wattage calculator?
- Thread starter kcombs
- Start date
timgr
Well-known member
power = current times voltage.
15 A * 120V = 1800 watts
15 A * 120V = 1800 watts
MAD
Well-known member
This is the "West Virginia" formula W = VA.
For continuous loads do not load the circuit to more than 80% of the number you come up with.
For continuous loads do not load the circuit to more than 80% of the number you come up with.
phorsfi
Member
(Amperage of circuit x .8) X Voltage = Acceptable load rating in watts. However you can Load a dedicated heating circuit to 100% of the circuit breaker rated amperage because it is a known continuous maximum load.
This is Canadian Electrical Code, I'm sure the NEC is similar however I work up here not down there so...
This is Canadian Electrical Code, I'm sure the NEC is similar however I work up here not down there so...
Charles (in GA)
Well-known member
NEC considers lighting a continuous load, which is something that is on for 3 hrs or more, uninterrupted. Continuous loads should not exceed 80% of breaker capacity.
Charles
Charles
My understanding is to get watts you take the Voltage x Amperage=Wattage
Assuming 110V and 15amp breaker that would be 1650 watts..You should be able to run 16 100watts lights off that breaker.Or at 80% 13 100watt bulbs.
If I am wrong please feel free to correct me because this is the formula I have been using.If it's wrong I would really like to know.
Assuming 110V and 15amp breaker that would be 1650 watts..You should be able to run 16 100watts lights off that breaker.Or at 80% 13 100watt bulbs.
If I am wrong please feel free to correct me because this is the formula I have been using.If it's wrong I would really like to know.
PAToyota
Well-known member
Online calculator for watts, amps, volts, and ohms: http://www.anderson-bolds.com/calculator.htm
porcupine73
Well-known member
That is the right method for loads such as light bulbs which are purely resistive. For motors and other loads that also have a reactive component the power factor has to be taken into account for calculating the current.
Your typical T-M thermal-magnetic breaker is 80% rated, that is it can trip at as low as 80% of its nominal rating on a continuous load. You can get 100% rated breakers but generally these are used for larger loads where you are trying to not have to go up to the next size cable.
For incandescent light bulbs
Pmax=I*V = power = current * voltage
Pmax = 15 amps * 120 volts rms * 80%
Pmax = 1440 watts
Your typical T-M thermal-magnetic breaker is 80% rated, that is it can trip at as low as 80% of its nominal rating on a continuous load. You can get 100% rated breakers but generally these are used for larger loads where you are trying to not have to go up to the next size cable.
For incandescent light bulbs
Pmax=I*V = power = current * voltage
Pmax = 15 amps * 120 volts rms * 80%
Pmax = 1440 watts
timgr
Well-known member
Is there an easy way to estimate the power factor for an inductive load?
74NovaSS
Member
This is probably TMI
....but it tells all about calculating power factor
http://www.allaboutcircuits.com/vol_2/chpt_11/3.html
Chris
....but it tells all about calculating power factorhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.html
Chris
porcupine73
Well-known member
It depends; SCIM squirrel cage induction motors can be maybe .7 to .9 lag when running (can be much lower during starting), but some may have power factor correction capacitors in them. Usually the nameplate will tell the PF.
Apparent power (VA - volt-amps) is the total power
and is comprised of
average power (in watts), the real power component
and reactive power (VARs - volt-amps, reactive)
Apparent power (VA - volt-amps) is the total power
and is comprised of
average power (in watts), the real power component
and reactive power (VARs - volt-amps, reactive)
timgr
Well-known member
This is probably TMI
No, that's cool!
I didn't realize that the starter caps were meant to compensate for the winding inductance. The starter cap should make the load look resistive ... though I gather from porcupine73's post that the correction isn't perfect.Lag appears to be phase lag, though I'm not sure how that affects power rating - oh, I read more, now it's clear.
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MMMMM...I used the wrong formulas when figguring out what size generator I needed for power outages..
I calculated a 5K would cover every I wanted to run.I went with a 6.5K that has(i think) a 500 watt surge.
This explaines why it bogs down so bad when something like the boiler pump kicks in with everything running and seems to be working pretty hard.I am probably close to max output instead of having 1.5k more than I need.
I calculated a 5K would cover every I wanted to run.I went with a 6.5K that has(i think) a 500 watt surge.
This explaines why it bogs down so bad when something like the boiler pump kicks in with everything running and seems to be working pretty hard.I am probably close to max output instead of having 1.5k more than I need.
Tscott
Well-known member
Ripp,
Electric Motors, such as your boiler pump, will pull alot of current on start up. Depending on the motor code ( a letter on the name plate) they can pull 5 times or more of their running amps for a second or so on startup. This amperage is represented on the data plate as LRA or "Lock Rotor Amps" This is why your generator bogs when large motor loads start. this is not a big deal as long as it's not so drastic that it stalls your generator, and you can stand the flicker of the lights. I would say as long as the generator stays running you will be fine.
Tom
Electric Motors, such as your boiler pump, will pull alot of current on start up. Depending on the motor code ( a letter on the name plate) they can pull 5 times or more of their running amps for a second or so on startup. This amperage is represented on the data plate as LRA or "Lock Rotor Amps" This is why your generator bogs when large motor loads start. this is not a big deal as long as it's not so drastic that it stalls your generator, and you can stand the flicker of the lights. I would say as long as the generator stays running you will be fine.
Tom