What size (service) breaker is required for 72amps

No problem but you can use a smaller diameter wire either copper or aluminum to support a 200 amp entrance. I have included a few links to help. Typically aluminum wire is a gauge larger (lower number) then Copper.

Thread What wire type is acceptable by NEC Code For Service Entrance

Can use 3 ott 4 wire mc for 200 amp service indoors

What size wire is required for 200 amp service



What is the wire size for 200 amp service

Typically a welder is 240v requiring a Double pole breaker, the size would depend on the equipment amps or watts?
30 amps X 240 volts = 7200 Watts

Either the breaker rating is too small for the air conditioner or the unit is defective. Choose the right size breaker for the air conditioner power requirements and ensure the wire size to the unit is correct.

Hi - I'm an electrican and would like to help.

If the wire you're trying to install on a circuit breaker doesn't fit - then something is wrong. Typically, circuits are designed around the amount of voltage and current a product requires. The voltage determines the combination of material & thickness of the insulation on the wire and the the amount of current (in amps) determines the size of the conductor or wire. The appropriate circuit protection (fuse or circuit breaker) is selected to protect the circuit from trying to deliver more current than the product requires (in the case of a fault, etc.) which would cause the wire to over heat and potentially cause a fire. So, if the product requires (for simplicity) 120 volts and 20 amps, a wire is selected with the proper insulation for 120 volts or more and conductor sized to carry no less than 20 amps. Aluminum and copper is expensive, so providing larger sizes than needed is a waste of resources and money. A #12 copper wire is suitable for this amount of amps. A circuit breaker rated for 20 amps is chosen. A 20 amp circuit breaker must be able to accept a wire capable of 20 amps - other wise it's not really a 20 amp circuit breaker. Most circuit breakers are designed to accept LARGER wires than needed - because often times circuits will need a wire that is one or two sizes larger due to the length of the circuit (how far the product is from the electrical panel).

If you're seeing a circuit breaker that will not accept the wire, the circuit breaker is probably the wrong size (and if you could force the wire in it - it would probably trip instantly when turned on) or someone has made a very expensive blunder when chosing the wire type and size for the circuit.

If the the latter is the case, simply connect a short length of the correct size wire to the oversized wire in an appropriate connector and secure to the circuit breaker terminal screw. otherwise, have a qualified person evaluate the situation. Be smart. Be safe.

A 200 amp circuit breaker has a large spring to assist in rapid opening and closing a load of this size to minimize damaging arcing every time is it operated under electrical load

The larger the circuit breaker is and the more poles (1, 2 or 3) that are being opened / closed; the more force it will require to operate - both by hand or when tripping. Compare the tension or force you need to apply to a similar sized circuit breaker at Home Depot, etc.

The troubling issue about this for me is the fact that the 200 amp service disconnect / main is tripping. This is an indication of an overloaded panel / circuit. I usually see individual circuits that trip in a panel - but often find the that main breaker has only 20% - 60% of its rating on it at any given time. If you're tripping a 200 amp service disconnect / main breaker repeatedly - something has got to give - and eventually the circuit breaker will fail. That may be where you are now with this breaker. You may be in need of a service upgrade (if it is the service disconnect) as clearly, you have out grown the 200 amp size one you currently have or need add a new sub-panel to ease the load that this 200 amp main is trying to supply now.

Either way, you should call a reputable electrical contractor to have your service / sub-panel evaluated very soon. Good luck!

1) You got a FIRE truck coming.

2) Wire is too small.
Problem is NOT circuit breaker.

3) Both 240Volt appliances on same breaker is a hazard, especially if space available in 200 amp service panel for more breakers.

4) Usually each 240V appliance has separate breaker.

5) Circuit breaker trips because of High heat on the wire.
If wire gets hot, it will start a fire inside the wall.

Electric code requires wire-size match breaker-size.

6) If you put larger amp breaker on same wire that is getting hot, then wire will get hotter.
Result: FIRE truck middle of night with folks jumping out window in glass-cut bare run across yard.

7) Each appliance has volts and watt rating on label.
EVERY appliance has label.

8) For example stove might be rated 8000 watts and 240Volt.
8000 watts divided by 240 volts = 33.3 amps
Stove would require 40 amp breaker and 8 gauge wire.

9) How to figure it out:
http://waterheatertimer.org/Color-codewire.html
http://waterheatertimer.org/How-to-install-a-subpanel.html

10) Do same calculation for new furnace.
12000 watt furnace divided by 240 volts = 50 amps.
Use 60 amp breaker and 6 gauge wire.

11) Summary: fixya wants you to be safe, and buy stuff showing in the ads.
Use a bigger breaker ONLY when bigger wire is also installed.
Call furnace installer, the installer should know to check safe wiring before installing.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Why would you ask about a breaker size?

Has it not been properly installed for the unit
& there for years with no problem?

You must know ,that you would need to see
the wiring diagram for the A/C unit, to check on
the required breaker Amperage

You need to call a service tech to troubleshoot
what has failed on the unit & is tripping the breaker

Bad Compressor or Motor,maybe

I don't have specific suggestion for tankless tripping breaker or if that is a circuit breaker problem or a tankless problem.

1) Move wires to another same-size breaker and see if problem persists.

2) Compare amp draw on tankless label with wire size and breaker size amp rating.
For example 30 amp breaker using 10ga wire is rated for 80% of listed amps or 24 amps.

3) If you are drawing full 30 amps, then 30 amp breaker is getting hot. Breaker trips with heat. Older breakers can trip more easily.
http://waterheatertimer.org/How-to-replace-circuit-breaker.html

4) Before calling service technician, open following link for Bosch troubleshooting steps.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

5) Be sure to read manual for yearly maintenance requirements.

6) Add a tempering tank for incoming cold water problem.
http://waterheatertimer.org/Tempering-tank.html

7) All gas tankless brands can be repaired by homeowner for $330.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Sounds like the breaker is doing it's job. Stopping an over amping condition. You need to find out what the breaker is feeding power to. If it is the outdoor unit or the indoor unit. Also, the wire used has to be sized to the breaker otherwise, it will burn inside the walls and start a fire! Both the indoor and outdoor units should have tags or lables stating what the required amount of power is required. Better not let them do anything else untill you get more info. Sounds very dangerous to me but, I'm not there seeing what's going on.
Hope this helps!

When breaking oversize material the breaker is expected to break the material down the middle into two pieces. This is optimum production. If the operator has to re-position the breaker towards the edge of the rock and gradually downsize the material, production rate slows down. To assess what size of breaker will effectively handle this application, the size and hardness of the material must be known. If a 4 cu. yard piece of hard rock (20,000 psi or greater) needs to be broken in half you will require a 7,500-ft. lb. or larger breaker. If a 2 cu .yd. piece of limestone (20,000 psi or less) needs to be broken in half you will require a 3,000 - 5,000-ft. lb. breaker.