Electric Heater Tripping Main Breaker - Electrical - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Like Tree2Likes
Reply
 
Thread Tools
Display Modes
Old 04-23-2018, 08:45 PM   #1
Newbie
 
Join Date: Apr 2018
Posts: 7
Rewards Points: 14
Default

Electric Heater Tripping Main Breaker


I have an electric heater that is tripping the main breaker at the main panel in the garage.

The Lennox electric heater (ECB29-15CB) is part of a Lennox Air Handler (CBX32M-048).

The Lennox electric heater is rated 15kw @ 240/208 volts and has two circuits. AMPS are for CKT 1: 20.8/18.1 and for CKT 2: 41.7/36.2

There is a 30 amp breaker and a 60 amp breaker for those circuits on the unit. Those breakers have not tripped.

The breaker at the main panel in the garage is a 40 amp breaker and is tripping. It does not trip immediately, but as the longer the unit stays on the more likely it is to trip.

The unit is wired as follows:
The 40 amp breaker supplies power to the 60 amp breaker as well as the 30 amp breaker. This this done by jumping/bridging the 30 amp breaker to the 60 amp breaker. Is this typical?

Based on my little understanding, it seems the 40 amp breaker should be at least a 60 amp breaker (15000/240=62.5) as some have suggested.

But what's "tripping me up" is the book says that if you install the optional single point power supply then it has a MCA of 81 and a MOP of 90. I'm not sure what gauge wire would carry 81 amps but I'm pretty sure that's not what their now.

So what would be the proper way to wire this if I don't purchase the single point power supply? Is a 60 amp breaker sufficient if I don't use a single point power supply?

Thanks for your replies.
Attached Thumbnails
Electric Heater Tripping Main Breaker-heat-label.jpg   Electric Heater Tripping Main Breaker-breaker-heat.jpg   Electric Heater Tripping Main Breaker-breaker-garage.jpg  
DIY45 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 04-23-2018, 09:07 PM   #2
A "Handy Husband"
 
rjniles's Avatar
 
Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 9,519
Rewards Points: 392
Default

Re: Electric Heater Tripping Main Breaker


You need to upgrade the feeder to the garage panel to at least 60 amps. This means a larger cable back to the panel supplying the garage panel.

Sent from my RCT6213W22 using Tapatalk
__________________
My electrical answers are based on 2014 NEC, you may have local amendments.

Location: Coastal South Carolina
rjniles is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 04-23-2018, 09:09 PM   #3
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 12,315
Rewards Points: 3,592
Default

Re: Electric Heater Tripping Main Breaker


You have too much load on the panel. You need a larger feeder breaker and wiring.
__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 04-23-2018, 09:18 PM   #4
Newbie
 
Join Date: Apr 2018
Posts: 7
Rewards Points: 14
Default

Re: Electric Heater Tripping Main Breaker


So after running the correct gauge wire with a 60 amp breaker and feeding it back to the unit, the way those two breakers are tied together is legit? It's hard to tell from the attached pic but the main line power source goes into the 60 amp breaker and two jumper wires (smaller gauge) tie into the 30 amp breaker. Basically the 60 amp breaker has four wires on the input side.

Thanks to both for your quick replies.
DIY45 is offline   Reply With Quote
Old 04-23-2018, 10:05 PM   #5
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 12,315
Rewards Points: 3,592
Default

Re: Electric Heater Tripping Main Breaker


That looks like factory wiring. I would not worry about it.
__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is offline   Reply With Quote
Old 04-24-2018, 02:32 AM   #6
Member
 
dmxtothemax's Avatar
 
Join Date: Oct 2010
Location: Brisbane, Australia.
Posts: 5,179
Rewards Points: 7,318
Default

Re: Electric Heater Tripping Main Breaker


You have answered your own question -

Based on my little understanding, it seems the 40 amp breaker should be at least a 60 amp breaker (15000/240=62.5) as some have suggested.-

Correct !
dmxtothemax is online now   Reply With Quote
Old 04-24-2018, 05:06 AM   #7
A "Handy Husband"
 
rjniles's Avatar
 
Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 9,519
Rewards Points: 392
Default

Re: Electric Heater Tripping Main Breaker


I also see the 40 ampo breaker is a Challenger and the 30 and 60 are Square D, that is wrong. The panel and breakers must match.

Sent from my RCT6213W22 using Tapatalk
__________________
My electrical answers are based on 2014 NEC, you may have local amendments.

Location: Coastal South Carolina
rjniles is offline   Reply With Quote
The Following User Says Thank You to rjniles For This Useful Post:
Jim Port (04-24-2018)
Old 04-24-2018, 05:51 AM   #8
Member
 
CodeMatters's Avatar
 
Join Date: Aug 2017
Location: Canada
Posts: 3,078
Rewards Points: 6,154
Default

Re: Electric Heater Tripping Main Breaker


I have more questions than answers. To start with, where are those 30 & 60A
breakers mounted? Are they integral to the furnace?
CodeMatters is offline   Reply With Quote
Old 04-24-2018, 07:52 AM   #9
Newbie
 
Join Date: Apr 2018
Posts: 7
Rewards Points: 14
Default

Re: Electric Heater Tripping Main Breaker


Yes, they are mounted on the unit. I've attached a drawing.

