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Can I use a larger HVAC Hard Start kit than is recommended?

Advice for replacement/repair of an HVAC with a cracked heat exchanger?Is a PTHP an HVAC option for a super or well insulated structure?How well does a single AC unit provide 2 zone cooling?Undersized AC - Options?Can I connect the R and C wires directly to the HVAC transformer?Studio HVAC SolutionAnyone installed a hot water coil in their HVAC ductwork to increase heat pump efficiency?How can I get my upper level to be as cool as the lower level?What kind of professional to call for help with structure-borne noise issues from HVACStart capacitor size

3

I've got a 2.5 ton HVAC system. I've been looking at adding one of the 5-2-1 Hard Start kits to reduce the wear on the system. I see that they have recommended sizes for 1-2-3 ton, 4 ton, and 5 ton systems.

Is there a reason I can't use the 4 ton kit on my 2.5 ton unit? Would it not just supply more support?

hvac

share|improve this question

edited 16 hours ago

Jeffery Thomas

asked 16 hours ago

Jeffery ThomasJeffery Thomas

1537

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The capacitor is creating a phase shift, the size of the cap needs to match up with the motor size to large of a cap can cause problems also.
  
  – Ed Beal
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I was curious, so I'm just going to leave this here. The 5-2-1 name comes from the standard numbering of the relay terminals on the relay this type of device uses. Similar to the terminal numbers on automotive relays (85-86-87-30).
  
  – JPhi1618
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Just curious, where did you even get the idea that this is something you should do?
  
  – R..
  12 hours ago
  

  
  
  
  

add a comment | 

3

I've got a 2.5 ton HVAC system. I've been looking at adding one of the 5-2-1 Hard Start kits to reduce the wear on the system. I see that they have recommended sizes for 1-2-3 ton, 4 ton, and 5 ton systems.

Is there a reason I can't use the 4 ton kit on my 2.5 ton unit? Would it not just supply more support?

hvac

share|improve this question

edited 16 hours ago

Jeffery Thomas

asked 16 hours ago

Jeffery ThomasJeffery Thomas

1537

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The capacitor is creating a phase shift, the size of the cap needs to match up with the motor size to large of a cap can cause problems also.
  
  – Ed Beal
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I was curious, so I'm just going to leave this here. The 5-2-1 name comes from the standard numbering of the relay terminals on the relay this type of device uses. Similar to the terminal numbers on automotive relays (85-86-87-30).
  
  – JPhi1618
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Just curious, where did you even get the idea that this is something you should do?
  
  – R..
  12 hours ago
  

  
  
  
  

add a comment | 

I've got a 2.5 ton HVAC system. I've been looking at adding one of the 5-2-1 Hard Start kits to reduce the wear on the system. I see that they have recommended sizes for 1-2-3 ton, 4 ton, and 5 ton systems.

Is there a reason I can't use the 4 ton kit on my 2.5 ton unit? Would it not just supply more support?

hvac

share|improve this question

edited 16 hours ago

Jeffery Thomas

asked 16 hours ago

Jeffery ThomasJeffery Thomas

1537

share|improve this question

edited 16 hours ago

Jeffery Thomas

asked 16 hours ago

Jeffery ThomasJeffery Thomas

1537

share|improve this question

edited 16 hours ago

Jeffery Thomas

asked 16 hours ago

Jeffery ThomasJeffery Thomas

1537

asked 16 hours ago

Jeffery ThomasJeffery Thomas

1537

asked 16 hours ago

Jeffery ThomasJeffery Thomas

1537

2 Answers
2

active

oldest

votes

7

Does your compressor start now? If it does, adding a hard start kit does absolutely nothing beneficial for you and in fact might be harmful. The original intent of a hard start kit was to compensate for voltage drop in the wiring by the time it gets out to a compressor, especially in areas where the utility supply may drop during high use days (i.e. all of your neighbors are home using their AC systems). But for the people who make them, that was not enough sales volume, so they "invented" a problem needing a solution. Their claim is that a compressor starts with high current and that this is damaging the compressor; which is an utter falsehood. The 5-2-1 sales literature starts out with a LIE! It states that "Amps x Volts = wattage" and that wattage is what you pay for. So per their concept, when the starting current goes to 600% (they say 700% witch is an exaggeration), the watts go up so high that the motor over heats. The lie is that watts = amps x volts x POWER FACTOR, and when a motor first starts, the power factor is extremely low. So for example if your 230V motor draws 10A when running, and the PF = 80%, the watts used is 230 x 10 x .8 or 1840W. On starting though, it is going to be 60A x 230V, but the PF is .2, so the watts are 2760, not 13,800 as they would claim.

