Ran orange from thermo to heat pump then the red yellow from thermo to air handler to heat pump. Check connection. In the event of a short circuit the fuse blows cutting power and stopping wires melting. It was a bad cooling contactor coil. Just had one yesterday- sov wire rubbing the louvered door on side of unit. I installed a new fuse, and it burned up immediately. Without the proper amount of refrigerant, your AC has to work harder to maintain its performance. 3 amp fuse keeps blowing on my ac unit i checked the wiring… 3 amp fuse keeps blowing... 3 amp fuse keeps blowing on my ac unit i checked the wiring form the in door unit to the outside unit and no shorts any sugestions. Using the correct fuse is important because a undersized fuse can stop circuits operating by cutting power at low currents. Rheem ac troubleshooting keep blowing the 3a fuses now starts and shuts off. Another cause of blown AC fuses could be a low refrigerant level. Reply. The unit was off and the 3 amp fuse was blown. Some CBs also perform switching function with or without current flowing in the circuit. You may also cut off the REV valve low-voltage wire. Fast-acting fuses open circuits quickly when surges are detected. Rated Voltage AC 500V* / DC 440V upto 630A (DC 250V for size 00) AC 690V/DC 440V (DC 250V for size 00) Rated Current Range 2A-800A, AC 500V 40A-500A, AC 690V Rated Breaking Capacity AC 120kA / DC 25kA Mounting position as desired but preferably vertical Resistance to climate -30°C to +50°C at 95% relative humidity HRC fuse is the fuse element of high-grade copper. Subscribe me. Member. Low voltage fuse blowing in furnace. small nick in wire, but enough to blow fuse. I ran through a checklist that came with my furnace and found that the low voltage fuse had burned up. Exact same problem. this video shows what a low voltage fuse looks like in an air handler. HELP!!! Low voltage: Check that nameplate voltage is maintained. Problem: My 24 volt low voltage transformer continues to burn up.This is the second transformer. It kept blowing the 3a fuse immediately when attempting to start; so I replaced it with a 5a fuse. Have a specialty? When a fuse is in an electronic circuit and the current exceeds the rated level, the fuse melts (blows), thus breaking the circuit and preventing the excessive current from flowing. I noticed it blew when I switch from heat to AC, but now, it just blows within minutes when I put the fuse in. I even installed a new t-stat. Answer: I have encountered this problem several times.Most of the time the problem ends up blowing the fuse on the control board, (if your control board has a fuse) instead of the transformer. Jump to Latest Follow 1 - 20 of 22 Posts. Low-voltage high rupture capacity (HRC) fuses are used in the area of main distribution boards in low-voltage networks where there is a high prospective short circuit current. Low refrigerant. Much like having a dirty air filter, this could cause your air conditioner to blow a fuse simply from overworking. Use with Fuse Blocks for Automotive Fuses. What causes a blown fuse at the low voltage transformer in ac unit? Save Share. Once of my customers had a similar problem last week. Blowing low voltage fuse breaker trip control wiring troubleshooting ive got a 5 amp fuse that keeps popping on a circuit board. The fuse is downstream from a transformer. To protect your family and ensure your furnace keeps working as it should, you need to find the source of the problem. Fuses are available in AC and DC circuits from extra low voltages to high voltages. Show More. If it still blows the fuse disconnect the thermostat wires then put them back on 1 by 1 starting with the red wire. Last. Is there any situation at all that this would be true? There are many possible reasons for AC fuses to blow, and sometimes they are connected. It burned up immediately. And in article electrical wiring diagrams for air conditioning systems part one i explained the following points. I let the unit run the A/C. C1 and C2 are the same, each has 200V voltage max rating. So, I disconnected all thermostat wires from inside the furnace and installed a new fuse. a) the fuse blows: The fault is in PSU b) fuse doesn’t blow = the short causing the fuse blowing is DEFINITELY between the power socket on the back of the Mac, and the PSU. Breakthrough current, labeled on the fuse as IR, is the maximum current that a fuse can safely stop in the event of a short circuit. Open circuit: Fuses blown. Open a low voltage DC circuit (like when you blow a fuse) and there will be a small arc. Thermistor is MF72-5D9 Surge Current Limiting. A fuse is an inexpensive device that can carry only a certain amount of current. This defeats the purpose of using a fuse as a safety device. The capacitor is important because it helps run the cooling system, known as the condenser . So, I disconnected all thermostat wires from inside the furnace and installed a new fuse. Fuses are rated by current, voltage, breaking capacity (interrupt capability) and whether they are designed to operate on AC or DC circuits. most the low voltage shorts are in the side door access on Tranes, either against the grill, or a tube. Location: San Jose,Ca. Select a fuse In three simple steps. Share this conversation. Fuses aren't rated for voltage carrying purposes, the rating come into effect when and if the fuse blows, you do not want a low voltage rated fuse on a high supply, the construction of which may allow conduction after blowing. These fuses are suitable for low-voltage automotive and other electronic applications. I have a rheem classic 90 plus heating and air unit. Any ideas. Low voltage fuses are defined as fuses with a voltage rating less than or equal to 1,500V. The first step is to convert AC-DC. My AC stopped working during the night last night. Types of Fuses. Post to Twitter . Sponsored Links #2 10-28-09, 05:15 PM M. mbk3. By the way, would you be so kind as to post a really good close up image of this area of the PSU. AC works fine but as soon a I switch to heat the fuse blows. Active 11 months ago. 0 Why is my trans blowing on the primary? Open a high voltage DC circuit (like when you blow a fuse) and there will be a huge (long) and super hot arc (spark). hvac1000 