Electronic – Pressure switch and wattage temperature control of water heater

heater

I need this last data to help decide what to do with it. Note for Multipoint heaters located not inside shower area, one doesnt usually turn if off, so this safety is bypassed. Anyway this photo shows another brand with thermostat control from low to high like in a radio button or volume

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 It can even get warm with very little water. Does electronic control of temperature give another layer of safety? Like it cant suddenly go to maximum? Because i may buy another just like in the picture if electronic control of temperature add another safety layer and give away the old heater or take it apart as an electronic collection.

Previous post

The instant tankless water heater has 3 switches: low, medium and high. The spec mentions when at low, 2.5kw is used, medium at 3.5kw and high at 6kw. Does it use full wattage is used or can it adjust at say low temp switch to say just 1kw. Here is the power diagram.

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In the original i was contemplating about replacing the pressure switch with a flow switch so it can turn on at lower water pressure:

Any illustration what is inside the pressure switch water pusher (the white round thing encircled in green label) of this instant tankless multipoint water heater? When there is certain pressure, it pushes the switch on the left of the round white part

Also why don't they just use a flow switch instead of a pressure switch?

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Best Answer

It will contain a diaphragm and a spring applying opposing pressure to a load-spreading plate or washer on the dry side of the diaphragm (to prevent rupture).

Also why don't they just use a flow switch instead of a pressure switch?

"Just"? A flow switch is more complex, more expensive and more likely to jam due to foreign material ingress.

I plan to replace it with a flow switch hence electronic question.

Talk to your home insurance provider first.

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The thermostat seems connected to the low medium high switch. Shoudn't it be connected to some sort of relays?

Relays would be required if the switch and thermostat contacts were not capable of switching the current. Cost can be saved by avoiding them.

Haven't you come across heaters where high setting means full 6.5 kW heat used, perhaps in old style heater?

I'm not sure what your question is.

The sensible thing to do would be to use two heaters and have the two switches cam operated as follows:

2.5 kW | 3.5 kW | Result
-------+--------+--------
 Off   |  Off   | 0.0 kW
 On    |  Off   | 2.5 kW
 Off   |  On    | 3.5 kW
 On    |  On    | 6.0 kW

If the pressure switch or flow switch malfunctions will the heater still give say 6 kW full power?

There are two other levels of protection. The rotary switches should normally be off and the thermostat contacts would open when the temperature rises.

If yes, this can cause too high temperature and melt the case.

Melting the case is not the problem. Generating steam and the risk of explosion is. Water expands to 1760 times its volume when converted to steam.

If not and the thermostat purpose is to control heater power what kind of circuit must it be?

It's a mechanical switch. If temperature goes above the rated temperature then the contacts open. If the temperature goes below the rated temperature then the contacts close.

The heater unit has only few components, which should the one that regulate heater power, usually?

Thermostat. 100% on or 0% on.

Or how does the thermostat or switch regulate current? You have seen this done?

On - off control. Yes, I have seen it done on water heaters, electric ovens, clothes irons, washing machines, hair driers, waffle makers, central heating boilers and pumps, dishwashers, ... and they're just things around the house.