Question 1

will it work with 120 volts?

Accepted Answer

Yes and No. This is a double pole breaker and intended to be for 220/240 volt usage which means it is for something big, like a range, a dryer, or in my case, a tankless water heater.  This would instantly kill (blow up) anything 110/120V that you tried to plug into if both poles were hooked up.  For 110/120 volts you really want a single pole breaker.  You also want to pay attention to the amps.  Most items that run off of 110/120 volts wouldn't need more than 10 amps.  Microwaves and Power tools would be the common exceptions.  Most people will run more than 10 amp breakers so you can run more than one thing at a time.  15 or 20 amps are the most common for homes (20 for Microwaves and outlets used for Power Tools).  The only possibility I could imagine why a panel in a house would have a single pole 70 amp breaker in it would be that it was acting as a sort of main breaker for all the smaller breakers (meaning not the double pole breakers).  If you ran too many items in your house at once, you could trip the 70 amp breaker while never tripping any of the smaller ones. This would be the nuisance of this arrangement (The advantage would be having a way to turn off everything all at once without having to turn off the big stuff).  But for that I'd just stay with the single pole.  As for the Yes argument, You could just hook up one side and that would allow you to run 110/120 Volts, but it takes up an extra slot in your panel and for many of us all those slots are precious.  You could use the other side for something else (I'm not sure what), but you need to remove the bar connecting the two switches so they can operate independently.  At this point you would just have two single pole 70 amp breakers that happen to be attached to each other.  Not knowing your application, I would really recommend a single pole for 110/120 Volts.

Question 2

Can this breaker be used as a main breaker with a hold down kit ?

Accepted Answer

Yes as long as you use the hold down kit

Question 3

what brand circuit breakers will fit in a murray box?

Accepted Answer

The Siemens QP, QT, QAF, and QPF are the standard "interchangeable" plug-on type breakers used in load centers under several brand names including Siemens, Murray, Gould, and Sylvania to name the most common

Question 4

will this fit crouse hinds breaker?

Accepted Answer

All I know is that,"...Crouse-Hinds bought Murray, and then Siemens bought Crouse-Hinds."

ASIN	B00002N7KX
Best Sellers Rank	#855 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #2 in Thermal-Magnetic Circuit Breakers
Brand	SIEMENS
Brand Name	SIEMENS
Circuit Breaker Type	Standard
Current Rating	50 A
Customer Reviews	4.8 out of 5 stars 3,278 Reviews
Global Trade Identification Number	00783643148642
Included Components	breaker
Item Dimensions D x W x H	10"D x 5"W x 8"H
Item Type Name	Circuit Breaker
Item Weight	8 ounces
Manufacturer	Siemens
Model	Q250
Mounting Type	Plug-In Mount
Number Of Poles	2
Number of Items	1
Number of Poles	2
Part Number	Q250
Product Dimensions	10"D x 5"W x 8"H
UPC	783643148642
Unit Count	1 Count
Voltage	240 volts
Warranty Description	1 Year

Q250 50-Amp Double Pole Type QP Circuit Breaker

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