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Hot Water Volume Advise...

Hello, I'm bidding a job that's a little out of my comfort zone, and I was hoping to get a little advise.

Thanks in advance for your help!

I'm looking for advise on how to get a larger volume of hot water at a ski resort, without using any more gas. (due to cost of resizing gas mains) I'm contenplating using a couple hybrid heaters, recirc pumps, and maybe a storage tank or electric storage heater.

Specifically I'm hoping for find suggestions for piping diagrams, websites or books to teach my self about water heating ideas beyond just putting a heater in and maybe adding a recirc pump. Or if you guys have any suggestions I haven't thought of, that would be great too!

Here are some details about the job I'm bidding:

It's a ski resort that's always run out of hot water since it was built. They have 2 existing State 75 gallon, 75,000 BTU water heaters. They've had them turned up to 160 degrees all this time, and still run out of hot water frequently.

But they got a customer complaint about scolding hot water in the bath lavi's, so now they want to fix it.

And they don't want to upsize the LP gas supply because of the cost invloved.

They have good water pressure and volume through out the system. (aprox 50 PSI, I eyballed it)

There incoming water in winter is 40 degrees. I need to raise it to 110 degrees. (70 degree temp rise) No dishwasher requiring 180 degrees.

I counted up 28 hot water fixture units. I can't find anything in my code book, but found information online saying I need to suppy 7 GPM to feed 28 F.U.'s. Which seems a little low to me???

I'm contenplating putting in 2 Eternal Hybrid Water Heaters. Which at a 70 degree temp rise will give me 11 GPM.

Then piping a recirc. system into the first heater and out to the far end of the hot supply to minimize wait time, and hot water use, at fixtures. (1-1/2" copper water mains aprox 100' long) And then insulating the water mains to minmize heat loss, and water use further.

Then because I'm a little worried about keeping up with demand during high use times, I'm debating on putting in a storage tank or electric storage water heater hooked to a second recirc pump on the second hybrid water heater to make up another 10 GPM or so if ever needed???

But I've been unable to find any resources to teach me how to do the proper calculations, or give me ideas on better ways to plum it. Or guidence on weather or not the storage tank is over kill? So I was hoping to get your guys input on my ideas, as well as any suggetions for resources I can get to teach myself about these kinds of more complex water heating systems.

Any input you might have is appreciated!

Matt @ Bluewater Plumbing...


  • SWEI
    SWEI Member Posts: 7,356
    load profile?

    How much hot water is needed per day, and over what peak period?  That will determine tank sizing.  You want to store at 140F (possibly higher, depends on that demand number again) and mix down for distribution.

    Higher thermal efficiency will pay off big-time on LPG - the Eternal is a condensing unit which will help a lot.
  • Zman
    Zman Member Posts: 7,573
    Modern hydronic heating

    Modern hydronic heating is an excellent book and is available on this sit. It is worth every cent.

    As for your project.. What type of facility is it? Public restrooms or condos? What are your specifics propane limitations? What other loads do you have?

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tim smith
    tim smith Member Posts: 2,765
    Re: hot water supply for ski resort

    I don't know how you could use Eternal's with limited gas supply. One Eternal uses more gas than those 2 water heaters.  I would probably recommend you use  a very reliable albeit less efficient little boiler.  AO Smith HW200 and a 200 gallon storage tank.  Other option is use a single Eternal 199  tied to storage tank with cold feed direct to Eternal and then recirc to tank to create circulation.  My only draw back to Eternal is the parts availability and reliabiltiy?  The 200 gallons will give you a great buffer and they last 20+ years.  The HW boiler lasts 20+ also with minor maintenance but yes less efficient?
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