Hazardous Snake Oil for your A/C: - Alert!

[TLS Guy]

I had a nice tech come today, to check our AC for summer duty today. He checked the starting caps among other routine issues. Our AC unit does not have running caps, most AC units do. The starting caps were well within spec.

Before leaving I got the usual upselling pitch. This is not the techs fault, but either managers and or unscrupulous travelling salesmen.

The sales pitch was to purchase add on booster caps to improve the AC starting and prolong the life of the AC.

Not only is this unnecessary, but harmful. This is all similar to speaker technology. An electric motor is a large inductive load powered by AC voltage. Now when powering inductive loads, there are always phase angles between voltage and current. In other words they are not in perfect phase. This leads to the concept of apparent and true power. So when you start a motor there is a large power draw and the large apparent power is provided and given back as the motor speeds up

In a large AC motor like in an AC, there is a high starting current which will drop voltage and cause the motor to struggle to start. This also would shorten the life of the motor and also dims the house lights and is prone to blow the AC circuit fuse at the panel.

To bring phase and current into better phase alignment and reduce start up current starting capacitors are placed in parallel with the motor, to align current and voltage angles. This reduces the discrepancy between true and apparent power and stops the motor struggling to start.

However, that starting cap needs to be he right cap, tuned to the inductance of the motor coils. So the capacitance has to be optimal, no more OR less.

So this sales pitch is harmful snake oil. I gather this is doing the rounds at the moment, and there is good advice the same as mine. Don't fall for it.

The tech was a very nice guy and had lots of questions for me. I explained all this to him, and I'm sure he understood.

Now I'm waiting for a call back from one of the bosses.

The cost of this "upgrade" by the way, was nearly $500.00.

Lastly you should have you AC caps checked yearly, as these large caps will fail over time, and shorten the life of your AC unit. So this is important yearly maintenance for all AC units and other large electric motors.

 

[cpp]

If you have your bi annual checkups on your AC system and IF its working according to a trusted AC tech's requirements, leave it alone. I've been using the same AC company for 13 years. Never have they tried to sell me something I never needed. As far as owner maintenance which is for our home is routinely flushing the AC drain/drip line to the outside and of course replacing the AC filter..

 

[Mikado463]

agree with Chris ! One other thing, I routinely clean the outside condenser, pay special attention to keeping the coils 'free flowing' for air. A good shop vac works well for me.

 

[highfigh]

I had a nice tech come today, to check our AC for summer duty today. He checked the starting caps among other routine issues. Our AC unit does not have running caps, most AC units do. The starting caps were well within spec.

Before leaving I got the usual upselling pitch. This is not the techs fault, but either managers and or unscrupulous travelling salesmen.

The sales pitch was to purchase add on booster caps to improve the AC starting and prolong the life of the AC.

Not only is this unnecessary, but harmful. This is all similar to speaker technology. An electric motor is a large inductive load powered by AC voltage. Now when powering inductive loads, there are always phase angles between voltage and current. In other words they are not in perfect phase. This leads to the concept of apparent and true power. So when you start a motor there is a large power draw and the large apparent power is provided and given back as the motor speeds up

In a large AC motor like in an AC, there is a high starting current which will drop voltage and cause the motor to struggle to start. This also would shorten the life of the motor and also dims the house lights and is prone to blow the AC circuit fuse at the panel.

To bring phase and current into better phase alignment and reduce start up current starting capacitors are placed in parallel with the motor, to align current and voltage angles. This reduces the discrepancy between true and apparent power and stops the motor struggling to start.

However, that starting cap needs to be he right cap, tuned to the inductance of the motor coils. So the capacitance has to be optimal, no more OR less.

So this sales pitch is harmful snake oil. I gather this is doing the rounds at the moment, and there is good advice the same as mine. Don't fall for it.

The tech was a very nice guy and had lots of questions for me. I explained all this to him, and I'm sure he understood.

Now I'm waiting for a call back from one of the bosses.

The cost of this "upgrade" by the way, was nearly $500.00.

Lastly you should have you AC caps checked yearly, as these large caps will fail over time, and shorten the life of your AC unit. So this is important yearly maintenance for all AC units and other large electric motors.

They seem to be using the "If a little is good, a lot has to be great" philosophy.

A good question might be "So, if these additional caps are needed, how would you explain electric motors from the 1950s that still operate normally?". FWIW- I have some motors from the '50s and as far as I know, they have never needed replacement caps.

 

[TLS Guy]

They seem to be using the "If a little is good, a lot has to be great" philosophy.

A good question might be "So, if these additional caps are needed, how would you explain electric motors from the 1950s that still operate normally?". FWIW- I have some motors from the '50s and as far as I know, they have never needed replacement caps.

It all depends on what type of motor you are talking about. AC units have AV 240 volt fast start motors and have to come to full power almost instantly.

Caps in AC units frequently go bad. When we moved into our townhome which was our bolt hole in Eagan the caps were shot. We also had to replace the caps once in our AC unit in GF.

One of our daughters recently had the caps go bad in her AC and it would not start all all, the motor just buzzed.

You don't want to let them go bad, but have them tested, as failing caps can cause the compressor to fail. It is routing preventive maintenance.

 

[highfigh]

It all depends on what type of motor you are talking about. AC units have AV 240 volt fast start motors and have to come to full power almost instantly.

Caps in AC units frequently go bad. When we moved into our townhome which was our bolt hole in Eagan the caps were shot. We also had to replace the caps once in our AC unit in GF.

One of our daughters recently had the caps go bad in her AC and it would not start all all, the motor just buzzed.

You don't want to let them go bad, but have them tested, as failing caps can cause the compressor to fail. It is routing preventive maintenance.

Wouldn't it make more sense to use motors that don't need to start fast and have a clutch that engages after the motor is at speed? I have to imagine it could be enclosed to prevent moisture ingress and it should be easy enough to develop a circuit for this- they only need 12VDC for a car's AC clutch and they're not in a dry environment.