Checking Fuses

[cabinetman]

I've got two of these fuses 60 AMP on the AC/heat in a breaker box. At times during the heat cycle one or both blow. Is there any way to check these?



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[davwho]

what is it you want to check?,the fuses themself or why they are blowing 1.to check the fuses you will need a multimeter,probe on either end if you have tone the fuse is ok,if not there is an open ,fuse is no good 2.as to why they are blowing mutiple reasons ,hard to answer,is this unit a heat pump ?need to know to answer the second part

hope that helps

refrigeration tech.
Dave

[Hellrazor]

Multimeter set to OHMS. You can either tone it as mentioned or just check the resistance.

The picture of the fuse you have is a normal fuse. You COULD buy a slow burn fuse, they do not go as fast. Whatever you do, don't just slap a bigger fuse in.

Search online for the model of the unit you have and see what size breaker/fuse it recommends.

[JSCOOK]

Need a few more details:

1) Is this just installed and New or an existing install that just started blowing buses after operating problem free for X period of time.

2) As DAVWHO stated, need to know what exactly is on this circuit

Had a similar issue a few years back and found that by installing a time-delay fuse it solve the problem ... as it woud blow only at start-up.

[Daryl]

Use a simple neon tester, load side to ground.

[bmyers]

If you want to find out what is shorting out to make the fuses blow you can use some copper pipe cut to length in place of the fuses. That'll find the short.. []

(just kidding)

Bill

[cabinetman]

This may sound stupid, but are they checked in place with power on? Or can they be tested loose? This is the multimeter I've got:
http://www.harborfreight.com/cpi/cta...emnumber=90899
I don't have the instructions anymore. The leads (red/black) get plugged into? The dial in the ohms section gets turned to? Thanks for bearing with me.



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[bmyers]

Wow, you really splurged on the volt meter huh Cabman? []


Set it to 200 Ohms, the display says 1. or something very much bigger than 0. Touch the leads together an the leads should says 0 or something very close to 0.

Now touch the leads to the ends of removed fuse, doesn't matter what end goes where. Again the meter should say something very close to 0.

Bill

[cabinetman]

Wow, you really splurged on the volt meter huh Cabman? []


Set it to 200 Ohms, the display says 1. or something very much bigger than 0. Touch the leads together an the leads should says 0 or something very close to 0.

Now touch the leads to the ends of removed fuse, doesn't matter what end goes where. Again the meter should say something very close to 0.

Bill

Actually I did splurge - I paid $3.99, and now it's down to $2.99. I hate it when that happens. They wait for me to buy something then they reduce it. So, using your method I already have eliminated one bad one. Having two in the box, and having the heat stop, I didn't know which one or both were bad. So I guess this method shoots a slight charge through. I get the same reading (pretty close) on a fuse that has a reading as touching the leads. BTW, I do have a A.W. Sperry analog meter, that I could never figure out the scales. Lost the instructions to that one too. Hey, I'm a woodworker, not an electrician. Thanks for the help.



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[Hellrazor]

cabinetman, that meter scares me...


Take the fuses out to test them. OHMS + Live circuit = popped meter. You can actually 'blowup' a dial meter doing that.

The last meter i bought was $100... Fluke 322 Clamp meter

[eezlock]

blown fuses...

I've got two of these fuses 60 AMP on the AC/heat in a breaker box. At times during the heat cycle one or both blow. Is there any way to check these?



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

Sounds as if there is an overload on the heat cycle that is causing the problem with your unit. If you ac/heat unit has auxillary strip heat installed
in the ductwork as most heat pumps do for use in the coldest type of weather, it my have one of the elements shorted out/burned out.
Another cause could be the crankcase heater element around the base
of the compressor could be burned out as well. A good a/c tech could find
out if you have either of these problems. eezlock

[JSCOOK]

That cheap meter made me shudder ...
I hope your pulling the main breaker before doing any of this testing ... electricity is something that doesn't often gives you a second chance if you screw up (let's just say I got a second chance with 220v)

You still haven't mentioned whether this is something newly installed, or an existing set-up that has just started giving you problems ... I'm assuming using 60amp breakers that imay be baseboard electric heat? ... have there been any recent changes made to the original system or circuit? ... any motors or elements replaced? ... by chance is the A/C and Heat both comming on at the same time (seen this once ... do you have separate A/C & Heat control)? ... is there heavy dust/dirt build-up on the heating elements if it's electric baseboards?

cabinetman, that meter scares me...


Take the fuses out to test them. OHMS + Live circuit = popped meter. You can actually 'blowup' a dial meter doing that.

The last meter i bought was $100... Fluke 322 Clamp meter

[cabinetman]

It's a box on the air handler for electric heat. No baseboard heat. The unit is a 4 ton, only 'bout 5 years old (Janitrol/Goodman). When using heat, it doesn't blow a fuse all the time. It's very sporatic.



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[crokett]

Ever had it serviced? Does it blow fuses when it starts or when running? My sister had a problem with her A/C where when the compressor started it was blowing fuses. It was 8 yrs old though. Advice from the HVAC guy was either add an auxilary to kickstart (basically a capacitor) or a bigger fuse (not to exceed the breaker rating).

[Ed62]

Is it possible that someone added something to that particular circuit? If it's sporadic, I could visualize something else turning on (maybe a toaster, vacuum cleaner, etc.) or using current at the time it's needed most. I'm guessing this should be on a dedicated circuit. The worst possible thing you could do would be to put in a larger fuse, that exceeds the capacity of the wiring. Then you're asking for a fire!

Ed