Testing and Checking the MFD uF rating of HVAC Capacitors- Start Capacitors and Run Capacitors!
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- เผยแพร่เมื่อ 9 ก.ย. 2024
- In This HVAC Video, I show how to Test and Read the MFD uF rating of Start Capacitors, Dual Run Capacitors, and Single Caps! I Explain Wiring, Shorting, Compressor Fan, and Common Terminal Identification. This is how to identify types of HVAC Capacitors, ratings, tests of capacitors, telltale signs of a bad capacitor, and what types of capacitors that you may run into while servicing HVACR units.
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Thanks.
This is exactly what I needed to know! Thank you!
I've been looking all over for a video that shows how to test with a simple multimeter. I still don't own a meter that tests capacitance for larger capacitors, but I really only need a pass/fail test and I was pretty sure it was possible. Thank you!
Did you ever figure this out? It seems like any digital multimeter under $20 have no setting to test MFD uF of start/run capacitor. Or at least, I have no idea how to dial up that setting.
@@mts7274 The $20 ones will not measure the capacitance of a start/run capacitor but should be able to to a pass/fail test as described in this video. You can find inexpensive models that will measure capacitance for much smaller mF values (like the small ones found on small electronics circuit boards), but you'll need to spend over $100 to get a meter that can measure capacitance on a capacitor as large as a start/run capacitor.
Thank you!
You're welcome!
good stuff! :D
I encountered a run capacitor with two terminals and no labels , which terminal is for Common. I noticed also that both Fan and Herm wires are connected on the second terminal. So let say that capacitor went bad and I disconnected the wires on those two terminals. On the new capacitor, since it is not marked, where do I connect the common wire and the fan and herm?
A capacitor for a compressor and a condenser fan motor would be a dual capacitor with three terminals. Common comes off the leg and is usually a yellow wire from the contactor, herm goes to compressor, and fan goes to the condenser fan. If it were just two terminals, that could be for just the compressor, just the condenser fan, or just the blower motor. Here is a video on a bad compressor with wiring for a capacitor but really you should check and follow the wiring diagram for the unit if it is available, unless that is, it is wore off. Thanks for the Comment!---th-cam.com/video/IASaWV3C1_Y/w-d-xo.html
I’m working on a portable AC unit and o have blower motor for the exhaust side that isn’t working. I’ve been told to check out the 12.5 MFD 440v capacitor. My question is does it matter what terminals I check on top of that oval shape capacitor???
sir wonderful lectute
Thank you!
Good! I always thought you had to remove the resistor to be able to test those start capacitors.
So start capacitors have a wide range of microfarad readings, for instance 400-450 mfd, 88-125mfd, 163- 193mfd, and so on. The bleed resistors add an additional 3 or 4 microfarad reading which the meter picks up. The question is, would you think it is wise to go clipping off all of the bleed resistors on those good start capacitors which limit their lifespan when you have that much of a mfd operating range? For me it is a no unless my meter will just not pick up the mfd reading, then I would move forward with cutting it off. I don't think most techs are soldering them back on after testing. Most of the time the reading is still usually in the middle of the mfd range such as a 163-193 capacitor reading a 185 with the bleed resistor. I am also only speaking about residential light commercial by the way. Thank you for your wonderful questions, thumbs up, and great comments!
Thanks for your vids. Learned a bunch.
Ok... so for my HVAC Tran 2.5 ton unit.. The start capacitor 135-162MFD...
Would not read on the mulimeter.. ie: gave an OL (it jumped around and then settled on the OL).
I clipped the resistor... and it gave a reading of approx 144...
You id say you were talking about "residential light commercial"...
So I don't know if it is different for the HVAC start capacitors.
or maybe the resistor is bad.
If the first relay you show keeps clicking and could that mean its bad or could it be a capacitor?
Great video. What do you do when you have a motor and capacitor with no labels. I suspect the start capacitor is bad, as i can manually spin the motor at startup and the motor will work. Want to replace the capacitor, but have no mfd/vac ratings to go by, except a '400' written in black marker.
If you are talking a run capacitor then you would need to look at the compressor rating plate or look up the compressor online to determine the size uF needed, thanks Bob!
I got big ones @ 50vdc 23200 it n I noticed they drain pretty fast after being charged, are that normal
You must remove the resistor to get the actual capacitance unless the resistor is bad.
can you have capacitors test ok but still be bad?
Mr Craig good afternoon ,thanks for your videos ,I have a quick question it is ok to installed a hard start capacitor on a 6 years old Goodman 2 tons ac that is working fine? Thanks again and stay safe
thank you for sharing!!!
