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Old 11-29-2008, 11:33 PM   #1
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Heil Electric furnace tripping breaker


Hi,
I have a Heil ebp4800a2 electric furnace. Heat packs are fed via 2 circuits, one of which keeps tripping the breaker so I have maybe 50% heating. Replacing coils looks like a very simple repair but before I throw money at parts I am hoping someone might be able to tell me the proper or most sensible diagnostic procedure to rule out anything else first. I have a digital multi meter.

Also, I noticed while looking through the humidifier hole in the plenum while system was running that the two coils that are still heating appear to have "dark spots" on them, that is, they are not glowing red 100%. If I end up replacing 2, should I just replace them all?

Furnace only has 3 heating seasons on it.
Thanks in advance to any pros out there willing to help.

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Old 11-30-2008, 01:12 AM   #2
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Heil Electric furnace tripping breaker


I can see two possibilities here;

The first is that the breaker is bad, or more likely, the wire terminations are loose causing heat to make it trip when there isn't an overload. This is the first thing I'd check.

The other one is that the heating element has developed a fault somewhere. Frequently, this is a ground-fault. With all power off to the furnace, measure resistance from each element lead wire to ground (the metal frame of the furnace will do, the actual ground wire is better). All of these must read infinite (open circuit) resistance.

If this checks out OK, the only way to know for sure if it's the elements or the breaker is by checking current during operation using a clamp-on amp meter. This can be done either at the breaker (preferred) or at the furnace.

To find the proper amperage, divide the wattage by the voltage. For example, if the stage you're having trouble with is 10KW (10,000 watts), and it operates on 240 volts (both of these figures are pretty common), 10,000 watts divided by 240 volts equals 41.6 amps. It'll vary a little because of voltage differences, but it should be close.

If the current looks good, and the connections are tight, replace the breaker. They don't go bad very often, but sometimes......

Rob

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Old 11-30-2008, 06:08 AM   #3
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Heil Electric furnace tripping breaker


Hate to tell you this.
But, they're not really suppose to glow red.
Thats an indication of low air flow.
Which can cause elements to burn up in just a few years.
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Old 11-30-2008, 07:55 AM   #4
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Heil Electric furnace tripping breaker


Thanks for the replies.

Could having the plenum open (humidifier off) while the system is running be the cause of the low airflow thereby causing the coils to glow?
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Old 11-30-2008, 09:08 AM   #5
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Heil Electric furnace tripping breaker


No, that would help to increase air flow.
Your return is probably too small/restrictive.
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Old 11-30-2008, 09:37 AM   #6
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Sounds like a lack of airflow to me. Check the A/C coil for dirt, make sure all registers are clean and open (both hot and cold). Those elements should last at least 10 yrs and never glow red. Possibly the furnace is too large for the house/ductwork. Was it sized properly by a pro?
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Old 11-30-2008, 11:40 PM   #7
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Heil Electric furnace tripping breaker


Thanks again everyone.
I'm beginning to get the idea that heating coils are the least of my problems. Everything is clear open and flowing, (always was) a/c coil is clean. I have 2 of 4 coils heating, and they are glowing red but their not supposed to - even when I have the humidifier off the plenum.
I always figured the blower system was too small since I bought the place this spring - the distant vents have never put out more than a hardly noticeable breeze.

I should have provided more info before so here's a few details.

Supposed to be 48k BTU and according to manual, flow at 1400 cfm. Blower indicates This furnace blows out of a 12x21X2' plenum into a 35x8 "distribution head" (forgive the guess-lingo) which splits off in two directions 70/30 with the 30 feeding 8' of 8 x14 feeding 5 6" rounds that run out all inclusive about 50' with PLENTY of elbows. The 70 is further split 70/30 with the 30 feeding 10' of 8x14 feeding another 5 6" rounds with even more elbows on them for about another 50 ft. The 70 that remains is 8X17.5 and runs 35 feet with a 10" lift and drop at either end, feeding about 12 6" rounds that probably total about 125 ft. There are 3 return mains that are all 8x14, only one from the basement, as I look at them in comparison to supply, I realize system is probabaly lean on returns.

I have a manual that shows configurations and power taps for blower motor, this installation is in the default (medium) speed. It seems like I should be ok to go to high speed given the "glowing" performance (pun intended) I am experiencing, or not?

How difficult is it to convert this to a 2 or three speed, anyone know?
Thanks again in advance, your help is greatly appreciated.
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Old 11-30-2008, 11:47 PM   #8
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Heil Electric furnace tripping breaker


If your air filter is at teh unit.
While the unit is running.
Pull the air filter out.
If its hard to do, your a bit lacking on return.

