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from what i know pigtail is to prevent back pressure or hammering effect to the pressure sensor diaphragm or capacitance sensing materials. check the system working pressure and check the pressure sensor specification, if the working pressure do not exceed burst pressure then it can install without the pigtail. if you want to avoid the copper piping loss or installation difficulties, http://www.setra.com/ProductDetails/...231RS_HVAC.htm you can try this differential pressure transmitter with remote sensor. so just install each pressure sensor on supply/return pipe and connect the wire back to the transmitter will have differential output.

I would sugggest to install the sensor on a tee in order to be able to bleed air easily. Install the sensor on the side port of tee with elbow to have sensor vertical, water line below, and drain with upper port. Even better, install gauge on upper port just to double check readings. And isolating valves for the day you will need to replace components (take off handles if needed).

Water hammer can happen on any size pipe, it just scares you a bunch more on bigger stuff.
I see it happen a lot on 1/2" and 3/4" pipe. http://www.pexsupply.com/Water-Hamme...stors-10951000
http://en.wikipedia.org/wiki/Water_hammer

Originally Posted by Nuclrchiller

Azka, can you just "Google" that? I don't know the definition, and I would probably end up talking in circles trying to describe it. But I believe it involves the quick shutting (or repositioning) of a valve in a piping system that can result in the rapid, repetitive sound- similar to a hammer banging on the pipe. In a chilled water plant, the result can be seen as movement of the pipes, sometimes a very large movement, along with a loud "bang" noise. I believe these noises and pipe movements are the results of sudden pressure changes and/or rapid fluctuations of pressure.

Thank you. Actually I never heard about that term "water hammer". But now I'm know it.

Originally Posted by milkyway

Azka,

Water hammer happens when a isolation valve closes too fast or suddenly.
This normally happens w 4" and up water piping,.
When it happens you will want to take cover!., I had a gasket blow out on me one time on an 8" pipe one time and my partner took off running lol

Thank you, I got it.

Azka,

Water hammer happens when a isolation valve closes too fast or suddenly.
This normally happens w 4" and up water piping,.
When it happens you will want to take cover!., I had a gasket blow out on me one time on an 8" pipe one time and my partner took off running lol

Originally Posted by milkyway

water hammer can be VARY SCARY!!

You got that right!

Originally Posted by azka

Dear Nuclrchiller
What is water hammer ? Can you explain to me. Is it cause by high pressure water ?

Azka, can you just "Google" that? I don't know the definition, and I would probably end up talking in circles trying to describe it. But I believe it involves the quick shutting (or repositioning) of a valve in a piping system that can result in the rapid, repetitive sound- similar to a hammer banging on the pipe. In a chilled water plant, the result can be seen as movement of the pipes, sometimes a very large movement, along with a loud "bang" noise. I believe these noises and pipe movements are the results of sudden pressure changes and/or rapid fluctuations of pressure.

Originally Posted by desert guy

The sensor electronics are sealed so condensation should not effect the sensor. Once the operating pressure of the system is established by the Water Balance Contractor it should not deviate very much. What is the range of the sensor you are using and what is the maximun system pressure.
When I looked at the Catalogue Sheet for the sensor the Max Pressure was 2.5 to 3 times the pressure range so I don't think that the sensor failures are attributed to pressure or condensation.
How much pressure is indicated on the gauge at the discharge of the pump?

Dear desert guy,
I'm forgot what the reading at pressure gauge. I'm always use that pressure sensor with max pressure is 300psi.

Originally Posted by Nuclrchiller

Sealed electronics, stainless steel housing, nice. I would have no problem mounting this directly on chilled water pipe. The only thing I wonder about past failures is maybe water hammer from automatic valves and/or check valves? I have seen a couple of sites where it was bad enough to make me want to run for cover.

Dear Nuclrchiller
What is water hammer ? Can you explain to me. Is it cause by high pressure water ?

water hammer can be VARY SCARY!!

Sealed electronics, stainless steel housing, nice. I would have no problem mounting this directly on chilled water pipe. The only thing I wonder about past failures is maybe water hammer from automatic valves and/or check valves? I have seen a couple of sites where it was bad enough to make me want to run for cover.

