I replaced the transformer but the 3 amp fuse blows every time I change the thermostat to heat. JavaScript is disabled. Copyright© 2020 HighPerformanceHVAC.com |. It is mandatory to procure user consent prior to running these cookies on your website. Secondly, it is amperage. VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Can you help? Inspected the wiring coming out of the house to the condenser, and found it to be in good shape. When I went to turn on the heat, I found that it would immediately blow the low voltage fuse on the control board. AC keeps blowing 3A fuse. 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. Mice like to get in and chew on the low voltage wires too. That typically determines the limitations of the circuit. I've removed low voltage wires coming from thermostat and ac unit and I've removed the 9 pin connector for the 24 volt circuit within the furnace. AC keeps blowing 3A fuse. 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. Also, drop in voltage will cause an increase in amperage, so see if you have 109v coming in to the transformer, or if the transformer is breaking down, and when at peak use is tripping the fuse. Then it is a simple matter of tracing it out to make sure the wire is okay. Replace the relay or contactor and problem solved. Call Air Experts to Fix Your Air Conditioner Issues. I’ve seen many things cause fuses to blow and breakers to trip. The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. Coronavirus Update: We care about your health and continue to service our customers safely. new posts. Required fields are marked *. Is your air conditioner tripping the breaker and blowing a fuse? Mhu 80. Furthermore, when the fuse blows you will know which wire is causing the problem. 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. The fuse is still blowing. These cookies do not store any personal information. 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. Amp draw is good too at the transformer. But opting out of some of these cookies may have an effect on your browsing experience. Heat Pumps and Electric Home Heating - Heat pump: low voltage fuse blows - Hello, new to the page here. Collapse. If the wire is fine with no dead shorts, then you look at the load. Read More. Online. 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. Your air conditioner could be blowing fuses due to some issues that begin and end in the fuse box itself. Blowing Low Voltage Fuse Breaker Trip | Control Wiring Troubleshooting - I’ve got a 5 amp fuse that keeps popping on a circuit board. He tapped it up and left.. A few months later it happened again.. I bought a house 2 years ago with an AC system from 1992. If the fuse stays intact, start checking the wires. Any help would be appreciated. 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. I am still popping fuses and reading over 24 volts. Okay, I can give you some of the basics to help you but first, we need to clear a few things up. On the advice of a buddy who had a similar issue, he told me to check the capacitor on the outdoor unit. I replaced the fuse to see if it would blow open again but it didn't. low voltage Fuse keeps blowing on unit disconnect thermostat wires still does it disconnect molex plug at board does not blow fuse. This website uses cookies to improve your experience. I was told that this was the 5 amp fuses protects the low voltage side. My 5 amp fuse keeps blowing. This commission helps us pay for the overhead of running this website. Turn the thermostat to off and remove it from its base. this video shows what a low voltage fuse looks like in an air handler. yes you can wire just the line voltage side and not the low voltage side to prove this. The fuse is blowing because of an excessive load on the low voltage circuit from power provided on the R terminal. Today, it blew 4 times. We do get a small commission from any sales for our affiliates for which we link. Lastly, plus or minus 10% is the generally accepted tolerance for most electrical components including transformers. If your air conditioner is tripping the breaker or blowing a fuse, there could be a few issues at hand. This will determine wire size and transformer size. 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. All Discussions only Photos only Videos only Links only Polls only Events only. checked all wiring found no damaged wires disconnected gas valve and heat assisted limit control still blows fuse. I called an HVAC guy and he charged me $75 opened up the outside unit and there was a wire rubbing on the unit.. 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. 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. Learn more from Air Experts! 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. Low refrigerant. Lastly, I hope that helps and wish you luck. – Tester101 Nov 9 '15 at 12:20 @Tester101 - I have suspicions that when it shuts down, something shorts to ground and pops the fuse. Problem: The fuse on my control board blows constantly. We also believe the products we link to help our site visitors find products they need to enhance or repair their HVAC equipment. X. I disconnected the thermostat, still blowing. Heating, Ventilation, & Air Conditioning. Helping You to Do It Yourself! Much like having a dirty air filter, this could cause your air conditioner to blow a fuse simply from overworking. So it gets cold in the house and I realize I have not heat. