ACHRNEWS

Again with the ‘Sizing'

January 14, 2011

Welcome back! Alright, enough small talk already, let’s get down to business. What do you know about tankless water heaters? Just the gas fired units, natural or LP; we’ll leave the electric, diesel, and nuclear powered ones for another time. Well? O.K. yes, they are more expensive. And yes, most of them hang on the wall, good. Anyone else? No? How about BTUs; any ideas? Well, since they make hot water so quickly, they must have an awful lot of fire in that little box, and in fact they do. Many will fire up to 199,000 BTUs, sometimes even more. So, just for comparison’s sake, do you recall how many of those British Thermal thingies a regular 40 gallon heater uses? Jake says “three”; anyone agree? Good; Jake, go sit in the corner.

Most residential water heaters use around 40,000 BTUs to get the job done. So, without getting into a discussion about which actually uses more or less gas in the long run, let’s just toss around some of the most common installation problems that we’re seeing out there. Actually, the most common are indeed all the same. Ninety percent of all tankless water heater installation problems are due to…. gas pipe sizing, of all things! I know the drill; “ahhh, yeah this one must have a defect from the factory”, and “Those things suck. They never work”. More likely though, somebody didn’t read the directions, or was texting their girlfriend during that part of the class.

But what about the common sense? Does it make sense that this unit that uses FIVE TIMES as much gas would use the same size pipe? Take out your gas pipe sizing chart that you keep in your shirt pocket and refer to on a daily basis, and try it here. Do ya see what I’m talkin’ about? You’re not even close, so stop blaming the equipment; it’s your helper’s fault, of course. Now, the capacity of the gas meter…..