[Greenbuilding] Commercial Water Heaters

Jessica pipeworks100 at gmail.com
Tue Jul 17 10:40:40 CDT 2012


Volume storage could allow you to cascade around peak demand times, reduce
standby losses and make monitoring easy.

On Tue, Jul 17, 2012 at 11:32 AM, Paul Eldridge <
paul.eldridge at ns.sympatico.ca> wrote:

> Hi Peter,
>
> It's hard for me to provide you with a proper answer; data loggers would
> certainly help us to determine this more accurately.
>
> I can confirm that the heating system is natural gas, that there are no
> supplemental baseboard strips or in-duct re-heats, and that the average
> monthly peak is 318 kW.  Unfortunately, I don't know the seasonal
> variation, so I can't properly account for the air conditioning load.
>  FWIW, we had pegged the original lighting load at 87.5 kW, so lighting,
> pre-retrofit, would account for just over one-quarter of the building's
> average electrical demand.
>
> As previously noted, the two 36.0 kW tanks are ganged together, so there's
> a high probability that their operation will overlap at some point during
> the monthly billing cycle.  If I were to guess, coincident peak most likely
> occurs somewhere around the mid-day mark, and this would be presumably a
> period of higher hot water demand due to heavier use of the wash rooms and
> staff kitchens.  The other two satellite tanks serve kitchens as well, so
> it's not unreasonable to expect that they too would fire-up around the
> mid-day peak.
>
> Cheers,
> Paul
>
>
> |great example of re-commissioning. that said, is the building
> |electrically heated, and with that low a hot water demand, are they
> |likely to see that reduction in coincident demand?
>
>  /  My firm just wrapped up a lighting retrofit at a local municipal
>>
> />/  building where, as best as I can tell, there are four high capacity
> />/  electric water heaters.  The two shown in this first picture
> />/  (http://i362.photobucket.com/**albums/oo69/HereinHalifax/Img_**
> 1547.jpg<http://i362.photobucket.com/albums/oo69/HereinHalifax/Img_1547.jpg>
> )
> />/  each draw 36.0 kW and the remaining two (one of which is shown here:
> />/  http://i362.photobucket.com/**albums/oo69/HereinHalifax/Img_**
> 1550.jpg<http://i362.photobucket.com/albums/oo69/HereinHalifax/Img_1550.jpg>
> )
> />/  are rated at 18.0 kW. Thus, the combined load of these four tanks is
> />/  108.0 kW.
> />/
> />/  These tanks are used almost exclusively for hand washing purposes, and
> />/  so we will be disconnecting all three top elements in the two 36.0 kW
> />/  tanks, as well as two of the three bottom elements, effectively
> />/  de-rating each tank to 6.0 kW.  As you can see in the first
> />/  photograph, the two tanks feed a common supply, and 12.0 kW combined
> />/  with almost 1,000 litres of storage capacity is more than sufficient
> />/  to meet all of their requirements.  The two remaining tanks likewise
> />/  serve mostly hand washing needs and will be de-rated to 6.0 kW as
> />/  well; with that, the total connected load falls to 24.0 kW, for a net
> />/  savings of 84.0 kW.
> />/
> />/  In terms of cost savings, an 84.0 kW reduction in coincident demand
> />/  will reduce our client's demand charges by $9,350.21 a year, i.e.,
> />/  84.0 kW x $9.276 per kW, per month x 12 months/year. It will also
> />/  shift some 16,800 kWh of energy each month to Nova Scotia Power's
> />/  lower cost second tier, for an additional savings of $5,842.37 a year,
> />/  i.e., 84.0 kW x 200 kWh/month, per kW x ($0.09904 - $0.07006 per kWh)
> />/  x 12 months/year.  Taken together, this represents a savings of over
> />/  $15,000.00 a year, at current rates, achievable with no discernible
> />/  loss in water heater performance.
> />/
> />/  By simply reducing the power draw of these tanks, we will save our
> />/  client more money each year than by upgrading the facility's entire
> />/  lighting system, and will have done so at effectively zero cost (their
> />/  lighting retrofit will reduce coincident demand by an estimated 37.7
> />/  kW, and de-rating their water heaters will more than triple that).
> />/  Five to ten minutes is all that's required to remove the jumper wires
> />/  that connect the terminal block to each corresponding heating element.
> />/
> />/  We've de-rated dozens of similarly oversized water heaters over the
> />/  years and in many cases implemented timer controls to lock-out their
> />/  operation during normal business hours, thereby reducing the
> />/  customer's peak demand even further; thankfully, there have been no
> />/  complaints of hot water run-out to date, and so the results have
> />/  proven more than satisfactory.  This particular building initially
> />/  served as a police station, and so these water heaters originally feed
> />/  a bank of showers; the building was subsequently converted to general
> />/  offices and, consequently, their DHW usage is vastly lower.
> />/
> />/  The other thing we like to do is run the circulator pumps on
> />/  multi-program timers so that they operate only as required.  For
> />/  example, we may run a circulator pump a couple hours at the start of
> />/  each weekday morning, shut it off, then turn it back on for an hour or
> />/  so mid-day and perhaps another hour later in the day.  In most cases,
> />/  we can limit the operation of a pump to twenty or twenty-five hours a
> />/  week, as opposed to one hundred and sixty-eight; after all, there's
> />/  really no need to push hot water through an extensive network of pipes
> />/  at 02h00 or 03h00 in the morning (with all the inherent losses), when
> />/  the last person had left the building eight hours prior.
> />/
> />/  BTW, you can view one of the rooms that we had upgraded at:
> />/  http://i362.photobucket.com/**albums/oo69/HereinHalifax/Img_**
> 1546.jpg<http://i362.photobucket.com/albums/oo69/HereinHalifax/Img_1546.jpg>.
>  />/  Here, we replaced 3-lamp F34T12 prismatic troffers that consumed
> />/  130-watts each with 2-lamp 28-watt 850 series T8 troffers that draw
> />/  just 42-watts, for a two-thirds reduction in demand. Amazingly, light
> />/  levels in this area increased two and a half to three fold
> />/  (originally, 14 to 17 foot candles, now 43 to 46 foot candles).  Far
> />/  more light and much better light quality, with fewer watts to boot.
> />/
> />/  Cheers,
> />/  Paul
> />
>
>
> --
>
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-- 

Jessica Baldwin
917-207-2403
Solar Plumbing Design <http://www.solarplumbingdesign.com>
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