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Boiler gauge

Chad Fabry

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There are certain words that I've only read. One of the words that I've never uttered nor have I heard uttered is "tridicator" as in tridicator gauge for a boiler that provides information about the boiler temp and pressure.

I have two questions:

How is it pronounced? I'm saying it like try-dih-kay-tore with the accent on try or kay.

Why is called a tridicator gauge if all it does is report data about two subjects? It should be a twodicator. Or a onedicator on steroids.

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I wasn't just funnin' everyone with my reply.

1 Temperature (yeah, F and C)

The pressure scale sometimes offers two things:

2 Pressure in psi

3 Head in feet-H2O

That's three things. Unfortunately, most gauges now seem to forego the Head scale in favor of offering kPa instead. So you have to calculate head. Anyway, that's my splanation.

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Thank you gents for the explantion.

Gary, how does the gauge measure head? Head at the gauge would be represented by an increase in system pressure equal to the weight of the water column and pumping effort ..no?

And, even though we have two scales for temp, and two scales for pressure isn't the data representing just two things? a mm is a mm but can be represented in inches. It's still the same measurement but expressed differently.

I'm beggin for a better education here.

Some should be called a quadicator: fahrenheit, celsius, psi & kPa.

I'm going to call it a fournicator, just for fun.

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I guess you can use the term head to refer to pressure however head pressure is typically used in reference to circulating pumps.

On most smaller systems the city water supply valve is set to 12psi. This is a simple PDF explaining why 12psi: http://www.bellgossett.com/literature/files/4247.pdf As we fill and vent the system, with the circ pump off, we fill to a static pressure of 12psi static pressure. On systems that have an expansion tank with a sight glass you try to get the water to fill about half way in the sight glass using the airtrol. Refer to this PDF for more information on the B-G Airtrol system: http://www.bellgossett.com/literature/files/599.pdf

Now that we have the system filled and vented we can now run the pump. Pump head should not be confused with static pressure. Another simple pdf: http://www.bellgossett.com/literature/files/4264.pdf

We had a good discussion here a few years back on whether a pump should be on the return line or supply line. Although it might not make much difference on a small residential application with fractional horse pumps it makes a big difference with commercial application and bigger motors. If you pushing water into the boiler you automatically raise the pressure inside the boiler. Add heat, which expands water, and now you're flirting with causing the safety valve to weep (30+psi inside the boiler). When you pull out of the boiler the you're not artificially raising the pressure inside the boiler. This problem really comes to light when a heat exchanger starts to leak on a boiler that should still have a lot of life left in it. As the relief valve weeps it is draining water to get the pressure down. Most building custodians just keep adding water to the boiler or the automatic fill valve does it for them. As a constant supply of new water comes in the mineral deposits drop out at the bottom of the heat exchanger in the form of scale. If anyone has taken apart a section of boiler there will surely know what I'm talking about. As the scale builds up it acts as an insulation barrier between the water and the heat exchanger. Now all we have to do is add heat, keep the water from carrying the heat away and now the cast cracks due to over heating. Unfortunately, most companies chalk it up to a defective heat exchanger with out troubleshooting the entire system. This is another PDF that talks about pumping away: http://www.bellgossett.com/Press/Counte ... 2001-A.pdf Go to http://www.bellgossett.com/ and spend an hour or so browsing their PDF, you'll be glad you did.

Well, looks like I strayed from the path again, what else is new?

If my car speedometer shows MPH as well as KM/H shouldn't it be a speedsometer?

What is the air-speed velocity of an unladen swallow?

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That's good info. You're right, head is a common term used in pumping. Head is used whenever pressure needs to be measured in height.

There is a head (pressure) present at an orifice with 12 feet (vertical) of water above it. This is true for a pump emptying a basement, or for a full pipe extending to a second floor radiator. Head is simply pressure created by gravity. All head is pressure, but not all pressure is head.

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You are correct (of course!) and I am saying the same thing you are, but I need a picture to explain what I mean. It doesn't matter that C & F, or psi & kPa are shown - those are four ways to say the same thing.

No, what I'm saying is that many of these tridicators have no right to call themselves such. Go here to see a REAL tridicator: http://www.cpigauges.com/part_numbers/t ... -gauge.htm

Look at the lower (round) tridicator. A close look at the top scale, right side, shows units "H2O Feet". This tridicator gives temp, pressure, head.

Got it friend????

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  • 7 months later...

A Tridicator measures 3 things; temperature, pressure & vacuum. It is a thermometer combined with a compound gauge. The thermometer is typically expressed in F & C. The compound gauge measures pressure in PSI & kPa. It also measures vacuum (negative pressure or suction) in "Hg (inches of mercury).

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  • 4 months later...

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