It's a Tankless Job, But Everybody's Gotta Do It

Ever wonder what it would cost to leave your car running in your garage all night long, just so it would be warm when you got up to go to work? Or to leave your heat at 75 degrees while you were on vacation, just so the house would be warm when you get home? What about turning all the lights on in your house all day long while you are at work, just so you wouldn’t have to turn them on when you get home? I think you get the point. Tremendous and useless wastes of energy, right?

Well, these are not too far off what it’s like to have a water tank in your basement churning away all day long while nobody is there to use that water, and all night long while you are asleep. The energy being generated by your water heater (at a miserable 60% efficiency) is lost through the jacket and chimney, along with the natural cooling of the water. We call these “standby losses” and they are excessive and unnecessary.

Also, water tanks accumulate sediment, which naturally destroys their already-poor efficiency. By design, a water heater is nothing but a big kettle of water with a tube running up the middle of it that takes flue gases out. The only thing that slows down the flue gases is a baffle that is inside this heat exchange tube. In 2004, the N.A.E.C.A. (National Appliance Energy Conservation Act) Standards were finally mandated for water heaters. You have probably seen them on other appliances like air conditioners (going to 12 SEER this year) and furnaces (80% AFUE). The government had tried for a very long time to determine how they could apply these standards to water tanks, and finally determined the only way to do so is to thin the wall of the heat exchange tube. While this gained 1.5% efficiency, it meant all the manufacturers had to retool and the price went up over $100 in many places. It also meant that a thinner heat exchanger and jacket would mean less longevity. The predicted lifespan of new water tanks is 5-7 years! So, for an average yearly savings of under $10, you will spend more money on the new one and it will only last half as long as the old one did!

Then there’s the real issue of what happens when your water tank decides to give up the ghost. It happens often without warning. For the lucky ones, a couple drips under the tank are noticed and it’s “time”. In the other 50% (yep, half!) of the cases, the bottom drops out or the side splits from a faulty relief valve and the basement becomes a swimming pool, or the crawlspace a swamp. Or the condo below fills up with water. Or the main level becomes an ice skating rink, or… you get the picture. Perhaps you have been in this situation. It’s not pretty.

Tankless water heaters are proven technology around the world. The problem is they haven’t really caught on yet here in America. Elsewhere in the world, tankless technology is the only method of heating water, from point of use electric to whole-house gas systems. Most places in the world do not have the space or energy to waste on a tank of water that heats up constantly. Nor would it be conceivable to run out of hot water. Why pay to heat water over and over again at 60% efficiency when you can pay to heat it once at 85% and never run out? And why would you have a system that needs replacement every few years when you can have one that will last virtually forever? The fact is tankless water heaters are “component” systems, which means they have parts inside that work together to heat the water, all of which can easily and inexpensively be replaced when they fail. When your car needs a tune-up, you don’t rebuild the engine, right? Or your house needs a paint job, so you don’t call a demolition crew in to scrape it and start over! That would be absurd. The beauty of tankless technology is the replaceable parts, right down to the heat exchanger. That is what gives them 3 to 4 times the longevity of a tank.

I have seen some really big water tanks. The other day I was at a house in Boulder with 2 75-gallon tanks that took up almost an entire utility room. Now none of their domestic hot water system is inside the house. The space we freed up by installing the units outside was tremendous. And the cold snap in ’05 that brought 25 below zero was never a factor, with the internal freeze protection system of the Rinnai Tankless water heater. Not all tankless systems are approved for outdoor use, however, so it’s best to consult the specifications. The great thing is that even installed inside they take up no space at all. They just hang on the wall waiting for someone to turn on a faucet. That’s how it should be.

Some pretty interesting things often come out when you drain a water tank. I once had a customer compare it to the ectoplasm in “Ghost Busters”. I have to agree; it was green and slimy and maybe not dangerous, but certainly not what I would want to shower in. Our family doctor gave me the idea that water tanks can be a health hazard. He said that the sediment can attract some pretty interesting microorganisms, since stagnant water at 100-120 degrees is a darn good science experiment. More than one of my customers has put that at the top of their list for reasons to go tankless. In fact, one of them became deathly ill with a bacterial infection after returning from vacation and taking a shower. Her doctor traced it to the water tank that had been sitting hot long enough to have burned off the chlorine and breed bacteria while she was gone and she ingested it. I am sure this was an extreme case, but not totally out of the ordinary. Tankless systems will not develop sediment, and since they are not kept warm all the time, are less likely to breed bacteria.

