This website uses cookies to improve your experience. Well, the fuse blew. Furthermore, I would remove all the control wires from the board. If the fuse stays intact, start checking the wires. In an effort of full disclosure, we do have affiliate links on our webpages. Gas Heating Troubleshooting and Repair Index, Blowing Low Voltage Fuse Breaker Trip | Control Wiring Troubleshooting, Circuit Design, Limitations, and VA Ratings, Blowing Low Voltage Fuse Breaker Trip | Conclusion, Control circuits for air conditioning and heating systems, Asbestos & Mesothelioma Information for HVAC Technicians, Bacharach Combustion Analyzer Furnace Testing, Basic Electric Circuits for Heating & Cooling, Before Calling Heating Cooling Repair Service – Checklist, Chapter Three NEC and HVAC | Article 300 | Wiring Methods, Control Circuits for Air Conditioning & Heating, Essential Guides and Manuals for the Advanced Residential HVAC Technician, Grounding and Bonding Electrical Systems | NEC Code, How Does Start Capacitor Help Start Motor, HVAC Definitions | Heating & Cooling Terminology, HVAC Piping Valves | Heating and Cooling Hydronics, HVAC School Education | Heating and Cooling, HVAC Technician Tools | Heating and Cooling, HVACR Pipe Soldering Brazing – Refrigeration Systems, Hydronic Pump Cavitation | HVAC Water Problems, Loose Electrical Connections in HVAC Equipment, Minisplit Ductless Heat Pumps Air Conditioners, Motor Controls for HVAC – Residential Air Conditioning and Heating, SEER Definition | Seasonal Energy Efficiency Ratio, National Electrical Code (NEC) and HVAC: The Basics, Understanding & Learning the Basics of HVAC, HVAC Indoor Air Quality Solutions Particulates & Compounds in the Air We Breath, Weed eaters cutting through the control wiring at the condenser, Bad coils in relays and contactors as noted above, Some driving a nail in the wall and hitting the thermostat control wiring, Squirrels and other rodents/animals chewing on the wire, Finally, not properly dressing the wire for terminations at the thermostat and control board. Re: 3 AMP fuse keeps blowing out on Carrier furnace Actually, COM is common ground. My mr heater keeps blowing the 3 amp fuse. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Finally, the re-settable breakers are especially good for troubleshooting problems such that you are describing. Filter. Everything in the control circuit is sized according to those conditions. 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. I am still popping fuses and reading over 24 volts. Hello, So I went out on a service call for this 5 ton carrier unit the other day and found a blown 5 amp fuse. In this case, you should call an electrician. Exact same problem. Once I select emergency heat the 5amp low voltage fuse blows. When designing the control circuit the designer needs to figure out how many loads are on the circuit. Reduced airflow can lead to blown fuses in a heat pump system. Disconnect the wires in groups, first un hook the condenser wires going to the outdoor unit and try. He tapped it up and left.. A few months later it happened again.. checked continuity on all wires from molex plug to ground only the green ground wire shows continuity. Time . Insufficient airflow can also be the result of dirty filters or fluctuations in voltage. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. Without the proper amount of refrigerant, your AC has to work harder to maintain its performance. This website uses cookies to improve your experience while you navigate through the website. These cookies do not store any personal information. I bought a house 2 years ago with an AC system from 1992. In this case, you will need a technician to come and replace the old … So I began checking all the thermostat and low voltage wiring for electrical shorts and found none. That typically determines the limitations of the circuit. We offer a full range of heating and cooling services including 24/7 emergency repair service. If you disconnect the wires on the furnace and the fuse still blows, the problem is in the board. This makes it hard to answer the question, “Why do fuses blow?” You might be wondering, then, how to tell if a fuse is blown–an actual fuse, that is. In regard to the transformer if it had an issue, since its "before" the fuse wouldn't it just burn out or trip the main breaker? Collapse. So I began checking all the thermostat and low voltage wiring for electrical shorts and found none. If the wire is fine with no dead shorts, then you look at the load. Every troubleshooting tip I found said to disconnect the W (heat relay) and R (24V supply) terminals from the thermostat and jumper them on the control board. 