What the "hard start" kit does is add another capacitor to the motor only for start-up, which compensates for the low power factor, then automatically switches it out of the circuit when the motor gets to 80% speed, usually less than 1 second. It ALSO increases the voltage, which increases the torque, which can be potentially DAMAGING to the compressor. They don't tell you that part!

Hard start kits have a legitimate purpose, but making your compressor last longer when it is not having trouble starting is bogus.

As to your question; yes, if you use a hard start kit intended for a larger motor, it can INCREASE that potential for excess torque damage.

share|improve this answer

answered 15 hours ago

J. RaefieldJ. Raefield

2,92328

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  They also say that a worn run capacitor can make the compressor use 10-20% more electricity vs a new capacitor. Seems like if that was true, installing a new run capacitor would be a regular maintenance task like changing an air filter (albeit less frequently...). Now I'm really curious if there's any truth to the "old capacitor" logic.
  
  – JPhi1618
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Just curious, how do you know so much about this? You seem to have a good understanding.
  
  – Jeffery Thomas
  13 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JPhi1618 Testing the run capacitor is recommended as part of regular service visits.
  
  – user71659
  10 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Do I understand it correctly that adding a capacitor just for the start actually increases the electricity bill, as it functions as a sort of power factor corrector? (in other words the capacitor gets charged up with a higher power factor than with which the motor would be starting up without the capacitor present?)
  
  – Pavel
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Pavel, the capacitor itself has a low power factor as well, only the combination of motor and capacitor has a high power factor if they are well matched. From a cost point of view, this is a Tragedy of the Commons — if everyone kept their power factor low to pay less, the grid would be rather unstable, which is why commercial power contracts usually stipulate a minimum power factor.
  
  – Simon Richter
  3 hours ago
  

  
  
  
  

add a comment | 

3

The starting capacitor is the largest difference in the various 5-2-1 devices. You don't want too large of a starting capacitor. You need to use the correct one for your application.

FYI: Multiply the load amps by 2,650. Divide this number by the supply voltage. The resulting number is the capacity of the capacitor you need in microfarads (µF).

share|improve this answer

edited 15 hours ago

isherwood

48.3k456122

answered 15 hours ago

Jerry_ContraryJerry_Contrary

2,055315

add a comment | 

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7

Does your compressor start now? If it does, adding a hard start kit does absolutely nothing beneficial for you and in fact might be harmful. The original intent of a hard start kit was to compensate for voltage drop in the wiring by the time it gets out to a compressor, especially in areas where the utility supply may drop during high use days (i.e. all of your neighbors are home using their AC systems). But for the people who make them, that was not enough sales volume, so they "invented" a problem needing a solution. Their claim is that a compressor starts with high current and that this is damaging the compressor; which is an utter falsehood. The 5-2-1 sales literature starts out with a LIE! It states that "Amps x Volts = wattage" and that wattage is what you pay for. So per their concept, when the starting current goes to 600% (they say 700% witch is an exaggeration), the watts go up so high that the motor over heats. The lie is that watts = amps x volts x POWER FACTOR, and when a motor first starts, the power factor is extremely low. So for example if your 230V motor draws 10A when running, and the PF = 80%, the watts used is 230 x 10 x .8 or 1840W. On starting though, it is going to be 60A x 230V, but the PF is .2, so the watts are 2760, not 13,800 as they would claim.

What the "hard start" kit does is add another capacitor to the motor only for start-up, which compensates for the low power factor, then automatically switches it out of the circuit when the motor gets to 80% speed, usually less than 1 second. It ALSO increases the voltage, which increases the torque, which can be potentially DAMAGING to the compressor. They don't tell you that part!

