Fuses keep blowing out!

[hvac wiz 79]

i myself am nate certified & am pretty damn good at what it is i do & learn more every day & i love it .. sadly just because a person is nate certified, it doesnt make him a better tech then joe jerkoff with no cert. all it is is a piece of paper .... some will argue but i seen it first hand .. i hope the whole nate thing is different now & i dont mean to start a debate or make enemys .. it just reminds me of the epa cert & any other cert that as long as u show up for the instructional part .. u basically pass .. my tech school was like that as well

[Trublshter]

I agree with ya 110 % wiz, I've run across a few in my time that had certifications and licenses out the kazoo and could'nt fix crap and I've known others with years of experience that fixed everything they come up to but could'nt talk to the customer. So what can you do , you know! I see the same in all other endeavors too.

[MichaelPaladin]

I have a rooftop HP aprox 10 yrs. It keeps blowing fuses. I've cleaned the condenser & evap coils, changed the contacter, changed the cap & added a hard start. all pressures are good. Sometimes it will run for 2 months and sometimes for 2 hrs. depending on the weather. Should I replace the compressor or the whole unit?

Ok first off whats the primary voltage? 208/240 or 460? Second, is it just blowing one fuse or two?

Sometimes if its just one fuse, you may have a bad power feed, either from your panel or coming from the transformer to the building.

I've seen a simular problem in the past, and once the power company changed the transformer, the customer had no further problems.

[refer guy]

Every time I have a bad fuse the first thing i do is check all condensor motors, indoor motors, and compressors. I say about 80% of the time its a grounded compressor or motor. If its not one of those then I either find a wire rubbed out on copper tubbing or the disconnect is faulty.

[yp5]

O.K., I will lighten up a bit !! The point I was attempting to make was, there are other service guys out there who don't have a Nate patch on their shoulder - that might have a clue about this trade, and that the main purpose of fuses in a system(circuit breaker in panel)is to protect the non-grouded conductors, raceway, conduit, switch gear, and last the equipment.
Please correct me, if I'm wrong - conductor protection is paramount, and the NEC really does'nt care to much about what happens inside that A/C box as long as it is fused according to code. Just my opinion !!!!

NEC should care....How about the factory wiring of those power cabling and AC controls inside the AC unit? What Code and testing method is applicable? Megger testing on factory assembly as the Company quality assurance/quality control is conducted? was it an NEC clause that is a followed on it's power cabling or something else? I'm a mechanical engineer, perhaps an electrical engineer can answer this accurately.

[Aircooled81]

Don't just go replacing components without knowing what's wrong, why not just replace the whole peice of equipment, and then find out it had to do with the disconect, or the wiring to the unit. Can you confirm you put the correct size fuses in, are the slow blow fuses, are all the electrical connections tight? any wires going to major components having high resistance. Too much electricity is obviously blowing your fuses, high amperage is cause by high resistance or under working fan motors and over working compresors.
By the way, it could be as simple as a loose indfan belt, and every two months some one changes filters without shutting the equipment down, causing the indoor motor to over amp pulling to much air suddenly when the door is opened.
Also, hp... if that's heat pump, is your reheat wired through the same disconect? You can pull a large amount of current through a bad reheat coil that is only being used mayb 'every 2 months'...

[clgman]

NEC should care....How about the factory wiring of those power cabling and AC controls inside the AC unit? What Code and testing method is applicable? Megger testing on factory assembly as the Company quality assurance/quality control is conducted? was it an NEC clause that is a followed on it's power cabling or something else? I'm a mechanical engineer, perhaps an electrical engineer can answer this accurately.

I believe manufacturers fall into an acception clause, but must pass UL and the Candian safety standards. It's most likely a good thing for them(manufacturers) because according to NEC they violate several codes (I.E. number of conductors in a raceway, accessibility, number of conductors in a juction box, grounding, etc.,etc., & common sense). We all can be sure that they only meet minimum standards so as to save the very last penny. Interesting topic !!!

[yp5]

I believe manufacturers fall into an acception clause, but must pass UL and the Candian safety standards. It's most likely a good thing for them(manufacturers) because according to NEC they violate several codes (I.E. number of conductors in a raceway, accessibility, number of conductors in a juction box, grounding, etc.,etc., & common sense). We all can be sure that they only meet minimum standards so as to save the very last penny. Interesting topic !!!

I would have to agree on you, that is why end users or consumer suffers in these type of marketing strategy. Should they passed the standards in each localities or countries,They are still hiding the perfectness of thier own products. They have to be competitive with thier market pricing, main reason why selecting cheap equivalent raw materials which oftentimes affects the quality of thier products resulting to factory defects even it has marking "Passed" on thier so called QA/QC.

[javella]

You don't just want to replace a compressor with out determining why the fuses keep blowing. One option would be to install a data logger. It will track and log your voltages and amps for a few days, this will probably give you a good indication if it's related to your power. Could be a number of things, condenser motor overheats after awhile, checkvalves could be partially clogged, reversing valve. You are going to need to check all your amps and voltages for sure on every motor in your system.

[markwolf]

There can be a whole slew of things that can cause an intermittent fuse failure.
You said depending on the weater is when the fuse blows.
There would be several directions to follow depending on the condition that the fuses are blowing under.
Is it rain,high temperature,medium temperature's like 50-60,or other?
each condition has it's own basics to check for.

[phixitman]

Fuses are thermal devices, the fuses are are overheating due to bad connections or there is a short to ground. Focus on the obvious.

[JBM1000]

Dough Boy Copper at the fuse holders or at any point most likely in the disconnect. Infared shoot is dead on way to confirm. Above 130' to 140' would be not good. I want to see not more than 10' above ambient.