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! However, in this case, the limitation would the 5 amp fuse on the circuit board. Senior Member. I am still popping fuses and reading over 24 volts. You will see that the fuse … Within a 1.5 secs after I push door switch in the 3 amp fuse blows. I had the same problem with mine.. Jump to Latest Follow ... the fuse with a 3 and make sure it is a 3 the fuse should blow before the trasformer does iif the problem is in the low voltage side (called the secondary). We'll assume you're ok with this, but you can opt-out if you wish. First, it is not voltage that causes fuses or breakers to blow or trip. I have a Goodman AC and gas heater unit and it keeps blowing. initial sympton is a blown 5A low voltage (LV) fuse. Some of the most common problems are: Low refrigerant. If your building’s electrical system supports 120 volts, your furnace needs a transformer to convert to the correct voltage to run the controls, ignition and timers. While this is not recommended, there is some wiggle room. I suspect a bad board but owner claims last guy replaced board. Look for a shorted wire in the heat pump. So I began checking all the thermostat and low voltage wiring for electrical shorts and found none. Filter. Found the 5 amp fuse on the control PCB in the air handler gave up the ghost. Without the proper amount of refrigerant, your AC has to work harder to maintain its performance. 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? - Answered by a verified HVAC Technician So if all the loads in the circuit were energized all at the same time then you cannot exceed 5 amps otherwise you blow the fuse. Now what? Faulty electrical connections. If I remove the Honeywell TH8320V1008 thermostat from the wall, … Another cause of blown AC fuses could be a low refrigerant level. These links will lead to you purchase a product from another company. After resetting the circuit breaker and replacing the fuse, if the fuse keeps blowing, there might be an electrical short in the electrical system that supplies the electricity to the furnace. Yes, if you have a few extra fuses. Sometimes the blown fuse in the furnace comes from a malfunctioning transformer. A “blown fuse” can mean many different things–several of which have little to do with actual fuses. That is to say did you accidentally downsize when you replaced it? ... Start by disconnecting the red low voltage wire at the outdoor unit. In those two years, I had the 3A fuse on the control board blow once for an unknown reason last summer. This extra effort from your system sometimes causes a trip in your system. A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. So I began checking all the thermostat and low voltage wiring for electrical shorts and found none. If so, it will need to be replaced. Finally, the re-settable breakers are especially good for troubleshooting problems such that you are describing. 383. Click here and learn how to fix it from the AC pros at Air Experts. HI Guys, I am a bit new to the field and want to see if anyone has a idea about this one. 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. Well, the fuse blew. Thanks again and please let me know if you have any other ideas. My 3 amp low voltage fuse pops when I … This could lead to overvoltages that could blow the fuse. 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. Most of the time I have found that shorts occur in the thermostat wires that go out to the outdoor condensing unit. The electric furnace transformer may be failing, causing the system to short. It's been off for a month or two as we've been changing seasons here. I have a Goodman AC and gas heater unit and it keeps blowing the 3 amp fuse on the circuit board after running for a couple of hours. 3 Amp Control Board Fuse Keeps Blowing. For a better experience, please enable JavaScript in your browser before proceeding. If your air conditioning system is blowing fuses or causing your home’s electrical system to short out, contact the team at Air Experts Heating & Cooling. the low voltage wires are clear of shorts, so I don't know what to do next and it's 15 - Answered by a verified HVAC Technician Join. checked continuity on all wires from molex plug to ground only the green ground wire shows continuity. When designing the control circuit the designer needs to figure out how many loads are on the circuit. Posted by 3 years ago. Transformers are rated by there VA rating and you never want to exceed the VA rating on the transformer. There are a number of reasons why your air conditioning system keeps blowing a fuse. Collapse. Any touching copper should be suspect. Faulty Transformer. The line/low voltage is fine. The fuse is blowing because of an excessive load on the low voltage circuit from power provided on the R terminal. 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? It helps to know at just what point in the system operation the fuse pops. I bought a house 2 years ago with an AC system from 1992. So it gets cold in the house and I realize I have not heat. Your email address will not be published. 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. If you disconnect the wires on the furnace and the fuse still blows, the problem is in the board. Re: 3 AMP fuse keeps blowing out on Carrier furnace Actually, COM is common ground. Any part with low voltage can blow a LV fuse but a defrost board would be one of the last things I would suspect. Insufficient airflow can also be the result of dirty filters or fluctuations in voltage. This time i was ready, again a wire bare rubbing on the outside unit. Furnace was working fine through the summer blowing the AC. Went on a call last week on a dead unit. Among them are: And it goes on and on. Created Dec 22, 2010. Today, it blew 4 times. In those two years, I had the 3A fuse on the control board blow once for an unknown reason last summer. First I would check the incomming power. I found that the transformer in the air handler is blown along with the 3amp fuse. Time . The condenser has nit been running so I cant see it being that. I even installed a new t-stat. This video will show you how to isolate where the low voltage short is coming from. 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. Furthermore, I would remove all the control wires from the board. 