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Hi everyone,
Boy did I open up a subject line about keeping old heater valves lying around to work on.
Guess I’m not so eclectic after all.
Now I wish I hadn’t put off this project and could help more if I had more knowledge or hands on experience.
I will add what I know about thermostat or power head operation of expansion valves used in refrigeration systems. This I learn back in the seventies to get my AA degree in HVAC.
On expansion valves the “power heads” is the diaphragm on top. Capillary tubes are filled with an amount of liquid refrigerant after a vacuum is pulled on the sensing bulb, tubing and diaphragm.
The amount isn’t known but it is filled with the same refrigerant that the expansion valve is to be controlling with in the system.
The diaphragm is working with or against the systems internal operating pressure and spring differentials.
This sets the stroke of opening the valve more or less to prevent flood backs.
The setting involves readings of “superheating” and boiling off liquid to know vapor gases are going back to the compressor.
So the power heads have to be a close approximation range or with pressure/temperature responses for the best accuracy of the evaporators low side where the bulb is located.
Now in the case of mechanical thermostats a pressure “medium” in the sensing bulb has to be selected to change its pressure to operate a device according to range of temperature needing to be controlled.
Freezers, refrigerators, cabins or ovens etc.
In ovens at home, back before electronic sensors, a drop of mercury was put in the sensing bulb as its liquid to vapor expansion pressure is is up in the hundreds of degrees. Well above wax or refrigerants.
I was told it was only drop of mercury and never asked how the teacher knew this.
I have wondered if there could be other gases used to fill the whole space of the unit.
Because, When one or more gases are used in one contained vessel the two gases combine their sums. Dalton’s Law of partial pressure. I have learned to respect physics and it’s science.
So with the heater valve being used to sense heated cabin air flow.
I would not discount a wax or refrigerant or bimetallic actuations.
Wax does seem very plausible as a wax pellet is used in automotive coolant thermostats.
The assembly is very short, immersed and compact for hose connections.
If you cut one open, I bet Art Benstein has, (:-) the wax pellet is packed in there.
Here is proof if he didn’t.
https://en.wikipedia.org/wiki/Wax_thermostatic_element
A special and precise formula wax is discussed along with it’s limited temperature ranges.
Cut open a heater valve assembly you might find nothing because any amount of refrigerant would be instantly gone.
Maybe cut it under a liquid (water) and hope for a breathe of a gas bubble. If not an ooze of a wax.
I have thought that I could replenish the sensor bulb by adding refrigerant to a vacuumed out assembly and using the pinch off method after setting the range close.
I’m sure the factory has a refined technique.
Finally soldering the tube end past the pinch point sealed.
Thats how it’s done on hermetic refrigeration units.
Thermostats and power heads systems can be equal.
This is where of either method of mediums has to allow an adjustment point for variances in charges and mechanical fit up.
The gases or wax has to or will expand and the amount sets the design of the mechanical action or stroke to provide flow through the valve.
The opening and closing stroke points is where we adjust the cable along a cam or linkage of some type.
It’s really simple physics applied but IMHO you can see why electronics changed the scene and to drop the use of Mercury there.
Some very high current relays still use mercury because the mercury stirs and is sealed from oxidizing.
No mechanical contacts to burn away.
As far as the name ”Ranco” I picked that up somewhere in my junkyard finds and it’s a common refrigeration name in the trades or industries.
Apparently a car I picked from had a new source provided by Volvo or aftermarket.
Curiosity led me to this site.
It is now called RobertShaw or were both the same? Only A Limited history on it.
https://www.robertshaw.com/About-Robertshaw/.
The first thermostat started there according to them.
They do automotive still and are reaching into electric vehicles production solutions with motor operated valves. IAC … or Coolant Water Diverter CWD… the automated heating or cooling of cabin or the electric motors. (:)
Before computers there used to be book type catalogs. You know. Pictures and specifications.
The engineers I rubbed elbows with suggested that I check into a certain dumpster ever so often.
They culled catalogs as vendors issued new ones.
I was told designing engineers are only as good as their sources to fit ideas.
Those friends told me to dumpster dive since I was sort of an unpaid “liaison” between machining and prototype work in my formative years.
Reading trash lead to several challenges within R&D projects and then career changes as production trade jobs left to be off shore.
Actually with my overtime I made more money than most engineers so machine tool metalworking was my open door to nice hallways.
If I had been born about thirty years later and of course had richer parents it’s possible that the information coming out of the internet would have made me more of a shaker and moving nerd?
Oh well, the hallways had enough door knobs!
Phil
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