You do need a releif valve so that if the heating does not stop and the water expands it can expand through the releif valve letting you know that the unit is malfunctioning.
Tankless water heater expansion tank.
For the hybrid series data is based on the tankless water heater unit attached to the storage tank.
The water expands as it heats and on a tank you are raising the temp of water trapped in the tank because the water continues to heat after the tap is closed but on a tankless the heating stops as the tap is closed or its suppoesd too so you do not need an expansion tank on a tankless.
The risk of pressure damage along with your tankless water heater is very common.
Since water expands when it is heated due to thermal expansion the water heater creates extra water volume every time it heats water.
Most tankless water heaters electric or gas do not need a thermal expansion tank.
Plumbing difficulties may happen at any time and any date.
Likewise if your home runs on an open water supply system where excess water goes back into the municipal water supply it won t place any strain on your home s plumbing system.
What does an expansion tank do.
If you have a tankless water heater you don t have to worry about an expansion tank because you don t have a primary tank to begin with.
If you are suffering from any type of thermal expansion in your home then the best option is to get the help of a water heater expansion tank.
Proper venting gas and propane heaters emit carbon monoxide which must be vented outside.
The water heater expansion tank serves as an overflow receptacle by absorbing excess water volume that occurs when water is heated as well as absorbing fluctuations in the incoming water supply pressure.
Location in the case of gas or propane heaters the location for your heater may be restricted.
This may also expand the risks of the plumbing configuration.
Your guide to energy efficient products.
On a tank type heater it will be working in a static environment and needs to escape either in an expansion tank or back up the cold water service or blowing out your plumbing.
The reason being is that a tankless water heater only produces hot water as requested.
These restrictions are meant to reduce the risk of co poisoning.
When the hot water supply is opened the tankless unit starts to produce hot water.
However if you have a traditional tank style water heater you will most definitely need to consider if an expansion tank is needed.
Expanding hot water needs to have somewhere to go.
Expansion tanks are required if your system fails a water pressure psi test.
But the tankless heater isn t on unless the water is flowing so no issue there.