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Luke warm shower this morning.
Every 2 weeks we have my mother in law stay with us and at about 5am we will have 2 showers for about 10 minutes, then at 5:30am another single shower. This morning was the first day we had this many showers for this visit, while heating the house, and the water wasn't hot. Last Feb and Mar we were able to repeat this, but we had hot water for both showers. I had the later shower and right after I got out and got dressed, I went to the boiler and it showed Domestic and Central were both ON. I had the boiler annually cleaned about a month ago and I'm wondering if any settings or anything was changed. We have a Burnahm Alpine ALP105 and a Taco SR503-4. The Taco has 3 central heating zones. We have a 40gal Ultra Storage tank. When I get home tonight I can get some drawings for how the Taco and Boiler are wired, but as I recall, each of the 3 zones are directly wired to its own thermostat. The Isolated End Switch terminals have wires, but I haven't confirmed where they land on the boiler.