Issue with fuse

[FionaZuppa]

So if this is just a blower motor on an air handler and you say is 2/3HP, 5.3A, what is that nameplate for? It clearly says 14A. You can't run 14A continuously on 14ga wire, so something is missing or the info is inconsistent in this puzzle.

i will verify the blower motor specs.

the plug wire did not seem to get warm during the initail temp test, but the socket box/cover did. i suspect i will be changing the socket to a hard wired breaker type, and changing the 14ga plug/cord over to 12ga cord (the end inside the unit connects to board via push on blade connectors, etc).

more to come.

 

[FionaZuppa]

anyone have suggestion on a lever type breaker that works with motors and can fit into 1gang box, or a standalone unit. 120vac 15A "motor" is what it should be rated for. i am planning to ditch the screw-in fuse / outlet crud for something better, etc.

 

[SceneryDriver]

FionaZuppa,
Why can't you simply protect the circuit feeding the HVAC unit with the appropriate breaker in the panel? That has to be more convenient than trudging up to the attic to see if the local circuit protection has tripped. Is this setup serving as a local disconnect for servicing the unit? Can you use a non-fused disconnect to comply with that requirement?

Perhaps high ambient temperature (it's in an attic) coupled with vibration from the blowers are helping the fuse to blow?

If you want to use a local circuit breaker, check out these:

http://www.grainger.com/product/SQUARE-D-Load-Center-5B755?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/5B755_AS01?$smthumb$

It will take two single-pole breakers, or one double pole breaker. Wire up and use only one pole of the load center, and drop in a single pole QO breaker of your choosing.

Be careful about ditching the cord-and-plug. If it came that way from the factory, you will probably void its UL listing by hardwiring it. That said, I'd probably hard wire it anyway in your position. Use greenfield, and stranded conductors with the proper terminal crimping tool, and you'll be all set.



ScenreryDriver

 

[FionaZuppa]

i think the "T" fuse is just there as an additional protection. all my breakers in main panel are std types except for a few afci's and gfi's i put in for other things. the unit is in attic space that is roof-line insulated, the ambient temp in the attic stays below 80F, and there are no vibrations that i can tell, the plug is mounted ~3ft away from the actual unit on another truss.

the setup just seems odd. 10-2 romex to a cheap screw fuse / snap-in single outlet, then 14-2 cord to a unit that is rated 14A.

once i test actual current on the wire i can then figure out if there is blower motor issue or not. the plug may be a local disconnect, thus a lever type of breaker could serve as the local disco and also allow me to rid the plug for hardwire, etc. any crimps i do onto stranded usually means i will also solder the connection.


this is what is there now, its only rated 15A and for 1/2HP(max) motor.

Model # SRU-BC

The Cooper Bussmann Plug Fuse Holder with Outlet Box Cover Unit is rated for up to a 1/2 HP motor, 15 Amps and a maximum of 125 Volts. The Edison-base unit is UL listed.

• For use as a fuse holder and receptacle
• Edison base
• 15 amps, 125 volts
• Up to 1/2 HP motor
• UL listed

 

[FionaZuppa]

i am thinking maybe i go to the SOU item, then jump out to another 1-box that has a std 20A toggle switch, and hardwire back to unit with 12-2 cord. might be easier than installing a new "1-pole" load center. the switch serves as disco, but the fuse serves as the safety/service disco since a std switch can be accidentally knocked back to "on" position.

http://www.cooperindustries.com/con...essories/fuses/plug_fuses_box_coverunits.html

 

[kwired]

i am thinking maybe i go to the SOU item, then jump out to another 1-box that has a std 20A toggle switch, and hardwire back to unit with 12-2 cord. might be easier than installing a new "1-pole" load center. the switch serves as disco, but the fuse serves as the safety/service disco since a std switch can be accidentally knocked back to "on" position.

http://www.cooperindustries.com/con...essories/fuses/plug_fuses_box_coverunits.html

Unless you for some reason need supplemental protection or fuse only protection is required - I'd lose the fuse and just replace with a standard switch. If you are concerned about accidentally turning on the switch they do make attachments that allow for a lock to be installed for typical wall switches.

