The "instantaneous water heater" is one big heating coil sitting over a large flame. The flame only turns on when there is a demand for hot water. Since there is No storage tank, all of the hot water is produces only when needed. The heater is a sealed unit and the water flow rate is restricted so that the water leaving the heater is already at the desired Hot water temperature. Physics says that an "instantaneous heater" can only produce a certain amount of Hot water, at a certain flow rate (see attached chart). Typically the instantaneous heater will produce 9-10 GPM (gallons per minute) of flow rate for a 30 degree rise in temperature. The difference between the desired Hot water temperature (typically 125 degrees) and the temperature of the incoming cold water, is called the "# of Degree (of) Rise" in temperature. For example in the NY area incoming water temperature in the winter can be as cold as 40 degrees (see attached chart for your area). If our desired Hot Water temperature is 125 degrees then we need an 85 degree rise in temperature. The water heater with an 85 degree temperature rise will only have a flow rate of 4 GPM. Note that the typical front load washer fills at between 5-7 GPM. With an "instantaneous water heater" the higher the degree rise, the lower the hot water flow rate. Multiple "instantaneous water heaters" are required to produce enough Hot water (flow rate) to satisfy the demands of even a modest Laundromat. If the hot water heating system is designed correctly then both heating systems will operate properly and the Laundromat customers will have plenty of Hot water. If the water heating system is sized wrong or under-sized, then the Laundromat will experience noticeable problems.

Ordering the System

In a situation where the water heaters are undersized, the Laundromat washers will suffer and the lack of hot water will become apparent to your Laundromat customers. Laundromats are busiest during Saturday and Sunday usually between 8am to 6pm. If the "storage tank heating system" is under-sized the temperature in the storage tank will Not reach the desired temperature. The heater will be operating almost continuously, trying to make enough hot water (which shortens the heater life) and the customers will be getting cooler and cooler "Hot" water.

With an "Instantaneous water heater" if there is too much hot water demand the heaters will only produce 4 GPM of hot water per heater (with an 85 deg rise) and the Hot water flow rate will diminish. If the hot water demand exceeds the capacity the heaters, the result will be very little Hot water flowing to the washers and the washer cycle times will increase. For example, imagine turning on every water faucet in your house, the flow rate to each faucet will drop as more and more faucets are turned on. This is what happens in your Laundromat. As more washers call for Hot water, the flow rate will decrease with each washer and the water will trickle into the machines. Some Laundromat owners will install 2 "instantaneous heaters" when 3 or 4 should have been installed. In 90% of the time this is not a problem, but for the busiest 10% of the times, the Laundromat washers will start filling slower and the washer cycle times will increase from 30 to possibly 45 minute per cycle.

Next week we will discuss how to size your water heating system.