Why is Tridicator just two gauges in one?

Paul Fredricks_5

I believe the feet may have been set manually and the pressure in the boiler needed to meet or exceed that number.

Then again, I could be wrong.

Bob Vennerbeck

Enquiring minds want to know

Why is a 'tridicator gauge' just two gauges-in-one? Shouldn't it be three?

Robert O'Brien

The 3rd

is feet of water.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

Common misnomer at the parts counter...

Its a throw back of the old days of gravity heating where elevation of the water was critical. The name stuck. The newer gauges are actually bidicators, but what warehouseman worth his burly salt is going to call a gauge a BIdicator... All the other guys would think maybe he is a closet sissy, noted for hanging out near the ball cocks and push nipples section...

The correct formal name is pressure/temperature indicator.

Bidicator my butt... on second thought, NOT!!

ME

STEVEN MARKS

tridicator

Tridicator gauge indicates pressure, temperature and feet of water (elevation).

Bob Vennerbeck

how is/was the 'feet of water' measured?

Mark - Robert - Steven - thanks for the answers - as always, leading to more questions!....
How would the elevation of water have been measured and displayed?

Thanks

Vbob

Robert O'Brien

One

foot of water is equal to .433 PSI.There are still ft/h20 markings on most tridicators.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

Wouldn't that...

fall under "Don't ask, don't tell"?

Unknown

Not bidicators...

Dudicators!

Mike T., Swampeast MO

Feet of water and pounds per square inch are different ways of expressing the exact same thing and their relationship is perfectly linear.

Both are indicated by a single needle on tridicators--there are just two different scales for that needle.

As someone else mentioned, these go back to the days of gravity hot water systems. While trained engineers likely "thought" in PSI, mechanics and particularly homeowners found it easier to think in feet of elevation above the boiler. Gravity systems were open to the atmosphere via the attic expansion tank and required occasional topping off to replace water that evaporated (or was forced out of the system if it attempted to overheat).

The tridicator gauges also had an adjustable needle (usually red). The installer would set this needle to the proper elevation and instruct the homeowner to keep the moving elevation/PSI needle centered on top of the red needle.

Unknown

thanks Noel..

For that correction...
Now the bicycles are dudicycle? From a straidude....

Bruce M

Third Part of Gauge

I sort of remember that the third part of the old gauges was "Altitude".

Bob Vennerbeck

right answer and best answer

Thanks to all, but particularly Mike T. for what is clearly the right answer, and Noel for the 'best' answer!

Vbob

bill nye_3

Theraltimeter

Theraltimeter was another name for the tridicator. Like Mike T. said, it was from the gravity open tank on the second floor days.

The installer set the movable needle over the pressure needle at proper static fill pressure. The owner or operater was instructed to maintain water at that pressure.

Altitude or altimiter were words used with this also. So feet of water column were important before the closed system came to be. Then pressure was important. So the gauge measured temperature, pressure and feet of water column.

Most plumbing drainage systems are still tested with a ten foot column of water or roughly 5psi.


"Marsh Instruments Tridicators (Boiler Gauges) are designed and suitable for hot water heating systems. These instruments indicate pressure in psi and altitude for pools and spa’s in feet of H2O; in °F and °C. All models feature a set hand for setting the desired pressure and altitude of the installation"