AIR CONDITIONING & HEATING EQUIPMENT

Match-Ups for DT4QD Series Units FOR USE WITH M1 & M3 FURNACES

CAT. NO. MFG. NO. 3B301 3B302 3B303 3B304 3B305 3B306

DT4QD-024K DT4QD-030K DT4QD-036K DT4QD-042K DT4QD-048K DT4QD-060K*

COIL CAT. NO. COIL MFG. NO. COOLING CAPACITY HEATING CAPACITY S.E.E.R. E.E.R. H.S.P.F. 3B260 3B261 3B262 3B266 3B266 3B267

C5QA-X25U-B C5QA-X30U-B C5QA-X36U-B CM4Q-53U CM4Q-53U

CM4Q-54U***

* 5 ton not valid match with M3 furnace *** Requires 5 ton blower set at high speed

23,600 29,200 35,400 39,000 45,500 51,000

23,600 30,000 36,000 40,500 46,500 51,000

13.0 13.0 13.0 13.0 13.0 13.0

12.6 12.0 11.8 11.5 11.7 11.5

9.0 8.0 8.0 8.0 8.0 7.6

FOR USE WITH E3 FURNACES

CAT. NO. MFG. NO. 3B301 3B302 3B303

3B304 3B305 3B306

DT4QD-024K DT4QD-030K DT4QD-036K

DT4QD-042K DT4QD-048K DT4QD-060K ** Requires 5 ton blower

COIL CAT. NO. COIL MFG. NO. COOLING CAPACITY HEATING CAPACITY S.E.E.R. E.E.R. H.S.P.F. 3B260 3B261 3B262 3B263 3B266 3B267 3B266 3B268 3B268

C5QA-X25U-B C5QA-X30U-B C5QA-X36U-B C5QA-X37U-B CM4Q-53U CM4Q-54U CM4Q-53U CM4Q-56U** CM4Q-56U**

23,600 29,200 35,400 35,400 39,000 41,500 45,500 46,500 53,000

23,600 30,000 36,000 36,000 40,500 41,500 46,500 46,500 54,000

13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0

12.6 12.0 11.8 11.8 11.5 11.7 11.7 12.0 11.7

9.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

HERMETIC AC-HP COMPRESSOR OVERLOADS

By far, the most commonly used overload on hermetic air conditioning and heat pump compressors is an internal (inside the sealed shell), embedded (placed in the windings), auto reset, type overload. This typically doesn’t mean much, as we can’t see or fix, or change the overloads in today’s hermetic air conditioning/heat pump compressors. However, many compressors are con- demned with “open windings” when the actual cause is simply an open overload.

Ohmic measurements taken on the windings indicate no continuity between the common terminal and the start, or run winding. Readings from the start terminal to the run terminal indicate continuity. If this is the scenario you find, STOP! DO NOT con- demn the compressor! These are exactly the readings you would find when the internal overload is tripped open. (The overload is normally placed between the common and start/ run windings) The overload has opened in response to excessive heat built up in the windings. The heat build up is normally caused by additional amperage draw, resulting from a number of causes, some of which are listed below:

Voltage drops off during peak usage periods causing the amperage to increase condenser fan motor shut down on overload (Of course the auto reset overload on the condenser fan motor has reset and it is running now). A run capacitor breaking down under load causing the amperage to increase. Contacts on the contactor have pitted, or melted. This reduces the voltage, causing the am- perage to increase. A loose wire will cause additional amperage draw. This occurs more frequently when aluminum wiring is used with out the special connectors. An incorrect system refrigerant charge causing additional amperage draw. Marginal wire sizing to the unit causing additional amperage draw. If this is the instance, frequent overload trips will occur during periods of peak electric use as the voltage drops off.

What can be done when it is determined a compressor is off on the internal overload? Disconnect all power to the compressor and allow the windings to cool down, allowing the overload to close. (Don’t leave power on to the contactor, as one leg may still be feeding the compressor windings. Leaving power to the windings will result in extended periods required for cool down.) Even with all power shut off to the compressor; cool down may require 3 hours or more. We can determine when the overload has closed, as we will have continuity readings between all terminals on the compressor. Once this occurs, reconnect power to the compressor and operate the system to determine what caused the overload to open. Note: Scroll compressors operate normally at higher temperatures than reciprocating compressors and may take somewhat longer to cool down.

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