[indiguy]

Hi,
Im writing from India.
I got 4 1.5 tonne carriers split acs installed.carrier 1.5 tonne durakool.
BTU per hours 18000.power consumption 1990 watts.eer 9.0.

I have a three phase circuit board installed with individual 32 amp mcbs for acs and one single 40 amp elcb on each phase.

Initially I had a 20amp mcb for acs.I have two acs running per phase.

The problem I am facing is that after the 3 acs run for quite a few hours I am having a problem of the mcb and elcb tripping in one phase despite equal distribution of power.
Sometime the main circuit breaker which is 40amps also trips after 3 acs running for quite some time at night.

The electrical company whish installed the wiring have checked my wires again and again.They replaced the ac mcbs from 20amps with 32amps but still the circuit breaker is tripping.
Now they are suggesting calling the ac guys to check the power consumed.The acs are new.Please advise as to where the fault could lie.

Also if I call the ac guys please tell me what all should they check so that I can tell the same.
This is urgent.

[tkrussell]

The electrician could be doing a recording of the power using a power recording meter, which can be connected for a period to measure the amp load per phase. Depending on the meter, it may print out a paper report or one viewable through software.

The breaker that is tripping should be inspected with an infrared camera to detect hot connections due to loose mechanical connections at the line or load of the tripping breaker. A loose connection at or near a breaker will create heat, and the heat will migrate into the breaker and affect the thermal device inside the breaker causing a nuisance trip.

If the main CB is 40 amps, what size is each branch circuit? The main needs to be able to handle the total load of all units running, and be sized high enough to be able to handle the locked rotor amps, or starting current, of one or more units.

[BTA]

Hi,
Im writing from India.
I got 4 1.5 tonne carriers split acs installed.carrier 1.5 tonne durakool.
btu per hours 18000.power consumption 1990 watts.eer 9.0.

I have a three phase circuit board installed with individual 32 amp mcbs for acs and one single 40 amp elcb on each phase.

Initially I had a 20amp mcb for acs.I have two acs running per phase.

The problem I am facing is that after the 3 acs run for quite a few hours I am having a problem of the mcb and elcb tripping in one phase despite equal distribution of power.
Sometime the main circuit breaker which is 40amps also trips after 3 acs running for quite some time at night.

The electrical company whish installed the wiring have checked my wires again and again.They replaced the ac mcbs from 20amps with 32amps but still the circuit breaker is tripping.
Now they are suggesting calling the ac guys to check the power consumed.The acs are new.Please advise as to where the fault could lie.

Also if I call the ac guys please tell me what all should they check so that I can tell the the same.
This is urgent.

If it's a single phase tripping, and the wires are fine, then issue could be a short on that phase in one (or more) of your units.

As a side-issue, since the main breaker is sometimes tripping, I would suggest double-checking your breaker coordination study... if the issue is in a branch circuit, you don't want your main breaker tripping all the time and shutting down other equipment unnecessarily.

Best luck.

[JackT]

Are your circuit breakers approved for HVAC, not all circuit breakers have this rating. You may also want to install hard start kits on your compressors and if you don't already have them I would also install time delay relays and set each one at least 30 seconds apart. This will avoid all of your ac units from coming on at the same time if your power goes off. As tkrussel mentioned, check your connections, I have know idea what kind of breaker box you have but sometimes your cheaper brands don't take the amperage they are designed for, also watch where the breaker connects to the buss bar, that also can be a trouble spot.

[shuntripper]

If the electrical company has checked their wires again and again does the that include the screw on a bolt in breaker? Have you tried a different known good breaker in it's place? Has each wire off the breaker been checked with an ohmeter?(may indicate where a bad connection lies) are all the wires for these circuits in the same pipe or if run in parallel all (two or three? Ambiguous question asked) legs in each pipe?(possible inductive heating ) What voltage are you working with? Do you have fused disconnects? Are these circuits untapped for other loads? There will be a plate on each unit stating max fuse size and minimum circuit ampacity, also FLA (full load amps). More info please.

[T-Top]

Hi,
Im writing from India.
I got 4 1.5 tonne carriers split acs installed.carrier 1.5 tonne durakool.
btu per hours 18000.power consumption 1990 watts.eer 9.0.

I have a three phase circuit board installed with individual 32 amp mcbs for acs and one single 40 amp elcb on each phase.

Initially I had a 20amp mcb for acs.I have two acs running per phase.

The problem I am facing is that after the 3 acs run for quite a few hours I am having a problem of the mcb and elcb tripping in one phase despite equal distribution of power.
Sometime the main circuit breaker which is 40amps also trips after 3 acs running for quite some time at night.

The electrical company whish installed the wiring have checked my wires again and again.They replaced the ac mcbs from 20amps with 32amps but still the circuit breaker is tripping.
Now they are suggesting calling the ac guys to check the power consumed.The acs are new.Please advise as to where the fault could lie.

Also if I call the ac guys please tell me what all should they check so that I can tell the the same.
This is urgent.

I may be reading your question wrong but if your running 3 single phase units off one three phase breaker. If two units start at the same time that gives your starting amps about 120 amps off a 40 amp breaker for a split second. Each unit needs its own power feed and breaker for this reason.

[tkrussell]

Lots of good suggestions, and good questions. Now all we need is some input from the poster.