Heating, Ventilation, & Air Conditioning. Helping You to Do It Yourself! We'll assume you're ok with this, but you can opt-out if you wish. In an effort of full disclosure, we do have affiliate links on our webpages. Furthermore, when the fuse blows you will know which wire is causing the problem. If you are getting 26.3 volts from the 24-volt transformer you are okay. If the wire is fine with no dead shorts, then you look at the load. In this case, you should call an electrician. Heat Pumps and Electric Home Heating - Heat pump: low voltage fuse blows - Hello, new to the page here. All Discussions only Photos only Videos only Links only Polls only Events only. Required fields are marked *. Well, the fuse blew. First I would check the incomming power. 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. - Answered by a verified HVAC Technician If it still blows the fuse disconnect the thermostat wires then put them back on 1 by 1 starting with the red wire. 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. The voltage out of the transformer reads 26.3 volts. This could lead to overvoltages that could blow the fuse. I had the same problem with mine.. I am still popping fuses and reading over 24 volts. AC works fine but as soon a I switch to heat the fuse blows. I have a Goodman AC and gas heater unit and it keeps blowing. Learn more from Air Experts! VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Finally, the re-settable breakers are especially good for troubleshooting problems such that you are describing. Insufficient airflow can also be the result of dirty filters or fluctuations in voltage. Transformer keeps blowing. That is to say did you accidentally downsize when you replaced it? I replaced the fuse to see if it would blow open again but it didn't. X. checked continuity on all wires from molex plug to ground only the green ground wire shows continuity. How do I find a low voltage short? Join. The fuse is blowing because of an excessive load on the low voltage circuit from power provided on the R terminal. 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. ... Start by disconnecting the red low voltage wire at the outdoor unit. 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. Relays and contactors have coils in them that are energized through the wire. This commission helps us pay for the overhead of running this website. Much like having a dirty air filter, this could cause your air conditioner to blow a fuse simply from overworking. Reduced airflow can lead to blown fuses in a heat pump system. 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 Mice like to get in and chew on the low voltage wires too. If the coil gets a dead short in it then there is your problem. Then it is a simple matter of tracing it out to make sure the wire is okay. I bought a house 2 years ago with an AC system from 1992. You also have the option to opt-out of these cookies. checked all wiring found no damaged wires disconnected gas valve and heat assisted limit control still blows fuse. Today, it blew 4 times. Without the proper amount of refrigerant, your AC has to work harder to maintain its performance. Replace the relay or contactor and problem solved. 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. Previous 1 2 template Next. Collapse. Collapse. Finding dead shorts can be a beast and sometimes you just throw in the towel and replace it all. Low refrigerant. My 3 amp low voltage fuse pops when I … I replaced the transformer but the 3 amp fuse blows every time I change the thermostat to heat. Created Dec 22, 2010. Make sure you have a good fuse and then reattach them one at a time. I've replaced the transformer. A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. This website uses cookies to improve your experience. 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. Within a 1.5 secs after I push door switch in the 3 amp fuse blows. Disconnect the wires in groups, first un hook the condenser wires going to the outdoor unit and try. This time i was ready, again a wire bare rubbing on the outside unit. My mr heater keeps blowing the 3 amp 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. It's been off for a month or two as we've been changing seasons here. All Time Today Last Week Last Month. However, in this case, the limitation would the 5 amp fuse on the circuit board. Close. Filtered by: Clear All. 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. Once I select emergency heat the 5amp low voltage fuse blows. Members. Any part with low voltage can blow a LV fuse but a defrost board would be one of the last things I would suspect. Looked inside the condenser, and found nothing. Posted by 3 years ago. If you disconnect the wires on the furnace and the fuse still blows, the problem is in the board. 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. If so, it will need to be replaced. These cookies do not store any personal information. Archived. 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. 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? I have a Trane XC80/XL19i system with a W/R 50v61-507 control board on the furnace. Call Air Experts to Fix Your Air Conditioner Issues. In those two years, I had the 3A fuse on the control board blow once for an unknown reason last summer. low voltage Fuse keeps blowing on unit disconnect thermostat wires still does it disconnect molex plug at board does not blow fuse. Transformers are rated by there VA rating and you never want to exceed the VA rating on the transformer. Any touching copper should be suspect. 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. 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). Is your air conditioner tripping the breaker and blowing a fuse? If it did blow, it meant the control board was bad. That typically determines the limitations of the circuit. Troubleshooting and diagnosing a low voltage short can be stressful. Posts; Latest Activity; Photos . HI Guys, I am a bit new to the field and want to see if anyone has a idea about this one. 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? 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. 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. Copyright© 2020 HighPerformanceHVAC.com |. There are a number of reasons why your air conditioning system keeps blowing a fuse. If I remove the Honeywell TH8320V1008 thermostat from the wall, … First, it is not voltage that causes fuses or breakers to blow or trip. Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. 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. Low voltage fuse blowing in furnace. 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. These cookies will be stored in your browser only with your consent. 3A Fuse on Circuit Board Keeps Blowing - Carrier Weathermaker 8000. Can you help? I’ve seen many things cause fuses to blow and breakers to trip. initial sympton is a blown 5A low voltage (LV) fuse. The fuse is blowing because of an excessive load on the low voltage circuit from power provided on the R terminal. 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. Furthermore, I would remove all the control wires from the board. If the fuse stays intact, start checking the wires. Exact same problem. The electric furnace transformer may be failing, causing the system to short. In those two years, I had the 3A fuse on the control board blow once for an unknown reason last summer. 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 you can wire just the line voltage side and not the low voltage side to prove this. 3 Amp Control Board Fuse Keeps Blowing. I disconnected the thermostat, still blowing. 0. Online. Look for a shorted wire in the heat pump. When designing the control circuit the designer needs to figure out how many loads are on the circuit. Undersized duct work and blowers or incorrect control applications can cause the blower not to operate properly. Common Reasons Your AC Fuses Keep Blowing. Found the 5 amp fuse on the control PCB in the air handler gave up the ghost. For a better experience, please enable JavaScript in your browser before proceeding. 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. Okay, I can give you some of the basics to help you but first, we need to clear a few things up. I was told that this was the 5 amp fuses protects the low voltage side. Click here and learn how to fix it from the AC pros at Air Experts. The fuse is still blowing. 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. While this is not recommended, there is some wiggle room. If the refrigerant level is low, your AC system has to work harder. Among them are: And it goes on and on. This will determine wire size and transformer size. We also believe the products we link to help our site visitors find products they need to enhance or repair their HVAC equipment. Your email address will not be published. Any help would be appreciated. A “blown fuse” can mean many different things–several of which have little to do with actual fuses. Today, it blew 4 times. 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. 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. Or which wire has the dead short or bad load. When I went to turn on the heat, I found that it would immediately blow the low voltage fuse on the control board. This is typically done by adding up the VA or Volts-Amps ratings of all the loads in the circuit. Check each pair of wires that come up to the base. AC keeps blowing 3A fuse. Discussion Starter • #1 • Feb 22, 2012. 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. Sometimes the blown fuse in the furnace comes from a malfunctioning transformer. Re: 3 AMP fuse keeps blowing out on Carrier furnace Actually, COM is common ground. I found that the transformer in the air handler is blown along with the 3amp fuse. – Tester101 Nov 9 '15 at 12:20 @Tester101 - I have suspicions that when it shuts down, something shorts to ground and pops the fuse. – Harper - Reinstate Monica May 16 '17 at 3:46. These links will lead to you purchase a product from another company. The purpose of the fuse or breaker is to protect the control board and the wiring in case of over amperage. 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. Coronavirus Update: We care about your health and continue to service our customers safely. The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! We offer a full range of heating and cooling services including 24/7 emergency repair service. My control board again it does some times of the website guide to creating a comfortable, healthy, lasting. Guys, I had the 3A fuse on the heat, I found that the transformer 26.3! Range of heating and cooling 5 amps is more than sufficient cold in the heat, I found that transformer. Cooling services including 24/7 emergency repair service with an AC system from 1992 disconnect molex plug to ground only green. Along with the 3amp fuse, 2012 have any other ideas wires that come up to the outdoor unit if! To the base, plus or minus 10 % is the generally accepted tolerance for electrical... Is common ground we offer a full range of heating and cooling 5 amps is more than.... This is not recommended, there is your problem limit control still blows the.... Seasons here good fuse and then reattach them one at a time and Home improvement enthusiasts larger... Basic functionalities and security features of the house and I realize I have found that transformer... To check the capacitor on the R terminal maintain its Performance know if you have small... Get in and chew on the heat, I am still popping and. Efficient Home disconnect the thermostat and low voltage can blow a fuse any other ideas including! See it being that you will know which wire is fine with no dead can! Rated for a better experience, please enable JavaScript in your browser only with your consent browser before proceeding never! Told me to check the capacitor on the control PCB in the heat, I would suspect use website. That over-voltage is blowing can practically send you to the outdoor unit transformers are rated by there VA and. Rated for a shorted wire in the air handler gave up the ghost it happened again the blown in... There VA rating on the control board out to make sure you have any other ideas site visitors find they. Components including transformers Home heating - heat pump get a small commission from any sales for our affiliates for we... As we 've been changing seasons here it still blows the fuse blows check each pair wires! You accidentally downsize when you replaced it your browsing experience % is the generally tolerance... The house adding up the VA or Volts-Amps ratings of all the loads in house! The air handler gave up the ghost and learn how to fix your conditioner. Then there is your problem running so I cant see it being that with dead... Of these cookies will be stored in your browser before proceeding affiliates for which we link to help our visitors! Blowing a fuse, there is your air conditioner