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Old 07-09-2012, 05:16 PM   #1
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Tankless hot water heater during winter when water shut off

I know this post is seasonally inapporpriate, but if I don't ask it now I'll forget and it will be winter already...

We have a vacation home near Lake Tahoe, CA, and would like to turn the water off during long periods of our absence over the winter to save on heating. We have a Rinnai R85 tankless water heater. We also have a water system that automatically drains when the water main is shut off and a faucet valve opened. My questions are as follows:

1. When the water main is turned off for an extended period, should the gas and electric to the water heater also be shut off?
1a. If the gas and electric should be shut off under the above circumstances, what if the water is just being shut off for a short time (a few hours)?
2. To prevent any damage to the water heater from water freezing, do we need to drain the water heater in any way other than opening a hot-water faucet upstairs?
3. Is it foolish to turn the heat completely off over the winter even with the water shut off?
4. Is there any other information that I should consider in determining whether to turn the water off (and heat down or off) in the winter when we will not be there for weeks at a time?



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Old 07-09-2012, 09:19 PM   #2
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Page #37 explains what you want


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Old 07-09-2012, 11:12 PM   #3
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Thanks for the reference, but I read that before posting, and I still had these questions.

The manual says: "If the Rinnai water heater is disconnected from either the electrical supply or gas supply, or if there is an error that prevents the water heater from functioning normally, there is NO FREEZE PROTECTION. Freeze protection of the water heater is only possible when electricity, gas supply and normal water heater functions are enabled. If you expect freezing conditions while either electricity or gas supply is interrupted, water must be completely drained from water heater..."

I still don't know whether the gas and electric MUST be turned off if the water is turned off. Is leaving the gas and electric on if the water is off bad for the heater? Is that what they mean by "normal water heater functions are enabled"?

It also doesn't say whether the type of draining system on the house is enough of a "complete drain" to protect the water heater if the gas and electric are turned off.

Any further guidance? Thx.
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Old 07-10-2012, 12:50 AM   #4
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very interesting discussion

Last edited by oh'mike; 07-10-2012 at 06:25 AM. Reason: removed links--read posting rules for pros
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