Elusive Btus

Dec. 3, 2012
“Ask him, he knows about indirect water heaters,” I heard as I entered the no-spin zone: a local supply house where a competitor was seeking help from his inside salesman.

“Ask him, he knows about indirect water heaters,” I heard as I entered the no-spin zone: a local supply house where a competitor was seeking help from his inside salesman.

“What’s the issue?”

“I installed a boiler with five zones of radiant heating and an indirect water heater,” said my friend. “They’re running out of hot water during cold weather — worked great all summer.”

“How’s the heating side?

“If any three zones are calling, everything is great, but add another zone and it doesn’t matter which one, and none of them will satisfy the thermostat,” said my friend.

“Your boiler is undersized.”

That’s when the supply house guru of system sizing (a free service our local suppliers offer to contractors), who was sitting in the corner, chimed in, “Can’t be.” (Naturally, I asked why not?) “Because I sized the boiler.”

“Install primary/secondary piping and that’ll solve the problem,” his inside sales guy added.

“Fellows, I don’t mean to trample any toes here, but, for starters, adding primary/secondary piping isn’t going to produce any additional Btus. And (for the corner-sitting guru of Btus) did you visit the site? What kinds of windows were installed?”

“Sure did visit the site,” said the guru. “Old single-pane wood sash with wavy hand-made glass — it’s an old stone home with 2-ft. thick stone walls.”

 “What R-value did you assign to the windows?”

“R-2,” he said.

“And what about those thick stone walls?”

“R-19,” he responded.

Was there access to the attic?”

 “Yes, there was a stairway,” he said.

“What about insulation?”

“Yes, R-30,” he said, “but I don’t know the type.”

Well, how did you determine it had an R-30 value?”

“The homeowner told me,” was his explanation.

“Where did you come up with R-2 for those old drafty windows and R-19 for the stone walls?”

“I was told those were appropriate values by someone,” was his final answer.

Once outside in the parking lot, and out of reach from eager ears, I asked my friend why he wasn’t doing his own heat loss/gain calculations. He told me that it is too much of a hassle and he can get them done for free at the supply house.

This is fair enough, but I asked him, “Who is going to pay for the new boiler and its installation?”

“I don’t know,” said my friend.

“Guess what, you are.” 

And, that’s exactly how that played out…

Yesterday, I received an e-mail from a frustrated homeowner while I was in the middle of measuring a vintage mansion for a Manual-J calculation. He has disconnected two 50-gal. indirect water heaters from his two hybrid heat pumps and reverted back to his older 80-gal. propane water heater. The homeowner told me that he couldn’t generate a sufficient amount of hot water. Meanwhile, he cannot adequately heat his 4,200-sq.ft. home with the two 30,000-Btu hybrid air-to-water heat pumps. He’s mad as hell at the manufacturer. Time for the 20 questions session!

Was a Manual-J heat loss/gain calculation performed? He doesn’t know, and assumes the installer did something along those lines. It turned out this was a retro-fit application, and I wanted to know what equipment had been removed. I found out there were two propane gas-fired furnaces with two 4-ton A/C systems. The hybrid heat pumps were 2.5-tons each. Good grief!

If we graciously granted the A/C side a rule-of-thumb (and, I do not use rules of thumbs for sizing because there’s a guy named Vinny who likes to break those thumbs of rules) 600-sq.ft. per ton, that would mean a minimum of seven tons were needed, and he had eight tons previously. Now he has just five tons? Bearing in mind that that’s the A/C side and the heat-load in the northeast is almost always the larger load. He’s directing his anger in the wrong direction methinks, but until I do a Manual-J, all else is little more than a shot-in-the-dark where the shooter is likely to shoot themselves in the foot (or their posterior region)!

I’ll be the first to admit I’m no rocket scientist. ACCA’s Manual-J heat loss/gain program is an excellent tool, if it is used properly, which requires a wee bit of training. If I can be trained (don’t ask my bride), anyone can be trained. I also use the Uponor and Watts programs for radiant hydronic projects. These programs provide the rock-solid foundation from which I can build fortresses of exquisitely, comfortable solitude that operate at peak efficiency while squeezing every last penny from their fuel source to provide outstanding ECV and the best ROI. Do they take time to complete? Yes, but less than you might think.

Going through the exercise gives me a familiarity with the building — an intimate relationship regarding the processes of energy flow — that allows me to exercise greater flexibility in selections of equipment, energy-transfer (sizing ducts or piping), and delivery (low-temp to hi-temp or registers and noise-related issues). If I’m retro-fitting hi-tech equipment into low-tech older structures, I can crosscheck the potential for heat-outputs from existing heat emitters (ductwork, baseboard or standing cast iron radiators) and determine exactly what water temperatures are required at design-day (coldest anticipated outdoor air temps) conditions. In short, these programs put me in the driver’s seat and allow me to program the cruise control for creature comfort, be it cooling or heating. My short-term investments have resulted in long-term profits.  

Why would anyone ever turn control of their fate over to anyone else when they can be the master of their own destiny?       

All Dave Yates material in print and on Contractor's Website is protected by Copyright 2012. Any reuse of this material (print or electronic) must first have the expressed written permission of Dave Yates and Contractor magazine. Please contact via email at: [email protected].

About the Author

Dave Yates

Dave Yates material in print and on Contractor’s Website is protected by Copyright 2017. Any reuse of this material (print or electronic) must first have the expressed written permission of Dave Yates and Contractor magazine.

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