Electric Shower Water Heater

[thaisail]

I spent all of my money building this house and now I am short of funds needed to buy the solar water heater. I did however complete the entire network of green PP-R piping to the new bathtub and the shower in the house. We installed the 3.5 Kw on demand electric water heater in the garage bathroom where we lived during the house construction so we can still take hot showers but we have to go to the garage which is a minor inconvenience. But I just got a brilliant idea. Why can't I Tee into the hot water outlet from the electric water heater and use a hose to connect it to the hot water piping network which runs around the house to the kitchen sink and then around the corner to the house to the bathroom using the PP-R pipe that feeds the bathtub and the hot water pipe to the shower? All I would have to do is make sure that the cold water inlet valve to the hot water heater in the garage was open and then close off the water to the to the shower head in the garage. As soon as the hot water piping system would be pressurized with hot water, there would be hot water on demand to the entire house! 

 

My concern with this idea is that these on demand water heaters in Thailand are normally not under pressure. So that under normal circumstances, when you finish your shower, you normally turn off the cold water valve that supplies water to the shower and the heater stops on the safety flow switch. I wonder first if operating the system pressurized, would the safety flow switch turn off the power to the heater when the water is no longer flowing? If the safety flow switch operates as it should while the system is pressurized when the hose is connected to the hot water system in the house, theoretically, as soon as the hot water is supplied to the other bathroom, the heater should come on and heat the water and eventually hot water would arrive through the long pipe and no need to go the garage to get a hot shower! I just don't know if these type of heater are built for this kind of abuse. Of course when funds are available, I will fit the solar water heater but at 15,000 baht it may take some time to be able to place the order. I really don't have enough electrical capacity to run another electric electric heater as my meter is a 15 (45) meter and I am already running to much load with the 5 air conditioners to be able to add a second electric water heater in the house bathroom. 

 

Will this blow up my 3.5 Kw water heater if using it under constant pressure?

[sezze]

A normal water heater cannot be used as a multipoint 1 , as far as i know .

Multipoint water heaters use a flow detector to put the power on/off . A standard water heater got a pressure switch instead .

I got a gas water heater multipoint , , but it works the same ( only uses no electric but gas ) , there has been a topic of it before .

[thaisail]

2 minutes ago, sezze said:

A normal water heater cannot be used as a multipoint 1 , as far as i know .

Multipoint water heaters use a flow detector to put the power on/off . A standard water heater got a pressure switch instead .

I got a gas water heater multipoint , , but it works the same ( only uses no electric but gas ) , there has been a topic of it before .

So if the safety switch operates on pressure and not flow, my idea will not work. Too bad!

[sometimewoodworker]

1 hour ago, sezze said:

A normal water heater cannot be used as a multipoint 1 , as far as i know .

Multipoint water heaters use a flow detector to put the power on/off . A standard water heater got a pressure switch instead .

The normal function of a shower heater has different ways of turning the power off. Mine cut the water and power on the unit, some hotels I’ve been in have a flow detector to switch the power.

2 hours ago, thaisail said:

All I would have to do is make sure that the cold water inlet valve to the hot water heater in the garage was open and then close off the water to the to the shower head in the garage. As soon as the hot water piping system would be pressurized with hot water, there would be hot water on demand to the entire house! 

With some shower units you could do that but even if you could it’s going to take a lot of water to flow before you got heated water and I doubt that it would be more than slightly warm, your heater is too small.

[Crossy]

You can get a gas multi-point water heater for <2,000 Baht from Lazada which you could hook up to supply your house in place of the solar.

 

The couple I looked at are about 12kW equivalent, would be more than enough hot water.