Carrier 69NT40 - Current Limiting Transformer

[djbe]

Hi,

Can anyone tell me what is the purpose of the current limiting transformer on a 69NT40.

The unit is about 20 yrs. old, my manual makes reference to it as an option but does not say what it does.

One of the phase wires for the compressor goes through the transformer, but the transformer has burnt out causing the compressor to trip.

I've linked it out of the circuit and everything runs OK. Just want to know if it is essential.

Cheers,
djbe.

[Will]

The controller uses it to read current/amperage.

[mafoi]

The reading of the current sensor (the transformer) is used to operate the unit within current limit. For example, if the reading is too high, the unit may shut down to protect the compressor. If you run a PreTrip on this unit, you may find some error though you can run the unit anyway.

[djbe]

Thanks for the answers.

So will it cause any problems to unit operation if I don't replace, or am I just losing some inbuilt protection from early compressor failure if the loading on it gets too great?

[Toosh]

Hi,

Can anyone tell me what is the purpose of the current limiting transformer on a 69NT40.

The unit is about 20 yrs. old, my manual makes reference to it as an option but does not say what it does.

One of the phase wires for the compressor goes through the transformer, but the transformer has burnt out causing the compressor to trip.

I've linked it out of the circuit and everything runs OK. Just want to know if it is essential.

Cheers,
djbe.

Hi djbe The current transformer controls high amperage during high loads it keeps the current in range till this load comes down replace it as soon as possible.

regards Norm :)

[djbe]

Hi djbe The current transformer controls high amperage during high loads it keeps the current in range till this load comes down replace it as soon as possible.

regards Norm :)

Good enough for me, i'll order a new one tommorow.

Thanks.

[Sophoslim]

Hi djbe. Norm is correct. Also in summer with high ambient temperature the discharge pressure may go very high if your condenser coil is not new so you can set your current limit to a lower value in order to force unit to make a restriction to the low side as a result to drop the pressure to the high side.

[djbe]

So would I be correct in assuming it regulates load on the compressor using the suction modulation valve?

[bruisermac]

all it does is tell the micro or solid state controller the compressor amp draw. the logic in the micro will control the other valves in the system thus controlling the head pressure (or other issue) accordingly.

[Toosh]

So would I be correct in assuming it regulates load on the compressor using the suction modulation valve?

Yes it senses current and in turn sends it to the current limiter I explained it wrong at beginning but its very important to change it. The current limiter controls the gas intake to the compressor during high loads or other problems that could cause high amperage
Norm

[djbe]

Will replace it as soon as I get the new one.

Once again thanks for all of the answers.