Upgrading home HVAC - do I need a bigger main panel?

[musgofasta]

1975 home with 100 amp main panel and original 3 ton packaged rooftop HVAC system. HVAC currently is on a 50 amp breaker.

My system needs replaced before summer heat and will need a 5 ton for the square footage added.

My HVAC friend doing the install said a 5 ton unit needs a 60 amp breaker and wouldn't be supported from a 100 amp panel and would need to move up to 200 amps.

Why couldn't (or shouldn't) I swap the 50 amp breaker for a 60 and run bigger wire to the HVAC unit?

This adds $2k to my HVAC install - not the end of the world but blows the budget!

 

[going4speed]

If you have all gas appliances a 100 amp might be okay. 100 amp is really marginal in today's power hungry society. If all your appliances like water heater, dryer, stove and range are electric then a 200 amp service should be considered. It may even be code in your area.

 

[musgofasta]

Water heater gas
Dryer gas
Range gas
Stove electric

 

[Stuff]

A 60 amp breaker is fine in a 100 amp panel. The question is how much power does the unit draw? Check the "Minimum Circuit Ampacity" spec. Probably around 30 amps with your unit. Most likely you will be fine but you should get a load calc done to be sure. Might even be required as part of your addition.

 

[zmaxmotorsports]

A 60 amp breaker is fine in a 100 amp panel. The question is how much power does the unit draw? Check the "Minimum Circuit Ampacity" spec. Probably around 30 amps with your unit. Most likely you will be fine but you should get a load calc done to be sure. Might even be required as part of your addition.

The newewr equipment usually draws a lot less amperage than the older stuff.

 

[Pwrgeek]

One thing you may run into is problems starting the compressor. A 100A panel would imply a 100A wire run from the utility (though some just run the same wire for anything smaller than 200 so you'd need to check). If it is smaller you may get a voltage flicker issue every time the compressor kicks on. If so you can try a larger starting capacitor but you may end up with a 200A panel no matter what you do. If it were me I'd get a cheap clamp on meter and put it on the panel and see what you pull with everything but the AC you're likely to use at the same time (oven, stove, hair dryer, and well pump was my magic combination). Then add the running amps for the new AC unit. If you get anything less than 80 you're good otherwise I see a new panel in your future.


Sent from my iPhone using Tapatalk

 

[bazar01]

A 5-ton Rheem RQPM packaged heat pump only needs 50A circuit with a 10kW back up heat strip. If gas heat, it will be way less than 50A.
As Zmax said, newer units have a lot less amperage draw.

 

[musgofasta]

I'm in So Cal so it will be gas heat and electric cooling. I'm will run check the amp draw on my current unit but I think I will be ok without a new panel.

At least until the second garage gets built !

 

[musgofasta]

Thanks everyone!

 

[musgofasta]

Minimum circuit amps on the new unit is 41.8, now I just need to determine it for my current unit.

 

[theoldwizard1]

If you have all gas appliances a 100 amp might be okay. 100 amp is really marginal in today's power hungry society.

Water heater gas
Dryer gas
Range gas
Stove electric

Convince the wife that a gas stove is better !

Depending on the brand of panel, you might easily (inexpensively) be able to upgrade to 125A

 

[DC73]

1975 home with 100 amp main panel and original 3 ton packaged rooftop HVAC system. HVAC currently is on a 50 amp breaker.

My system needs replaced before summer heat and will need a 5 ton for the square footage added.

Be sure and advise the power company that you are upgrading from a 3 ton to a 5 ton unit. Power companies don't always install service wire that matches the customers main size. They understand the panel rating is a max that is not likely to be seen and so they diversify the wire size down. Especially given the age of your home, it's quite likely the power company only has service wire of around 75 amps or so.

Voltage drop can become an issue with the larger AC unit. You may notice your lights dim or go out each time the compressor starts. If the power company tells you the existing service wire is sufficient for the load, ask them if it is sufficient for the voltage drop incurred when the new AC compressor kicks on.

Good luck,

DC

 

[zmaxmotorsports]

Minimum circuit amps on the new unit is 41.8, now I just need to determine it for my current unit.

Id run it on your current 50a breaker with the existing 100a service for now to see what it does before upgrading to a new 200a service.

 

[75gmck25]

Moving from a 3 ton to a 5 ton is a big step unless you have really added a lot of extra conditioned space. Have you had an HVAC contractor do a manual J calculation to verify that you need a unit that big?

If you go too big on the AC capacity it may short cycle on and off and you will not get the level of de-humidification you want. Newer AC units are more effective and more efficient, so going bigger is not always the best choice.

Bruce

 

[Stuff]

Also question if the supply and return ducts were increased to handle the additional airflow.

 

[theoldwizard1]

Id run it on your current 50a breaker with the existing 100a service for now to see what it does before upgrading to a new 200a service.

CONCUR !

Big $$$ to go to 200A !

 

[BadgerBoilerMN]

If you move up to an air-to-air heat pump you may use half the breaker and a third the power. This is money well spent.

 

[csp]

Also question if the supply and return ducts were increased to handle the additional airflow.

x2!!!