If you are leaving the cord and plug for some reason - unplugging the unit is a fairly positive disconnecting means and generally is a permitted disconnection method where cord and plug usage is permitted - those cords don't get up on their own too often and jump back into the receptacle

 

[FionaZuppa]

Unless you for some reason need supplemental protection or fuse only protection is required - I'd lose the fuse and just replace with a standard switch. If you are concerned about accidentally turning on the switch they do make attachments that allow for a lock to be installed for typical wall switches.

If you are leaving the cord and plug for some reason - unplugging the unit is a fairly positive disconnecting means and generally is a permitted disconnection method where cord and plug usage is permitted - those cords don't get up on their own too often and jump back into the receptacle

no plug, just cord and hardwire, etc. i think the fuse is there just as extra protection against motor overload. this was new build home so not sure why the electrical outfit installed it this way.

 

[SceneryDriver]

any crimps i do onto stranded usually means i will also solder the connection.

Actually, a properly done crimp is better than soldering. I thought different for years, but it was pointed out to me:

1) a proper crimp is a gas-tight connection so it is immune to corrosion.

2) solder wicks down the strands of wire, no matter how good and fast of a solderer you are. That now solid bit of wire creates a stress riser, and can lead to conductor failure if flexed or exposed to vibration. Among other reasons, that's why the pins of most cables are crimped and not soldered. Soldered connectors are convenient if you only have a few connectors to make up; you don't have to buy the $$$ crimping tool.

3) flux residue from soldering can be slightly corrosive under some circumstances, and can attract moisture in damp environments unless it is cleaned off; hard to do with wires.

4) solder is a poorer conductor than the copper wire or the tin plated terminal, and if exposed to high currents, it can melt and open like a fuse. Crimped connections won't do that.

5) NASA tries to avoid soldered connections. They like crimped. If it's good for NASA, I'm a fan.

Grab yourself a good ratcheting crimper and use the correct terminals with the correct dies. You'll make good solid connections, and in much less time than it takes to fire up the soldering iron too.



SceneryDriver

 

[FionaZuppa]

my PACE iron station is PWM controlled with thermocouple in iron, it gets to temp in about 20sec

not sure how a crimp makes gas tight connection on stranded wire, possible yes for maybe NASA, for the avg joe using hardware store bought connectors, no.

i do crimp the connector some, then i solder it. i would have just 3 connectors to do, and of the thousands of connectors i have soldered in the past (from welding machine connectors, automotive connectors, irrigation connectors, electrical connectors, etc etc) not one has ever failed. for some i use high % silver solder. flux has pros & cons, but a quick spray of flux cleaner is ok.

i have seen many crimps where wire was loose in crimp. i dont go crazy with the solder.

the comparison to Aircraft & NASA is a bit beyond this level. the wire and connectors they use are special and matched. not likely i am gong to the orange store and buying anything special or matched to some off-the-reel copper cord, etc.

 

[cowboyjwc]

Apparently we are drawing more then the earlier mentioned ~2 amps.

I myself would use a 20 amp fuse based on what that nameplate says. Running current is not likley high enough to be a problem (assuming no excess heating from bad fuseholder or connection to it), but maybe it does get to where it runs for a long period, maybe has a short off cycle and then can't hold for the next startup.

BTW a 1/3 120 volt motor draws 7.2 amps according to NEC tables, that is low enough that a 15 amp fuse isn't likely blowing during starting if motor/bearings/capacitors/etc. are in good condition, but is just high enough that some of those issues mentioned may cause starting duration to be long enough to be a problem with a 15 amp fuse - plus it was mentioned there is a draft inducer motor which is probably where the ~2 amp figure earlier mentioned comes from.

I agree.

