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Community and Q&A

Intergrating cooling tower loop into a hot water supply sytem.

erik66 | Posted in Mechanicals on

I’ve been looking for a good way to reclaim the heat produced by my refrigeration equipment and use it in my domestic hot water production.

Currently I have a tank less heater (Navien) that provides heat to my restaurant through a radiant floor and hot water to two bathrooms, a few bar/kitchen prep sinks and a dishwasher. I also have air cooled refrigeration equipment that has been retrofitted with water jackets which reject their heat to a cooling tower. I put the system together hoping to at some point add piping that could reclaim heat from the cooling tower loop. Unfortunately, the demands of the kitchen activity and the lack of a storage tank, have led to a host of other problems. I’ve had a boiler failure and inconsistent hot water supply to the dishwasher. The dishwasher is about 30 linear piping feet away from the boiler.

My first thought was to add a recirculating system and a storage tank and that the storage tank would have a heat exchanger in the lower half of the tank. Here are my concerns:

1. Is the return temperature of the cooling tower loop (I have no real data on this but think return temperature is around 100 deg F) high enough to transfer heat in the storage tank. What if the storage tank temperature at the bottom of the tank is greater than the return temperature of the cooling tower loop.
2. What size tank do I need and where should it be placed. My thinking is that it should be near the dishwasher. The dishwasher is a low-temp unit (140 deg F) that uses less than two gallons per cycle. Cycles are about 90 seconds. I doubt we use the dishwasher more than 5 cycles in a row. Usually, it runs every five minutes at its peak. Is a 20 gallon tank enough to keep the boiler from short cycling?
3. I need a recirculating loop to provide instantaneous hot water at all the bar and kitchen equipment.

Anybody have a diagram of a system like this? Tank you

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  1. GBA Editor
    Martin Holladay | | #1

    GBA focuses on residential construction, not commercial construction, so I doubt if this is the best place to get advice on your refrigeration loop and cooling tower.

    Mechanical engineers are wonderful people. You need to hire one.

    -- Martin Holladay

  2. SwitchgrassFarmer | | #2

    This is the kind of question that John Siegenthaler would excel at diving into.

    BTW, where are you located?

    (If you happen to be near NYC or central PA I could also give you the name of local commercial mechanical engineers who have worked for me and that I know can think out of the box.)

  3. erik66 | | #3

    Martin and Andrew,

    Thanks for your responses. I realize this is commercial, but I'm a small mom and pop operation and since I'm looking for a solution to saving water and reclaiming heat, I thought this would be a good Green Building question. I actually got my BME from Georgia Tech eons ago, but never got a chance to practice. It did come in handy when I rebuilt the Navien combustion chamber. The head gasket blew from the constant cycling and is now a much more bullet proof unit.

    I wish I had known about Siggy's design tool when I first put together the system. I think I will reach out to him. Again, I'm a small restaurant trying to make my little plant as efficient as possible and just don't have a huge budget. The small restaurant industry here wastes a lot of energy and could use a forum similar to this to provide solutions.

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