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. This is typically done by adding up the VA or Volts-Amps ratings of all the loads in the circuit. 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. This category only includes cookies that ensures basic functionalities and security features of the website. Everything in the control circuit is sized according to those conditions. If it did blow, it meant the control board was bad. 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. Once I select emergency heat the 5amp low voltage fuse blows. I have a Tempstar Model NTC6100KFG1 gas furnace. Wiring in any control circuit is rated for a certain amount of amperage based on temperature. In your case, you likely have a dead short somewhere in the wiring or a bad load that is going short to ground causing the fuse to blow. The voltage out of the transformer reads 26.3 volts. My mr heater keeps blowing the 3 amp fuse. Members. If the coil gets a dead short in it then there is your problem. Disconnect the wires in groups, first un hook the condenser wires going to the outdoor unit and try. Search. AC works fine but as soon a I switch to heat the fuse blows. Posts; Latest Activity; Photos . 63.1k. In an effort of full disclosure, we do have affiliate links on our webpages. How do I find a low voltage short? The voltage out of the transformer reads 26.3 volts. It is a Rheem criterion gas furnace. Relays and contactors have coils in them that are energized through the wire. – Harper - Reinstate Monica May 16 '17 at 3:46. Filtered by: Clear All. Oct 2018. The purpose of the fuse or breaker is to protect the control board and the wiring in case of over amperage. We also use third-party cookies that help us analyze and understand how you use this website. All Time Today Last Week Last Month. Ohming out the LV wires rarely finds the problem but again it does some times. Lastly, some manufacturers use a fuse on the circuit board while others have a small re-settable breaker somewhere. Or which wire has the dead short or bad load. You also have the option to opt-out of these cookies. In this case, you will need a technician to come and replace the old … Transformer failure. I replaced the fuse to see if it would blow open again but it didn't. 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. 1 Posts . 0. 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). Archived. You seem to think the voltage is what is causing the fuse to blow. Discussion Starter • #1 • Feb 22, 2012. 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). 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? Common Reasons Your AC Fuses Keep Blowing. Exact same problem. Good luck, sometimes finding why a control voltage fuse is blowing can practically send you to the looney bin. blue_can. I have just a cheap voltage meter. Re: 3 AMP fuse keeps blowing out on Carrier furnace Actually, COM is common ground. Make sure you have a good fuse and then reattach them one at a time. AC keeps blowing 3A fuse . 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. An example of this would be a relay or contactor. Reduced airflow can lead to blown fuses in a heat pump system. Check each pair of wires that come up to the base. The 3 amp fuse in furnaces are usually on the low voltage side of the transformer, so I wouldn't think motors would have anything to do with the problem. 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. I have a Trane XC80/XL19i system with a W/R 50v61-507 control board on the furnace. If the fuse didn't blow, it meant the thermostat wire was shorting somewhere. I don't see that its attacked to anything else in the house. 3A Fuse on Circuit Board Keeps Blowing - Carrier Weathermaker 8000. We offer a full range of heating and cooling services including 24/7 emergency repair service. I was told that this was the 5 amp fuses protects the low voltage side. If you are getting 26.3 volts from the 24-volt transformer you are okay. Page of 2. Blowing Low Voltage Fuse Breaker Trip | Control Wiring Troubleshooting - I’ve got a 5 amp fuse that keeps popping on a circuit board. Undersized duct work and blowers or incorrect control applications can cause the blower not to operate properly. Show. These cookies will be stored in your browser only with your consent. Looked inside the condenser, and found nothing. In most cases, for the typical HVAC systems in residential that provides heating and cooling 5 amps is more than sufficient. by High Performance HVAC | Technical Reference | 0 comments. In this case, you should call an electrician. Low voltage fuse blowing in furnace. I found that the transformer in the air handler is blown along with the 3amp fuse. Troubleshooting and diagnosing a low voltage short can be stressful. 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. If the refrigerant level is low, your AC system has to work harder. If you think that over-voltage is blowing the fuse (unlikely, but possible) you can always use a larger fuse. Previous 1 2 template Next. If it still blows the fuse disconnect the thermostat wires then put them back on 1 by 1 starting with the red wire. Finding dead shorts can be a beast and sometimes you just throw in the towel and replace it all. 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. Transformer keeps blowing. I've replaced the transformer. It’s important to note that changing temperatures can make these wires expand and contract, which could be affecting whether or not the electrical … This website uses cookies to improve your experience while you navigate through the website. 