Breaker feeding an electric heater trips after one minute
I purchased a Comfort Zone Heater. Model CZ230ER. It is a 7,500 watt 240V unit.
This was installed with 10/2 wire to a brand new 30 amp breaker. Once the heater has been running for about a minute it trips the breaker. I have verified there are no shorts.
I do have it about 60 feet from the panel and my wire conduit was only 25 feet long. The connections are made using wire nuts mounted in a metal box.
Any thoughts?
circuit-breaker
edited Feb 1 at 20:02
isherwood
48.8k456123
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
add a comment |
I purchased a Comfort Zone Heater. Model CZ230ER. It is a 7,500 watt 240V unit.
This was installed with 10/2 wire to a brand new 30 amp breaker. Once the heater has been running for about a minute it trips the breaker. I have verified there are no shorts.
I do have it about 60 feet from the panel and my wire conduit was only 25 feet long. The connections are made using wire nuts mounted in a metal box.
Any thoughts?
circuit-breaker
edited Feb 1 at 20:02
isherwood
48.8k456123
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
add a comment |
I purchased a Comfort Zone Heater. Model CZ230ER. It is a 7,500 watt 240V unit.
This was installed with 10/2 wire to a brand new 30 amp breaker. Once the heater has been running for about a minute it trips the breaker. I have verified there are no shorts.
I do have it about 60 feet from the panel and my wire conduit was only 25 feet long. The connections are made using wire nuts mounted in a metal box.
Any thoughts?
circuit-breaker
edited Feb 1 at 20:02
isherwood
48.8k456123
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
I purchased a Comfort Zone Heater. Model CZ230ER. It is a 7,500 watt 240V unit.
This was installed with 10/2 wire to a brand new 30 amp breaker. Once the heater has been running for about a minute it trips the breaker. I have verified there are no shorts.
I do have it about 60 feet from the panel and my wire conduit was only 25 feet long. The connections are made using wire nuts mounted in a metal box.
Any thoughts?
circuit-breaker
circuit-breaker
edited Feb 1 at 20:02
isherwood
48.8k456123
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
edited Feb 1 at 20:02
isherwood
48.8k456123
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
edited Feb 1 at 20:02
isherwood
48.8k456123
edited Feb 1 at 20:02
isherwood
48.8k456123
edited Feb 1 at 20:02
isherwood
48.8k456123
48.8k456123
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
asked Feb 1 at 19:45
Rick RobertsonRick Robertson
61
61
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
As noted by isherwood, you are pulling too much power. 7,500 W /240 V = 31.25 A on a 30 A circuit. Circuit breakers are typically designed to handle a somewhat higher than rated current for a short time - e.g., motor startup, a really high current (e.g., hundreds of Amps on a 30 A circuit) for an extremely short time, and a moderate overage for a moderate amount of time. This actually matches well with another rule: continuous loads should not exceed 80% of the rated circuit. In the case of 30 A, that means your continuous load should be no more than 24 A = 7,200 W.
So this is actually normal operation.
You need either a slightly smaller heater or a larger breaker with matching appropriately sized wiring.
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
1
24 amps at 240v is 5760 watts. 30 amps at 240v is 7200 watts. The proper circuit size for the 7500w heater would be (1.2 * 7500w) / 240v = 37.5 amps (40 amp).
– JPhi1618
Feb 1 at 21:06
1
Actually I think 0.8 down equals 1.25 up so 1.25x7500/240=39. But still 40A breaker.
– manassehkatz
Feb 1 at 21:57
You're right. 80% and 125% match up (1.25). The 1.2 was a mistake.
– JPhi1618
Feb 1 at 22:00
Comments are fair game. Don't shout-out to them. Especially if they get deleted ;)
– Mazura
Feb 2 at 3:28
add a comment |
Right off the bat you have overloaded the breaker. 7500W > the 7200W a 30A circuit can carry.
7200W = 30A x 240V.
240V is actual voltage in USA.
I see where the installation instructions are ambiguous about wire size. That is very typical of heater instructions; they are absolutely as vague and generic as they can possibly be, because writing manuals is expensive and they want the flexibility to use the same instructions for as many models as possible.
So they mention 10 AWG wire in the prose of the "how to wire" section. But they are talking about the machine's internal wires, which are allowed to be 10AWG. Only later in a chart do they have a table indicating 31.25A and 8 AWG wire for 7500W models. I am surprised UL listed it that way.
