Go Back  DoItYourself.com Community Forums > Electrical, AC & DC. Electronic Equipment and Computers > Electrical - AC & DC
Reload this Page >

A/C start up current double the service amps. Is light dimming unavoidable?

A/C start up current double the service amps. Is light dimming unavoidable?

Reply

  #1  
Old 04-14-15, 10:52 AM
Member
Thread Starter
Join Date: Oct 2014
Posts: 643
Received 0 Votes on 0 Posts
A/C start up current double the service amps. Is light dimming unavoidable?

Note:I'm in Argentina power is 220/380 50hz

Lights dim every single time the A/C motor starts. Can this be helped by anything on this side of the meter?

I find the dimming to be quite annoying so if this can be fixed by changing something in the house I'd be very interested in doing it. The annoyance of the dimming lights however is substantially less than the satisfaction I get from paying $1/month + $.02/kwh. That happy price is predicated on the 15 minute average draw never exceeding 10kw. Maybe to ensure compliance the meter is wired with 6mm2 conductors and protected by a 32a (380v) breaker on the service side

Would a hard start kit or soft start system or something of the sort make this better?

When the AC starts up it makes a noise that sounds a bit like a car that was shifted without a clutch, I was worried that this was bad but the technician assured me this was normal.



The A/C is a Lennox HS29 - 060 - 9M

The label has the following electric info:

[table="width: 500"]
[tr]
[td]Electric Rating[/td]
[td]Nominal: 380/420 volts[/td]
[/tr]
[tr]
[td]3 ph | 50 hz[/td]
[td]Min: 342 | Max: 462[/td]
[/tr]
[tr]
[td]Compresor(s): (1)[/td]
[td]* Fan Motor(s): (1)[/td]
[/tr]
[tr]
[td]PH 3[/td]
[td]PH 1[/td]
[/tr]
[tr]
[td]RLA 9.0[/td]
[td]FLA .9[/td]
[/tr]
[tr]
[td]LRA 64[/td]
[td]Kw .249[/td]
[/tr]
[tr]
[td]Min. Circuit[/td]
[td]Max Fuse or[/td]
[/tr]
[tr]
[td]Amps 12.2[/td]
[td]Circ. Brkr 20[/td]
[/tr]
[tr]
[td] *Fan motor tension: 460v[/td]
[/tr]
[/table]


It's connected with 4x 4mm2 pvc insulated wires, (which local code rates at 25 amps) which are spliced at the air handler probably about 25ft away and then ran 28 ft to this breaker 25a and GFCI breaker which is connected to the 6mm wires from the service entrance (~65ft).

Would switching to 6mm2 help or even larger? The run to the panel appears to be vertical with no bends so changing those cables would not be a unsurmountable task.

Or is the solution in the lighting circuits? Is it easier to beef those up.
 

Last edited by Esand1; 04-14-15 at 01:17 PM.
Sponsored Links
  #2  
Old 04-14-15, 11:11 AM
Member
Join Date: Oct 2005
Location: USA
Posts: 1,432
Received 13 Votes on 13 Posts
I'd be thinking about going to LED lamps. Don't know of a great way to reduce compressor starting current, which in your case is 64 Amps.
Now, you have to pick the LED's with care. Dimmable LEDs may not solve your issue. You want some powered by a regulated circuit.
 
  #3  
Old 04-14-15, 12:13 PM
Member
Thread Starter
Join Date: Oct 2014
Posts: 643
Received 0 Votes on 0 Posts
Led lights will solve this problem. Regular screw in light bulbs replacements with built-in transformers?
 
  #4  
Old 04-14-15, 12:55 PM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,944
Received 42 Votes on 40 Posts
A hard start kit will reduce the effect, but probably will not eliminate it. The only good solution is larger wires all the way to the pole, and sometimes an upgrade of the power company transformer -- typically not a viable option. It also may help to put a delay relay on the air handler blower to make sure the compressor and the blower start at least 10 sec apart. The hard start kit may or may not include it, but you could also install a delay relay inside the compressor unit to stagger the start up of the compressor itself and the compressor cooling fan by at least 10 sec also.
 
  #5  
Old 04-14-15, 01:14 PM
Member
Thread Starter
Join Date: Oct 2014
Posts: 643
Received 0 Votes on 0 Posts
Ok what about a capacitor? If the problem is starting current, couldn't I have an electritan add a starting capacitor (or three) to the starter relay. Like this Mobile Site Preview
 
  #6  
Old 04-14-15, 01:58 PM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,944
Received 42 Votes on 40 Posts
Yep, the primary (maybe only) component in the hard start kit will be a bigger start capacitor. The time delays to stagger each motor may also help.
 
  #7  
Old 04-14-15, 03:55 PM
Member
Join Date: Nov 2011
Location: USA
Posts: 699
Received 2 Votes on 2 Posts
Components too far out of sequence can be harmful to the whole system.My guess is even 5 seconds can do harm long term,say compressor first then condenser fan.
 
  #8  
Old 04-14-15, 06:51 PM
Member
Join Date: Mar 2010
Location: USA
Posts: 3,676
Received 30 Votes on 29 Posts
Can you explain why starting the compressor unit fan and then the evaporator unit fan on perhaps successive 10 second delays might cause problems?

Getting the air moving quickly also prevent having the coils get too hot or too cold. But the coils are not going to get that hot/cold that fast.
 
  #9  
Old 04-14-15, 06:56 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,166
Received 475 Votes on 445 Posts
You've got a three phase system there. Starting capacitors or hard start kits are not used on a three phase compressor.

The only way to reduce dimming is larger wiring.... especially on the service end.
 
  #10  
Old 04-14-15, 07:07 PM
Member
Join Date: Nov 2011
Location: USA
Posts: 699
Received 2 Votes on 2 Posts
@AllenJ,pressures,especially the example I stated can rise very quickly.As for the evap. motor,compressor needs to cool fast too.
 
  #11  
Old 04-14-15, 07:11 PM
Member
Thread Starter
Join Date: Oct 2014
Posts: 643
Received 0 Votes on 0 Posts
If I want to measure voltage drop to get an idea how much this flickering light represents in real numbers. would be where should I do it. At the breaker or at the contact on the outside unit?

As for setting a delay, I'll have to open up my air handler tomorrow but I think it may actually have an option for something like that already on the panel. Or maybe that was something else.

@guyold. While I can see your point about the condenser fan, it seems hard to imagine the evaporator freezing up in that short of a time.

On a side note it just happened again while I was typing this edit, it's pretty annoying.
 
  #12  
Old 04-14-15, 09:07 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,166
Received 475 Votes on 445 Posts
The closer you measure it towards the compressor..... the larger the drop will be.
 
  #13  
Old 04-14-15, 09:42 PM
Member
Join Date: Nov 2011
Location: USA
Posts: 699
Received 2 Votes on 2 Posts
Esand1,the windings in the compressor is what needs to be cooled.That's the suction pipe coming from the evap. coil.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: