Hi, I am building a custom home. I need advice on recirculating hot water pump set-up. I have a gas on-demand hot water heater and I want to install a solar tube roof mounted hot water system in conjunction with it. I need a tank with a heat exchanger and the pump will sense when the gas unit kicks on in the event the sun doesn’t shine. Has anyone got advice on pros and cons of this set-up?
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Need more info to give a good answer. I would use the solar as a pre heater for the hot on demand. The controls for the solar would be independent of the (on-demand) for the most part.
You may be defeating the purpose of the on-demand?
re-circulated on demand? Maybe? sounds expensive!
Edited 10/19/2006 8:24 pm ET by VAVince
Most of my plumbing is very close to the Rennai gas fired on-demand hot water unit. However the kitchen is quite a distance away. Since we planned a recirculation pump we plumbed for it under the slab. My plummer said that we need a tank for the system to work but that the on-demad gas unit will keep tripping on to keep the temperature at a constant level. We have a good situation for solar and I need a tank anyway so I thought why not keep the water at temperature with the solar collector. On cloudy days the gas will kick in. We need the recirculation because we have need to conserve our well water. We can't let it run for the time it takes to warm -up. I guess we could scrap the gas heater and go to electric but I really like the gas on demand heater if I can figure out how to work this combination. Any thoughts??
How about a recirc pump with a remote timer switch. A push of the button runs the pump for a minute, bringing hot water to the end of the loop. It would be simple to wire in a 24V time delay relay (look at grainger.com you need one that is a "single shot", off delay, meaning that you close a momentary switch, the relay energizes for 1 minute, then resets). You would have to wait a few seconds for hot water, but it would save a lot of energy not keeping a system hot all day and night.I have been thinking about solar tubes as well and a way to get the solar hot water to the circulate and keep the system "hot". Haven't figured it out either.