water heater
- Thread starter ronson
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jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: water heater
any real electric supply house has 25 amp breakers.
Chances are it might trip often and cause unwanted service call (free)
[ July 06, 2004, 05:41 AM: Message edited by: jimwalker ]
any real electric supply house has 25 amp breakers.
Chances are it might trip often and cause unwanted service call (free)
[ July 06, 2004, 05:41 AM: Message edited by: jimwalker ]
bphgravity
Senior Member
- Location
- Florida
Re: water heater
Is that 2000W at 240V? If so, a 20A OCD would be more than sufficent to allow proper operation. Considering the manufacturer calls for a 25A OCD, it makes me think the water heater is a 120V appliance in which case a 20A OCD will be slightly too small.
Is that 2000W at 240V? If so, a 20A OCD would be more than sufficent to allow proper operation. Considering the manufacturer calls for a 25A OCD, it makes me think the water heater is a 120V appliance in which case a 20A OCD will be slightly too small.
Re: water heater
its a 120v wtr htr. if i divide the 2000w by 120v, i get 16.7A. i think GE got the 25A from NEC 422-11e3. why does NEC require 150%? how does a wtr htr really operate? does the wtr htr require 1.5 times the normal amperage to startup? could the thermostat be set at a lower setting that would allow the wtr htr to pull a lower amperage? with a 30A brkr & #10's could the wtr htr be dangerous & pull more current than it should?
[ July 06, 2004, 11:45 AM: Message edited by: ronson ]
its a 120v wtr htr. if i divide the 2000w by 120v, i get 16.7A. i think GE got the 25A from NEC 422-11e3. why does NEC require 150%? how does a wtr htr really operate? does the wtr htr require 1.5 times the normal amperage to startup? could the thermostat be set at a lower setting that would allow the wtr htr to pull a lower amperage? with a 30A brkr & #10's could the wtr htr be dangerous & pull more current than it should?
[ July 06, 2004, 11:45 AM: Message edited by: ronson ]
bphgravity
Senior Member
- Location
- Florida
Re: water heater
The code doesn't require 150%, it permits it. Section 422.13 requires a minimum rating of 125% of the appliance nameplate.
It comes down to testing and listing. The water heater is tested and listed with conductors and overcurrent devices at not less than 125% of the load and not more than 150% of the load. So in effect, UL or whatever NRTL that provides the listing cannot guaranty proper operation with wiring and protection outside those specifications.
The code doesn't require 150%, it permits it. Section 422.13 requires a minimum rating of 125% of the appliance nameplate.
It comes down to testing and listing. The water heater is tested and listed with conductors and overcurrent devices at not less than 125% of the load and not more than 150% of the load. So in effect, UL or whatever NRTL that provides the listing cannot guaranty proper operation with wiring and protection outside those specifications.
T
taylorp
Guest
Re: water heater
Ronson:
Bryan is right. If you look at 422.13 you will see that water heater branch circuits are required to be sized at 125%. 2000 Watts/120V = 16.66 x 125% = 20.83. Your circuit must have the ampacity of over 20 Amps. Therefore you would need #10 conductors and I would use a 25A circuit breaker if I had one. Otherwise a 30A would do with #10 conductors IMO.
Ronson:
Bryan is right. If you look at 422.13 you will see that water heater branch circuits are required to be sized at 125%. 2000 Watts/120V = 16.66 x 125% = 20.83. Your circuit must have the ampacity of over 20 Amps. Therefore you would need #10 conductors and I would use a 25A circuit breaker if I had one. Otherwise a 30A would do with #10 conductors IMO.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: water heater
2ndrat Your close but most 240vac home water heaters are a two stage system with two heating elements, one at the top and one at the bottom. With two temp controls that will either turn off the top element or place the two elements in series. This is why you might have two 4800 watt elements on a water heater but the total current that the heater draws will be only 20 amps@240 volts. When the water heater calls for heat both elements turn on in series but when the top thermostat reaches set temp it turns off and places the full voltage to the bottom element and only the bottom element is on until it reaches set temp. When you loose a top element the water heater will continue to provide hot water but at a very low recovery rate and will run at full wattage for a much longer time. and will be very noticeable on your electric bill.
As for a 120 volt unit most of these only have one element and have a very low recovery rate anyway. but operate like 2ndrat had said when it reaches set temp it turns off.
Hope this helps Ronson
2ndrat Your close but most 240vac home water heaters are a two stage system with two heating elements, one at the top and one at the bottom. With two temp controls that will either turn off the top element or place the two elements in series. This is why you might have two 4800 watt elements on a water heater but the total current that the heater draws will be only 20 amps@240 volts. When the water heater calls for heat both elements turn on in series but when the top thermostat reaches set temp it turns off and places the full voltage to the bottom element and only the bottom element is on until it reaches set temp. When you loose a top element the water heater will continue to provide hot water but at a very low recovery rate and will run at full wattage for a much longer time. and will be very noticeable on your electric bill.
As for a 120 volt unit most of these only have one element and have a very low recovery rate anyway. but operate like 2ndrat had said when it reaches set temp it turns off.
Hope this helps Ronson
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: water heater
they are not in series.Think about it with double resistance it would never get hot.What they do is allow 1 at a time to operate,makes up for water not moving and having colder spots.But it is either on or off no in between loads.
they are not in series.Think about it with double resistance it would never get hot.What they do is allow 1 at a time to operate,makes up for water not moving and having colder spots.But it is either on or off no in between loads.
electricman2
Senior Member
- Location
- North Carolina
- Occupation
- Retired Electrical Contractor
Re: water heater
Jim is right. Only one element at a time is on. Normally only the lower element cycles on and off. If the water temp at the upper thermostat drops below the set point it switches the bottom element off and the top one on.
Jim is right. Only one element at a time is on. Normally only the lower element cycles on and off. If the water temp at the upper thermostat drops below the set point it switches the bottom element off and the top one on.
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