 

[FionaZuppa]

I agree.

i like your sig, .... i have these paper checks that are like 8ft long and about 3.5ft wide. i can draw what i want for my backyard on back of check, but the check amount is only $2. can you do the job

 

[cowboyjwc]

i like your sig, .... i have these paper checks that are like 8ft long and about 3.5ft wide. i can draw what i want for my backyard on back of check, but the check amount is only $2. can you do the job

Wrong size.:roll: You just start writing zeros after that two and I'll tell you when to stop. :happyyes:

 

[FionaZuppa]

here's the #'s

two modes of operation

Heat mode (evac motor already running)
inrush ~30A (seems like this clamp meter added peak inrush + the ~2A of the running evac motor)
running 14.8A

AC mode (main blower motor only)
inrush ~28.95A
running 12.94A


continuous 14.8A on 14ga stranded cord in a cheapy outlet,.......... doesnt sound good to me.


i think my plan is this using TL-20 fuse (SOU item says 3/4hp 15amps):

i am thinking maybe i go to the SOU item, then jump out to another 1-box that has a std 20A toggle switch, and hardwire back to unit with 12-2 cord. might be easier than installing a new "1-pole" load center. the switch serves as disco, but the fuse serves as the safety/service disco since a std switch can be accidentally knocked back to "on" position.

http://www.cooperindustries.com/con...essories/fuses/plug_fuses_box_coverunits.html

 

[FionaZuppa]

fuse blew again, but after some digging i dound some issues. from this info the motor seems to be running at the amps of its nameplate, which to me seems like motor is ok. but from what i found the wiring of this unit seems jacked.

its a York unit GY9S100C20DH11J (5 Burner)
York Controls S1-024-32056-000 1HP 115V 1075RPM 4Spd 48 Motor
York part #024-32056-000
motor amps 14.1 per nameplate of motor

i can only assume these motors are near 50-60% efficient to be a 1HP @ 14.1A (PF 85%)?? a 90% efficient motor (85% PF) would be just 8A (10FLA).

oddly, the wires running inside the unit to the motor are thick (hi temp) insulated 18awg !! its a UL listed unit, so how could it use 18awg on a motor that shows 30A inrush and then ~14A running?

as for the edison fuse, gonna ditch that for a Siemens hvac fused disco.

found some burned wires

 

[cowboyjwc]

Well looks like you found the problem.:happyyes:

 

[jim dungar]

its a UL listed unit, so how could it use 18awg on a motor that shows 30A inrush and then ~14A running...

Internal wiring is not the same as premises wiring. As soon as you open the cover of a UL Listed item, you should forget about the NEC once you get past the supply connections.

 

[iwire]

continuous 14.8A on 14ga stranded cord in a cheapy outlet,.......... doesnt sound good to me.

Sounds fine to me.

IF the NEC applied to this cord it would be rated 18 amps, see Table 400.5(A)(1) Allowable Ampacity for Flexible Cords and Cables

oddly, the wires running inside the unit to the motor are thick (hi temp) insulated 18awg !! its a UL listed unit, so how could it use 18awg on a motor that shows 30A inrush and then ~14A running?

As Jim said forget the NEC once you are inside, manufacturers can run the conductors at higher temps then we can.

Keep in mind the NEC ampacity ratings are very conservative.

Looking at the picture I would blame the failure on the terminal not the conductor.

 

[FionaZuppa]

well, i upgraded to a std 30A hvac disco (fused with blade handle, 20A TL fuse). i fixed the wires, put it all back, went to turn on the AC and the blower tried to start for about 0.25sec and then quit. now i get nothing for AC or heat mode. this is odd, wondering if the upgrade allowed more current than before and now maybe a board relay took a dump?
http://www.northamericahvac.com/yor...e-control-board-031-01972-000-p031-01972-000/

the board LED blinks 9 times error code, so now i am looking for what that means. 9 for some similar York board means reversed polarity, but my polarity is correct....

what a pita

 

[FionaZuppa]

yes, a real pita, one of the smaller relays on the board decided to fry. i might try to replace just the relay. not really sure why the relay would burn up like this.

 

[FionaZuppa]

yesp, one relay pin looks like it vaporized, and pin from big relay looks like the PCB solder lander came undown from the pin. why? makes me think me fixing the wires allowed the perhaps already weak relays to try and pass more current, and voila, fried.

this is the what the PCB mounts to. at 1st i thought maybe the pins touched and shorted, but the PCB has stand-off's so the board cant touch the metal. the center section was all black, i touched it just before taking this pic.