Anyway, the basic rule is that heaters are a continuous load and you must provision power for 125% of their nameplate. 125% of 7500 is 9375 watts, which fits very nicely inside 9600 watts, the capacity of a 40A circuit. That's why that heater is sized that way.
A 40A circuit calls for 8 AWG wire.
answered Feb 1 at 23:19
HarperHarper
71.7k448143
1
Thanks...wish I understood that before I ran 50 feet of flex with 10/2!!! Live and learn. Re-installing with 8/2 and a 40A breaker as we speak. Thanks for the info!
– Rick Robertson
Feb 2 at 20:17
add a comment |
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2 Answers
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2 Answers
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As noted by isherwood, you are pulling too much power. 7,500 W /240 V = 31.25 A on a 30 A circuit. Circuit breakers are typically designed to handle a somewhat higher than rated current for a short time - e.g., motor startup, a really high current (e.g., hundreds of Amps on a 30 A circuit) for an extremely short time, and a moderate overage for a moderate amount of time. This actually matches well with another rule: continuous loads should not exceed 80% of the rated circuit. In the case of 30 A, that means your continuous load should be no more than 24 A = 7,200 W.
So this is actually normal operation.
You need either a slightly smaller heater or a larger breaker with matching appropriately sized wiring.
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
1
24 amps at 240v is 5760 watts. 30 amps at 240v is 7200 watts. The proper circuit size for the 7500w heater would be (1.2 * 7500w) / 240v = 37.5 amps (40 amp).
– JPhi1618
Feb 1 at 21:06
1
Actually I think 0.8 down equals 1.25 up so 1.25x7500/240=39. But still 40A breaker.
– manassehkatz
Feb 1 at 21:57
You're right. 80% and 125% match up (1.25). The 1.2 was a mistake.
– JPhi1618
Feb 1 at 22:00
Comments are fair game. Don't shout-out to them. Especially if they get deleted ;)
– Mazura
Feb 2 at 3:28
add a comment |
As noted by isherwood, you are pulling too much power. 7,500 W /240 V = 31.25 A on a 30 A circuit. Circuit breakers are typically designed to handle a somewhat higher than rated current for a short time - e.g., motor startup, a really high current (e.g., hundreds of Amps on a 30 A circuit) for an extremely short time, and a moderate overage for a moderate amount of time. This actually matches well with another rule: continuous loads should not exceed 80% of the rated circuit. In the case of 30 A, that means your continuous load should be no more than 24 A = 7,200 W.
So this is actually normal operation.
You need either a slightly smaller heater or a larger breaker with matching appropriately sized wiring.
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
1
24 amps at 240v is 5760 watts. 30 amps at 240v is 7200 watts. The proper circuit size for the 7500w heater would be (1.2 * 7500w) / 240v = 37.5 amps (40 amp).
– JPhi1618
Feb 1 at 21:06
1
Actually I think 0.8 down equals 1.25 up so 1.25x7500/240=39. But still 40A breaker.
– manassehkatz
Feb 1 at 21:57
You're right. 80% and 125% match up (1.25). The 1.2 was a mistake.
– JPhi1618
Feb 1 at 22:00
Comments are fair game. Don't shout-out to them. Especially if they get deleted ;)
– Mazura
Feb 2 at 3:28
add a comment |
As noted by isherwood, you are pulling too much power. 7,500 W /240 V = 31.25 A on a 30 A circuit. Circuit breakers are typically designed to handle a somewhat higher than rated current for a short time - e.g., motor startup, a really high current (e.g., hundreds of Amps on a 30 A circuit) for an extremely short time, and a moderate overage for a moderate amount of time. This actually matches well with another rule: continuous loads should not exceed 80% of the rated circuit. In the case of 30 A, that means your continuous load should be no more than 24 A = 7,200 W.
So this is actually normal operation.
You need either a slightly smaller heater or a larger breaker with matching appropriately sized wiring.
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
As noted by isherwood, you are pulling too much power. 7,500 W /240 V = 31.25 A on a 30 A circuit. Circuit breakers are typically designed to handle a somewhat higher than rated current for a short time - e.g., motor startup, a really high current (e.g., hundreds of Amps on a 30 A circuit) for an extremely short time, and a moderate overage for a moderate amount of time. This actually matches well with another rule: continuous loads should not exceed 80% of the rated circuit. In the case of 30 A, that means your continuous load should be no more than 24 A = 7,200 W.