Many people ask me how tankless systems work; in a word- modulation. The burners modulate up and down depending on how cold and fast the water is coming in. So if the water coming in is 40 degrees, it takes more gas to heat it up (so the burners modulate up) than it does if the incoming water is 60 degrees. Likewise, if only one sink is being used (roughly 1.5 gallons per minute or GPM) it takes less gas (so the burners modulate down) than it does if two showers are on simultaneously. Most tankless systems will easily handle two showers simultaneously at 40-degree incoming water at high altitude. Much more than that, and the water goes cold or the flow is decreased, depending on the brand.

The wonderful thing is that those 2 showers can be taken forever! When your old water tank would run out in about 12 minutes, the tankless system will keep going and going and going. Sort of like that bunny on TV. And nothing feels as good as a clean, long shower, wrapped in the knowledge that it’s dead cold when you’re done and no energy is wasted. If you have a jetted or soaking tub, you’ll never fill it with a 50-gallon water tank. Even 2 tanks (think about that waste!) would have a hard time. By contrast, I fill my hot tub with my tankless system. That’s 330 gallons of water that’s heated by gas at 87% efficiency and I’m in my hot tub that night! Those who want to be part of the solution (but still want to have some luxury in their lives) have to go tankless. It’s the smart thing to do.

While going tankless is a great idea no matter what the case, it’s definitely a “buyer beware” situation. I have seen many installations done by “professional plumbers” that were so far off the installation instructions they were in fact dangerous. Most tankless systems cannot utilize the existing water heater vent, require either sealed-combustion venting or additional combustion air, may require a bigger gas line, need a buffer-pipe for cold water sandwich alleviation, require a service manifold with ball valves and boiler drains and need specialized personnel to install them. Not to mention that educating the customer is the most important part of the job.

When customers do not understand how tankless sytems work, they may be disappointed. A water tank “thermally siphons” all the time, since the water is hot all the time. This means it takes less time for a water tank to deliver water, since a tankless system has to fire up first and get the water and the pipes hot. With a tank, the pipes are already hot. So longer lag times may be experienced. This problem can easily be overcome with a recirculation system like the Metlund D’mand system (http://gothotwater.com/). Also, tankless systems require a minimum flow to activate them, which means you may not be able to “trickle” water in the sink and still get hot water. Going tankless is the smart thing to do, but you need to know what to look for and how much it should cost. Be sure the system has at least a 3 GPM flow at a 70 degree rise at this altitude, or you may not get the flow you need. Also be sure the unit will protect itself from freezing, even if it’s inside. Believe it or not, a tankless system that isn’t freeze protected can freeze simply from the cold air dropping across the heat exchanger while the furnace is operating.

What is a forced air furnace anyway? It’s just a big box with a fan in it, right? Right. It’s just a fan in a box with a flame-fired (direct-fired) heat exchanger. One way to get more mileage out of a furnace is to convert it to a hot water air handler using an efficient tankless water heater and some proper planning. When a furnace is converted, the burner, heat exchanger and gas valve are removed and a hot water coil, similar to a car radiator, is installed inside the box. The fan and some of the controls are retained, but otherwise the system is now without any combustion gases or flame whatsoever. This means the system is more safe and reliable; furnace flues and combustion air holes can all be eliminated, making the building more energy efficient simply by eliminating some huge sources of air infiltration. It also eliminates gas-fired heat exchangers that can create noxious gases.

After the conversion, when the thermostat calls for heat, a pump comes on and pumps water from the tankless water heater through the coil and back to the water heater. This circulation brings on the burners in the water heater, taking the temperature of the water up to 140-150 degrees. This is where the modulation I mentioned earlier really benefits the system. The burners will only produce the BTU’s needed to keep the water hot and no more. Then the fan on the “hot water air handler” comes on and produces warm air, just not as dry as that from a standard furnace. This gentler source of heat will likely never need maintenance, with the exception of fan servicing and filter replacement. The pump is a cartridge pump that is easily repaired if it fails. Heat is being produced at the efficiency of the tankless system and has little effect on the amount of hot water that is available for domestic use. This type of system solves many problems and means nobody will ever have to haul a furnace or water tank out of your basement again. Ever.

Tankless systems can even be used in hydronic heating situations, as replacement for old, inefficient boiler systems. Again, with full modulation, the efficiency of a radiant floor system or baseboard hot water will be greatly increased over a standard boiler. In many cases, space heat and domestic hot water can be integrated into one unit, if the unit is rated for space heat. If solar or geothermal is used as a pre-heat source, the savings can be tremendous. It is just a matter of proper design and load calculation.

Going Tankless is the smart thing to do. Just make sure you are getting it done right. Call 303-546-0448 or email us for additional information.