Friedrich H)A09K25, V(E service manual Room Thermostats, Heat Anticipators

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Room Thermostats

Room thermostats are available from several different manufacturers in a wide variety of styles. They range from the very simple Bimetallic type to the complex electronic set-back type. In all cases, no matter how simple or complex, they are simply a switch (or series of switches) designed to turn equipment (or components) "ON" or "OFF" at the desired conditions.

An improperly operating, or poorly located room thermostat can be the source of perceived equipment problems. A careful check of the thermostat and wiring must be made then to insure that it is not the source of problems.

Location

The thermostat should not be mounted where it may be affected by drafts, discharge air from registers (hot or cold), or heat radiated from the sun or appliances.

The thermostat should be located about 5 Ft. above the

oor in an area of average temperature, with good air circulation. Close proximity to the return air grille is the best choice.

Mercury bulb type thermostats MUST be level to control temperature accurately to the desired set-point. Electronic digital type thermostats SHOULD be level for aesthetics.

Measuring Current Draw

Heat Anticipators

Heat anticipators are small resistance heaters (wired in series with the "W" circuit) and built into most electromechanical thermostats. Their purpose is to prevent wide swings in room temperature during system operation in the HEATING mode. Since they are wired in series, the "W" circuit will open if one burns out preventing heat operation.

The heat anticipator provides a small amount of heat to the thermostat causing it to cycle (turn off) the heat source just prior to reaching the set point of the thermostat. This prevents exceeding the set point.

Thermostat Location

In order to accomplish this, the heat output from the anticipator must be the same regardless of the current

owing through it. Consequently, some thermostats have an adjustment to compensate for varying current draw in the thermostat circuits.

The proper setting of heat anticipators then is important to insure proper temperature control and customer satisfaction. A Heat anticipator that is set too low will cause the heat source to cycle prematurely possibly never reaching set point. A heat anticipator that is set too high will cause the heat source to cycle too late over shooting the set point.

The best method to obtain the required setting for the heat anticipator, is to measure the actual current draw in the control circuit ("W") using a low range (0-2.0 Amps) Ammeter. After measuring the current draw, simply set the heat anticipator to match that value.

If a low range ammeter is not available, a "Clamp-on" type ammeter may be used as follows:

1.Wrap EXACTLY ten (10) turns of wire around the jaws of a clamp-on type ammeter.

2.Connect one end of the wire to the "W" terminal of the thermostat sub-base, and the other to the "R" terminal.

3.Turn power on, and wait approximately 1 minute, then read meter.

4.Divide meter reading by 10 to obtain correct anticipator setting.

Electronic thermostats do not use a resistance type anticipator. These thermostats use a microprocessor (computer) that determines a cycle rate based on a program loaded into it at the factory.

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Contents VE,HA18K25 VE,HA18K34 VE,HA09K25 VE,HA09K34VE,HA12K25 VE,HA12K34 VE,HA24K25 VE,HA24K34Table of Contents Introduction Serial Number Identification Guide VERT-I-PAKH Suffix Chassis Specifications VERT-I-PAKE & G Suffix Chassis Specifications VERT-I-PAKA D Suffix Chassis Specifications Refrigeration Assembly Sequence of OperationSupply Voltage Electrical SupplySupply Circuit Control Low VoltageRoom Thermostats Heat AnticipatorsTypical Electrical & Thermostat Wiring Diagrams Typical Electrical & Thermostat Wiring Diagrams Suffix For 208 Volt Models only Move the White Wire AS Shown below Blower Wheel Inspection Indoor Blower AirflowCondenser Fan Motors CoolingChecking Approximate Airflow Checking External Static PressureElectric Heat Strips Ductwork Preparation Explanation of chartsRefrigerant Charging Method Of Charging Undercharged Refrigerant SystemsOvercharged Refrigerant Systems Restricted Refrigerant SystemsReversing Valve Description/Operation Testing CoilMetering Device Capillary Tube Systems Electrical Circuit and CoilChecking Reversing Valve Touch Test in Heating/Cooling CycleCompressor Checks From Electrical ShockSingle Phase Resistance Test Recommended Procedure for Compressor ReplacementCapacitors Capacitor ConnectionsElectric Heat Switch Operation Electric Heat Switch Check OutWiring Diagram Index VHA09K25RTG Suffix only Suffix only Suffix only Page Page Page Page Page Page Page Page Page Electrical Troubleshooting Chart Cooling TON Electrical Troubleshooting Chart Cooling Troubleshooting Chart Cooling Electrical Troubleshooting Chart Heat Pump Page Use Factory Certified Parts