So this is actually normal operation.
You need either a slightly smaller heater or a larger breaker with matching appropriately sized wiring.
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
answered Feb 1 at 19:53
manassehkatzmanassehkatz
8,9971335
8,9971335
1
24 amps at 240v is 5760 watts. 30 amps at 240v is 7200 watts. The proper circuit size for the 7500w heater would be (1.2 * 7500w) / 240v = 37.5 amps (40 amp).
– JPhi1618
Feb 1 at 21:06
1
Actually I think 0.8 down equals 1.25 up so 1.25x7500/240=39. But still 40A breaker.
– manassehkatz
Feb 1 at 21:57
You're right. 80% and 125% match up (1.25). The 1.2 was a mistake.
– JPhi1618
Feb 1 at 22:00
Comments are fair game. Don't shout-out to them. Especially if they get deleted ;)
– Mazura
Feb 2 at 3:28
add a comment |
1
24 amps at 240v is 5760 watts. 30 amps at 240v is 7200 watts. The proper circuit size for the 7500w heater would be (1.2 * 7500w) / 240v = 37.5 amps (40 amp).
– JPhi1618
Feb 1 at 21:06
1
Actually I think 0.8 down equals 1.25 up so 1.25x7500/240=39. But still 40A breaker.
– manassehkatz
Feb 1 at 21:57
You're right. 80% and 125% match up (1.25). The 1.2 was a mistake.
– JPhi1618
Feb 1 at 22:00
Comments are fair game. Don't shout-out to them. Especially if they get deleted ;)
– Mazura
Feb 2 at 3:28
1
1
24 amps at 240v is 5760 watts. 30 amps at 240v is 7200 watts. The proper circuit size for the 7500w heater would be (1.2 * 7500w) / 240v = 37.5 amps (40 amp).
– JPhi1618
Feb 1 at 21:06
24 amps at 240v is 5760 watts. 30 amps at 240v is 7200 watts. The proper circuit size for the 7500w heater would be (1.2 * 7500w) / 240v = 37.5 amps (40 amp).
– JPhi1618
Feb 1 at 21:06
1
1
Actually I think 0.8 down equals 1.25 up so 1.25x7500/240=39. But still 40A breaker.
– manassehkatz
Feb 1 at 21:57
Actually I think 0.8 down equals 1.25 up so 1.25x7500/240=39. But still 40A breaker.
– manassehkatz
Feb 1 at 21:57
You're right. 80% and 125% match up (1.25). The 1.2 was a mistake.
– JPhi1618
Feb 1 at 22:00
You're right. 80% and 125% match up (1.25). The 1.2 was a mistake.
– JPhi1618
Feb 1 at 22:00
Comments are fair game. Don't shout-out to them. Especially if they get deleted ;)
– Mazura
Feb 2 at 3:28
Comments are fair game. Don't shout-out to them. Especially if they get deleted ;)
– Mazura
Feb 2 at 3:28
add a comment |
Right off the bat you have overloaded the breaker. 7500W > the 7200W a 30A circuit can carry.
7200W = 30A x 240V.
240V is actual voltage in USA.
I see where the installation instructions are ambiguous about wire size. That is very typical of heater instructions; they are absolutely as vague and generic as they can possibly be, because writing manuals is expensive and they want the flexibility to use the same instructions for as many models as possible.
So they mention 10 AWG wire in the prose of the "how to wire" section. But they are talking about the machine's internal wires, which are allowed to be 10AWG. Only later in a chart do they have a table indicating 31.25A and 8 AWG wire for 7500W models. I am surprised UL listed it that way.
Anyway, the basic rule is that heaters are a continuous load and you must provision power for 125% of their nameplate. 125% of 7500 is 9375 watts, which fits very nicely inside 9600 watts, the capacity of a 40A circuit. That's why that heater is sized that way.
A 40A circuit calls for 8 AWG wire.
answered Feb 1 at 23:19
HarperHarper
71.7k448143
1
Thanks...wish I understood that before I ran 50 feet of flex with 10/2!!! Live and learn. Re-installing with 8/2 and a 40A breaker as we speak. Thanks for the info!
– Rick Robertson
Feb 2 at 20:17
add a comment |
Right off the bat you have overloaded the breaker. 7500W > the 7200W a 30A circuit can carry.