Posts: 14,540, Reputation: 435. So at low voltage say 12 volts there is not much tendency to arc across the gap when the fuse blows but at 240 volts or higher the arcing becomes quite significant. Above is my schematic. Answered in 2 minutes by: 2/25/2011. Fuses are essentially classified into several types which are based on the application namely AC type fuse and DC type fuse. Ask Your Own HVAC Question. I ran through a checklist that came with my furnace and found that the low voltage fuse had burned up. It burned up immediately. Low voltage fuses have a voltage rating of less than or equal to 1,500V. Thanks for any insight you can help provide. If the arcing melts more of the wire no problem because the gap gets bigger, but if the wire melts to the ends and the arcing continues until there is an arc between the caps then you have a fire in the fuse box. Replacing the fuse or resetting the breaker can temporarily fix the problem, but if the underlying issue is not fixed, the fuse will just blow again. If there's no AC voltage on the transformer, check the gate of the MOSFET: if there's a PWM signal there, the SMPS IC is still alive, and replacing the FET can bring the PSU back to life. A circuit breaker also does similar type of function as a fuse. wmodavis. Level 1 (Contributor) 1 Answer: 1. The following diagram clearly depicts the electrical fuse types chart depending on the AC fuse and DC fuse. High rupture capacity fuses may be rated to interrupt current of 120 kA. Which wire on my transformer to do install the 5 amp fuse for low voltage . Fuse keeps blowing on AC/DC Adapter. The 5 amp fuse is on the low voltage side, so its not the blower motor causing it to blow. Now it will run for about 60 secs, shut off, start again and keep repeating that cycle. Low voltage fuses are very common in electrical systems and they come in different shapes and designs. Users who viewed this problem also viewed: prinaudo. The fuse is downstream from a transformer. 5-Amp fuse keeps blowing on AC. Out the door I ended up paying $51 for the contactor relay and DCB another $36 for the solenoid coil (all replaced by me) then $49 for the service call and $100 for the Low Voltage Wiring Repair. This small part helps to regulate the electrical current as it flows … If not, you need to replace the IC, and I wouldn't bother trying to repair it. The Military standard for Fuses; MIL-PRF-23419 does not seem to differentiate between AC or DC voltages for low voltage fuses.-- From Military sources Voltage rating. Disconnect the compressor contactor; Once you disconnect the compressor contactor, set thermostats to cooling mode and tape off the low voltage wire to restart. What could be the problem? Hi, I am trying to build a 5VDC from my 220VAC (Switched-mode power supply). Last. Ended up getting a "free" transformer out of the deal but all together spent a grand total of $236 and my heat is working again with no famous blown 3 amp fuse. Any help would be appreciated. Like Reply. 1; 2; Next. Ask Question Asked 5 years, 1 month ago. 1 - 20 of 22 Posts. They are generally larger than screw-type fuses, and have ferrule cap or blade contacts. The current rating of a fuse is the current that it can carry for indefinite time periods without opening. Col 3:23 questions asked, answers received, ignorance abated. And again these are further classified into various kinds based on the voltage levels. Low voltage fuses are very common in electrical systems and they come in diverse styles, shapes and sizes. Viewed 33k times 1. ac keeps blowing the 5 amp fuse. I replaced the fuse and used the thermostat to turn the fan on followed by the heater then the A/C. Is this a heat pump, or straight A/C. Things can get ugly fast! It is really making me curious. HVAC … Show Less. Max. He told me that he has seen when low voltage had caused a fuse to blow or breaker to trip (in high voltage machines). Yes, if you have a few extra fuses. The use of fuses in a circuit provides cheap insurance should there be an accidental or unintentional fault in the system wiring or components. Graphics in this document are for representation only. Post to Facebook . This is where the problem lies. 1 of 2 Go to page. V1 is 220VAC, the peak is about 300V. Hello. Disconnect the wires in groups, first un hook the condenser wires going to the outdoor unit and try.. Ask Question Asked 3 months ago. 1; 2; Next. I have an outside A/C compressor and indoor furnace fan combo in the attic. Joined Oct 23, 2010 739. 4 years ago. If the fuse is blown or the low-voltage breaker is tripped, as will generally be the case in a short, first replace the fuse, or, better yet, use a test breaker, like the Supco Pro Fuse (in place of the fuse while testing) to eliminate wasting fuses. An over-sized fuse will allow too much current to flow. My AC stopped working during the night last night. Go. Here is a list of some of the most common reasons: Old or Blocked Motor; An old or blocked motor causes the capacitor to work over-time. 1 of 2 Go to page. I installed a new fuse, and it burned up immediately. When I turn on the power, F1 blows immediately. Go. The voltage rating relates to the ability of the fuse to function and extinguish internal arcs when it opens. This is one reason that re-wireable fuses are no longer allowed under NEC. I assumed it was the low voltage wiring from the wall t-stat to the control board so I got new wire and ran up to the attic. Answers and Replies Related Electrical Engineering News on Phys.org. Check overload relay, stator and push buttons: Motor runs and then dies down: Power failure: Check for loose connections to line, to fuses and to control: Motor does not come up to speed: Motor is applied for the wrong application Click to expand... this is a straight ac . Apply to be an Expert. Join Date: Dec 2004. Unlike a circuit breaker, fuse is self-destructive which requires replacement after it disconnects a circuit. I'm out of fuses - LOL and before I call the tech back out, I'm trying to get some answers.. Blade contacts enough to blow, and i would n't bother trying to some... A few extra fuses rating relates to the ability of the fuse disconnect the thermostat to turn fan... 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