First: Wow - what a great resource this site is. I'm impressed.
I'm in need of replacing the run capacitor in my air conditioning unit once again - it's a recurring event that's been going on for a few years now, each spring.
I'm not sure how much background info is required so I'll keep it to a minimum and hopefully not bore anyone with irrelevant details.
Re my skill level: I've only just rekindled my passion for electronics this year and never really received any formal training in it other than an introduction in high school. I have monkeyed with it some over the years getting more into it with Xbox console modding and then this year discovered the wonderous world of microcontrollers.
In the past I have not used a bleed resistor on the replacement but I recall that the original capacitor had one soldered in place (although I had no idea why it was there at the time). But I'm now thinking that this is the reason that I have been having to replace them so often since (we have cold dry winters here and I'm thinking that the cap is discharging itself catastrophically at some point (see attached pictures).
It's a dual cap with 35uF and 5uF values. It's rated at 370 volts but the unit runs on 220 (operating min:197, max:253).
I've used the capacitor discharge calculator at http://www.welwyn-tt.com/products/resistors/calculation-tools.asp to try to determine an appropriate bleed resistor but I was hoping to get confirmation from some pros who understand the formulas involved and the assumptions that I'm (obviously) ignorant of.
I used the following values: 35 uF capacitance, 370 volts inital charge (or should I use 240-260?), 24 volts safety threshold (should this be lower?) and a 60 second discharge time. This indicates a resistance of 626K Ohms and less than a 1/4 watt. Replacing the resistance value with a standard 560K Ohm value drops the discharge time to 53.6 seconds and the power rating is still (just) under 1/4 watt.
So, is this a sane bleed resistor value (560K Ohm, 1/4 watt) for this scenario? What questions am I not asking that I should be?
Thanks for your time and consideration.
... Al
EDIT: In the picture, it's the common post that's blown out. The Fan post is the upper right and the Herm post is the upper left.
I'm in need of replacing the run capacitor in my air conditioning unit once again - it's a recurring event that's been going on for a few years now, each spring.
I'm not sure how much background info is required so I'll keep it to a minimum and hopefully not bore anyone with irrelevant details.
Re my skill level: I've only just rekindled my passion for electronics this year and never really received any formal training in it other than an introduction in high school. I have monkeyed with it some over the years getting more into it with Xbox console modding and then this year discovered the wonderous world of microcontrollers.
In the past I have not used a bleed resistor on the replacement but I recall that the original capacitor had one soldered in place (although I had no idea why it was there at the time). But I'm now thinking that this is the reason that I have been having to replace them so often since (we have cold dry winters here and I'm thinking that the cap is discharging itself catastrophically at some point (see attached pictures).
It's a dual cap with 35uF and 5uF values. It's rated at 370 volts but the unit runs on 220 (operating min:197, max:253).
I've used the capacitor discharge calculator at http://www.welwyn-tt.com/products/resistors/calculation-tools.asp to try to determine an appropriate bleed resistor but I was hoping to get confirmation from some pros who understand the formulas involved and the assumptions that I'm (obviously) ignorant of.
I used the following values: 35 uF capacitance, 370 volts inital charge (or should I use 240-260?), 24 volts safety threshold (should this be lower?) and a 60 second discharge time. This indicates a resistance of 626K Ohms and less than a 1/4 watt. Replacing the resistance value with a standard 560K Ohm value drops the discharge time to 53.6 seconds and the power rating is still (just) under 1/4 watt.
So, is this a sane bleed resistor value (560K Ohm, 1/4 watt) for this scenario? What questions am I not asking that I should be?
Thanks for your time and consideration.
... Al
EDIT: In the picture, it's the common post that's blown out. The Fan post is the upper right and the Herm post is the upper left.
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