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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 797
Experience:  I have been an HVAC/R mechanic/technician for 30+ years.
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Have a disconnect box issue

Customer Question

have a disconnect box issue
Submitted: 1 year ago.
Category: HVAC
Expert:  Brian HVAC Guy replied 1 year ago.
Hi I'm Brian and I'm here to help! What kind of issue are you having with your disconnect?
Customer: replied 1 year ago.
My fuse had burned and melted, the fan was running and stopping getting hot prior to that. I got a new disconnect and fuse same amps and volts just set up a bit different. followed the load line line load diagram. but now the ac unit just clicks one time when I turn it on, nothing else. Is it something else, is it the box, or my wiring?
Expert:  Brian HVAC Guy replied 1 year ago.
If the disconnect was wired incorrectly, chances are you would have heard a loud pop with sparks and the breaker would have tripped or the fuses would have blown. It's possible there may be some type of power company load management device attached or even unit provided time delay. I would give it up to 10 minutes after you close the disconnect to see if your unit starts then. Of course make sure the thermostat is set properly and your breaker or fuses inside are set to on. Some power company load management delays can be up to 10 minutes long. If you can upload a picture of your disconnect wiring using the 'Attach Files' button or the Paper clip icon in your reply dialog box, I'd be happy to double check your wiring for you! Thanks, -Brian
Customer: replied 1 year ago.
you just need a pic of the actual wiring I did. How will you tell which wire is which by looking at the pic?
Expert:  Brian HVAC Guy replied 1 year ago.
I may need to ask for some clarification but chances are good I may be able to tell with just a picture.
Customer: replied 1 year ago.
ok will do
Expert:  Brian HVAC Guy replied 1 year ago.
A close up shot and a wide shot will help. That way I can see the conduit(s) or flexible conduit(s) are attached.
Expert:  Brian HVAC Guy replied 1 year ago.
*how they're attached.
Customer: replied 1 year ago.
ok, but I have the type that goes into the wall as you will see. But I took a photo of the back panel of the ac where the capacitor is. Again it clicks like its trying to come on but that's it. uploading pics now
Expert:  Brian HVAC Guy replied 1 year ago.
Ok, I'm sure we can figure this out together! btw the pics are still not posted. Are you having upload issues? It does happen occasionally. -Brian
Customer: replied 1 year ago.
yes I am
Expert:  Brian HVAC Guy replied 1 year ago.
Let me see if I can get some help for you to get the pictures uploaded. If you have an account with a third party picture site you could upload them there and share the link with me but I will try to get some help for you from customer service. Sorry for the issue and thanks for your patience.
Customer: replied 1 year ago.
I got it now
Expert:  Brian HVAC Guy replied 1 year ago.
That's good because when I tried to get help for you the app locked my browser up! Sorry for the delay! I'll review your pics now. Thanks for uploading them!
Expert:  Brian HVAC Guy replied 1 year ago.
The wiring on the disconnect looks ok. If you hear a click when you turn your system on, that could be coming from the thermostat sending a signal to your unit outside and the contactor (the device with the two large line voltage wires are connected) is engaging. It's possible even though you replaced the disconnect (and I assume fuses if the new one holds them) that your are still not getting 240 volts to the outdoor unit. It would really require a volt meter to check some voltages for me to help you determine where the problem still lies. Do you have access to and knowledge of a volt meter?
Customer: replied 1 year ago.
not at the moment. why would I all of a sudden not be receiving the 240 volts just from changing the disconnect.
Customer: replied 1 year ago.
I am checking with my neighbor for a meter. could it be the capacitor?
Expert:  Brian HVAC Guy replied 1 year ago.
It could be possible that the breaker that feeds that disconnect did not fully turn back on after you replaced the disconnect. This is a common occurrence on a circuit that has been overheating like yours has. If the disconnect was wired wrong it would only do one of two things: 1) either pop the breaker that feeds it immediately and you would have known because it would have popped in your hand when you inserted the disconnect handle, or the breaker would have popped in your hand if the disconnect handle was already in when you turned the breaker on. OR 2) nothing would have happened and the unit would have power if your breaker was ok even if two of the line load wires were in the wrong side. It could be a capacitor but as long as you had the unit off chances are you would have heard the groan of the fan and/or compressor trying to start. So that is low on the list of possibilities for the moment. Let me know if you score a meter and I'll help you check some voltages and that will tell us what's going on. Thanks, -Brian
Customer: replied 1 year ago.
ok thanks. if not the capacitor is there really any other easy fix.
Expert:  Brian HVAC Guy replied 1 year ago.
If it's the breaker not resetting, sometimes you can work it off then on very firmly and it will reset. Without knowing whether it's a voltage issue or a signal issue from the thermostat It's hard to tell if there could be any other easy fix. Is the air blowing inside from the inside unit? Looking at the capacitor, it is not swollen at all and nothing else I can see within the unit jumps out at me visually. I wish I could be more help but this is a case where the right tool for the job is necessary. Let me know how I can help further. We have as much time as you need, even if it goes into tomorrow or even later. Thanks, -Brian
Customer: replied 1 year ago.
ok will get a meter tomorrow
Expert:  Brian HVAC Guy replied 1 year ago.