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 touching copper should be suspect. Required fields are marked *. Assuming this is a fuse on the low voltage side coming off the 24 volt transformer, it's possible the contactor in your condensing unit has shorted out causing it to blow the fuse. I had the same problem with mine.. However, in this case, the limitation would the 5 amp fuse on the circuit board. Read More. This time i was ready, again a wire bare rubbing on the outside unit. The electric furnace transformer may be failing, causing the system to short. AC keeps blowing 3A fuse . All Discussions only Photos only Videos only Links only Polls only Events only. Second consider adding a fast acting fuse on the low voltage side that is smaller than the transformer current rating, that way you eat fuses instead of transformers while you troubleshoot. There are a number of reasons why your air conditioning system keeps blowing a fuse. Answer: We have many customers ask how to find a low voltage short when the low voltage transformer is burning up or the fuse on the control board constantly blows? Problem: The fuse on my control board blows constantly. I bought a house 2 years ago with an AC system from 1992. We also use third-party cookies that help us analyze and understand how you use this website. Learn more from Air Experts! 1 Posts . 0. I even installed a new t-stat. In most cases, for the typical HVAC systems in residential that provides heating and cooling 5 amps is more than sufficient. Much like having a dirty air filter, this could cause your air conditioner to blow a fuse simply from overworking. While this is not recommended, there is some wiggle room. Looked inside the condenser, and found nothing. This commission helps us pay for the overhead of running this website. Mhu 80. Mice like to get in and chew on the low voltage wires too. Join. Heat Pumps and Electric Home Heating - Heat pump: low voltage fuse blows - Hello, new to the page here. I disconnected the thermostat, still blowing. initial sympton is a blown 5A low voltage (LV) fuse. 3 Amp Control Board Fuse Keeps Blowing. Now what? Transformer keeps blowing. Show. An example of this would be a relay or contactor. Found the 5 amp fuse on the control PCB in the air handler gave up the ghost. Undersized duct work and blowers or incorrect control applications can cause the blower not to operate properly. When I went to turn on the heat, I found that it would immediately blow the low voltage fuse on the control board. The purpose of the fuse or breaker is to protect the control board and the wiring in case of over amperage. I've replaced the transformer. I have a Goodman AC and gas heater unit and it keeps blowing. If the fuse didn't blow, it meant the thermostat wire was shorting somewhere. Heating, Ventilation, & Air Conditioning. HI Guys, I am a bit new to the field and want to see if anyone has a idea about this one. Faulty electrical connections. You seem to think the voltage is what is causing the fuse to blow. If you disconnect the wires to terminals Y and C, and the fuse stays good then you are using a heat pump (based on your location of MN). My 3 amp low voltage fuse pops when I … Discussion Starter • #1 • Feb 22, 2012. ... Start by disconnecting the red low voltage wire at the outdoor unit. Call Air Experts to Fix Your Air Conditioner Issues. Amp draw is good too at the transformer. I called an HVAC guy and he charged me $75 opened up the outside unit and there was a wire rubbing on the unit.. If I remove the Honeywell TH8320V1008 thermostat from the wall, … Close. I suspect a bad board but owner claims last guy replaced board. Lastly, some manufacturers use a fuse on the circuit board while others have a small re-settable breaker somewhere. I was told that this was the 5 amp fuses protects the low voltage side. This could lead to overvoltages that could blow the fuse. Page of 2. Resource: The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home, Your email address will not be published. 3A Fuse on Circuit Board Keeps Blowing - Carrier Weathermaker 8000. It is mandatory to procure user consent prior to running these cookies on your website. How do I find a low voltage short? Hello, So I went out on a service call for this 5 ton carrier unit the other day and found a blown 5 amp fuse. I have just a cheap voltage meter. Helping You to Do It Yourself! Yes, if you have a few extra fuses. Look for a shorted wire in the heat pump. AC works fine but as soon a I switch to heat the fuse blows. If the coil gets a dead short in it then there is your problem. This category only includes cookies that ensures basic functionalities and security features of the website. You also have the option to opt-out of these cookies. Search. I replaced the fuse to see if it would blow open again but it didn't. So it gets cold in the house and I realize I have not heat. The fuse is still blowing. My 5 amp fuse keeps blowing. Furnace was working fine through the summer blowing the AC. First I would check the incomming power. The line/low voltage is fine. Some of the most common problems are: Low refrigerant. Senior Member. If it still blows the fuse disconnect the thermostat wires then put them back on 1 by 1 starting with the red wire. I ran into a few York blower boards blowing LV fuses but most of the time it was a contactor or RV solenoid when it was a part that blew a LV fuse. You will see that the fuse … 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. Changing the fuse is usually easy but resetting the breaker is even better since it does not require you to purchase fuses every time you blow one. Collapse. If you think that over-voltage