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I wondered for a bit what I would write about for my first blog. Should I write about boiler concepts, good preventative maintenance or finding a good contractor? Then it hit me, why not write about a problem that just about every home in America has…an oversized heating system. I dare you to take a trip over to your heating system at take a look at the rating plate. What does it say? I can assure you that the input is probably over 100,000 BTUH. Am I right? I decided to run my own real numbers test.
My near 30 year old hot water boiler is rated at 133,000 input with a rough output of about 109,000, a perfect example for my test. I’ve done the calculations for my home and came up with just under 32,000 BTUH to heat my 1,200 sq ft main level. I was a tad skeptical, but nonetheless the freezing weather came and my eyes lit up at the opportunity to really crunch the numbers. I took down readings of outdoor and indoor temperatures as well as cycle times.
Quick side note here on system design. Each climate zone, state, region has their own set of design temperatures. North Jersey has a design temperature of 0 degrees and we size our systems…..supposed to size our systems to 70 degrees inside with our given outdoor design. Now when you arrive at your finalized calculation, this is the amount of heat needed to maintain 70 degrees inside when it’s the given design temperature outside, in this case, 0 degrees. Considering we rarely ever see the “worst case scenario”, you can even say a properly sized heating system is oversized nearly all the time. However, boilers are sized for this “worst case scenario” based on design.
Back to the numbers now. What I found brought a boiler sized smile to my face. My grossly oversized boiler ran a total of 4 cycles during a one hour span for roughly 3 to 3-1/2 minutes a piece totaling around 30,000 BTUH with the current outdoor conditions at its worst. A properly sized boiler should have ran non stop during that cold stretch, not 25% of the time. Just for fun, I tried to see how I could tweak my calculations to get it up to 100,000 BTUH. I got up to 90 degrees inside at -30 degrees outside before I gave up and that only came out to a whopping 53,000 BTUH.
Boiler oversizing has several problems. Installation costs are higher for starters, but over the lifespan of the system, you will have wasted more money on running, efficiency and breakdown costs than a system that was initially sized properly. Take a vehicle for example, you go buy a used car and the salesman tells you, “this car here runs great, its got 100,000 “highway miles” on it!” What does he mean by “highway miles”? If I had to put it into one word, EFFICIENCY. Highway miles are much much easier on a car and engine than those dreaded stop and go city miles. It allows everything to run at a steady temperature and RPM for all moving parts. It allows the engine to get into a steady state comfort zone where everything is running like a well oiled machine. Those stop and go miles add loads of stress to an engine, from operating temps to the constant fluctuation of engine and part speeds causing inefficiency, more fuel and more potential breakdowns. The same goes for your heating system, an oversized heating system costs more to install, more to run and most importantly, more in the long haul. So again, I dare you to take a look at that rating plate, but don’t be shocked at what you find.
Have a smart phone? Try out the Slant-Fin heat loss calculator, this will give you an excellent look into what your house really needs and the next time you need to replace your boiler, please make sure it’s not oversized……..
*Please note, system sizing to the proper heat loss only works for hot water and hot air systems. Steam systems MUST be sized by the connected load and not the heat loss of the home*