Question about refrigerative A/C causing lights to dim momentarily

[rowan194]

I recently purchased a refrigerative A/C unit and notice the lights
dim for a moment each time the compressor kicks in.

I presume this is normal due to a huge startup current requirement.

A thought springs to mind: how is it that this device is affecting
other items hanging off the same switchboard/power source yet my
neighbour's A/C units do not seem to interfere? The only time I've
noticed any flickering previously was a more serious dip, and nothing
consistent like a thermostat cycling on and off.

Just curious.

 

[Alan Rutlidge]

I recently purchased a refrigerative A/C unit and notice the lights
dim for a moment each time the compressor kicks in.

I presume this is normal due to a huge startup current requirement.
Yes.


A thought springs to mind: how is it that this device is affecting
other items hanging off the same switchboard/power source yet my
neighbour's A/C units do not seem to interfere?

Your neighbour is on their own circuit or possibly even a different phase.
Normally shouldn't cause problems with their supply.

The only time I've
noticed any flickering previously was a more serious dip, and nothing
consistent like a thermostat cycling on and off.

Just curious.

Nothing much to worry about, but call the sparkie who installed it if you
have issues with this affecting other appliances in your own home.

Cheers,
Alan

 

[John Tserkezis]

I recently purchased a refrigerative A/C unit and notice the lights
dim for a moment each time the compressor kicks in.

I presume this is normal due to a huge startup current requirement.
Yep.

A thought springs to mind: how is it that this device is affecting
other items hanging off the same switchboard/power source yet my
neighbour's A/C units do not seem to interfere? The only time I've
noticed any flickering previously was a more serious dip, and nothing
consistent like a thermostat cycling on and off.

Just curious.

Resistance of power cables. If all cables were chunky thick, then you
wouldn't notice minor drops like that.
But here in real life, we use only "enough" copper to do the job. Little
drops like that are not deemed consequential enough to change anything.

You don't notice your neighbour, because his fridge is not sucking enough to
make a difference at the street level, where the cabling is much thicker to
cater for a naturally higher load.
And even if your neighbour is sucking enough power from the grid in short
bursts for you to notice, it would depend if you're on the same phase they're
on, if not it would be much harder to notice, because the heavy load would
have to go back to the local transformer and induce enough of a difference to
be indicated onto the other phases.

But basically, that's not going to happen.

 

[Trevor Wilson]

I recently purchased a refrigerative A/C unit and notice the lights
dim for a moment each time the compressor kicks in.

I presume this is normal due to a huge startup current requirement.

**Dump it and buy an inverter type. Problem solved.

Trevor Wilson

 

[rowan194]

**Dump it and buy an inverter type. Problem solved.

No worries, I'll just throw away several hundreds of dollars worth of
equipment so my lights don't flicker slightly every few minutes when
it's a warm day.

 

[Russ]

No worries, I'll just throw away several hundreds of dollars worth of
equipment so my lights don't flicker slightly every few minutes when
it's a warm day.

It's also worth noting that on days when the aircon is running flat-out,
it's actually more efficient than the same size inverter would be.

 

[Trevor Wilson]

No worries, I'll just throw away several hundreds of dollars worth of
equipment so my lights don't flicker slightly every few minutes when
it's a warm day.

**Not quite. You'll be throwing away an old, inefficient air con and
replacing it with a far more efficient one (expect around 50% better
efficiency). In the long run, the inverter model will pay for itself in
saved electricity charges. The benefits don't stop there. Inverter models
are far more compatible with motor/gen or Solar/battery arrays, due to their
soft starting systems.

Trevor Wilson

 

[Phil in Melbourne]

**Not quite. You'll be throwing away an old, inefficient air con and

replacing it with a far more efficient one (expect around 50% better
efficiency).

That's quite a claim. Any stats to back that up?

 

[Trevor Wilson]

That's quite a claim. Any stats to back that up?

**Yup. Check out the specs on quality inverter models, using the latest gas,
with non-inverter. I selected two, similar models from the same
manufacturer. They use the same gas (R-410A) and are both spilt system
models.

The Panasonic CS-E9GKR (Inverter) has a COP of 4.33
The Panasonic CS-WDKR (Non-inverter) has a COP of 3.19

Obviously not a 50% difference, but a measurable one. That does not tell the
whole story, however. Cheap, window (Chinese manufactured) air cons, often
don't use R-410A and often over-state their real efficiency. As a person who
has owned a number of air conditioners, I will never go back to a
non-inverter type. A quality inverter model is quieter, more efficient, has
soft starting and is generally much nicer to live with.

Trevor Wilson