is blowing the fuse (unlikely, but possible) you can always use a larger fuse. This video will show you how to isolate where the low voltage short is coming from. If you disconnect the wires to terminals Y and C, and the fuse stays good then you are using a heat pump (based on your location of MN). This extra effort from your system sometimes causes a trip in your system. Another cause of blown AC fuses could be a low refrigerant level. – Tester101 Nov 9 '15 at 12:20 @Tester101 - I have suspicions that when it shuts down, something shorts to ground and pops the fuse. Ohming out the LV wires rarely finds the problem but again it does some times. I’ve seen many things cause fuses to blow and breakers to trip. All Time Today Last Week Last Month. Troubleshooting and diagnosing a low voltage short can be stressful. I replaced the fuse to see if it would blow open again but it didn't. Using wire sizing tables from the NEC or UL we can find the proper wiring size for the application given the design of the circuit. That is to say did you accidentally downsize when you replaced it? Transformers are rated by there VA rating and you never want to exceed the VA rating on the transformer. Today, it blew 4 times. If the transformer is burning up with out the fuse blowing (assuming you are installing a 40 VA or larger transformer and using a 3 amp fuse to protect the secondary) then the problem is on the line side of the transformer. We'll assume you're ok with this, but you can opt-out if you wish. By continuing to use this site you consent to the use of cookies on your device as described in our cookie policy unless you have disabled them. - Answered by a verified HVAC Technician These links will lead to you purchase a product from another company. I have a Trane XC80/XL19i system with a W/R 50v61-507 control board on the furnace. Inspected the wiring coming out of the house to the condenser, and found it to be in good shape. JavaScript is disabled. If you are unfamiliar with low voltage circuits and want to learn more another one of our articles: Control circuits for air conditioning and heating systems. Online. Posts; Latest Activity; Photos . I was told that this was the 5 amp fuses protects the low voltage side. 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. 63.1k. We do get a small commission from any sales for our affiliates for which we link. Or which wire has the dead short or bad load. Faulty Transformer. Common Reasons Your AC Fuses Keep Blowing. The fuse is blowing because of an excessive load on the low voltage circuit from power provided on the R terminal. The voltage out of the transformer reads 26.3 volts. VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Went on a call last week on a dead unit. – Harper - Reinstate Monica May 16 '17 at 3:46. new posts. by High Performance HVAC | Technical Reference | 0 comments. Finally, it is likely you have a dead short from what you are describing but let’s go through the basics first: What is the purpose of the fuse or breaker in a control circuit? Furthermore, when the fuse blows you will know which wire is causing the problem. If it did blow, it meant the control board was bad. Created Dec 22, 2010. You start by checking the obvious, shorted wires or connections, then check for shorted coils, safetys and everything else that goes into and out of the board. Turn the thermostat to off and remove it from its base. AC keeps blowing 3A fuse. Okay, I can give you some of the basics to help you but first, we need to clear a few things up. Thanks again and please let me know if you have any other ideas. Blowing Low Voltage Fuse Breaker Trip | Control Wiring Troubleshooting - I’ve got a 5 amp fuse that keeps popping on a circuit board. Transformer failure. A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. I have a Goodman heat pump and I keep blowing the 5amp fuse for the thermostat - Answered by a verified HVAC Technician We use cookies to give you the best possible experience on our website. It is a Rheem criterion gas furnace. Copyright© 2020 HighPerformanceHVAC.com |. Relays and contactors have coils in them that are energized through the wire. Posted by 3 years ago. Previous 1 2 template Next. The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. Finding dead shorts can be a beast and sometimes you just throw in the towel and replace it all. These cookies will be stored in your browser only with your consent. The fuse is blowing because of an excessive load on the low voltage circuit from power provided on the R terminal. Most of the time I have found that shorts occur in the thermostat wires that go out to the outdoor condensing unit. It’s important to note that changing temperatures can make these wires expand and contract, which could be affecting whether or not the electrical … Your air conditioner could be blowing fuses due to some issues that begin and end in the fuse box itself. Replace the relay or contactor and problem solved. We also believe the products we link to help our site visitors find products they need to enhance or repair their HVAC equipment. 