SDHW heat dump?

CC.Rob_7

Good point about the cooling load. Fortunately, we don't have A/C so there is no load to increase. If we leave the dehumidifier on for several hours, it actually warms the basement just by itself. Doesn't have a noticeable effect on the living space above. (Basement is unfinished. It's the boiler room, laundry, and tool/junk storage.)

In terms of dump capacity, you've got me thinking. Some quick numbers.

The max output of the system on a clear summer day is around 60000 BTU/day.

10 ft of MP-80 puts out about 4500-6100 BTU/hr with supply temps of 140-160F. Figure a max of 6 hr/day at these high temps and the total dump capacity is around 27-37k BTU. Or about half the total potential system output. Seem reasonable?

Now to figure out what the space temp will do with that input....

Thanks.

CC.Rob_4

thoughts on this?

One of our local solar installers offers as an option to his standard closed loop SDHW system a ~10ft section of Slantfin MP-80 baseboard as a heat dump / dehumidification loop. It's run off a 3-way thermostatic valve that opens once the 119gal Superstor gets to about 150-160F.

Idea being that the baseboard serves in part as a heat dump during periods of high tank temps and light DHW loads, and also (because it's in the basement) helps to reduce humidity.

Our basement does not get truly damp, but does need periodic dehumidification. This might alleviate or eliminate the need for the dehumidifier.

Any thoughts on this would be most appreciated.

Thanks.

bill nye_3

heat dump

Well, just forget about the dehumidifier for a minute and think about it this way. The water heater demand is satisfied, so, a normal water heater would just shut off. But you can't shut the sun off. You have to get rid of the heated water [or glycol]

If you don't waste it to the basement, you could waste it to the outdoors. Or get a bigger storage tank? If I was cooling the house I don't think I would want to increase the cooling load.

But on the other hand, dehumidifiers consume a lot of electricity.

Sorry I didn't answer your question. Good question.

scott337

StorageTank

Your installaer seems on track, however, were you quoted a dual coil tank or a singl coil tank that will work in conjunction with your exisiting DHW tank (indirect, electric, etc.)
The reason I ask is, if you have the "extra" tank, you most likely will fill the first solar tank, then begin heatingthe second tank and receive no "excess" dhw. meaning your baseboard humidifier will only be a decoration in your basement-thankfully he is installing Slant Fin 80 so your decoration will not be a rusting eyesore like other baseboards
What are the tanks you have now?
If 40 gal or 80 gal combined with a 80 or 115 gal solar tank, you will have "excess" storage capacity. However,IF youhave a thankless coil, hiw option may be suitable for the application.

CC.Rob_7

specs

This is the straight single coil superstor SSU-119 for the solar. It has two means to supply DHW:

1) preheat to existing 40gal indirect. Domestic cold feed goes into SSU-119. SSU-119 hot out goes to cold input on existing indirect. Hot output of indirect goes to taps (already have a Sparco/Honeywell anti-scald on the indirect output).

2) for summer, there is a 3-way manual bypass that allows the SSU-119 to go directly to taps (through anti-scald valve).

The latter option would be when the heat dump is most likely to be used. Around here, that would be approximately early May to mid-September. This mode of operation sounds like it addresses what you're concerned about. Am I reading things right?

Thanks.