4:13 is that necessary? Sure discharge it but do you have to 'nails on chalkboard' it? lol ~thx for posting
Yes absolutely, ha ha, thanks Bobby!
Does the MFD uF rating have to be the same? I have the old dual capacitor that says 30+5uf but the one in amazon says 35+5 mf. Would that be a problem when I change it?
That is the same, just make sure the voltage is the same or higher. For instance, if you have a 370v then you can use a 370v or 440v, thanks- Here is a genteq 30+5uf 440v capacitor- amzn.to/2rGDRcD -, here is a genteq 30+5uf 370v capacitor- amzn.to/2rVL0tU -- These are both round. The 440v would be a little bigger than an old 370 so it won't fit in the same bracket. Packard and Mars are good cap names as well. There are oval ones listed in amazon as well. Make sure that you replace the cap with the exact same ratings like what you are saying 30+5uf, thanks
What all do you like about the UEI Multimeter?
Reliability and price for me. Look up "acservicetech UEI multimeter" thanks
I also love that dual st4 temp meter for the same reasons, look up "acservicetech st4" thanks
AC Service Tech LLC Heck Yea!!!
I'm still learning and one month in to the trade what is the setting I need to put on the meter? Thanks
Cap, mfd, uF, it would say one of those, thanks Gilberto!
We are working on a home generator with 2 31,5 capacitors that we think one may be bad because the generator won't put out the correct power on one side of the 220. Do you think that this is the problen? Thanks
Honestly I really don't work on generators other than the combustion side, thanks
I mean is there a expiration on a capacitor?
For the most part, not really but if it is for a customer I would buy a new one. They are cheap enough. Thanks
I check my herm-fan capacitor every couple of months. It was 45 and 10 then it was 44.17 and 9.9 now its 43.79 and 9.8. Is that a good indicator its time to replace as its losing MFD over time?
If it's within plus or minus 6 percent of the microfarad
Will the bleeding resistor on the start capacitor affect the mfd result? My 521 start capacitor is rated for 186-227 mfd and it showed 256mfd all the time when I checked it. Thanks and I love all your videos.
Usually it will only affect the reading a little bit and will still be within the start cap mfd range but in a situation like that where the reading is outside the parameters, go ahead and unsolder or cut the bleed resister out to check it if you suspect it is the problem. You can always solder it back on if it is long enough, thanks
can I check the continuity to check a capacitor ?
Just capacitance in mfd, thanks
How do you know from the reading if it's still good or not?
If your reading is within + or minus 5% of what the uf/mfd says on the cap
@@acservicetechchannel Your only testing the uF value. They need to be tested under Working Voltage for leakage. Electronic leakage.. not physical leakage.
Hi should i use a brand new capacitor that expired?
I just replied to the other post, thanks!
Do you ever replace caps when they get very old, even if they still measure ok, or only if they fail? I measured mine, which are about 25 years old and they are between 5% to 10% out of there rated value.
The older caps seem to last much longer due to the type of dielectric fluid. Like everything else, they can't use that anymore and go for the cheaper non toxic fluid. That is fine. I do replace them when they are under the rated value if they are old, thanks
I didn't know why but I did think that the old ones would probably outlast the new ones. I will replace them and save them for a backup in case the new ones fail.Thanks for the reply.
Got ya, thanks kwd57
hi. my 2 hp single phase motor start capacitor is burnt out. unfortunately capacitor has no marking on it. how i will find out the rating of this cap ??
I would look up the motor model# specs online if the cap size is not stated on the motor rating plate.
CATALOG NUMBER: L3605T Baldor motor.
2HP, 230V, 11.5 AMP, 1725RPM. Starting capacitor rating required
hard to see the meter setting in the video. be nice for us folks watching if we could actually see the setting on that yellow meter.
it is capacitance reading mfd which is the same as uF, thanks!
@@acservicetechchannel cool... I do appreciate your efforts very much. I'm having a hard time testing as I don't have a setting just for caps... been using the ohm setting. I see there is a separate tester just for caps. I hate to buy another meter but will if it's going to help me text a/c units quickly. Thanks!
