Need solenoid valve which won't open when ice in pipe.

[schnell]

Hello,

Is it possible to get a solenoid valve which won't open if the water pipe is iced up?
-but will open if its not?



We design domestic showers which are tmperature controlled by stepper valves.

If its cold and the cold pipe ices up , then only hot can get through and the customer gets scalded.(as the controller does not act quickly enough)

so is their such thing as a solenoid which will open if the water is ice, and won't open if it is not?


we can then detect "not-open" since solenoids have less inductance when not fully actuated....so we can detect higher peak current in the switch mode solenoid driver....and hence...we could then detect ice in the pipe.


(here are more general details about the thread if you wish....)

http://www.eng-tips.com/viewthread.cfm?qid=291536&page=1

 

[gerhardl]

Here is the answer from Scandinavia, and the answer I believe to be a no!

The real problem is that a frozen pipeline is not a defined or exact repeting phenomen, and you will not be able to foresee the result on a pipeline, regarding pressure and water flow.

(Remember that ice will have larger volume than water and that tawing
phenomena with different volumes also can give damage, as well as ice itself that can burst a weak pipeline, valves or connections!)

For countries with cold climate the art is to hinder waterpipes and equipment to freeze, eg. with isolated pipelines, outside or inside traced el.heating, pipelines inside isolated and heated buildings,running water through pipeline to hinder freezing by static water, stop and drain pipelines if fear of frost, bury pipelines at frostfree depth etc.

Anyway to your question: I presume that you will place the solenoid valve frostfree to stop the flow of the hot water, in the hotwater line before mixing, and that the coldwater pipeline is stopped by ice well before any valve.

In this case the solenoid valve can open and close as under normal conditions.

The question then is if the solenoid can be connected to a thermostat or a pressure switch that somehow can react fast eneough to prevent the 'hot water only' flow. I doubt this solution will be safe enough under all circumstances.

Unassisted (without electrical controlling signal) the solenoide valve will not be able to generate the correct reaction.

The only possible solution I can think of is to connect a fast acting pressure switch to the incoming coldwater pipeline, with a set pressure of (say) 60% of the normal incoming coldwater pressure as a requirement to open the hotwater line with the solenoid valve. If lower pressure the hotwater line to be closed. (Pressure switch to break electrical connection to the solenoid valve by sinking coldwater pressure, hotwater solenoid valve to be of NC type (close without current).

The conclusion is, i am afraid, still the same: Try to look for other types of control than the solenoid!

Although I am no expert on water mixing there exists on the market a vast number of possible solutions, ranging from temeprature controlled valves to mechanically blanced systems on pressure from two sources, and limiting temperature at heating source.

Good luck!