Prioritizing solar hot water load

[bernard]

Hi,
I have been puzzled with something I could not find in the theoretical books about solar hot water systems.

How does the SWH system prioritize between different hot water fixtures and its draws(loads)?
For example, if SWH system is used for heating the domestic hot water, and there in one bathtub, one shower, one kitchen sink, and two bathroom sinks. Does SWH system prioritize one of these sanitary objects when it comes to hot water draw? Is there some sort of switch which regulates this?


And what about the case when SWH system is used for both domestic hot water, and solar space heating? Is there again some sort of way (switch?) by which SWH system prioritizes between sanitary hot water objects and heating radiator ?

Thank you for the reply.

[J.P.M.]

Hi,
I have been puzzled with something I could not find in the theoretical books about solar hot water systems.

How does the SWH system prioritize between different hot water fixtures?
For example, if SWH system is used for heating the domestic hot water, and there in one bathtub, one shower, one kitchen sink, and two bathroom sinks. Does some SWH system prioritize one of these sanitary objects when it comes to hot water draw? Is there some sort of switch which regulates this?


And what about the case when SWH system is used for both domestic hot water, and solar space heating? Is there again some sort of switch which prioritizes between sanitary hot water objects and a heating radiator?

Thank you for the reply.

Short and likely answers in the order of your questions: It doesn't, no, not usually, and probably not.

As I suggested to you in prior posts: See Duffie & Beckman: Solar Engineering of Thermal Processes. Most all the answers to your current questions and those of your prior posts are in there. I could answer your questions but it would take longer for me to do properly than this format allows.

That text does a much better job and, given all your questions over the last few months, seems like something that could have saved you a lot of time by now. Check it out.

[Mike90250]

I use solar how water preheat in the summer, and in the winter, I have a exchange loop in my wood heater. So all seasons I feed my tankless water heater preheated water, and it saves fuel. The main hot water line feeds all appliances needing it (dishwasher, shower, sinks)

[peakbagger]

Nope. Solar hot water is dumb. You basically have two choices, evacuated tubes heat up smaller volumes of water to a hotter temperature and flat plates heat more volume to a lower temp. Few folks do space heating with SHW, the problem is when you need it most in the winter the solar resource is the worst. In the summer when you don't want heating you have plenty of heat.

I have a manual setup configured somewhat like Mike, during the spring summer and fall I flip two valves and run directly off my solar hot water storage tank, in the winter I use the SHW for preheat to a "hot water maker" which is basically a hot water tank with an internal coil that runs back to my oil boiler and my wood boiler. I normally run my wood boiler daily in the winter so I charge up the hot water maker and it lasts a long time if I am feeding it 110 deg F makeup from the solar hot water tank. Worst case is I can run my oil boiler. The SHW tank has an electric element so I could also heat it up with electric and since I usually have a credit due to net metering with my solar, it would effectively be "free" but I have never hooked it up.

[organic farmer]

I have a few different neighbors who are able to use Solar-Thermal to great advantage.

[bernard]

It seems I never thank you for your replies. I apologize for that.
Thank you: J.P.M., Mike90250 and peakbagger.