A Plumber Talks About the Rennai Tankless Water Heater

  • Print Article |
  • Send to a Friend |
  • |
  • Add to Google |

Hi, and welcome to another episode of "What's New in Plumbing." I'm Bob Fishman, and I just had a talk yesterday with Alan Urszuy, the co-owner of A-1 Plumbing of Baltimore, a that specializes in . and Alan filled me in on some new developments in the area of .

As Americans look for more ways of conserving fuel, and domestic space as well, homeowners are turning to tankless, (hot water on demand), heaters to supply their domestic hot water needs. Tankless heaters are attached to the wall. They only heat up water on demand, and therefore save lots of money on the energy bill.

A number of companies are offering tankless heaters to the American market. To illustrate some of their specific pluses and minuses, I will consider the Rennai tankless heater. I learned about the Rennai during a recent talk with Alan Urszuy. Alan had lost of praise for the units, noting their energy efficiency, and sophisticated digital sensory system.

In addition to providing the tankless heating unit, the Rennai heater has a lot of features, which are attractive to consumers. The unit is 95% energy efficient, which means the great majority of the heat generated by gas combustion is transferred to the water.

The heater, is also a condensation heater, featuring a stainless steel system that recaptures residual heat from flue gases to pre-heat incoming ground water, which then circulates to the primary copper heater exchanger.

The Rennai can produce up to 8 gpm, (gallons per minute), of water whose temperature has been raised 35 degrees above the inlet temperature. On cold day, when the inlet temperature is low, a 37 degree rise may not be sufficient to produce usable domestic hot water, so the actual amount of available hot water is decreased.

Nevertheless, the installation is touted as being sufficient for moderate to large size homes. Just for comparison sake, with the increased use of low flow showers the average shower might use as little as .6 to 1.5 gpm of hot water.

Another attractive feature of the Rennai heater is its concentric vent pipe. All gas powered heaters need vent pipes. They bring in fresh air for combustion and they remove gaseous combustion products. While most heaters have two separate vent pipes, which means two holes in the roof, the Rennai combines the function of both pipes into one.

The hot gases are expelled through a central outflow pipe and the outdoor air is sucked in through the surrounding intake pipe. The double layered pvc pipe also provides increased protection against the possible leak of poisonous carbon monoxide from corroded vent pipes.

Users of the Rennai tankless water heaters report that the device does has some negatives. Because the heater is an on demand unit, it is not triggered to produce heat until its digital sensors perceive a water flow of at least .6gpm.

Unfortunately, some of the new ultra low-flow shower heads restrict water flow to this very level, and reports have circulated about Rennai owners experiencing hot water cut offs during their showers. The same problem has been seen with hot water flow in the dishwasher, and this is not surprising since dishwashers generally require fewer gpms than showers,

Consumers also complain about the "cold water sandwich," a complaint made about all the tankless units. This problem occurs when the units are first triggered to heat water for a shower. Users experience a rush of hot water followed by a temporary drop in the water temperature, before the water again heats up. Not the type of sandwich you'll want to enjoy, during your summer fun.

Homeowners are developing ways of adjusting to these problems including removal of the low flow shower nozzle and installation of small point of use hot water tanks. But these methods are expensive and also fraught with difficulties.

The problems seen with tankless heaters today are reminiscent of the problems first encountered with the low flush toilets in the 90s. And, it is likely that enterprising manufacturers will see these problems as challenges to find a more perfect tankless water heater.

Well that's it folks for another episode of What's New in Plumbing, Have a great day!

Article Rating (5 stars):
  • article full star
  • article full star
  • article full star
  • article full star
  • article full star
Rate this Article:
  • Article Word Count: 687
  • |
  • Total Views: 52
  • |
  • permalink
  • Print Article |
  • Send to a Friend |
  • |
  • Add to Google |
>