Thinking Outside the Box DHW Systems

I HEARD A TERM from a contractor customer the other day that conjured up visions of an antique domestic hot water system I remember my dad talking about. It was referred to as a range tank heating system, also known as a side arm. The latter term is the one he used. Back in the days of solid-fuel fired stoves in the kitchen, many stove manufacturers offered an add-on device for heating domestic hot

I HEARD A TERM from a contractor customer the other day that conjured up visions of an antique domestic hot water system I remember my dad talking about. It was referred to as a range tank heating system, also known as a “side arm.” The latter term is the one he used.

Back in the days of solid-fuel fired stoves in the kitchen, many stove manufacturers offered an add-on device for heating domestic hot water. It was a feature that had coils that were directly or indirectly in the firebox. As a matter of convenience and design, these coils were on the side of the stove, hence the term side arm.

This coil was then connected to a range tank that was always elevated above the stove, generally near the stove, but also located near a bathtub. It allowed the occupants to heat up their DHW with gravity circulation and then the hot water could be used to fill the bathtub for their weekly Saturday night bath.

Oddly enough, the quart drum trap that is typically found in the floor near these old leg-style tubs was used because of the infrequency of the bathtub’s usage. The quart trap was used to avoid trap seal evaporation between baths. Cool stuff, eh?

All this has to do with the plumbers protecting the health of the nation. It’s a job we do on a daily basis, and one we should be proud of. ‘Tis a noble trade.

Fast forward. In last month’s column (“My new, upside-down DHW system,” pg. 34), I discussed the innovative DHW tank that the Amtrol had offered to me for use in my ultra-efficient hydronic heating scheme. I hope I didn’t frustrate too many people out there, because the tank I’m using is not yet a regular product in Amtrol’s line of storage tanks. I suspect that there will be enough of a demand with the introduction of these high-efficiency, low-mass boilers to warrant a place on the assembly line but, for the time being, they are not available.

However, the folks at Amtrol offer another interesting product worth mentioning. They have introduced a double-coil tank with one coil located low in the storage tank for energy input, and another coil located in the top of the tank for either energy input or output. This opens up a lot of possibilities. Let’s look at a few.

Quick and easy radiant. How many times have you been out to replace a water heater on a job with a high-recovery, large-volume side-arm tank and been asked by the consumer how much it would cost to install a radiant floor-heating system for his bathroom? You immediately start conjuring up a “system” in your mind that requires a mixing device, outdoor reset package, and so on and so forth to the point that you realize it’s going to be an expensive proposition. It’s usually more than the consumer had planned on spending.

With the newest addition to the Amtrol line, it’s as simple as adding a pump, air control/expansion package, some tubing with heat transfer plates, and, voila, the consumer has his own personal version of a “This Old House” radiantly heated floor in a small bathroom, kitchen or family room.

Although not capable of whole house heating, it offers consumers the opportunity to experience the comfort afforded by radiant heating and makes them want for more! The coil in the top of the tank is your simple, properly isolated heat source. And you can bet that the next home these people build will have radiant floor-heating systems included as a part of the package.

Future solar heating option. As the cost of energy continues to increase, the calls from consumers wanting to know if they can augment their energy bills are on a steady increase. With the dual-coil storage tank, the top coil can become the alternative energy input coil, and the bottom coil can remain there for those cloudy days. This tank, when incorporated with a small circulator and additional storage, can substantially reduce our dependence on fossil fuels, thereby lessening the draw on our pocketbooks and helping the environment.

The teen-aged daughter syndrome. Everyone’s gone through this, either with a sibling or as a parent. For some odd fluke of nature, when girls make the transition to the beginnings of becoming a woman, they discover hot water, and they can’t seem to get enough. They stand in the shower for what seems like an eternity, soaking up all the hot water and leaving nothing for the other people in the house. Many times, there is a large boiler sitting there, just waiting for a major heating load to come along and make it do its job. With two coils, you can pack energy into the storage tank at almost twice the normal rate, thereby reducing the recovery time and allowing the whole family the opportunity to enjoy a hot shower in the morning.

Tune in next month when we’ll look at “real time” heat-loss calculations. Until then, Happy Think Outside the Box Hydronicing!

Mark Eatherton is a Denver-based hydronics contractor. He can be reached via e-mail at [email protected] or by phone at 303/778-7772.

TAGS: Hydronics