7200W = 30A x 240V.
240V is actual voltage in USA.
I see where the installation instructions are ambiguous about wire size. That is very typical of heater instructions; they are absolutely as vague and generic as they can possibly be, because writing manuals is expensive and they want the flexibility to use the same instructions for as many models as possible.
So they mention 10 AWG wire in the prose of the "how to wire" section. But they are talking about the machine's internal wires, which are allowed to be 10AWG. Only later in a chart do they have a table indicating 31.25A and 8 AWG wire for 7500W models. I am surprised UL listed it that way.
Anyway, the basic rule is that heaters are a continuous load and you must provision power for 125% of their nameplate. 125% of 7500 is 9375 watts, which fits very nicely inside 9600 watts, the capacity of a 40A circuit. That's why that heater is sized that way.
A 40A circuit calls for 8 AWG wire.
answered Feb 1 at 23:19
HarperHarper
71.7k448143
1
Thanks...wish I understood that before I ran 50 feet of flex with 10/2!!! Live and learn. Re-installing with 8/2 and a 40A breaker as we speak. Thanks for the info!
– Rick Robertson
Feb 2 at 20:17
add a comment |
Right off the bat you have overloaded the breaker. 7500W > the 7200W a 30A circuit can carry.
7200W = 30A x 240V.
240V is actual voltage in USA.
I see where the installation instructions are ambiguous about wire size. That is very typical of heater instructions; they are absolutely as vague and generic as they can possibly be, because writing manuals is expensive and they want the flexibility to use the same instructions for as many models as possible.
So they mention 10 AWG wire in the prose of the "how to wire" section. But they are talking about the machine's internal wires, which are allowed to be 10AWG. Only later in a chart do they have a table indicating 31.25A and 8 AWG wire for 7500W models. I am surprised UL listed it that way.
Anyway, the basic rule is that heaters are a continuous load and you must provision power for 125% of their nameplate. 125% of 7500 is 9375 watts, which fits very nicely inside 9600 watts, the capacity of a 40A circuit. That's why that heater is sized that way.
A 40A circuit calls for 8 AWG wire.
answered Feb 1 at 23:19
HarperHarper
71.7k448143
Right off the bat you have overloaded the breaker. 7500W > the 7200W a 30A circuit can carry.
7200W = 30A x 240V.
240V is actual voltage in USA.
I see where the installation instructions are ambiguous about wire size. That is very typical of heater instructions; they are absolutely as vague and generic as they can possibly be, because writing manuals is expensive and they want the flexibility to use the same instructions for as many models as possible.
So they mention 10 AWG wire in the prose of the "how to wire" section. But they are talking about the machine's internal wires, which are allowed to be 10AWG. Only later in a chart do they have a table indicating 31.25A and 8 AWG wire for 7500W models. I am surprised UL listed it that way.
Anyway, the basic rule is that heaters are a continuous load and you must provision power for 125% of their nameplate. 125% of 7500 is 9375 watts, which fits very nicely inside 9600 watts, the capacity of a 40A circuit. That's why that heater is sized that way.
A 40A circuit calls for 8 AWG wire.
answered Feb 1 at 23:19
HarperHarper
71.7k448143
answered Feb 1 at 23:19
HarperHarper
71.7k448143
answered Feb 1 at 23:19
HarperHarper
71.7k448143
answered Feb 1 at 23:19
HarperHarper
71.7k448143
71.7k448143
1
Thanks...wish I understood that before I ran 50 feet of flex with 10/2!!! Live and learn. Re-installing with 8/2 and a 40A breaker as we speak. Thanks for the info!
– Rick Robertson
Feb 2 at 20:17
add a comment |
1
Thanks...wish I understood that before I ran 50 feet of flex with 10/2!!! Live and learn. Re-installing with 8/2 and a 40A breaker as we speak. Thanks for the info!
– Rick Robertson
Feb 2 at 20:17
1
1
Thanks...wish I understood that before I ran 50 feet of flex with 10/2!!! Live and learn. Re-installing with 8/2 and a 40A breaker as we speak. Thanks for the info!
– Rick Robertson
Feb 2 at 20:17
Thanks...wish I understood that before I ran 50 feet of flex with 10/2!!! Live and learn. Re-installing with 8/2 and a 40A breaker as we speak. Thanks for the info!
– Rick Robertson
Feb 2 at 20:17
add a comment |
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