Heat pump power draw ramp up

[mike93lx]

Curious if this is normal. System is 1 year old and performing fine, no concerns, just curious. Not variable speed, just a basic 14seer system.

This is an example of a recent run from my emporia. First full minute averaged about 8.5a, ramping up to about 10.3a. Is that just from pressure increasing with run time? Something else?

 

[bluedog225]

Nice there is no start up surge.

 

[mike93lx]

Nice there is no start up surge.

That graph shows 1 minute averages, so I wouldn't expect to see that, but it also doesn't show on the 1 sec interval. I would just assume that the monitoring device cant measure it

 

[micromind]

A lot of compressors these days are the PSC (Permanent Split Capacitor) type. These are known for high efficiency, low starting current and very low starting torque.

This is quite likely why you have.

A typical A/C compressor will have lower amps at first and go up as the system stabilizes.

 

[dcg9381]

I'm not home, but here's mine.. Likely this draw is from the garage apartment. Note the green is energy production from solar, so you can see the start up swings on a 1.5T - 2T SEER unit.. (could be one of the larger units in the house, no remote control over thermostats)

 

[mike93lx]

Interesting, thanks.

 

[American Locomotive]

The work a compressor has to do is proportional to the mass flow rate of refrigerant and compression ratio (pressure difference between the hot side and cold side). As condenser temperatures increases and evaporator temperatures decrease, the compression ratio increases and the mechanical work the compressor will need to do increases.

 

[mike93lx]

The work a compressor has to do is proportional to the mass flow rate of refrigerant and compression ratio (pressure difference between the hot side and cold side). As condenser temperatures increases and evaporator temperatures decrease, the compression ratio increases and the mechanical work the compressor will need to do increases.

Makes sense, thanks

 

[wyliesdiesels]

Nice there is no start up surge.

Some meters cannot read in-rush current…

 

[u3b3rg33k]

Some meters cannot read in-rush current…

I'd say it slightly differently:
most meters don't read inrush, most that do have to be put in "inrush" mode.

definitely not gonna see it on a 1Hz (maximum) home energy monitor.

 

[TRWham]

The work a compressor has to do is proportional to the mass flow rate of refrigerant and compression ratio (pressure difference between the hot side and cold side). As condenser temperatures increases and evaporator temperatures decrease, the compression ratio increases and the mechanical work the compressor will need to do increases.

But mass flow decreases as evaporator pressure decreases, so the work done may be less depending on exactly how high the compression ratio is.

 

[American Locomotive]

But mass flow decreases as evaporator pressure decreases, so the work done may be less depending on exactly how high the compression ratio is.

Depends on the type of metering device. On a cap tube or fixed orifice system, condensing pressure has a big influence on mass flow rate.

 

[TRWham]

Depends on the type of metering device. On a cap tube or fixed orifice system, condensing pressure has a big influence on mass flow rate.

Mass flow is entirely dependent on suction gas density and compressor displacement. If a metering device flows more or less refrigerant, then suction pressure will balance accordingly to match mass flow.

 

[wyliesdiesels]

I'd say it slightly differently:
most meters don't read inrush, most that do have to be put in "inrush" mode.

definitely not gonna see it on a 1Hz (maximum) home energy monitor.

agreed. my fluke 381 has a button for in-rush current metering