Sounds good, I will be in and out here tomorrow but leave a reply and I'll post back as soon as I can. Thanks and have a great night! -Brian
Customer: replied 1 year ago.
whats the first thing I need to check with the meter
Expert:  Brian HVAC Guy replied 1 year ago.
Good morning! Ok with your meter set to read ac voltage (make sure the meter leads are plugged into Com and V sockets on the meter) The ac voltage range should be left at auto or at least 400 volts ac. Now, in the disconnect, pull the handle out and measure the voltage at the two LINE terminals. You should read 240 volts nominal there. Let me know what you get and we'll go from there. Thanks, -Brian
Expert:  Brian HVAC Guy replied 1 year ago.
Sorry!!! that should have read "at the two LINE terminals" on the disconnect, NOT LOAD yet!
Customer: replied 1 year ago.
ok I go 240 from the line terminals
Expert:  Brian HVAC Guy replied 1 year ago.
Awesome! Now plug the disconnect handle back in and check the voltage at the LOAD terminals on the disconnect please.
Customer: replied 1 year ago.
nothing at all from the load
Expert:  Brian HVAC Guy replied 1 year ago.
Ok, the 240 volts on the LINE terminals tells me your breaker is fine in the panel and you have wired your disconnect correctly. Since you have voltage on the LINE but not the LOAD, it can only mean that the fuse(s) in the handle fuse cartridge are blown. If the meter has an OHM scale (resistance) you can pull the handle and check the fuses with the meter set to its lowest resistance scale. The reading across the fuse cartridges should be close to zero ohms. If you had put new fuses in and they are already blown, you may have a deeper problem in your ac unit. Let me know what you find, thanks.
Customer: replied 1 year ago.
where are the fuses?
Customer: replied 1 year ago.
nevermind that I assume there the slots the handle goes in. do we need to check the line, or load or both with the resistance
Expert:  Brian HVAC Guy replied 1 year ago.
Edit: after reading last post (was writing response below) DO NOT check resistance on the LINE or LOAD terminals! That will damage your meter! Test the fuses themselves which should be in the pull out handle if the disconnect has fuses. Pictures of the handle and the disconnect with the cover removed may be helpful to me here. Because of the readings you are getting (voltage on LINE but not LOAD with disconnect plugged in) I am assuming this is the type of disconnect that has the fuses in the disconnect handle itself. If there are no fuses in that disconnect then the disconnect is faulty. Do you still have voltage on the LINE terminals when the disconnect pull-out handle is pushed in and ON is up? and you don't have voltage on the LOAD terminals with the disconnect handle in with ON up?
Customer: replied 1 year ago.
ok when I check the load terminals it goes to 0. when I check the line it bounces around between -110 to -130
and that's set on the resistance.
Customer: replied 1 year ago.
The voltage on the LINE have 240 whether the handle is in the off or on position. The LOAD voltage does not read anything when the handle is in the off or on position.
Expert:  Brian HVAC Guy replied 1 year ago.
Edit: Thanks for that clarification! I was writing everything you see below and was about to send it when you posted your last reply ;) My response below should explain. Let me know if you have questions. It appears there are either fuses in the disconnect that are blown OR if there are no fuses in the disconnect, the disconnect is faulty. But read the post below for more clarification. Post before the edit above:Yeah, again we shouldn't be checking resistance on the terminals with the wires in them. Just voltage on those spots! Your meter probably has an auto protection in it fortunately. Let me tell you what you should and shouldn't have for voltage on the terminals in the disconnect and maybe that will be helpful for you:1) When the disconnect handle is NOT plugged in you should have 240 volts ac on between the two LINE terminals and zero voltage on the two LOAD terminals.2) When the disconnect handle IS plugged in you should have 240 volts between the two LINE terminals AND 240 volts between the two LOAD terminals. You said earlier that you had 240 volts on the line terminals and zero volts on the load terminals with the handle in and ON is up. That indicates either blown fuses in the disconnect (if there are fuses in it) OR the disconnect handle is in and in the OFF position (handle upside down) OR the handle is in and in the ON position and the new disconnect has an issue. I was just suggesting you use the resistance scale to test the fuses (if there are fuses in the disconnect). It appears there may be a problem with that disconnect. That's why I asked for the pictures. Thanks, -Brian
Customer: replied 1 year ago.
here is the handle and the inside of the disconnect
Expert:  Brian HVAC Guy replied 1 year ago.
