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Heating, Air Conditioning, Fridge, HVAC/Carrier Heat & Air System (heat pump)


QUESTION: I have a situation where my system keeps blowing the 5 amp fuse in the air handler about every 3 to 4 days.  I have replaced the contactor, transformer assembly, and thermostat.  This is a Model FK4C air handler with variable speed.

ANSWER: my computer had a problem when I tried to answer this question I don't know how much of what I did to actually even made it into the answer but I know I didn't complete the answer because the computer blackout so if I can help you further please sub right back on the computer

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QUESTION: Sorry but no part of your answer to my question came through.  Can you send your original reply again?  Thank you!

 There i no set item in any carrier product that we can look at first to make it easier, Carrier is quality Equipment.  So, since you changed the thermostat and the step down transformer we can also eliminate the spade, terminal, and wire nut connections associated with those three places, although as a last place to trace this problem, the outdoor unit has a defrost control board that also comes into play in the cooling season, as, Carrier fails in heating mode.  What that means is it takes 24 volts initiated from the defrost board even in the cooling mode ass, the reversing valve has to shift, into the cooling position. But we are getting ahead of ourselves.
 Without the serial number of both units I don't know the age.  But unless the house and/or the entire wiring system is new, we look there first.  Usually the highest percentage of causes for that symtom is in the thermostat wire in the wall, attic, under house between the thermostat and the Air Handler.  A mouse, nail, almost anything can do that, and where the wire enters the cabinet, the metal if not bushinged can cut the wire.  Unless you have a very accurate meter and practice with it, the way is by elimination,if there are enough wires and you find a short you can just use another color.  
  Luck has it that you are in cooling mode, as, you are only using 3 wires to  cool and a 4th for ground. So, since you changed the t-stat you can handle this.  For cooling 24 volts leaves the stat through the Green G wire for indoor fan(blower) the Yellow Y wire for the contactor and the Orange O wire for the revering Valve.  And depending on the apprentiship of the installer should be Blue B for ground, but Rheem usses brown and Trane black.  
 You can tag or record ( or today snap a pic from your phone) and use other colors all at once then one at a time if that is it to find which one.  All the other color are for other things or seasons.  Now, only do this from the t-stat to the Air handler, but be sure you have examined all places even outside wires could be damaged.
 If that is not it, you will need to get a tech, as I do not give instructions troubleshooting inside the cabinets of the equipment, as, it is next probably a limit, sequencer, or strip control and that is too cloe to the high voltage for an untrained hand to be.  
 Be there when the N.A.T.E certified tech arrives and watch and ask questions, you have a better understanding now and if something is not explained from the tech write back for more help.  But the certified tech should make you secure with hi/her work and charges.

Heating, Air Conditioning, Fridge, HVAC

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john t. borgman


I am in Portland Oregon at Ben's heating 503-233-1779. I work days, so I can only answer early in the day or later in the evening. I only answer public questions for residential equipment. I am very well versed in gas, electric and heat pumps and will only answer residential applications. I have been known the past decade or so, by my employers as the guy you send when no one can figure it out. Trouble shooting is my special. I understand the physics behind air flow, refrigerants and electricity. I understand programmable t-stats, zone controls, economizers, fossil fuel kits and the engineering thought process in the wiring and construction of residential equipment


I was lucky enough to start in this field almost 30 years ago as an installer, for a company that installed the best duct systems I have ever seen, even to this day. The best ,as far as understanding the way air really flows through a duct system, from the return air to the very last supply register . They also had great pride and the duct work was put in, not only to last 50 years, but to look exceptional. Then as I started doing service work, I was again fortunate that I found a 3 year engineering class being put on be a man that was the educational director for the Entire united states for a society called " the Refrigeration Service Engineering Society " And for the next 3 years I schooled at night and practiced what I learned during the day, a great advantage over schooling and then trying to remember it years later.. Versed in duct design manual J heat gain/loss calculations.

Refrigeration Service Engineer's Society

I have 2 inventions that have gone through the process and been recorded at the National Institute of Standards and Technology from start to finish and thus been invited to national innovation workshops by the dept. of Commerce and the dept. of Energy. They are waste heat recovery devices that N.I.S.T approved as valid and am currently looking for marketing partners to get this product into the hands of consumers and make a BIG difference in Energy savings for every Household and Eatery and take a big bite in the the peak hours power consumption that face our Utilities companies.

factory training in Lennox ,Rheem, Ruud ,Trane, Tempstar ,Carrier, Day&Night, Payne, Bryant, Coleman, Intertherm, York, Goodman, Ultra boilers, Unico, Mitsubishi,Sanyo, Taylor, Nicewonger, Navien. Associates degree in Refrigeration Engineering. Certified with Energy Department, Check-me Program, P.T.C.S (performance tested comfort systems ), have N.A.T.E. certifications in gas, a/c & heat pump.

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