Hot water doesn't stay on - Triangle Tube Instinct Combi FSB 199

mroger

I had the TT Instinct Combi installed and can't get the hot water to stay hot if I turn the water off and on for short bursts (e.g., while doing dishes and rinsing items). It takes about 45 seconds to get medium hot in the first place (to be expected) then another minute to get really hot (a pain if I need really hot water to wash greasy items) but then stays really hot for about 3 minutes and after that - if I've been turning water off and on to rinse items - starts to get cool and then ice cold until it starts the warm-up cycle again. I only have one sink and no dishwasher. I don't want to keep the hot water running for no reason just to maintain the hot water stream. Instead, I seem to be sending an awful lot of water down the drain either waiting to get and keep the hot water. Anyone else experienced this?

EdTheHeaterMan

How good is your water pressure? Are you on city water or well water? There is a flow meter/control that will activate the burners based on how much water is traveling past that control. If there is a blockage in a filter or strainer, that is causing the flow to be below the minimum needed to activate the gas valve, then that may be your problem.

If you have a well pump and your water pressure fluctuates as the pump turns on and turns off then that could also be a problem. You might need to have the pressure switch and well-X-trol tank pressure adjusted so your pump does not cycle the whole time your kitchen water faucet is open. Ignore this if you are connected to a city water utility

GGross

" I don't want to keep the hot water running for no reason just to maintain the hot water stream." Unfortunately this is a design requirement of a combi or tankless water heater. The unit detects flow from a fixture, then the unit fires up, then heat transfer begins, and finally you get a steady stream of hot water. If you turn the fixture off the process ends, which means you will be getting a cold water sandwich at some point since there will be 30 seconds to 1 minute of flow that is not being heated while the unit fires back up once the fixture is opened again.

You could have a plumber take a look at the possibility of a recirc line, maybe add a push button or timer control for it at the kitchen sink, this may allow for the water to recirculate while you turn off the fixture and keep the hot water line hot.

Personally I ditched my tankless and went back to a tank