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How do I know if I can fit (3) 40 amp breakers in my box?

I want to buy a tankless water heater to replace my old tank style. Our water is so hard that sludge builds up in the tank. I checked my box and the main breaker says "200" on it, so I'm assuming I have a 200 Amp breaker panel. There are 40 numbered "slots" on the panel, but several of them aren't open (i.e. have metal from the panel box covering them). I do have three slots with knockouts in them, but it looks like most of the installed breakers say 10ka. How do I know if I have enough room? Here are the specs for the water heater: Requires 240V Hard Wiring and 120 Amps. This Model Requires 3 Separate 40 Amp 2-Pole Circuit Breakers and Six #8 Awg Wires + Ground (Min. 200 Amp Breaker Panel) Of course I will have this professionally installed, but I don't want to order the thing only to find out my panel can't support it.

Re: How do I know if I can fit (3) 40 amp breakers in my box?

Each 2 pole breaker takes up 2 spaces in the panel .... so ... 3 X 2 = 6 spaces.

If your existing panel currently has more than 32 breakers installed you may need to have a subpanel installed for these water heater breakers.

At least around here the inspectors don't like to see a fully stuffed panel.

Hope this helps.:)

Re: How do I know if I can fit (3) 40 amp breakers in my box?

Yup, sounds like you have a 200 amp panel with a 200 amp main.
If your existing water heater is electric that would account for two pole spaces that would be available. That would mean you would need to have two more spots that had two adjacent spaces.

Do you know the KW rating of the water heater? I doubt it would be more than 80% of the 120 amps but that is still a big load.

I'd sure take a look at an electric bill and calculate at least the average amperage that you are using.

Oh, the 10ka you see on the breakers has to do with the fault current available from the supplier and rating of the breaker. It does not really apply as to whether or not you can install the water heater.

Re: How do I know if I can fit (3) 40 amp breakers in my box?

No idea what the KW rating is, but maybe it's in this list:

Amperage : 120 A.
Voltage : 240 V.
Watts : 26850 W.

It's a Powerstar AE 125 Electric at Home Depot if that helps.

From the electric bill it looks like we use 2000KWH per month. The current heater is a 50 gallon tank and takes up two slots on the panel. Directly above it, there is a flat black piece underneath the panel cover (filling two slots) that says "interrupting rating 120/240." There are no switches on it or anything so I'm not really sure what it is. Is it just another knockout? If it is, that would give me four adjacent spaces, and I do have two more slots that are empty (although not adjacent). Can things be moved around at the panel to accomodate that or is that a huge pain? Right now there are 32 slots occupied in the box. So if I go from 2 being used now to 4 (or 6?) would that be to much?

Moon Over My Hammy
Re: How do I know if I can fit (3) 40 amp breakers in my box?

In Canada you're required to have the Bosch PowerStar AE125 installed on one 120 amp breaker (Min AWG #2 2-wire plus ground) and use a terminal block adapter for a single supply.

If room in your main panel is a problem you could always install a feeder circuit to a remote panel, you could use AWG #2 or AWG #1 plus ground, then install the three x 120/240 GFCI breakers in the remote panel and use AWG #8 or AWG #6 to wire to the terminal block.

The breaker would be more expensive and the wiring but you'd have to spend that money anyway to have a remote panel if the tankless water heater is out of sight of the service panel for an electrical disconnect.

Have you seen the specs? barely enough of a flow rate for a tub only at less than 110 degrees F. I read that if the voltage is low GPM is further reduced, reduced max flow rate by 84% if only 220V, and reduced max. flow rate by 75% if 208V.

A KW is a kilowatt, watts divided by 1000.

Do you have another fuel source for water heating Tankless Electric can be very expensive to run with dissapointing results.

Bosch has a toll-free technical support line you could call them.

No way to know the AWG of your service entrance - if that isn't rated for 200 amps and/or your main disconnect isn't rated for 200 amps it doesn't matter what your panel or bus bar is rated for if the wiring to the panel can't handle 200 amps.

Here is a link to the installation instructions: http://www.tanklesswaters.com/manuals/powerstarmanual.pdf

The AE125 replaces the discontinued PS28T. End-user reviews of both were disappointing, especially for those on public water supplies in northern climates where the incoming water temperature can dip to 40 degrees or below in the winter when a lake or resevoir supply and its sub zero outside, and for southern climates where the incoming water distribution system/mains are nearer the soil surface and in the summer the water temperature can be very warm, almost hot.

High usage times like air conditioning season you might have lower voltage available from the power company.

I'm very suspicious of a newer model number/product that has a huge "reconditioned" supply to the market place:eek:. In my mind that indicates a huge amount of warranty failures and warranty replacments that had to be replaced, the old units repaired or reconditioned and are now being remarketed.

Re: How do I know if I can fit (3) 40 amp breakers in my box?

If it were me I would shy away from this unit. It is not an Energy Stare appliance, it only supplies a 45 degree rise @ 4 gal/min that would only give you 105 degree water with a 60 degree input so flow rate would have to be reduced for desired results.. I believe you will be disappointed in this unit.

Re: How do I know if I can fit (3) 40 amp breakers in my box?

Wow! Thanks guys. I guess I need to keep looking. We don't have any other source for our hot water (gas or oil). We're in NC, live in a split level house with a finished basement and the water heater is right in the middle of the finished basement in a closet. There is a drain in the floor, but it's not big and I think if the tank failed it would destroy our walls/carpet/etc. Since our water is so hard, stuff builds up in it and turns our clothes brown, corrodes our stainless steel sink, and destroys all water-touching appliances within 3 years. Unfortunately, there are so many problems with the water (off the charts hardness, manganese, and iron bacteria) that a $500 water softener won't fix it. We would have to spend about $10K to even come close, and even then they won't guarantee it! So what can I do for an electric unit that can handle water so bad? Are there other tankless electric units that will do the job or tank heaters that won't rot?

Re: How do I know if I can fit (3) 40 amp breakers in my box?

I would suggest you get a watter test done and look into water conditioning system. It sounds like nothing else is goig to hold up.

Union Sparkie
Re: How do I know if I can fit (3) 40 amp breakers in my box?

You should put in a nat. gas or LP tankless tank. It only needs a 120 volt outlet. Here's a good brand http://www.rinnai.us/


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