Ok thanks for those pictures! This clears everything up! That handle is also a fuse holder and will hold FRN style 250 volt buss cartridge fuses! There are no fuses in it and that's why things aren't working. If you have the proper size breaker in your breaker panel that supplies that circuit you can put 60 amp fuses in the handler fuse receptacles. The LINK HERE provides an example of what the fuse looks like. Ace Hardware or a similar hardware store is probably the best place to find them. Call first, a lot of hardware stores aren't open on Sunday! Turn your breaker off inside, install the fuses in the disconnect handle, insert the disconnect handle, then turn you breaker back on. That will take care of your issue if there is no other problem in the unit! Thanks, -Brian
Customer: replied 1 year ago.
Thanks, ***** ***** tell we are new to this, I feel real silly. I didn't see fuses in the last disconnect handle, so I just assumed the new one would be the same. Makes sense though. We will get fuses and see how that works.
Expert:  Brian HVAC Guy replied 1 year ago.
No worries. That's what we're here for! This stuff is second nature to us but can be hard to explain to the layman. Let me know how it goes and if it works! Thanks, ***** ***** If it worked before you changed the disconnect, it should work fine once you get the fuse in!
Customer: replied 1 year ago.
ok that got it. Our problem now is what probably melted the last fuse box in the first place, which was the fan not turning, when we turn the unit on it will start to move slowly then stop, then the unit gets real hot. Im assuming the fan motor, it was replaced about 2 years ago.
Expert:  Brian HVAC Guy replied 1 year ago.
Yeah, it sounds like the fan motor has gone bad. It may have been the disconnect that took out the fan motor and not the opposite. Even at locked rotor current, the fan motor itself will not make the disconnect burn. By the looks of the wires in your disconnect it would appear one or more of them may have been loose and caused the issue. Does the compressor run ok?
Customer: replied 1 year ago.
yes it runs but the fan will not move. it sounds like the motor is getting ready to go but the fan never moves.
Expert:  Brian HVAC Guy replied 1 year ago.
Yep, no real sense looking further, I would say your fan motor is shot indeed. Sorry for the bad news :( would you like me to source one online for you?
Customer: replied 1 year ago.
we got one from grainer 2 years ago, is there some place better/cheaper? I don't remember off hand how much it was but I think it was over $200
Customer: replied 1 year ago.
sorry grainger
Expert:  Brian HVAC Guy replied 1 year ago.
Yeah, Grainger is historically very expensive! You can get an aftermarket one online for less than half that. I'll see what I can find. You should also replace the dual run capacitor at the same time. Can you tell me what the Mfd rating of the capacitor is please? I'll look for one of those as well, they are really cheap online! It will be something like 50+5 Mfd-370 volts ac or 45/7.5 mfd at 440 VAC or something very similar.
Expert:  Brian HVAC Guy replied 1 year ago.
Oh, and I will need the make and model number of the unit itself to source the motor! If you have the motor specs that would be helpful too. All I need it RPM, HP and rotation. I know the rest. Or a motor model will get me there too. Make and model of the unit is important though.
Customer: replied 1 year ago.
the tag on the actual motor is really faded but if you need that information I can get it. We have to leave for a few hours but will be back. let me know if the pic's are enough. Will be back in a few!
Expert:  Brian HVAC Guy replied 1 year ago.
Yeah I've gotta go offline for a bit too. I'll post back a little later with the info I find for you. Thanks, -Brian
Expert:  Brian HVAC Guy replied 1 year ago.
Boy, I'm having trouble locating the specs on the motor! I see the motor is 1/4 horsepower by the unit data plate but I can't get any more info! All I really need is the RPM and the rotation of the motor. You can just tell me whether the motor turns clockwise or counter-clockwise as you look down at the fan blade in your unit. I can take it from there. I believe I can find you an aftermarket motor for around $75! The capacitor size will depend on the motor I find for you. If you like, I can probably also find the OEM motor with the info above as well. Thanks, -Brian
Customer: replied 1 year ago.
Not sure on rmp. but it turns clockwise
Expert:  Brian HVAC Guy replied 1 year ago.
Ok thanks. I will continue to try to look when I get back online tomorrow and reply with what I can find. It appears that model series could either have a standard 1100 rpm motor or a slower 850 rpm motor and that's a huge difference so I have to find that out before I can recommend a motor for you! Thanks and have a good night,Brian
Customer: replied 1 year ago.
We will find the rpm and let you know you don't have to worry about that. Thanks though
Customer: replied 1 year ago.
Ok went ahead and got a new motor and capacitor. Everything was installed and was running fine, but now cuts of and on. It will run for a minute or two then stop, no noise at all and start up again later.
Expert:  Brian HVAC Guy replied 1 year ago.
Hello again and sorry for the slow response. This sounds a bit like you may have a high or low refrigerant pressure switch tripping and cutting the unit off and on. I would check to make sure the condenser coils are clean and when the unit is running the larger of the two copper lines attached to it from the house is cool to the touch, the smaller copper line should be no higher than 20 degrees above the outdoor temperature. If the copper lines are outside of those ranges when the unit does run, then you probably have a very dirty coil (even if it doesn't look like it) or a low refrigerant condition. It would require manifold gauges to test the refrigerant level. Thanks, -Brian