor heaters. I would not like to overburden the electric system beyond its capacity.

House Covered area: 1460 sq feet Meter photo: enter image description here

Here is the excerpt from inspection report:

Some more context, the house is 70+ years old, and was built in two steps. Original part was built in 1940s, later another portion was added in 1970s.

Volts: 120/240
Service Entrance: Overhead mast
Service Capacity: Undetermined
Main Panel Protection: Breakers.
Subpanel Protection: Circuit breakers and fuses
Subpanel Location: hallway, garage.

The electrical main service panel is older and utilizes outdated technology. However, it was opened and the inspected circuitry was found to be properly installed and correctly fused, with exceptions noted elsewhere in this report. Upgrading should be performed in the course of on going improvements.

Note: The main electrical panel was manufactured by Federal Pacific Electric.

The electrical service capacity is minimal by all current standards (100 amps) and may prove inadequate for today's lifestyles. We recommend further review by a licensed electrician, and the electric service upgraded as recommended.

There was an older glass fuse subpanel. This electrical panel uses outdated technology and is intended to meet minimal loads. With any remodeling or expansion the panel would need to be updated. Additionally the panel does not include modern safety standards

Initially, I was naively adding up all Amperes to total it to 100, which they don't. After reading up similar questions on this site, I have figured out that it is not even expected; so I am asking for specific help for my situation.

Note: I am using a gas dryer.

Main panel: The marking in Red deciphered as 'Kitchen' enter image description here

Subpanel1: (in the hallway, this is the one which is very high as mentioned in the notes) enter image description here

Subpanel2: (This is physically located in the garage, ironically the other subpanel has a marking "Garage") enter image description here

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    It's rather important, at this point, that you tell us you're in Canada. – Harper - Reinstate Monica Oct 6 at 1:10
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    Based on travel.stackexchange.com/questions/41798/… OP lives in Seattle – manassehkatz Oct 6 at 1:13
  • Actually, i am in US , California these days. I will add it to the original post. How did you assume that I am in Canada? @Harper – Asad Iqbal Oct 6 at 1:13
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    The Canada question is because some of the Stab-Lok in Canada are not necessarily firestarters. Harper was being optimistic. – manassehkatz Oct 6 at 1:15
  • If you're still about, can you post photos of the meter and the square footage of your house? – ThreePhaseEel Oct 31 at 4:17
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You're going to have to start by mapping your house. It helps to have a whole bunch of night lights, or any kind of lights, or loads of some sort that light up clearly when the power is on. One for each receptacle in the house.

I'm fond of making up names for them. So for instance the Square D breaker box, I might call those Quill, Rocket, Gamora, Groot. Then in the fuse block, call those Thor, Loki, Sif. Then in the main one, use names of other Avengers not affiliated with the Guardians or Asgard.

Starting with the subpanels, pull one breaker or fuse. Then walk the house to see what dies. Label them as you please, so you know what that outlet or hardwired device is powered from. Repeat for each subpanel breaker or fuse.

Next, go to the main panel (the StabLok?) and do the same thing. Two of them will most likely shut off power to each subpanel, and you'll know that because everything connected with the subpanel will die. Label that Asgard, Guardians or whatever grouping you are using. All the other fuses will shut off some loads or one load. Again mark the outlets/hardwired loads.

Now you know what circuit every outlet and hardwired load is on.

Next, read the number on the breaker or fuse. That is your circuit limit for that circuit. Figure 80% of that (12 amps for most of them) and do not exceed that.

Generally, as far as the common 1500W heaters, you can put one of them per circuit, with nothing else except maybe a cell phone charger or at most a TV.

To find out what loads draw, either read their labeling, or get a Kill-a-Watt and measure them (at maximum working load, e.g. Full-on FPS gaming, not editing a Word document).

  • Thanks @harper for the detailed response. when you say "you can put one of them per circuit, with nothing else except maybe a cell phone charger or at most a TV. " Do you mean one heater per room, OR one heater per breaker/fuse OR one heater in one of the two electric sockets (as sockets are generally installed in pairs in USA. imgur.com/a/TAtFll1 ) – Asad Iqbal Oct 6 at 1:45
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    @AsadIqbal I mean one per circuit. one on Thor, one on Sif, one on Ironman, etc. – Harper - Reinstate Monica Oct 6 at 3:19
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Subpanel 1 is old fuses. Small, but nothing inherently wrong with it (at least not without more details/examination).

Subpanel 2 is Square D - Good stuff.

Main panel is a Federal Pacific Stab-Lok firestarter

I am not a professional electrician (barely an amateur) but I have seen enough here on DIY and on other sites to know that is a BIG problem. See, for example:

Should all Federal Pacific panels be replaced?

In addition, even not being a professional, those breakers look nasty.

Replace as soon as you can afford to do so.

Now that you are in replacement mode, the specifics matter a lot because you don't want to replace once for safety and then replace again due to capacity.

Current code typically requires:

  • AFCI for many circuits
  • GFCI for many circuits

plus there are many reasons to have additional circuits, such as more circuits for the kitchen to prevent nuisance overload trips with multiple appliances, additional circuits for more receptacles in useful places and many other things.

You may not need to do "everything" at one time, but you don't want to use a panel with double-stuff breakers to support more circuits and then find you have to replace later with GFCI or AFCI and can't use double-stuff breakers and then run out of space.

So you want to get a big main panel, provided you have the physical space for it.

You may also want to replace the small fuse subpanel for similar reasons (GFCI, AFCI, add more circuits, etc.) but that is NOT a known danger like the Stab-Lok panel.

Provide more details about your kitchen, HVAC and other major power uses and I am sure the pros will come in with a LOT more specific recommendations.

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