Can you post pics of your duct system.

Might want to set the blower to high speed.

If your moving 1400 CFM. With just 2 strip heaters on, The air out of the registers should feel cool, to just barely warm.
At 10KW of strip moving 1400 CFM, the air should only be 22 to 23 degrees warmer then the return air.
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Old 12-02-2008, 12:46 PM   #9
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Heil Electric furnace tripping breaker


I set the blower to high, which seems to bring the airflow at the registers up to where it should be throughout the house. Breaker still tripped. Had an extra breaker so I replaced breaker, no more tripping. Flow at registers is 114. About 60% of the coils are glowing as before. Ran system with blower cover off and humidifier out so it could draw and force air unimpeded, and still have the exact same amount of red glowing coils. I noticed Airflow in the very center of the plenum riser seems weak, like it has a bit of a "hollow" spot, but is very strong more towards the sides. Sliding out the air filter with system closed back up and fan on highest speed requires a little pull, but doesn't seem too difficult due to air flow. It's not too easy to get out even when the system isn't running.

It was 28 degrees last night, ran the system on auto, set at 72 for a few hours to see what it would do with the high speed fan setting. It ran for 9 minute cycles with 7 minutes in between for about 3 hours, I'm not sure if that is excessive or not, but I noticed rh dropping fast so I set fan to on and let it run overnight in hopes we dont dry up like the sahara.

This morning the RH was at 24. My humidifier is an (aprilaire 400a) which has a sump and wicks the water that makes it to the sump until float calls for more, which is very frequently, it is cranked up all the way. The most I got out of it before was about 32 after several days with fan running 24/7. I bought that model because we're on septic and it doesn't dump water but now I'm thinking it's not going to be sufficient. Think I could add a booster fan or relocate the by pass and increase it's output?

Duct work pics attached.

Thanks again to everyone for all your advise.
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Old 12-09-2008, 09:51 PM   #10
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Heil Electric furnace tripping breaker


The 400a has to go, I wish I'd known I needed something different with electric heat, just not hot enough for the bypass I guess. I even added a 400 cfm fan to it which only got me a few points rh in a weeks time, even with rising temps and a LOT of sealing up the house. Oh well. Live and learn.

Switched the lowest end 3m filter and still have few partially glowing coils. Keep in mind that is after I switched the fan from medium to high speed.
I think the system could use a bit more return, but I also think the supply plenum is too small and poorly configured considering what goes on beyond it. I've looked at several furnace installations since these problems began, including one on my prior home (now a rental). I had an excellent craftsman install that system. I remember commenting on the nice quality work he did on the penum riser he made and him telling me how many hvac pros dont take the time to learn good metalworking skills or are too lazy and therefore dont do much other than stuff a stock plenum in whenever they can. It seems to me that is what I may have here. I think the supply plenum could be significantly less restrictive and turbulence inducing than it is and that it is the primary reason I have glowing coils. Anyone willing to offer an opinion based on the pictures?
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Old 12-09-2008, 11:21 PM   #11
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Heil Electric furnace tripping breaker


Check out steam humidifiers.
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Old 12-10-2008, 06:11 AM   #12
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The plenum to trunk line connection is more restrictive then some may think.

The plenum could be modified, or replaced with a lot less restrictive set up.

Although, somewhat unavoidable. The Tee being so close to the plenum to trunk line connection, is also causing some turbulance. Which also slows down the air flow.
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Old 10-19-2011, 11:15 PM   #13
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Heil Electric furnace tripping breaker


Back at it again. I have installed a white rodgers steam humidifier which works excellent, a diverter in the riser to smooth out airflow, and added a return as well which has improved system performance. I still have glowing coils and big electric bills. I'm thinking this system is oversized or underblown. I was considering disconnecting the two coil packs that are glowing out the five in the system, wondering if that's ok to do.
I noticed one that is glowing, however, has an extra blue wire coming off of the limit switch and an extra black coming off the sequencer - both run to the fan relay. If disconnecting is possible to do, can I make those connections to another coil pack and sequencer in place of their current location?
Thanks in advance!
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Old 10-20-2011, 05:15 AM   #14
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They can be moved to which ever heater becomes the first one to come on.
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Old 10-20-2011, 11:04 AM   #15
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Thanks!
I'm wondering....Does anyone know what causes the "dead spot" in the airflow right in the middle of the furnace 6" +- above the blower housing (right where the heating coils are) and is there a solution?

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