Emerson ZB Copeland Scroll Service Manual download pdf (Page 8)

ZB Series

Application guide

Minimum operating time

The number of times a compressor can start and stop within a period of one hour depends on the system configuration to a great extent. By

nature, the scroll compressor starts unloaded; therefore the minimum operation time is not specified. The quantity of lubricating oil that

returns to the compressor at start is, however, a critical measurement. The simplest is by means of the sight glass (optional item), but the

longest piping permitted for the system should be connected at the time of this measurement.

The minimum operation time means the time necessary for the normal oil level in the sight glass to be restored from compressor start-up to

shut-down. If the compressor start-stop cycles are shorter than the minimum operation time, for example, to maintain exact temperature

control, the compressor will gradually lose the lubricating oil and may even be damaged. For more information on compressor start-stop cycle

and frequency, see the engineering application manual numbered 17-1262.

Accessories

Discharge temperature protection

If the system design does not ensure compressor operation within the range specified or if the system layout is not reasonable, very high

discharge temperature could be caused, thereby leading to carburization of the lubricating oil, irregular compressor operation or even

compressor failure. A Discharge Temperature Controll (DTC) valve should be installed in the system.

The DTC valves supplied by Emerson are as below. The control circuit will be cut off when the discharge temperature exceeds 126

Compressor Models DTC type Lead wire terminals Alarm interface Suitable pipe size

998-0540-00 NA NA

ZB15-ZB45 998-0548-00 NA Yes 1/2''

998-7022-02 Yes Yes

ZB50-ZB88

998-0540-03 Without lead wire NA

7/8''

998-7022-05 With lead wire NA

When the compressor is not equipped with a block valve, the DTC is installed at a distance of 178mm from the outlet. When the

compressor is equipped with a block valve, the DTC is installed at a distance of 127mm from the outlet. When installing the block valve,

the DTC should adhere to the surface of the discharge pipe, and should be fixed by means of the clamp supplied with the assembly.

Copeland DTC can be connected with 120V or 240V control circuit.

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Emerson ZB Copeland Scroll Service Manual Page 8