Here is a link to the manual. Mine is an 048. https://www.google.com/url?sa=t&rct=...3qEhoGKj9fsuS5

The breaker in the garage at the main panel is the on tripping. (40 amp)
Attached Thumbnails
Electric Heater Tripping Main Breaker-drawing-unit.jpg  
DIY45 is offline   Reply With Quote
Old 04-24-2018, 07:56 AM   #10
Newbie
 
Join Date: Apr 2018
Posts: 7
Rewards Points: 14
Default

Re: Electric Heater Tripping Main Breaker


Also here is a link to the installation instructions for the heater. Mine is the ECB29-15CB for a CBX32-048.

https://www.google.com/url?sa=t&rct=...iEkae2e-6ClMI3
DIY45 is offline   Reply With Quote
Old 04-24-2018, 09:15 AM   #11
Member
 
Join Date: Oct 2011
Posts: 791
Rewards Points: 1,290
Default

Re: Electric Heater Tripping Main Breaker


you need a 80A breaker for this (62.5A x 1.25 (continuous load))
MCA of 81 and a MOP of 90 means minimum wire must be ok for 81A and max breaker is 90A
carmusic is offline   Reply With Quote
Old 04-24-2018, 09:27 AM   #12
Newbie
 
Join Date: Apr 2018
Posts: 7
Rewards Points: 14
Default

Re: Electric Heater Tripping Main Breaker


Quote:
Originally Posted by carmusic View Post
you need a 80A breaker for this (62.5A x 1.25 (continuous load))
MCA of 81 and a MOP of 90 means minimum wire must be ok for 81A and max breaker is 90A
That gives me some insight as to where the 81 MCA and 90 MOP specs come from. It seems to me then that purchasing the Single Point Power Supply would be the best option. Then rewire for 81 amp load and use a 90 amp breaker.

Single Point Power Supply:
https://www.ebay.com/p/LENNOX-Single...75.c100623.m-1
DIY45 is offline   Reply With Quote
Old 04-24-2018, 10:31 AM   #13
Deleted Member
 
Shadow99's Avatar
 
Join Date: Nov 2017
Location: Canada
Posts: 429
Rewards Points: 858
Default

Re: Electric Heater Tripping Main Breaker


Quote:
Originally Posted by DIY45 View Post
That gives me some insight as to where the 81 MCA and 90 MOP specs come from. It seems to me then that purchasing the Single Point Power Supply would be the best option. Then rewire for 81 amp load and use a 90 amp breaker.

Single Point Power Supply:
I don't think you want to do that. The 30 and 60 A breakers are your disconnect. Unless this unit is within sight of the Main Breaker, you need it there.

Either way, unit is 62.5A + 2.4A for the motor, 64.9A X 1.25 is 81A.
If NEC allows 75˚C Ampacity, thats #4cu on 90A breaker.
Feed direct if you don't need disconnect, or feed the dual breakers if (local) disconnect required.
Shadow99 is offline   Reply With Quote
Old 04-25-2018, 09:31 AM   #14
Newbie
 
Join Date: Apr 2018
Posts: 7
Rewards Points: 14
Default

Re: Electric Heater Tripping Main Breaker


Thanks to all. I appreciate the help. The information about the continuous load and including the FLA of the motor gave me the understanding I needed. Now I'm looking into the local codes (Plano, TX) and going on from there.
DIY45 is offline   Reply With Quote
Old 04-25-2018, 07:58 PM   #15
Disrespectful to dirt
 
Fishbulb28's Avatar
 
Join Date: Jul 2016
Posts: 970
Rewards Points: 1,942
Default

Re: Electric Heater Tripping Main Breaker


Quote:
Originally Posted by DIY45 View Post
So what would be the proper way to wire this if I don't purchase the single point power supply?
As the unit is configured right now, without the single point adapter, two branch circuits are required. A single branch circuit may not supply both heating circuits even if the branch circuit has sufficient ampacity. You must supply both a 60A and a 30A branch circuit. With the single point adapter installed a single 90A branch circuit would be allowed.

Quote:
It seems to me then that purchasing the Single Point Power Supply would be the best option. Then rewire for 81 amp load and use a 90 amp breaker.
You need to decide yourself which way would be best and least expensive. Here is how I would proceed.

1. A 15 kW heater load is not at all insignificant. Do a total load calculation for your service and verify there is sufficient ampacity available. Given the way the furnace is presently installed, I very much doubt the installer ever did this. (Hopefully it wasn't you so I don't have to feel bad about saying that.) There is no point in making a proper electrical installation for the furnace if your service cannot run it in the first place. Keep in mind you need to have 18.75 kVA available, not just the 15 kW.

2. Is the existing branch circuit wiring of sufficient size and type to carry 60A (#6 THHN in particular)? If so, use that for the 60A circuit conductors and install an additional 30A circuit. Nothing is going to be cheaper than this option. It's not possible to tell the size from the photo provided, but the individual strands do look a little large to be from #8 conductors.

3. Verify your panel can support a 90A breaker. Some panels have limits on how much current can be used by each bus stab. Check the panel stickers (inside and out) for any limits or post pictures of them here. If you cannot install a 90A breaker the decision is already made for you.

4. Compare the cost of materials for both methods. Even if not sufficient for 60A, the existing wiring is surely okay for the 30A circuit. You would then need only install an additional 60A circuit. Installing the single source option requires you to buy the hardware and install heavier conductors.

Dual branch circuits:
60A conductors
60A breaker
30A breaker

Single source option:
Conversion hardware
90A conductors
90A breaker
Fishbulb28 is online now   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Crackling from circuit breaker for electric water heater uvalaw Electrical 8 01-25-2018 06:48 PM
Electric Hot Water Heater Not Working - No Hot Water - Troubleshooting tips needed amodoko Plumbing 56 08-12-2016 04:27 PM
Garage breaker keeps tripping rhanson85 Electrical 5 07-19-2012 06:24 AM
ele water heater tripping breaker emmy Plumbing 2 12-06-2010 03:33 PM
Hot water heater keeps tripping breaker ronkar88 Electrical 3 07-30-2008 12:44 PM




Top of Page | View New Posts