Booster heaters are normally electric or steam operated; gas models are also available, but they are rarely used. The unit should be installed as close as possible to the final rinse end (exit end) of the dishwasher. The purpose of a booster heater is to provide final rinse water at a temperature of 180° F minimum to 195° F maximum.
This is based on the expectation of water coming into the booster heater at a temperature of 140° F. In some installations, mainly in medical institutions, only 110° to 120° F hot water is provided throughout the building.
In order to obtain the desired 180° F rinse water in such installations, it is necessary to install a larger booster or two regular units in series. (The units in series must be electric models).
Combination temperature/pressure gauges should be installed on all booster heaters-one on the inlet side of the heater, and one on the outlet side. These can be used in checking water temperature and pressure problems.
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The recommended water pressure for the final rinse cycle is 1.4 Kg/Cm2 When a steam-operated booster heater is installed, the recommended minimum steam pressure is 0.7 Kg/ cm2 and the recommended maximum pressure is 3.15 Kg/cm2.
Maintenance of Electric Models of Booster Heater:
Never turn on the current to the booster heater until the tank has been filled with water and all air has been vented through the dishwasher’s rinse nozzles. This will help you avoid burning out heating elements in-advertently.
If the temperature in the heater exceeds 210°F, the high-temperature limit switches will shut off the power. The switches must then be manually reset by pushing the red buttons.
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The thermostats are checked and set at the factory. If recalibration becomes necessary, a quarter-turn of the screw clockwise will decrease the temperature by approximately 12 Fahrenheit degree. Before attempting to remove a thermo state, turn off the power and drain the tank.
Then remove the leads from the thermostat terminals, and remove the nuts and the bushing. To install a new thermostat, perform the following steps:
1. Pull the end of the sensor bulb into the recess in the bushing; then insert the bulb into the tank, holding it in place with the capillary tube.
2. Tighten the bushing.
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3. Lock the sensor bulb and the capillary tube in place by tightening the nut.
4. Place the bracket on which the thermostat is mounted onto the element studs and tighten it.
5. Reconnect the leads to the thermostat terminals.
6. Make sure that the tank is refilled before you turn the power back on.
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To replace an immersion-type element (figure 4.53) perform the following steps:
1. Turn off the power, and drain the tank.
2. Remove the leads from the element.
3. Remove the hexagonal nuts, the element flange studs, and the element.
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4. Clean the gasket surface on the element tank flange, making sure that you remove all of the old gaskets.
5. Turn off the power, and remove the leads from the terminals.
6. Remove the contactor from the control panel, remove the screws in the top of the contactor, and lift the contactor off (with the armature).
7. Remove the cotter pin from the lower solenoid frame, and slide the sleeves out of the center of the coil.
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8. Remove that coil from the contactor, and install the new coil by reversing this procedure.
To replace contacts, perform the following steps:
1. Turn off the power, and remove the leads from the terminal.
2. Remove the outer screws, the small special washer, and the spring.
3. Remove the contact bridge.
4. Remove the inner screws, and remove the lower contacts. Install new contacts by reversing this procedure.
Preventive Maintenance-
This type of item does not require any daily, weekly, or even monthly preventive maintenance. Draining the tank periodically, however, will prolong the life of the heating elements. Such draining should be done at least once every six months, and more often in areas where hard water conditions prevail.
Maintenance of steam-operated models-
The steam-operated booster heater is a heat exchanger consisting basically of copper helical coils enclosed in a cast iron casing. The coil is connected to the water lines and surrounded by the steam chamber. If this heat exchanger becomes defective, it should not be repaired; it should be replaced. Preventive Maintenance Schedule
Monthly:
» Remove and clean the strainer screen.
» Check the inside of the solenoid valve for dirt. Remove any accumulated dirt.
Yearly:
* Remove the seat and seat gasket of the steam trap, and clean them.
* Remove the steam trap’s cleanout plug, and flush it out with water.