Efficient hot water delivery for group lodging?
While most advice on Green Building Advisor focuses on the case of the single-family home, I'm hoping for some guidance about making hot water for a group lodging:
48 beds, common bathrooms with 8 showers and 12 sinks total.
We have propane service, typically somewhere between $1.50-2.50/gal.
Electricity just crept up again to 19 cents/kwh.
Lodging is unoccupied most of July (summer camp), and for the rest of the year varies between groups staying for just 2 days a week and groups that stay for 7 days.
The lodging in question is located at a camp/retreat center in eastern San Diego County, California. It's about 30 years old and was designed with a south-facing roof to accommodate solar. For many years the hot water needs were served by a 5 collector open-loop solar hot water system with 240 gallons of storage and a 100 gallon gas heater for backup. We're at over 4000 feet and last winter during an extremely cold week, the circulation system failed/was overwhelmed and the collectors were ruined. Basically, the entire hot water system needs to be replaced as the gas heater is also failing. Interestingly, since the freeze, we've only had the aging 100 gallon LP hwh servicing the building and it's met the demands of the guests with almost no complaints of hot water shortage.
In various other (newer) buildings we have either a pumped closed loop glycol system or a passive, roof-mounted integrated thermosiphon system feeding a propane on-demand heater. This makes sense in a lot of ways, since many weeks the lodges are only occupied 2-3 days out of 7, and when there is demand it's typically high since it's multiple showers running at once.
On the other hand, particularly in the case of the roof-mounted thermosiphon tank, it doesn't make sense to me to store solar hot water overnight on the roof when the majority is used first thing in the morning. The company we've worked with in the past is pushing for two new thermosiphon units with a LP tank backup.
I'm open to exploring all options here. For less the install price of solar, we could install a high-efficiency condensing hwh that would meet all our demands. I'm wary of the solar installer's advice since I get the feeling they push the thermosiphon units in almost all situations and totally dismissed me when I inquired about installing a drainback system utilizing a storage tank in our heated mechanical room with: "yeah, well, those sound all fancy and high-tech but they'll freeze on you."
Any help navigating this situation would be greatly appreciated. If I can provide additional helpful information, please let me know. Efficiency and conservation are an important part of the camp's mission and program.
Thanks for your expertise.
Posted Wed, 10/30/2013 - 13:46
Edited Wed, 10/30/2013 - 13:46
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