Hard start kits have a legitimate purpose, but making your compressor last longer when it is not having trouble starting is bogus.

As to your question; yes, if you use a hard start kit intended for a larger motor, it can INCREASE that potential for excess torque damage.

share|improve this answer

answered 15 hours ago

J. RaefieldJ. Raefield

2,92328

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  They also say that a worn run capacitor can make the compressor use 10-20% more electricity vs a new capacitor. Seems like if that was true, installing a new run capacitor would be a regular maintenance task like changing an air filter (albeit less frequently...). Now I'm really curious if there's any truth to the "old capacitor" logic.
  
  – JPhi1618
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Just curious, how do you know so much about this? You seem to have a good understanding.
  
  – Jeffery Thomas
  13 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JPhi1618 Testing the run capacitor is recommended as part of regular service visits.
  
  – user71659
  10 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Do I understand it correctly that adding a capacitor just for the start actually increases the electricity bill, as it functions as a sort of power factor corrector? (in other words the capacitor gets charged up with a higher power factor than with which the motor would be starting up without the capacitor present?)
  
  – Pavel
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Pavel, the capacitor itself has a low power factor as well, only the combination of motor and capacitor has a high power factor if they are well matched. From a cost point of view, this is a Tragedy of the Commons — if everyone kept their power factor low to pay less, the grid would be rather unstable, which is why commercial power contracts usually stipulate a minimum power factor.
  
  – Simon Richter
  3 hours ago
  

  
  
  
  

add a comment | 

7

Does your compressor start now? If it does, adding a hard start kit does absolutely nothing beneficial for you and in fact might be harmful. The original intent of a hard start kit was to compensate for voltage drop in the wiring by the time it gets out to a compressor, especially in areas where the utility supply may drop during high use days (i.e. all of your neighbors are home using their AC systems). But for the people who make them, that was not enough sales volume, so they "invented" a problem needing a solution. Their claim is that a compressor starts with high current and that this is damaging the compressor; which is an utter falsehood. The 5-2-1 sales literature starts out with a LIE! It states that "Amps x Volts = wattage" and that wattage is what you pay for. So per their concept, when the starting current goes to 600% (they say 700% witch is an exaggeration), the watts go up so high that the motor over heats. The lie is that watts = amps x volts x POWER FACTOR, and when a motor first starts, the power factor is extremely low. So for example if your 230V motor draws 10A when running, and the PF = 80%, the watts used is 230 x 10 x .8 or 1840W. On starting though, it is going to be 60A x 230V, but the PF is .2, so the watts are 2760, not 13,800 as they would claim.

What the "hard start" kit does is add another capacitor to the motor only for start-up, which compensates for the low power factor, then automatically switches it out of the circuit when the motor gets to 80% speed, usually less than 1 second. It ALSO increases the voltage, which increases the torque, which can be potentially DAMAGING to the compressor. They don't tell you that part!

Hard start kits have a legitimate purpose, but making your compressor last longer when it is not having trouble starting is bogus.

As to your question; yes, if you use a hard start kit intended for a larger motor, it can INCREASE that potential for excess torque damage.

share|improve this answer

answered 15 hours ago

J. RaefieldJ. Raefield

2,92328

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  They also say that a worn run capacitor can make the compressor use 10-20% more electricity vs a new capacitor. Seems like if that was true, installing a new run capacitor would be a regular maintenance task like changing an air filter (albeit less frequently...). Now I'm really curious if there's any truth to the "old capacitor" logic.
  
  – JPhi1618
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Just curious, how do you know so much about this? You seem to have a good understanding.
  
  – Jeffery Thomas
  13 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JPhi1618 Testing the run capacitor is recommended as part of regular service visits.
  
  – user71659
  10 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Do I understand it correctly that adding a capacitor just for the start actually increases the electricity bill, as it functions as a sort of power factor corrector? (in other words the capacitor gets charged up with a higher power factor than with which the motor would be starting up without the capacitor present?)
  
