oil furnace and cool shower problem

Jim_47

If its an old faucet in the problem shower, how about measuring the flow when you open the hot water valve up?
Many tankless coils are rated from 3-5gpm. If your usage is above the capacity of the coil then there is a good reason that that shower is cold.

chan

cool showers

We have an oil furnace that runs our forced hot water heating system. Out hot water also comes from it. Our hot water runs off of a coil and the issue is that showers start out really nice and hot but then cools down in the first two minutes. You can adjust the temp warmer and it warms up for a minute or so and then cools off again. Eventually the knob tops out. After about 5 min the water turns lukewarm to warm. It seems especially bad in the early morrning around 5 AM when my wife showers. I shower around 6 AM and it usually is a little better. Everywhere else hot water is fine, if not too hot. I checked the shower faucet and it does not seen to be an anti scald issue. It's a pretty old faucet.

Help

lee_7

Do you have a second shower? If so, how is water in that shower? Could be a bad shower valve, could be a dirty coil in heater. This is more likely the problem. Makes enough hot water for sinks, but not enough for high flow shower.