HVAC Run Capacitor

[perry]

When I had my AC serviced in the spring, they told me my run capacitor was getting weak. It's a 7.5 MFD (he wrote 7.5 run cap on the service history sheet) and apparently measured at 4.8. It was just 3 years old at the time. They were wanting $40 for a new one, but I decided to pass at the time. "Replace it now for $40 or pay $125 service call when it goes out plus the $40," they said. I rolled the dice.

Do I just need to get an oval 7.5 MFD 370V capacitor? Something like this CAPACITOR 7.5 MFD 370 VAC OVAL ONETRIP PARTS® DIRECT REPLACEMENT FOR YORK COLEMAN EVCON LUXAIRE OEM PART S1-02420045700: Amazon.com: Industrial & Scientific or DAYTON Run Capacitor, 7.5 MFD, 370 VAC, Oval - Capacitors - 2MDV6|2MDV6 - Grainger Industrial Supply

My furnace is a Bryant Plus 80 model ck5axa030000aaaa. I watched some Youtube videos and it looks easy enough to replace, or the guys are coming back Thursday to clean the furnace and I can just trade out the capacitor when they have it out again.

 

[Rhoadmar]

I 've replaced caps on my ac units over the years. As long as the voltage rating matches or higher and the mfd is that or higher, plug it in.

 

[Mr Evilwrench]

The shape is irrelevant if it fits. If the voltage rating is original or higher, you're good there. The capacitance sets the phase shift between the coils in the motor, so you don't want to play with it too much, but there's typically -20/+100% tolerance on the value. You're pretty low, but it's not something you use up, so it may keep running like that for years. My first source used to be to find a blower or something I could junk one out of, but at the time I had to squeeze the nickel until I shoved the indian's nose up the buffalo's butt.

 

[remauto1187]

Remember the whole purpose of a capacitor is to store voltage(Oppose a change in voltage). So your run cap WILL have voltage stored in it even when power is disconnected at the breaker OR even when the capacitor is disconnected from the wiring that feeds it. Once power is disconnected at the breaker or main disconnect, lay a screwdriver across the terminals until you hear a pop sound and leave it there for 5 seconds or so. Now the cap will be discharged and wont knock the pee out of you. The new cap MAY have some charge in it from quality control testing from the factory also!

 

[LtScott14]

Those are under $10.00 at a HVAC supply house! Go to a flea market, see if you can find one for cheap. I have seen boxes of used ones for $1.00 ea, but you don't own a multimeter to check them. That would be worth $40.00!
Good luck.

 

[perry]

Yea I ordered the one from Amazon for $9 + $4 overnight shipping. If the guy won't put it in Thursday, then I should be able to do it myself. It's just two screws to get the panel out, and the cap is on the back of that. I saw the tip about the screwdriver on Youtube... I have a healthy respect for electricity so I'll be careful.

 

[danbb]

Remember the whole purpose of a capacitor is to store voltage(Oppose a change in voltage). So your run cap WILL have voltage stored in it even when power is disconnected at the breaker OR even when the capacitor is disconnected from the wiring that feeds it. Once power is disconnected at the breaker or main disconnect, lay a screwdriver across the terminals until you hear a pop sound and leave it there for 5 seconds or so. Now the cap will be discharged and wont knock the pee out of you. The new cap MAY have some charge in it from quality control testing from the factory also!

A run cap on a working motor should discharge through the motor windings when power is removed, only start caps should hold any energy, and then only if the bleed resistor is missing. Still not a bad practice, but usually unneeded

 

[churchmouse]

The shape is irrelevant if it fits. If the voltage rating is original or higher, you're good there. The capacitance sets the phase shift between the coils in the motor, so you don't want to play with it too much, but there's typically -20/+100% tolerance on the value. You're pretty low, but it's not something you use up, so it may keep running like that for years. My first source used to be to find a blower or something I could junk one out of, but at the time I had to squeeze the nickel until I shoved the indian's nose up the buffalo's butt.

Man I have been there.................

 

[churchmouse]

A run cap on a working motor should discharge through the motor windings when power is removed, only start caps should hold any energy, and then only if the bleed resistor is missing. Still not a bad practice, but usually unneeded

Never had one bite me and never drained one either.....start caps are another story.

 

[remauto1187]

A run cap on a working motor should discharge through the motor windings when power is removed, only start caps should hold any energy, and then only if the bleed resistor is missing. Still not a bad practice, but usually unneeded

You arent one of those guys that assumes just because the breaker or disconnect is put in the off position that electrically everything disconnected. If so, we will read about you in the paper. Why on earth would you tell a guy (among others that fall into the group of novice on this open forum) that is NOT familar with electricity that it is ok to basically not discharge the cap? "working motor SHOULD discharge through the motor windings when powere is removed". So what if the cap is NOT discharged, go ahead and get the pee knocked out of themselves because you had to get technical?
I wonder about people like you sometimes....then the thought passes and I chalk it up to dangerous to themselves and others around them. So you keep assuming and that one day you see your life flash before your eyes as the 120,240,208 or even 480 runs through your body to ground, remember, I told you so..right before your lights go out.

 

[perry]

The cap had dropped to 4.6, and right as he was about to encourage me to replace it I gave him the new one.

Then he told me the heat exchanger is "dimpled" and will probably crack in the next year or two. Doh. At least I can start saving up for a new furnace now instead of getting the bad news in the dead of winter.

 

[remauto1187]

The cap had dropped to 4.6, and right as he was about to encourage me to replace it I gave him the new one.

Then he told me the heat exchanger is "dimpled" and will probably crack in the next year or two. Doh. At least I can start saving up for a new furnace now instead of getting the bad news in the dead of winter.

How old is the unit? Is it even above 80% efficient? If not....REPLACE IT if possible. If the unit is 90% or higher check into just replacing the heat exchanger. A new 95% efficient natural gas fired unit will run you around $900+ depending on size required if you go with a Goodman. Thats what I am running. ANYONE can buy one, there are many dealers on ebay that sell them. If you arent well versed in gas pipe then just pay someone to install it.

 

[perry]

It was built in 1997 and is 80% efficient.

 

[scott delaney]

The cap had dropped to 4.6, and right as he was about to encourage me to replace it I gave him the new one.

Then he told me the heat exchanger is "dimpled" and will probably crack in the next year or two. Doh. At least I can start saving up for a new furnace now instead of getting the bad news in the dead of winter.

when your ready to replace it I can make you one heck of a deal!