Power Rating:

The four-chamber models contain four electric heating elements whose combined wattage is the total power rating of the heater. For instance, the standard RA-28 model contains four 7000 watt elements for a total of 28,000 watts, or 28 kilowatts (kW) of power. The two-chamber model, RA-14, contains only two 7000 watt elements for a total power rating of 14,000 watts, or 14 kilowatts (kW). However, because of Seisco's "Power Sharing" technology, the heater may not always use the maximum available power. The power output can vary with flow rate and temperature rise. Refer to the Product Specifications Table above for the maximum power ratings of each model.

Heating Output:

The heating output of the Seisco is simply the total kilowatt power rating of the combined heating elements converted to BTUs using 3,413 BTU/kW. For instance, the RA-28 has a total power rating of 28 kW or a 95,564 BTU heat output rating. The four-chamber models have the higher output ratings; 61,434 BTUs for the RA-18 model, and 75,086 BTUs for the RA-22 model. The lower output two-chamber models, are; 47,782 BTUs for the RA-14, 37,543 BTUs for the RA-11, and 30,717 BTUs for the RA-9. These ratings vary with the operating voltage or service voltage to the heater. Refer to the Product Specifications Table for the BTU ratings of each model.

Voltage Rating:

Seisco heaters are manufactured with common 240 volt [AC] heating elements designed for optimum operation on a standard residential 240 volt [AC] electric service. Also, the Seisco will operate at 208 VAC, a typical commercial voltage, with standard 240 VAC heating elements. However, when operating the heater at 208 VAC, the power rating and the heat output rating is significantly reduced. Seisco models can be special ordered with 208 VAC heating elements to help maximize the power and heating output. Refer to the Product Specifications Table above for details on the various voltage ratings. 

Maximum Current Rating:

Each Seisco Model has a maximum electrical current rating [or amp rating] equivalent to the sum of the heating element ratings. For example, a four-chamber model, RA-28, operating at 240 VAC has four heating elements, each with a maximum rating of 29 amps. The maximum current rating or total current rating of the RA-28 is therefore 116 amps or the sum of the four heating elements. However, because of Seisco's "Power Modulating Technology", the actual current measured during relatively low flow rates and/or low temperature rises can be less than the maximum rating of the heater during operation. Refer to the A [max] or maximum amp rating under "Electrical" in the Product Specifications Table above for each model.

Temperature Rise:

The temperature rise must be determined in order to help choose the appropriate Seisco heater. The rise can be determined by knowing the input water temperature and the desired output temperature of the heater. The Seisco's output temperature is typically set for about 120 degrees F at the factory. Therefore, if the input or cold water inlet temperature is 50 degrees F, then the temperature rise is the difference or 70 degrees F. If the desired output temperature is 125 degrees F, then the temperature rise would be 75 degrees F. With the temperature rise determined, the Product Specification Table above provides the associated flow rate capacity of the various Seisco models.

Flow Rates:

The flow rate for each model is given in the "Temperature Rise" section of the Product Specification Table above. Along with the temperature rise, the flow rate must also be determined in order to choose the appropriate Seisco heater. The flow rate is determined by the type of faucet and also, life style. Refer to the chart below for typical faucet flow rates in the home. However, if the desired life style in the home requires running multiple faucets at the same time, then the flow rates must be added together to determine the peak flow demand. The Seisco or the possibility of multiple Seiscos should be selected to match the peak flow rate.

Below are typical flow rates for new residential construction. There may be exceptions with new designer type fixtures and faucets. For instance, large custom body spa showers whirl pool and Jacuzzi tubs may have faucets with flow rates ranging from 7 gpm to 14 gpm. However, a combination of multiple Seisco heaters [preferably plumbed in a parallel configuration] can be installed to match these higher flow rates. The same peak design approach would be necessary for the anticipated life style of multiple flow rates occurring at the same time. Otherwise, use the table below and match the Seisco according to the peak flow and associated temperature rise of a single tub or shower.

Typical Flow Rates in Gallon per Minute [gpm]
Fixture Type	Lavatory	Bathtub	Shower	Kitchen Sink	Pantry Sink	Laundry Sink	Dish-washer
Flow Rates	0.8 - 1.5	2.0 - 4.0	1.5 - 3.0	1.0 - 1.	1.5 - 2.5	2.5 - 3.0	2.0 - 3.0

 
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