It’s unfortunate that advanced technology is enabling more luxurious, indulgent, satisfying hot water applications at the same time the environment is crying for humans to be more sparing of limited natural resources. Twenty years ago, people were no more clamoring for a two-headed shower than they were for reduced flow levels. But a little knowledge can be a costly thing, once you know what’s out there. And increased options lead to lavish expectations.
    Fortunately for the environment, “green” systems seem to be winning out over luxury demands. Witness the rise of energy efficient appliances. Despite the higher set-up cost and reluctance of Americans to try anything new, tankless water heating is hot—but not in a wasteful way. Tankless’ virtue is that it heats water on demand, saving energy by not keeping water hot the rest of the time.
    But manufacturers can go on and on about their other positive qualities, as did this month’s participants: Edward Sullivan, North America director of training for Bosch Water Heating in Londonderry, N.H.; Frank Stiebel, president of Stiebel Eltron in Hatfield, Mass.; marketing manager Jim McGoldrick and product manager Eric Cytrynowicz from Bradford White Corp. in Ambler, Pa.; vice president of sales and marketing Aaron Siegel, of Eemax in Oxford, Conn.; and Peter Blaha, product manager for Rheem, in Montgomery, Ala.
    Their allegiances tend to be obvious but to help you keep the players straight, Stiebel Eltron and Eemax manufacture only electric units. Rheem is strictly gas. Bradford White and Bosch hit both sides, producing gas and electric tankless water heaters.  

Reeves Journal: Electric vs. Gas—which is better suited to what applications?  

Stiebel Eltron: Clearly, on the point of use side, I think only electric makes sense. If you’re just heating water for a hand wash sink, it doesn’t make sense to put in a big fancy gas unit that needs venting and all that kind of stuff.      
    On the residential side…I think that really depends on the energy costs in the area, how gas compares to electric per BTU. I know that in some areas electricity is really cheap, and gas is not and vice versa. And gas units tend to be more high in capacity, on average. They go up to 200,000 BTUs or even higher. Electric units do not go up that high because you can only get so much electrical capacity out of a typical electrical service [in your house]. So the electric units are a little bit limited on the flow rates that you can get. But of course in a warm climate, that problem kind of goes away because the incoming water temperature is already quite warm.

Rheem: Electric units are not practical for whole house water heating, and they’re not very practical for commercial use. The reason is the energy drain required to heat the water. U.S. power grids just aren’t set up to handle that load. First of all, the unit itself is going to be expensive but then on top of that, you’re going to have the electric bill skyrocketing.  

Bradford White: Traditionally, gas tankless water heaters have been used for ‘whole house’ applications, while electric tankless have been used for single point, or point of use applications. However, there have been some new product introductions that can provide ‘whole house’ water flows from electric tankless technology.      
    Before either tankless technology is used, proper investigation is needed to ensure that there is enough power available for these units. The rate that the power can be delivered to the tankless water heater is the limiting factor. For gas tankless units, the limiting factor is gas flow. For electric tankless units, the limiting factor is amperage draw.  

Eemax: They’re kind of like comparing apples and oranges. With the gas system, typically you have a venting issue to deal with, relative to venting the gases out someplace. So one of the advantages for the electric is obviously you don’t have to take that process into account when you do the installation. Whereas the electric is literally at 99 percent efficiency because all the energy is consumed by the product in the form of hot water coming out of the product. 

RJ: Is there an application in which a tankless heater would be a bad idea?  

Bradford White: Yes. If the customer has a need for high volume ‘dump’ of hot water.  The tankless units are limited by flow rates. Anything above that flow rate would require installation of another tankless unit. Another alternative would be to install a tank for the high volume dumps.  

Stiebel Eltron: Like restaurant kitchens where you need pretty fast fill rates for dishwashers at a very high temperature. That’s probably where the tankless does not make a lot of sense—any time you need to fill something really fast, with a very high flow rate.  

RJ: Is there a “proper” way for a contractor to size a tankless heater?  

Bosch: Absolutely, and it’s based on the demand of the house. Let’s say you have three shower heads but only two people living in the house, you only use one shower at a time. Whereas if you have three showerheads and six people living in the house, then the odds are you may have two or three running at the same time. So the amount of people living in the house and the amount of shower heads really determines how many gallons a minute you’re going to need at any one time.     
    It depends on the lifestyle. You know, if your parents are elderly, they’re not taking half-an-hour showers every day that a 16-year-old takes. So these all have to be considered. Do you have a full body spray or do you have a regular showerhead? There’s showers out there that will dump 30 gallons a minute.  

