Tankless WH errors out in winter

Old 12-09-09, 08:06 PM
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Join Date: Dec 2004
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Unhappy Tankless WH errors out in winter

We have a Bosch Aquastar AQ 250 S tankless water heater (propane gas) that was installed when our house was built 4 years ago. We love it, except for the amount of water that is wasted waiting for it to get hot at each location in the house (2 baths, laundry, kitchen - 1700 sf house).

Each winter (about 3 months long here in Texas) we start to see error codes (several different ones, but mostly "EC") and we have a lot of difficulty getting a shower started in the morning. If it's really cold outside it can take half an hour and several trips to the water heater to reset it. My husband will tire of it and finally attempt to get in touch with Bosch which often takes several days. He will tweak it here and there as requested by Bosch, then they will finally send a part out that my husband replaces. Things seem a little better for a little while, then all goes bad again. Before we know it, spring is here and we no longer have the problem.

To get hot water in the shower we have always started by turning on the sink (full hot) and when it gets hot, turning on the shower then turning off the sink. Then we adjust the shower with the cold water.

Our home is about 400 feet from the road where our water line meets up with the community water supply.

Wondering if anyone else has had trouble with error codes in the winter and if there is any advice anyone could lend. Thanks.
Old 12-10-09, 02:32 PM
Join Date: Dec 2008
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EC error code 9X out of 10 is insufficient gas to the unit.
Chances are and more often to show up in winter when inlet water temps are coldest, thus needing more gas.

Verify supply, pressure, pipe, valve and connections, pressure drop....................

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