Hi, i still not sure about the ac capacitor. Which is compressor (2) terminal. Which is common or fan or herv? I been stress about this. And the measurements i apply didn't show up. Kept showing 0.f or 0
On a dual capacitor, say 45+5uf, C to Fan is the 5mfd and C to Herm is the 45mfd. The common usually has the most male tabs sticking up, Herm usually has three tabs, and Fan usually has one or two tabs. Make sure to short between c to fan and c to herm first with a non painted screwdriver(bare metal) and hold the probes on there for up to two minutes if needed. Sometimes you need to scratch through the rust to get a good reading, thanks!
acservicetech
Sorry! I dont mean duel capacitor. My aircon capacitor didnt apply with duel. The terminal only have 2. Duel have 3 terminal. I dont know which is - or + terminal.
That is much easier then. It doesn't matter which side you connect in to supply and which side you discharge out of it. That is why it is not labeled as such.
acservicetech
I use digital or analog multimeter can't measure the mfd! Kept showing either 1. / 0.F / negative no.
Can teach me how to use it?
Hey Uchiha, did you check out these capacitor testing videos? -- th-cam.com/video/ObTpixRWzyQ/w-d-xo.html -- th-cam.com/video/zZXR5WC4WSE/w-d-xo.html -- th-cam.com/video/Xh11jN8YbIw/w-d-xo.html -- th-cam.com/video/flbUtLMeSOQ/w-d-xo.html -- th-cam.com/video/XVF4cR-1ceU/w-d-xo.html
Olá amigo tenho uma bateria de 150ahm 12v e minha energia aqui da minha casa e de 127v qual seria o melhor capacitor pra mim usar e diodo de quantos pra mim usar
I am very sorry Oscar, I can't read it. No habla espanol
Hello my friend In have a battery of 150ah 12v and my energy aq in my house and 127v which would be the best capacitor to use me.diodo of how much to use
can u plz tell me the rating of fan capacitor? like 4Mfd or 2.5 mfd?
They really are all different. You need to look at the rating plate on the side of the fan motor and match with that, thanks
hi, thanks for the video, very helpful. quick quesiton. capacitor need + and - to charge, in this case, common from capacitor and
(start wire from compressor and FAN) both are in the same leg.. the common of compressor and fan is going to other leg of 240.. but for capacitor to charge we need both leg right. so how is capacitor charging.. to make it simple if i have capacitor which is NOT dual KEEP it single.. i wire start wire of herm in capacitor to start wire of compressor, common in the capacitor i will connect to T1, i will connect RUN of compressotr to T1 and common to T2. being said that capacitor doesnt have both the leg to charge.. can u please explain.. no one have done this befofre..
If you are saying that instead of using a dual capacitor, you are using two single capacitors then you would connect common from the contactor to either of the tab centers on the capacitor. then coming off of the other tab center on the capacitor you would connect to the fan. Same thing for the compressor. There is no - and + on a single capacitor used for hvacr. You have an input and output which is reversible in a single run capacitor with only two tab centers. I hope that this answers your question, thanks!
ok Great got it.. In electronics world you need + and - to charge capacitor, in Hvac world it is an input and output .. thank much. I was always wondering that Start and Run from compressor should be one leg and Common from compressor should be another leg of 240. meaning i cant have common from compressor going to common on Capacitor??.
also i like to donate is there a way?.
Actually we have a platform where individuals support the making of these videos and in return, I try to take extra time answering their questions whether here on youtube or through Patreon.com/acservicetech or email and also I am in the process of writing more articles and making videos to Post on Patreon. You would see these rewards on the right hand side in the support, community, and insider levels. Let me know if you have any questions. Either way, I do appreciate your thought and taking the time to let me that you appreciate the videos and time it takes to answer questions for our subscribers! Thanks a lot sivaraj palanisamy!
Hi, Just joinned. this is the first time i never used the patreon concept.. i would appreciate if you can answer this..
I was always wondering that Start and Run from compressor should be one leg and Common from compressor should be another leg of 240. meaning i cant have common from compressor going to common on Capacitor, is that right.?
Awesome, I appreciate it! So on a 240v single phase compressor, run from the compressor is connected to one leg coming off of the contactor. This is the same leg that is also connected to the common on the capacitor which goes through the capacitor and enters the compressor on the start. Common from the compressor is connected to the other leg of the contactor. I hope that makes sense, thanks!
Can you just show how to test already 🙄
I really enjoy the videos you do but you really need to stop the screeching sound of the screwdriver over the terminals. It makes my skin crawl ever time you do that. You could just touch them together. Just saying!
The issue I have seen is the contact of the metal on old capacitors is not great so the rubbing in whatever way you want to do it ensures good contact across the top with your metal screwdriver. Now you could also use a crimp connector jumper wire that would slide down the whole spade connector and that would work as well, thanks Kelly Roy!