[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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