Originally Posted by azka

Hi guy, I'm using this type of sensor http://www.dwyer-inst.com/Product/Pr.../Series626-628
Before this I'm never use "pigtail". But some site that use this sensor got faulty. I don't know why this sensor faulty. Maybe due to condensation or high pressure water. All wiring is correct. That why I'm thinking to use "pigtail".

The sensor electronics are sealed so condensation should not effect the sensor. Once the operating pressure of the system is established by the Water Balance Contractor it should not deviate very much. What is the range of the sensor you are using and what is the maximun system pressure.
When I looked at the Catalogue Sheet for the sensor the Max Pressure was 2.5 to 3 times the pressure range so I don't think that the sensor failures are attributed to pressure or condensation.
How much pressure is indicated on the gauge at the discharge of the pump?

I use Setra model 206 for 4-20 applications.

A pigtail is only used in steam application to protect the gauge from heat caused by direct steam. There is a plug of water in the "trap" that keeps the steam from reaching the gauge.

Hi guy, I'm using this type of sensor http://www.dwyer-inst.com/Product/Pr.../Series626-628
Before this I'm never use "pigtail". But some site that use this sensor got faulty. I don't know why this sensor faulty. Maybe due to condensation or high pressure water. All wiring is correct. That why I'm thinking to use "pigtail".

You do not need a pigtail or the copper tubing most pressure transducers come male pt. In this case the trouble of remote mounting your transducer running copper tubbing is not worth the time or cost.

I really can't tell from here, looking at a hand-made drawing on my monitor, if that sensor has exposed wiring connections, or is made of a material that could be damaged by condensation causing an electrical short, or rust. And I'm also not able to tell if that pressure sensor is designed to be immersed in water. But if a pigtail, or anything similar is used, you (Azka) should be aware that the sensor needs to be kept at the height as the connection point on the pipe. I am also wondering what is the purpose of the sensor. As Desert Guy mentioned, a differential pressure sensor is usually used to control a VSD pump.

The pigtail is not required or necessary and there will not be any damage to the sensor if it is not used. For the sensor to function correctly it must be in contact with the liquid, in your case Chilled Water.
The sensor is designed to be immersed in the water.

Originally Posted by desert guy

Here is some info that may be helpful. http://www.kele.com/pressure/47b,-47...-747s,-pt.aspx

While a single pressure sensor can be used as a reference to control the speed of a pump the more common approach is to use a differential pressure transmitter between the CHWS and CHWR pipe. This is usually placed at the furthest branch of the piping run before the last AHU. For reference I'll show the following transmitter. http://www.veris.com/Item/PW2LX04S.aspx

Thank you for the link and info.

Originally Posted by Nuclrchiller

Desert guy, is the pigtail used to isolate the sensor from the high temperature of the steam pipe, to avoid heat damaging the sensor? Azka, desert guy is correct that you do not need it for chilled water, however, I would prefer it if it were my system. That is because of the potential for water damage to the sensor due to condensation on the sensor, since it will be at pipe (or chilled water) temperature. Using the "pigtail" will keep the pressure sensor's temperature closer to ambient and should greatly decrease the chances of condensation. The slightly higher cost of installation will be more than offset by longer life and reliability of the sensor. Not to mention downtime, or system malfunction, due to a failed sensor.

Dear Nuclrchiller,

I'm also afraid without "pigtail" will be damaged the sensor. This sensor will be use for control VSD pump. Maybe the best choice is to use "pigtail". Most of the pressure transmitter very costly.

Here is some info that may be helpful. http://www.kele.com/pressure/47b,-47...-747s,-pt.aspx

While a single pressure sensor can be used as a reference to control the speed of a pump the more common approach is to use a differential pressure transmitter between the CHWS and CHWR pipe. This is usually placed at the furthest branch of the piping run before the last AHU. For reference I'll show the following transmitter. http://www.veris.com/Item/PW2LX04S.aspx

Desert guy, is the pigtail used to isolate the sensor from the high temperature of the steam pipe, to avoid heat damaging the sensor? Azka, desert guy is correct that you do not need it for chilled water, however, I would prefer it if it were my system. That is because of the potential for water damage to the sensor due to condensation on the sensor, since it will be at pipe (or chilled water) temperature. Using the "pigtail" will keep the pressure sensor's temperature closer to ambient and should greatly decrease the chances of condensation. The slightly higher cost of installation will be more than offset by longer life and reliability of the sensor. Not to mention downtime, or system malfunction, due to a failed sensor.