How to stop making hot water with HPT water storage tank and energy kinetics boiler

caryfb

I have an Energy Kinetics 2000 boiler and HPT hot water storage tank at a vacation home. The hot water is made with the external heat exchanger on the EK 2000. When I am not there in cold weather (Long Island NY) I want to run the house heating system (55degrees)but see no reason to continually make hot water (with expensive oil). The storage tank has no off setting . The lowest water temperature setting on its thermostat is 120 degrees. I confirmed this with HPT directly. My thinking that the only way to stop making hot water is to disconnect one lead from the HPT thermostat to the EK 2000 “brains” so the the storage tank does not call for hot water. Any thoughts on this idea are greatly appreciated.

Steamhead

You could wire a switch into the tank thermostat circuit, and shut it off when you leave.

yellowdog

we do it all the time for second homes. break one leg of the wire going to the tank aquastat with a switch mounted right on the tank.

Roger

Thank you for your question, @caryfb , and for your good suggestions, @Steamhead and @yellowdog . For reference, I'll just add that the Energy Kinetics tank heated by the plate heat exchanger will typically use less than a gallon of oil per month in standby.
If there is a recirculation loop that is left operating to keep all the fixtures warm, the system would of course consume more energy.
Roger

yellowdog

@Roger can i play devils advocate for a minute? i fully buy into the efficiency of the system 2 platform, the reduced oil consumption speaks for itself, but can you show me the math on your above statement? even some of the best indirect water heaters (roughly 1/2° per hour of standby loss) i know of set at 120-140° are going to have to at least call for heat once a day while in standby with no hot water consumption. you are saying that a system 2 can satisfy the tank with 1/30th of a gallon of oil if it only calls to make domestic once a day? just seems like an awful short run time to satisfy a 40 gallon tank.

Brent H.

@yellowdog

I’ll give it a go…. Let’s assume a 40 gal tank.

40 gal x 8.34 lbs/gal = 333.6 lbs of water in the tank.

A BTU is defined as the energy needed to heat 1 gallon of water by 1 degree. If our 40 gallon tank loses 1/2 degree per hour that means we’ll lose 12 degrees in a day or 12 x 333.6 = 4000 BTUs per day to hold temperature. 4000 x 30 days = 120,000 BTUs/month to maintain water temperature.

Heating oil is 138,000 BTU/gallon. If we assume 85% efficiency then 138,000 x .85 = 117,000 BTUs which just about covers what we need to keep our water hot for a month.

yellowdog

i guess im more hung up on the run time. the above math means that the tank can satisfy itself with a 2 minute burn time? that seems a little short to me to make hot water. especially thru a plate exchanger.

ratio

Remember that per the OP it's only topping off the tank during extended unoccupied times, making up the difference between the cut in & cut out—not trying to reheat a tank that's being used. Personally, I'd see if I couldn't get an internet-enabled stat with an 'occupied' dry contact that could be used to disable the hot water (via a correctly-sized interposing relay, of course!), & then let the system know when I'm on the way.

But I tend towards complicated solutions.

STEVEusaPA

First of all, how big is the HPT storage tank?

hot_rod

The temperature around the tank will have some effect on the heatloss.
To get a low standby loss number from a insulated tank, some were tested in 80 degree rooms😏
There are formulas to calculate tank loss, like anything else.

Seems a $10 switch is the simplest solution?