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Cold Water Sandwich Effect in Tankless Water Heater
Cold water sandwich effect comes with instantaneous / tankless gas water heater
Cold water sandwich effect comes with tankless gas water heater. It feels like a sudden drop of the hot water temperature for a few seconds.
No tank means no stored hot water. Every time we open a hot water tap, cold water starts going through the tankless water heater. While the other name for tankless is instantaneous, it may take up to 10 seconds for the water heater to fire up and start heating water. Until then cold water keeps going through to the hot water tap. Finally, hot water arrives, but turn it off and the water heater immediately shuts off.
The next time we open hot water, the cycle has to start from the very beginning. Small amount of cold water again will make it to the hot water tap. That's why it's called "Cold Water Sandwich Effect".
No tank means no stored hot water. Every time we open a hot water tap, cold water starts going through the tankless water heater. While the other name for tankless is instantaneous, it may take up to 10 seconds for the water heater to fire up and start heating water. Until then cold water keeps going through to the hot water tap. Finally, hot water arrives, but turn it off and the water heater immediately shuts off.
The next time we open hot water, the cycle has to start from the very beginning. Small amount of cold water again will make it to the hot water tap. That's why it's called "Cold Water Sandwich Effect".
It's impossible to completely remove "cold sandwich effect", but methods to mute it do exist.
Rinnai tankless water heater for example does not go off when hot water stops. It stays completely ready for another 60 seconds. Just in case if we turn hot water back on. Also, heat accumulated in water piping softens "Cold Water Sandwich Effect".
From our experience, we don't get many complains on the "sandwich". The reason for that is that the effect does not appear at all during steady use of water, like shower or dishes washing. Pattern of use where hot water being turned on / off multiple times does not happen too often.
Rinnai tankless water heater for example does not go off when hot water stops. It stays completely ready for another 60 seconds. Just in case if we turn hot water back on. Also, heat accumulated in water piping softens "Cold Water Sandwich Effect".
From our experience, we don't get many complains on the "sandwich". The reason for that is that the effect does not appear at all during steady use of water, like shower or dishes washing. Pattern of use where hot water being turned on / off multiple times does not happen too often.