  – Pavel
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Pavel, the capacitor itself has a low power factor as well, only the combination of motor and capacitor has a high power factor if they are well matched. From a cost point of view, this is a Tragedy of the Commons — if everyone kept their power factor low to pay less, the grid would be rather unstable, which is why commercial power contracts usually stipulate a minimum power factor.
  
  – Simon Richter
  3 hours ago
  

  
  
  
  

add a comment | 

Does your compressor start now? If it does, adding a hard start kit does absolutely nothing beneficial for you and in fact might be harmful. The original intent of a hard start kit was to compensate for voltage drop in the wiring by the time it gets out to a compressor, especially in areas where the utility supply may drop during high use days (i.e. all of your neighbors are home using their AC systems). But for the people who make them, that was not enough sales volume, so they "invented" a problem needing a solution. Their claim is that a compressor starts with high current and that this is damaging the compressor; which is an utter falsehood. The 5-2-1 sales literature starts out with a LIE! It states that "Amps x Volts = wattage" and that wattage is what you pay for. So per their concept, when the starting current goes to 600% (they say 700% witch is an exaggeration), the watts go up so high that the motor over heats. The lie is that watts = amps x volts x POWER FACTOR, and when a motor first starts, the power factor is extremely low. So for example if your 230V motor draws 10A when running, and the PF = 80%, the watts used is 230 x 10 x .8 or 1840W. On starting though, it is going to be 60A x 230V, but the PF is .2, so the watts are 2760, not 13,800 as they would claim.

What the "hard start" kit does is add another capacitor to the motor only for start-up, which compensates for the low power factor, then automatically switches it out of the circuit when the motor gets to 80% speed, usually less than 1 second. It ALSO increases the voltage, which increases the torque, which can be potentially DAMAGING to the compressor. They don't tell you that part!

Hard start kits have a legitimate purpose, but making your compressor last longer when it is not having trouble starting is bogus.

As to your question; yes, if you use a hard start kit intended for a larger motor, it can INCREASE that potential for excess torque damage.

share|improve this answer

answered 15 hours ago

J. RaefieldJ. Raefield

2,92328

share|improve this answer

answered 15 hours ago

J. RaefieldJ. Raefield

2,92328

answered 15 hours ago

J. RaefieldJ. Raefield

2,92328

answered 15 hours ago

J. RaefieldJ. Raefield

2,92328

3

The starting capacitor is the largest difference in the various 5-2-1 devices. You don't want too large of a starting capacitor. You need to use the correct one for your application.

FYI: Multiply the load amps by 2,650. Divide this number by the supply voltage. The resulting number is the capacity of the capacitor you need in microfarads (µF).

share|improve this answer

edited 15 hours ago

isherwood

48.3k456122

answered 15 hours ago

Jerry_ContraryJerry_Contrary

2,055315

add a comment | 

3

The starting capacitor is the largest difference in the various 5-2-1 devices. You don't want too large of a starting capacitor. You need to use the correct one for your application.

FYI: Multiply the load amps by 2,650. Divide this number by the supply voltage. The resulting number is the capacity of the capacitor you need in microfarads (µF).

share|improve this answer

edited 15 hours ago

isherwood

48.3k456122

answered 15 hours ago

Jerry_ContraryJerry_Contrary

2,055315

add a comment | 

The starting capacitor is the largest difference in the various 5-2-1 devices. You don't want too large of a starting capacitor. You need to use the correct one for your application.

FYI: Multiply the load amps by 2,650. Divide this number by the supply voltage. The resulting number is the capacity of the capacitor you need in microfarads (µF).

share|improve this answer

edited 15 hours ago

isherwood

48.3k456122

answered 15 hours ago

Jerry_ContraryJerry_Contrary

2,055315

share|improve this answer

edited 15 hours ago

isherwood

48.3k456122

answered 15 hours ago

Jerry_ContraryJerry_Contrary

2,055315

edited 15 hours ago

isherwood

48.3k456122

edited 15 hours ago

isherwood

48.3k456122

answered 15 hours ago

Jerry_ContraryJerry_Contrary

2,055315

answered 15 hours ago

Jerry_ContraryJerry_Contrary

2,055315