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Energy Efficiency

Consider a similar example in the DHW industry.  Here again, planning to meet “peak potential demand” results in oversized systems and, once again, peak potential demand almost never actually occurs.  When energy efficiency consultancy firms like Energy Liberty Corporation actually measure hot water demand over a typical month, we find spikes and lulls in demand as would be anticipated; however, the peak demands that we actually measure are rarely more than 65% of the peak demand that DHW industry charts indicate as necessary by dwelling unit or occupant.

Consider a typical multi-residential DHW configuration of two 800MBTU 76% efficient boilers that share one 100 gallon storage tank.  Tenants complain of delivery deficiencies and upgrade becomes necessary.  The DHW industry representative would likely recommend two replacement boilers; each is 1,000MBTU and 85% efficient.  He also tells you that he can even save you some money by re-using the existing 100 gallon storage tank.  That will solve the hot water delivery issue and tenants will stop complaining; but, is the hot water problem actually solved?  The new system was expensive and energy consumption has increased.  The contractor cashed his check before the ink was dry and you just got your first, post upgrade, much higher than usual utility bill.

In actuality, one new boiler to replace the existing two boilers would be sufficient.  One 95% efficient 1,200MBTU mated to a 150 gallon, well insulated storage tank would effectively meet demand while decreasing stand by loss.  It would cost much less to purchase and install.  It would reduce energy consumption and costs while increase net operating income for the property owner.  Adding inexpensive faucet aerators to the boiler upgrade would reduce water consumption and water purchase costs as well.  Which solution would your DHW contractor recommend?

You really can’t blame the HVAC and DHW industry.  They set their standards based on meeting demand under worst case scenarios long before energy efficiency became a concern.  The American public came to them saying “I want my hotel to be cool even on the hottest days” and the contractors delivered.  Today, because energy has become increasingly more expensive, building owners and operators want mechanical appliances that will run the most efficiently and therefore cost the least to operate.  Unfortunately, most property owners and operators are still paying to operate legacy mechanical equipment that is oversized for their building’s true demand.  The cost of operating oversized equipment is significant and ongoing.

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