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. A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. All Time Today Last Week Last Month. While this is not recommended, there is some wiggle room. blue_can. When I went to turn on the heat, I found that it would immediately blow the low voltage fuse on the control board. The voltage out of the transformer reads 26.3 volts. 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. Re: 3 AMP fuse keeps blowing out on Carrier furnace Actually, COM is common ground. initial sympton is a blown 5A low voltage (LV) fuse. We do get a small commission from any sales for our affiliates for which we link. Relays and contactors have coils in them that are energized through the wire. This video will show you how to isolate where the low voltage short is coming from. You will see that the fuse … Amp draw is good too at the transformer. Join. 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. Troubleshooting and diagnosing a low voltage short can be stressful. First I would check the incomming power. My 3 amp low voltage fuse pops when I … Check each pair of wires that come up to the base. Without the proper amount of refrigerant, your AC has to work harder to maintain its performance. Show. Insufficient airflow can also be the result of dirty filters or fluctuations in voltage. I’ve seen many things cause fuses to blow and breakers to trip. 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. Common Reasons Your AC Fuses Keep Blowing. If the refrigerant level is low, your AC system has to work harder. Collapse. Everything in the control circuit is sized according to those conditions. this video shows what a low voltage fuse looks like in an air handler. 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. 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. But opting out of some of these cookies may have an effect on your browsing experience. I am still popping fuses and reading over 24 volts. checked continuity on all wires from molex plug to ground only the green ground wire shows continuity. If I remove the Honeywell TH8320V1008 thermostat from the wall, … I have a Tempstar Model NTC6100KFG1 gas furnace. So I began checking all the thermostat and low voltage wiring for electrical shorts and found none. The voltage out of the transformer reads 26.3 volts. Close. This website uses cookies to improve your experience. You seem to think the voltage is what is causing the fuse to blow. Search. These cookies will be stored in your browser only with your consent. I disconnected the thermostat, still blowing. 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. 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. Turn the thermostat to off and remove it from its base. 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. Finally, the re-settable breakers are especially good for troubleshooting problems such that you are describing. I am still popping fuses and reading over 24 volts. These cookies do not store any personal information. Copyright© 2020 HighPerformanceHVAC.com |. If you are getting 26.3 volts from the 24-volt transformer you are okay. Mhu 80. JavaScript is disabled. This time i was ready, again a wire bare rubbing on the outside unit. Among them are: And it goes on and on. Senior Member. Most of the time I have found that shorts occur in the thermostat wires that go out to the outdoor condensing unit. Blowing Low Voltage Fuse Breaker Trip | Control Wiring Troubleshooting - I’ve got a 5 amp fuse that keeps popping on a circuit board. In most cases, for the typical HVAC systems in residential that provides heating and cooling 5 amps is more than sufficient. Today, it blew 4 times. 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. Furthermore, when the fuse blows you will know which wire is causing the problem. However, in this case, the limitation would the 5 amp fuse on the circuit board. X. In those two years, I had the 3A fuse on the control board blow once for an unknown reason last summer. Discussion Starter • #1 • Feb 22, 2012. The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. Make sure you have a good fuse and then reattach them one at a time. Filter. Much like having a dirty air filter, this could cause your air conditioner to blow a fuse simply from overworking. So I began checking all the thermostat and low voltage wiring for electrical shorts and found none. Transformers are rated by there VA rating and you never want to exceed the VA rating on the transformer. Members. 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. Ohming out the LV wires rarely finds the problem but again it does some times. It’s important to note that changing temperatures can make these wires expand and contract, which could be affecting whether or not the electrical … Helping You to Do It Yourself! If it still blows the fuse disconnect the thermostat wires then put them back on 1 by 1 starting with the red wire. AC keeps blowing 3A fuse. In an effort of full disclosure, we do have affiliate links on our webpages. On the advice of a buddy who had a similar issue, he told me to check the capacitor on the outdoor unit. 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 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. Good luck, sometimes finding why a control voltage fuse is blowing can practically send you to the looney bin. Finding dead shorts can be a beast and sometimes you just throw in the towel and replace it all. It's been off for a month or two as we've been changing seasons here. Thanks again and please let me know if you have any other ideas. Your air conditioner could be blowing fuses due to some issues that begin and end in the fuse box itself. If so, it will need to be replaced. new posts. Within a 1.5 secs after I push door switch in the 3 amp fuse blows. 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. 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? checked all wiring found no damaged wires disconnected gas valve and heat assisted limit control still blows fuse. I suspect a bad board but owner claims last guy replaced board. Inspected the wiring coming out of the house to the condenser, and found it to be in good shape. Low refrigerant. 1 Posts . Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! I have a Goodman AC and gas heater unit and it keeps blowing. 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? Faulty electrical connections. Undersized duct work and blowers or incorrect control applications can cause the blower not to operate properly. That typically determines the limitations of the circuit. Page of 2. Required fields are marked *. 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. The electric furnace transformer may be failing, causing the system to short. Oct 2018. When designing the control circuit the designer needs to figure out how many loads are on the circuit. 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. The line/low voltage is fine. He tapped it up and left.. A few months later it happened again.. 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. Necessary cookies are absolutely essential for the website to function properly. Transformer failure. Look for a shorted wire in the heat pump. VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Secondly, it is amperage. Lastly, plus or minus 10% is the generally accepted tolerance for most electrical components including transformers. 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. All Discussions only Photos only Videos only Links only Polls only Events only. 383. I don't see that its attacked to anything else in the house. Any help would be appreciated. The purpose of the fuse or breaker is to protect the control board and the wiring in case of over amperage. Click here and learn how to fix it from the AC pros at Air Experts. In this case, you will need a technician to come and replace the old … In this case, you should call an electrician. 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. Once I select emergency heat the 5amp low voltage fuse blows. 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. 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). If the fuse stays intact, start checking the wires. Sometimes the blown fuse in the furnace comes from a malfunctioning transformer. 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. Furthermore, I would remove all the control wires from the board. Furnace was working fine through the summer blowing the AC. Any touching copper should be suspect. AC works fine but as soon a I switch to heat the fuse blows. 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. Today, it blew 4 times. 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. Reduced airflow can lead to blown fuses in a heat pump system. 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? This website uses cookies to improve your experience while you navigate through the website. We offer a full range of heating and cooling services including 24/7 emergency repair service. 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. This could lead to overvoltages that could blow 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. I even installed a new t-stat. Archived. Looked inside the condenser, and found nothing. My mr heater keeps blowing the 3 amp fuse. This commission helps us pay for the overhead of running this website. 3A Fuse on Circuit Board Keeps Blowing - Carrier Weathermaker 8000. Faulty Transformer. The condenser has nit been running so I cant see it being that. I was told that this was the 5 amp fuses protects the low voltage side. Well, the fuse blew. I bought a house 2 years ago with an AC system from 1992. Filtered by: Clear All. These links will lead to you purchase a product from another company. Is your air conditioner tripping the breaker and blowing a fuse? If the wire is fine with no dead shorts, then you look at the load. - Answered by a verified HVAC Technician low voltage Fuse keeps blowing on unit disconnect thermostat wires still does it disconnect molex plug at board does not blow fuse. I found that the transformer in the air handler is blown along with the 3amp fuse. 3 Amp Control Board Fuse Keeps Blowing. Few issues at hand or fluctuations in voltage fuse is blowing can practically you. 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