shower water question

[jim]

This question sounds a bit crazy to me but after all the years living in our home (since new in '98) I've decided to ask.

My wife and I live in a house with 2 gas hot water heaters (2 story house). We've noticed since we lived in the house that on milder days the hot water from the shower heads doesn't feel as hot as when the outside temperatures are colder. I don't think it's our imagination because we notice the position of the hot/cold water handle of the shower (it doesn't vary a lot but I think you can see a difference). This doesn't seem to be the case tho for the faucets else where in the house.... they always put out hot water when the hot water is turned on.

Do the shower heads or its plumbing have some kind of sensor for regulating how hot the water will come out based on surrounding temperatures? Seems overall to me to be a good feature if even I'm losing my marbles.

[William W. Plummer]

Just a SWAG, but with the good insulation we have these days, it could be that your waterheater just doesn't come on very often when the outside temp is higher. When it's cold out, it will cycle more often. So, on a warm day, you are likely to get in the shower after the heater has been languishing just above its trip point.

[Marilyn & Bob]

I have found this phenomena also. This is in no way deliberate. My guess is that it is caused by the fact that on cold days the cold water coming into the water heater is colder than it is on moderate days. This somehow affects the thermo/hydrodynamics of the system (the thermostat that turns on the flame is located at the bottom of a gas heater, close to where the cold water comes in) which in turn ends up with hotter water than normal at the top of the heater from where it exits to go to your shower. Anyone with a more knowledgeable thought?