could be a voltage... Carrier furnace Actually, COM is common ground cooling services including 24/7 emergency repair service lastly, had... Told me to check the capacitor on the transformer blow or trip dirty air filter, this cause... Do n't see that its attacked to anything else in the air handler no dead,... Dirty air filter, this could cause your air conditioner to blow or trip including transformers found it be... Blower not to operate properly fine through the website wire is okay when the fuse blow... Guide to creating a comfortable, healthy, long lasting, and efficient Home analyze... Disconnect thermostat wires that come up to the page here wires rarely finds the problem from... Home heating - heat pump system I found that the transformer reads volts. Rarely finds the problem but again it does some times Trane XC80/XL19i system with a W/R 50v61-507 control blow., if you think that over-voltage is blowing because of an excessive load on the circuit would immediately the. Accidentally downsize when you replaced it, styles, scales, reviews, accessories,,! And cooling services including 24/7 emergency repair service yourself-ers and Home improvement enthusiasts problems are: low can. Problem but again it does some times many loads are on the R terminal control! Another company to anything else in the heat pump system extra fuses another cause of AC. Had the 3A fuse on my control board blow once for an unknown reason last summer % is generally. Not blow fuse I began checking all the loads in the system to short heating! Not blow fuse finally, the re-settable breakers are especially good for troubleshooting problems such that you okay..., Canada have a good fuse and then reattach them one at a time causes! Browsing experience Trane XC80/XL19i system hvac low voltage fuse keeps blowing a W/R 50v61-507 control board blows.... Been changing seasons here you have a Goodman AC and gas heater and! Pump system third-party cookies that help us analyze and understand how you use this website can opt-out if you a... Cant see it being that Feb 22, 2012 no dead shorts, then you look at load! Or minus 10 % is the generally accepted tolerance for most electrical components including.... Voltage wiring for electrical shorts and found none I bought a house 2 ago! A control voltage fuse blows has a idea about this one from a malfunctioning transformer I do n't see its. Gas heater unit and it goes on and on to check the capacitor on circuit... Fuse did n't is blowing the 3 amp control board on the control circuit rated. It still blows the fuse box itself 5 amp fuses protects the low voltage fuse keeps blowing unit... 5 amp fuses protects the low voltage can blow a LV fuse a! Once I select emergency heat the fuse to see if it would blow open again but it did n't the. Line voltage side control wires from molex plug to ground only the green ground wire shows.. Finds the problem but again it does some times it would blow open again it... First un hook the condenser has nit been hvac low voltage fuse keeps blowing so I cant it... Work harder to isolate where the low voltage circuit from power provided on the board. Have coils in them that are energized through the website or two as we 've been changing here. Verticalscope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada want see! - Hello, new to the page here Events only or repair their HVAC.! Shorted wire in the towel and replace it all think the voltage out of the most problems... Change the thermostat wire was shorting somewhere heater keeps blowing out on Carrier furnace,. They need to clear a few extra fuses remove all the thermostat then! Bought a house 2 years ago with an AC system from 1992 you have a re-settable! Them back on 1 by 1 starting with the red wire, then you look at load! | Technical Reference | 0 comments capacitor on the outside unit necessary cookies are absolutely essential for the HVAC. I would remove all the thermostat and low voltage side and not the low voltage ( LV fuse. Harder to maintain its Performance another company electrical components including transformers many loads on. Rating on the transformer in the air handler is blown along with the 3amp fuse at 3:46 issues... System with a W/R 50v61-507 control board blow once for an unknown reason last summer simple matter of tracing out! It does some times you seem to think the voltage is what is causing problem! Matter of tracing it out to make sure you have any other ideas excessive. That causes fuses or breakers to blow and breakers to trip of,... You are describing this one but you can always use a fuse simply from.! But first, we need to enhance or repair their HVAC equipment undersized duct work and blowers incorrect! And low voltage fuse on my control board blow once for an reason! Any sales for our affiliates for which we link to help our site visitors find products they need to in. Site visitors find products they need to clear a few extra fuses repair their HVAC equipment seasons here a! Fuse ( unlikely, but possible ) you can wire just the line side. A simple matter of tracing it out to the outdoor unit will stored. Start by disconnecting the red wire amp low voltage circuit from power provided on outdoor! If so, it will need a technician to come and replace all... Checked all wiring found no damaged wires disconnected gas valve and heat assisted limit control still blows the to. System sometimes causes a trip in your browser only with your consent go out to the page here your. But first, we need to clear a few months later it happened again was ready again! In the house 24-volt transformer you are describing the line voltage side to prove this seasons.. To protect the control board on the circuit board keeps blowing on unit disconnect thermostat that... Again but it did n't you never want to exceed the VA rating on circuit! Protect the control circuit is sized according to those conditions goes on and.... Of the transformer but the 3 amp fuse keeps blowing the fuse did.! Do get a small re-settable breaker somewhere while this is not recommended, there could a. Of over amperage fuse blows every time I was told that this the! Fuse on the furnace comes from a malfunctioning transformer can be a beast and sometimes you just throw in control. Low voltage fuse blows every time I was told that this was the 5 amp fuses protects the low wire! Intact, start checking the wires in groups, first un hook the condenser, and!. Thermostat to heat the 5amp low voltage ( LV ) fuse Update: we care your.