Real-time energy load calculations, Part 1

BY MARK EATHERTON HYDRONIC HEATING AUTHORITY OVER THE YEARS, I've had the opportunity to spend many hours in working boiler rooms when the outside temperature is at or near "design conditions." On many of the older solid-fuel converted boilers, I've never seen the boilers running at full output capacity. They typically run for 15 minutes, then are off for 15 minutes, then back on, and so on and so

BY MARK EATHERTON
HYDRONIC HEATING AUTHORITY

OVER THE YEARS, I've had the opportunity to spend many hours in working boiler rooms when the outside temperature is at or near "design conditions." On many of the older solid-fuel converted boilers, I've never seen the boilers running at full output capacity. They typically run for 15 minutes, then are off for 15 minutes, then back on, and so on and so forth. Essentially, they end up firing for 50% of the hour, hence a 50% duty cycle.

This does not surprise me for these cast-iron behemoths. I understand that the dead men who designed these things took into consideration that the windows would probably be half open during design conditions, and that the homeowner really only wanted to stoke coal and haul ashes once a day. They intentionally oversized the heat source, in some cases by a factor of two. So, the question becomes, how do you do a proper job of sizing the replacement heater for one of these ancient beauties?

You could just clock the gas meter, presuming there is one, and determine the hourly firing capacity. That would most definitely keep the occupants warm, but it could also cause some problems with the physical plant because of short cycling during part-load situations.

You could do an equivalent developed radiation, or EDR, survey and match the boiler output to that load. That is, by the way, required for steam boiler replacements, but we are talking hot water heating systems here, so that option would also most definitely end up over-sizing the heat source, which, again, is not good for consumers.

Or, you could have a technician take meter readings on a regular basis to determine the amount of gas used during a given degree day exposure and extrapolate those numbers to the real needs of the building. This would require the technician to drop by the job on a regular basis in order to get as many useful data points as he can to fine tune your survey.

The tech would need to record gas and electrical consumption and have a device to record the outside exposure temperature. It would also be a good idea to record the operating temperature of the heat source if at all possible.

Man, that sounds like a lot of work just to size a boiler, doesn't it? Besides, what are the benefits to the contractor in downsizing the heat source? That would technically mean less money flowing into his bank account, so why would he want to do a proper job of sizing?

Fuel efficiency and lower maintenance costs for consumers. These features, if properly addressed, will get you more sales than you can shake a stick at. It will require a minor investment in monitoring equipment on your part, but it will give the consumers a higher degree of confidence in your capabilities, and it will allow you to give them a much better deal on the sizing of their heating system.

The bottom line to all this is that by properly sizing the heat source to the real demand factors, you will save consumers between 25% and 50% of their fuel bill. With the cost of energy rising as it is today, that's nothing to sneeze at.

If you set up the deal with consumers properly in the first place, they will sell your services for you. Remember that it costs anywhere from $50 to $100 per Yellow Pages customer for the privilege of advertising in that book. Also remember that word of mouth advertising is 90% more effective in selling your services than a full-page ad in the Yellow book. Now, if you give consumers a "Universal Gift Certificate" worth $50 for each referral they send you that turns into an actual job, you're money ahead and you're getting referrals that are almost certain to turn into real work.

By the way, the gift certificate is a crisp new $50 bill in an envelope with a Thank You note. But you probably didn't start to read this column so you could get a free course in Guerilla Marketing, did you? Consider it a side benefit. Back to the subject at hand.

For a minor investment of less than $ 500, any heating contractor can create his own real-time energy monitoring system, increase his professionalism and increase his profitability. Basically, the components needed to perform a proper "real time" audit are available from online suppliers and are installed using off-the-shelf components.

The system I use monitors runtime of the gas valve, the boiler supply water temperature, the boiler return water temperature, the outside air temperature and solar availability. That's five points of data that will result in a proper sizing of the heat source and will result in a substantial fuel savings that will come back to pay the customer season after season and will keep you busy doing efficiency upgrades.

Tune in next month as we continue our journey of monitoring firebreathing dragons in the basement. Until then, Happy Finely Tuned 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