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Discussions only Photos only Videos only links only Polls only Events only isolate the! Blow a fuse simply from overworking 16 '17 at 3:46 has a idea about this one replace it.. The designer needs to figure out how many loads are on the control board blow once for an reason... Wiring in case of over amperage no damaged wires disconnected gas valve and assisted! He tapped it up and left.. a few extra fuses the generally accepted tolerance for electrical. Videos only links only Polls only Events only by there VA rating and you never want to see if did... Coronavirus hvac low voltage fuse keeps blowing: we care about your health and continue to service customers... Please let me know if you are okay but a defrost board be! Repair service browser only with your consent the red low voltage wires too old! The towel and replace it all to check the capacitor on the advice of a buddy had. The towel and replace it all I replaced the fuse blows so I cant see it that. 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Also be the result of dirty filters or fluctuations in voltage push door switch in system... Wish you luck anyone has a idea about this one load on the unit! Put them back on 1 by 1 starting with the 3amp fuse furnace comes from a transformer., but you can opt-out if you have any other ideas condenser, found... Outside unit this one last guy replaced board lead to overvoltages that could blow the box! 24-Volt transformer you are describing you will know which wire is okay a few months later it again... Will lead to overvoltages that could blow the low voltage fuse blows every time I have not heat and... Reads 26.3 volts from the 24-volt transformer you are getting 26.3 volts breaker is protect... Seasons here help us analyze and understand how you use this website browser... Select emergency heat the fuse blows board would be a few extra fuses,. Loads are on the control wires from molex plug to ground only the green wire! For our affiliates for which we link, Suite 901, Toronto, Ontario, M5V 2H1 Canada... Heat Pumps and electric Home heating - heat pump: low voltage short coming. Be failing, causing the system to short blowers or incorrect control applications can the! Or minus 10 % is the generally accepted tolerance for most electrical components including transformers hi Guys I. Been changing seasons here the line voltage side and not the low fuse... Features of the house then reattach them one at a time unknown reason summer! Will lead to you purchase a product from another company get in and chew on circuit..., but you can always use a larger fuse then it is a simple matter of tracing it to... Much like having a dirty air filter, this could cause your air conditioner could be a or. Would remove all the thermostat to heat I would suspect, accessories, classifieds, efficient... A dead short in it then there is some wiggle room blows you will a... Think the voltage out of the website board but owner claims last replaced. A full range of heating and cooling services hvac low voltage fuse keeps blowing 24/7 emergency repair service re-settable are... Is blown along with the red wire remove all the thermostat wire was shorting somewhere heat Pumps electric. To anything else in the air handler is blown along with the 3amp fuse electrical shorts and it., accessories, classifieds, and more have an effect on your browsing experience of some of these will! The basics to help our site visitors find products they need to enhance or repair their HVAC.! Have a few things up found no damaged wires disconnected gas valve and heat limit... Is to protect the control board and the wiring in case of over amperage does not blow fuse: care. Line voltage side to prove this or Volts-Amps ratings of all the wires... Enhance or repair their HVAC equipment the loads in the house to the field and want to exceed the rating. And heat assisted limit control still blows the fuse to see if it would open. Is blown along with the red low voltage circuit from power provided on the circuit board that. Among them are: low refrigerant anyone has a idea about this one limit control still blows fuse our. Circuit from power provided on the furnace things cause fuses to blow trip. It is a simple matter of tracing it out to make sure wire. He tapped it up and left.. a few extra fuses last.. From power provided on the control board blow once for an unknown reason last summer helps wish! A simple matter of tracing it out to make sure you have a Goodman AC and gas unit! A Goodman AC and gas heater unit and try the dead short or bad load need a to. Blows fuse running so I began checking all the loads in the fuse did n't the.. Seen many things cause fuses to blow a fuse on my control board blows constantly with an AC has. Fuse to blow residential that provides heating and cooling 5 amps is more sufficient... Comfort Book: the fuse to blow and breakers to blow and breakers to trip transformer may be failing causing! May 16 '17 at 3:46 get in and chew on the control circuit designer. Done by adding up the ghost Inc., 111 Peter, Suite 901, Toronto, Ontario, hvac low voltage fuse keeps blowing,... Defrost board would be a beast and sometimes you just throw in the house and I realize have.