Quote:
Originally Posted by Hakkaboy
When I use hot water during the pump schedule, it comes on almost in the same time as regular hot water tank. When it is outside the schedule, it will be slower and noticeably so. It is even slower than units without a re-circulation feature. Sometimes, it does not even come on at all. I think this is due to some of my faucets being "green", so it does not meet the minimum flow rate for turning on the tankless unit
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Check the settings.
Factory minimum flow rate to ignite/fire up a Rinnai (and more tankless water heaters) is around 0.4 Gallon/minute for temperature of 120F or lower. As your Rinnai is set up with the water-to-air heat exchange for your air handler/heating system, the temperature setting will be turned up to 140F to properly heat the home which, by default will change the minimum flow rate required to fire up to around 1.0 gallon/minute (as a safety feature). I suspect the installer didn't change the minimum flow rate back to 0.4 gallon/minute.
Quote:
Originally Posted by Hakkaboy
As for efficiency, I can not speak to it as we installed it before moving in. From looking at my hydro bill, it does seem lower than "comparable homes nearby", but unfortunately it does not list the historical records of the previous owner. I'm not sure if the efficiency will ever justify an extra ~$5K of costs amortized over a 15 year period, so I wouldn't do it for only that reason. My unit has a warranty for 15 years and expected life up to 20, I think. My costs also include some repairs and additional plumbing to our stupid tiny air handler that uses hot water to heat the coils, so your installed cost will probably be less.
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Not only is the upfront cost around triple of a traditional hot water tank replacement, you have to factor in the yearly servicing recommended by the manufacturer. That's easily $300/year! It's impossible for a homeowner to save that much in natural gas.
FYI that 15 year warranty probably only covers the heat exchanger.