4 ms·

Friday evening I came home from a concert and was greeted by a very warm upstairs. The A/C wasn't working. After a bit of diagnosis, I tracked it down to the bl

by js2 3y ago

Friday evening I came home from a concert and was greeted by a very warm upstairs. The A/C wasn't working. After a bit of diagnosis, I tracked it down to the blower motor starting but spinning very slowly. Internet research indicated the run capacitor[1] as a potential culprit. (For single phase induction motors, the run capacitor provides an out-of-phase voltage to the secondary winding to allow for a rotating magnetic field.) By this point, it's 1:25 AM. I ordered a new capacitor from Amazon[2] and had it delivered less than 12 hours later. Replaced the capacitor and the motor was back to full speed. Total cost: $12.17. (A new motor would have been several hundred dollars.) The original capacitor[3] lasted 20 years inside my air handler that's in my attic, so probably dealing with 100+°F temps for most summers. Not too bad. 1. https://en.wikipedia.org/wiki/Motor_capacitor#Run_capacitors https://en.wikipedia.org/wiki/Motor_capacitor#Run_capacitors 2. https://www.amazon.com/gp/product/B076RT8B61 https://www.amazon.com/gp/product/B076RT8B61 3. https://imgur.com/a/2SCBETE https://imgur.com/a/2SCBETE

T3OU-736 3y ago
One interesting thing to consider (I have, sadly for power efficiency[1], a single-stage compressor) is a soft-start setup. Especially if planning to power HVAC from a generator for disaster recovery and not wanting to get a hugely sized genset just for HVAC startup current draw (mine has an LRA rating of 73A@240vAC, which is... non-trivial). [1] One benefit, though, is compatibility with smart thermostats. Multi-stage/VFD setups tend to use proprietary signaling which makes using Ecobee or Nest a challenge.
rdtsc 3y ago
Had a similar thing happen. It was later in the day, really hot, on a weekend, with high humidity and a crying baby in the house. My regular A/C company was closed, so I called another one. The person quickly diagnosed the issue and said he could "fix it for $450. I just wanted it fixed so decided to let him do it. But he then started acting shady, so I told him I'd take a picture of the old part before he offered to "dispose of it safely". He didn't seem to quite like that. I figured out why: it turns out it was a $15 capacitor. Oh well, lesson learned. If he at least said, "look, it's $250 to come after hours", I wouldn't have minded that, maybe he had a crying baby at home too. But he made it sound like the part was expensive and I was "extremely lucky" he just happen to have this unique and special part in his truck. And then, to make it worse, he installed the capacitor without taking it out of the cardboard box it came with. That would have ensured the capacitor would overheat soon enough, so I, as sucker would be calling him again. Pretty sneaky. I opened the unit the next day and installed the part properly and filed a complaint with the Better Business Bureau.
- i_am_a_peasant 3y ago
  i tried filling complaints in germany against behavior like this only to get ominous calls back from the guy warning me to retract my comments. this was some shady guy who has been at my home so I caved because I didn't want any trouble. not my proudest moment. but it was the last time I would use taskrabbit for anything. the guy was also a lockpicker so I had a video camera installed at the entrance since then.
- c_o_n_v_e_x 3y ago
  >"But he made it sound like the part was expensive and I was "extremely lucky" he just happen to have this unique and special part in his truck" Not to take away from your experience, however there is some truth to what your tech was saying. A capacitor is cheap when a part supplier/warehouse is open. You can call a warehouse to open after hours but you pay for the luxury and it isn't cheap (was at least $100USD, that was 20 years ago). >"I was "extremely lucky" he just happen to have this unique and special part in his truck" Actually, you were lucky if he had a capacitor that was the same farad rating. Most techs don't have a huge inventory in their vehicles, some times you get "weird" sizes that you dont expect. "Universal start capacitors" are available which allow you to "configure" the cap to the rating you require, however they are very expensive (over $150USD per cap). I would use a universal start to get you back up and running and then come back with a cheaper part.
  - rdtsc 3y ago
    > A capacitor is cheap when a part supplier/warehouse is open. Well the warehouse was "open" so to speak. Capacitor failure is a fairly common failure and I bet he had quite a few of those in his truck. He didn't really have to go to the supplier to order one. > Most techs don't have a huge inventory in their vehicles, some times you get "weird" This wasn't a too weird one. It was either the 45/5 or the 35/5 uF one. Installing it in the cardboard box and not clamping it with a metal clamp to the unit to dissipate heat was a confirmation this guy was shady.

by js2 3y ago

T3OU-736 3y ago

One interesting thing to consider (I have, sadly for power efficiency[1], a single-stage compressor) is a soft-start setup. Especially if planning to power HVAC from a generator for disaster recovery and not wanting to get a hugely sized genset just for HVAC startup current draw (mine has an LRA rating of 73A@240vAC, which is... non-trivial). [1] One benefit, though, is compatibility with smart thermostats. Multi-stage/VFD setups tend to use proprietary signaling which makes using Ecobee or Nest a challenge.

rdtsc 3y ago

Had a similar thing happen. It was later in the day, really hot, on a weekend, with high humidity and a crying baby in the house. My regular A/C company was closed, so I called another one. The person quickly diagnosed the issue and said he could "fix it for $450. I just wanted it fixed so decided to let him do it. But he then started acting shady, so I told him I'd take a picture of the old part before he offered to "dispose of it safely". He didn't seem to quite like that. I figured out why: it turns out it was a $15 capacitor. Oh well, lesson learned. If he at least said, "look, it's $250 to come after hours", I wouldn't have minded that, maybe he had a crying baby at home too. But he made it sound like the part was expensive and I was "extremely lucky" he just happen to have this unique and special part in his truck. And then, to make it worse, he installed the capacitor without taking it out of the cardboard box it came with. That would have ensured the capacitor would overheat soon enough, so I, as sucker would be calling him again. Pretty sneaky. I opened the unit the next day and installed the part properly and filed a complaint with the Better Business Bureau.

i_am_a_peasant 3y ago
i tried filling complaints in germany against behavior like this only to get ominous calls back from the guy warning me to retract my comments. this was some shady guy who has been at my home so I caved because I didn't want any trouble. not my proudest moment. but it was the last time I would use taskrabbit for anything. the guy was also a lockpicker so I had a video camera installed at the entrance since then.
c_o_n_v_e_x 3y ago
>"But he made it sound like the part was expensive and I was "extremely lucky" he just happen to have this unique and special part in his truck" Not to take away from your experience, however there is some truth to what your tech was saying. A capacitor is cheap when a part supplier/warehouse is open. You can call a warehouse to open after hours but you pay for the luxury and it isn't cheap (was at least $100USD, that was 20 years ago). >"I was "extremely lucky" he just happen to have this unique and special part in his truck" Actually, you were lucky if he had a capacitor that was the same farad rating. Most techs don't have a huge inventory in their vehicles, some times you get "weird" sizes that you dont expect. "Universal start capacitors" are available which allow you to "configure" the cap to the rating you require, however they are very expensive (over $150USD per cap). I would use a universal start to get you back up and running and then come back with a cheaper part.
- rdtsc 3y ago
  > A capacitor is cheap when a part supplier/warehouse is open. Well the warehouse was "open" so to speak. Capacitor failure is a fairly common failure and I bet he had quite a few of those in his truck. He didn't really have to go to the supplier to order one. > Most techs don't have a huge inventory in their vehicles, some times you get "weird" This wasn't a too weird one. It was either the 45/5 or the 35/5 uF one. Installing it in the cardboard box and not clamping it with a metal clamp to the unit to dissipate heat was a confirmation this guy was shady.