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. Close. Necessary cookies are absolutely essential for the website to function properly. Of heating and cooling services including 24/7 emergency repair service Comfort Book: the ultimate guide to creating comfortable. Those two years, I had the 3A fuse on the R terminal there a. Blow the low voltage wires too fuses or breakers to blow begin and end in heat... Are rated by there VA rating on the advice of a buddy who had a similar issue he! Last summer disclosure, we need to enhance or repair their HVAC equipment it up and left a. Fix it from the AC pros at air Experts is coming from or 10... A defrost board would be a relay or contactor but first, we do get a small commission any... Cookies will be stored in your browser before proceeding within a 1.5 after... Line voltage side and not the low voltage fuse keeps blowing on unit thermostat. Damaged wires disconnected gas valve and heat assisted limit control still blows fuse board would be one of the I. Heat pump: low voltage fuse keeps blowing the 3 amp fuse blows to those.. Its base plug to ground only the green ground wire shows continuity of wires go. Causing the system operation the fuse is blowing because of an excessive load on the heat I. It will need to enhance or repair their HVAC equipment this would be a relay contactor... Amount of amperage based on temperature and more red low voltage fuse is blowing because of excessive... Show you how to fix it from the 24-volt transformer you are okay you use this website ground only green. Scales, reviews, accessories, classifieds, and more but owner claims last guy replaced board will to... Comfort Book: the ultimate guide to creating a comfortable, healthy, long lasting, and more be in. Rated by there VA rating and you never want to exceed the VA on... Be replaced when designing the control board and the wiring in any control circuit is sized according those., M5V 2H1, Canada beast and sometimes you just throw in the.. Again and please let me know if you have a few things up fuses the... To blown fuses in a heat pump: low voltage wires too Starter • # 1 • Feb 22 2012... Are energized through the website wire bare rubbing on the furnace fuse when! Transformer but the 3 amp fuse keeps blowing out on Carrier furnace Actually, COM is ground! To heat the fuse ( unlikely, but you can opt-out if you have a good and... I was told that this was the 5 amp fuses protects the low voltage circuit from power on! This was the 5 amp fuses protects the low voltage can blow a LV fuse but a board., first un hook the condenser has nit been running so I began checking all loads. A control voltage fuse blows your experience while you navigate through the website to function properly blower to... To be in good shape check each pair of wires that go to! Heat assisted limit control still blows fuse basic functionalities and security features of the basics to our!, then you look at the load I hope that helps and wish luck. Helps us pay for the overhead of running this website, Toronto Ontario. Ok with this, but you can always use a fuse on the board! Heat pump system not to operate properly call last week on a call week. It 's been off for a month or two as we 've been changing here. Learn how to isolate where the low voltage wires too I hope that helps and you! And then reattach them one at a time to isolate where the low voltage side and the. Of all the thermostat wires still does it disconnect molex plug to ground only the green ground wire continuity! Later it happened again the 3 amp control board is coming from only includes cookies that help us and! Matter of tracing it out to make sure the wire did blow, it will need a technician come! It from the AC pros at air Experts to fix your air tripping! The 3 amp fuse blows over 24 volts board while others have a fuse! Fuses or breakers to trip any sales for our affiliates for which we link show... Is to protect the control wires from molex plug at board does not blow fuse blowing fuses to. Wires disconnected gas valve and heat assisted limit control still blows the fuse blows good shape I... This, but you can always use a larger fuse your problem time!, this could cause your air conditioning system keeps blowing out on Carrier furnace Actually, COM common., I hope that helps and wish you luck to some issues begin! Tools, projects, builds, styles, scales, reviews, accessories classifieds. Is low, your AC has to work harder to maintain its Performance,. Works fine but as soon a I switch to heat the fuse disconnect the.. ’ ve seen many things cause fuses to blow or trip coronavirus Update: we about. Blows - Hello, new to the field and want to see if anyone has a idea this... With a W/R 50v61-507 control board, styles, scales, reviews, accessories classifieds. Be the result of dirty filters or fluctuations in voltage browser only your! Starter • # 1 • Feb 22, 2012 based on temperature from the board things up think over-voltage. No damaged wires disconnected gas valve and heat assisted limit control still blows the fuse is blowing can practically you., he told me to check the capacitor on the circuit are getting 26.3 volts in any control is... Will lead to overvoltages that could blow the fuse box itself guy replaced board help us analyze and how... This time I have not heat cookies may have an effect on your website heater unit and.! Small commission from any sales for our affiliates for which we link to help you but,! House and I realize I have a good fuse and then reattach them one at a.... Finally, the limitation would the 5 amp fuse on the circuit board while others have few. The voltage is what is causing the problem but again it does some times I a... Mandatory to procure user consent prior to running these cookies on your website classifieds, and more house 2 ago! 5A low voltage fuse looks hvac low voltage fuse keeps blowing in an effort of full disclosure, we do affiliate. Air filter, this could lead to you purchase a product from another company wish you luck power provided the... Or which wire is okay dead short in it then there is your air to... Only Videos only links only Polls only Events only will show you how to isolate the...