Stiebel Eltron: We have sizing charts in the literature and that really seems to work 99 percent of the time. We don’t like people to do it on their own, with adding up all the flow rates. Some people call us and they say, ‘I have 3 bathrooms—that’s like 3 gallons per minute each, that’s 9—and then I have a dishwasher and a kitchen sink—there’s another 2—and then I have a laundry facility…I need 12 gallons a minute.’ Nobody can do that kind of flow rate and nobody uses all taps at the same time.   Bradford White: The proper way to size a tankless heater is similar to sizing a tank heater:   a. Calculate the hot water flow requirements. b. Identify any volume dumps that will be necessary. c. Evaluate hot water usage. d. Determine fuel source: Natural Gas? Propane? Electric?  

Eemax: The flow rate or the gallons per minute are really what determine the correct size of these products. So you have a volume of flow that you need to heat, and then you try to determine how much power you need to heat that volume of flow. There’s a matrix or a guideline that’ll help the contractor determine what product is correct for the application. You can do that on our Web site; there’s a guideline there. But often you want to try to figure out how much demand for hot water that they need and then size the heater according to the demand.  
   
Rheem: We have software on our Web site called EZ Spec, and it’s great for contractors. You can put how many lavatories you have, how many showers, dishwasher and it’s going to basically tell you what you need.  

RJ: Are there any pitfalls to installation or problems that could cause a tankless heater to fail inspection?

Bosch: The potential pitfalls for a contractor are really nothing different than what it would be if you were installing a gas fired type conventional water heater. It comes down to sizing the gas line properly in order to meet the demand of the unit. Just have enough pressure that you have at least 30 pounds of pressure coming into the unit.  

Bradford White: It’s important to ensure that the National Fuel Gas Code (ANSI Z223.1) is followed in all installations. Inspectors often find venting mistakes with respect to clearance from windows, doors and building air intakes. They also find undersized gas supply lines.        
    The same can be true with electric tankless. It’s important to follow UL requirements for installation. In either installation, inspectors read the installation manual carefully to ensure that the installation is as required by the manufacturer.  

Rheem: A common mistake people make is, they’ll take an indoor unit and they’ll put it in a closet that doesn’t have proper ventilation.      
    Another mistake people make is they put the wrong size gas line in. We require a ¾” gas line. Some people already have a ½” gas line and they’ll keep it that way but they’re not going to get enough fuel to the heater for optimal combustion.  

Eemax: Different parts of the country look at different things. A lot of inspectors, when they’re looking at products that are installed—like a water heater, for example—they’ll look for listings or ratings for the products or approvals for the products.   RJ: What’s next for tankless water heaters; will they continue to be made more compact?  

Rheem: I think you’re going to see .90, .95 (percent efficient) fully condensing heaters in the future. You’re going to see gas-electric hybrids. I think you’re going to see higher flow rates. I don’t see the size getting too much smaller. The size of a medicine chest is not that big to begin with for whole house water heating.      
    One of the issues with tankless water heaters is they don’t tend to work very well in hard water areas so I could see something coming down the pike for a solution for that. There are these magnetized water softening solutions that are around. Maybe something that attaches to the heater itself that keeps the lime scale from building up inside.  

Eemax: I think a lot of our focus will be on improved technology associated with electronics and improving the reliability of the product and obviously always trying to build the better system as new technology comes into the marketplace.  

Stiebel Eltron: The size is pretty much where it’s going to be. But we’re coming out with a new Tempra line with some new features. It will have a throttle valve that, if the unit is not able to maintain a set point temperature because the water is coming through too fast, it’s going to throttle it down to a flow rate where it’s still reaching the set point temperature.      
    There’s still a lot of growth potential in the U.S. I think they will continue to grow every year and will help people save money and save space.  

Bosch: As time goes on, the units may not get smaller, but you’ll get more gallons per minute out of the same size box. So maybe you got 5 gallons a minute out of a box. Now you’re making 7 or 8 gallons a minute out of that same size box. So you get more flow, more hot water at the faucet. It’s like going faster in the same size car.