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EC & CI
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Discussion Starter · #1 ·
This is regarding Infratech 240V electric patio heaters.
They have a 3000W heater at 12.5A and a 4000W heater at 16.7A that I have started using.

After adding 125% for continuous load,
  • 3000W heater is 15.625A rated conductor ampacity and OCPD.
  • 4000W heater is 20.875 rated conductor ampacity and OCPD.
Infratech's control panels have a 15A breaker for the 3K and a 20A breaker for the 4K unit that is UL listed.

If I am not using their control panel that is UL listed with that breaker size, does it seem that I have to use the next size up breaker and conductor size because it is technically over 15A and 20A after adjusting for continuous load?
For instance the 3000W heater with 20A breaker & #12 conductors AND 4000W heater with a 25A or 30A breaker & #10 conductors.
 

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Hackenschmidt
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I think you have it all right, I get the same numbers

3000/240 = 12.5 and 12.5 / .8 = 15.625
4000/240 = 16.666... and 16.666.../.8 20.8333... (a little different result due to rounding)

the only thing I could think of to check is that the manufacturer's instructions allow you to use the heaters without their control panel.
 
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EC & CI
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Discussion Starter · #3 ·
Yeah you can definitely use the heaters without the control panel. Sometimes I just use a local toggle switch On/Off for each heater.
The control panel allows you to bring all the heaters back to it and control them in zones with smart switches and dimmers.
 

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If I am not using their control panel that is UL listed with that breaker size, does it seem that I have to use the next size up breaker and conductor size because it is technically over 15A and 20A after adjusting for continuous load?
For instance the 3000W heater with 20A breaker & #12 conductors AND 4000W heater with a 25A or 30A breaker & #10 conductors.
I would say using their control panel is manufacturing spec. for these heaters so there is some leniency for required OCPD as its been engineered for these heaters specifically(assuming they are). But Yes, if not using their equipment all usual rules when installing an electric heater would apply.
 

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I would say using their control panel is manufacturing spec. for these heaters so there is some leniency for required OCPD as its been engineered for these heaters specifically(assuming they are). But Yes, if not using their equipment all usual rules when installing an electric heater would apply.
It's not leniency. The manufacturers use a high temperature rating wire and as such are not constrained by 80% loading rule.
 
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It's not leniency. The manufacturers use a high temperature rating wire and as such are not constrained by 80% loading rule.
That has nothing to do with the overcurrent protective device which is not rated for 100% continuous load.
 

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That has nothing to do with the overcurrent protective device which is not rated for 100% continuous load.
I was talking about the factory installed breaker in the control panels. ie the 3000W with a 15A breaker in the control, we still have to use a 20A and #12 wire to connect to it.
 

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I was talking about the factory installed breaker in the control panels. ie the 3000W with a 15A breaker in the control, we still have to use a 20A and #12 wire to connect to it.
Yeah I misunderstood the question being asked. Thanks for the correction
 

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EC & CI
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Discussion Starter · #9 ·
I've been using the 3000W with #12 and 20A OCP when using on/off switches.
I have a control panel that has 2 - 15A breakers for two 3000W heaters and the panel is feed with a 35A rated feed.

I have another job that has 6 - 20A breakers for six 4000W heaters and a 125A rated feed to the control panel.
I'm wondering whether I can run #12 or if I need to use #10 wire and conductors since each heater is protected at 20 Amps in the control panel.
Have to run several THHN conductors quite a distance to a pavilion then 6 runs of UF wire for each heater so there is a decent cost difference using either 12awg or 10awg.
 

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Hackenschmidt
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I've been using the 3000W with #12 and 20A OCP when using on/off switches.
I have a control panel that has 2 - 15A breakers for two 3000W heaters and the panel is feed with a 35A rated feed.

I have another job that has 6 - 20A breakers for six 4000W heaters and a 125A rated feed to the control panel.
I'm wondering whether I can run #12 or if I need to use #10 wire and conductors since each heater is protected at 20 Amps in the control panel.
Have to run several THHN conductors quite a distance to a pavilion then 6 runs of UF wire for each heater so there is a decent cost difference using either 12awg or 10awg.
I think there is an exception that answers this exact question:

210.19(A)(1)(b)

(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Conductors shall be sized to carry not less than the larger of 210.19(A)(1)(a) or (b).

(a) Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.

(b) The minimum branch-circuit conductor size shall have an allowable ampacity not less than the maximum load to be served after the application of any adjustment or correction factors.

Exception: If the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at 100 percent of its rating, the allowable ampacity of the branch-circuit conductors shall be permit‐ ted to be not less than the sum of the continuous load plus the noncontinuous load.
 
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