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dfru

dfru

Joined on November 16, 2011

Last Post on August 15, 2014

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Gas Piping - teflon tape

@ August 15, 2014 9:10 PM in Gas Piping - teflon tape

I was recently inspecting a project and found that the threaded pipe joints are sealed with white teflon tape, rather than approved yellow tape. I have heard of one plumbing inspector requiring gas piping systems which are installed as such to be ripped out entirely. Has anyone experienced this? Are there any repairs which could be done which would allow the existing system to remain intact?

Any thoughts would be much appreciated.

High rise hydronic heating and chilled water piping supports

@ December 21, 2013 1:32 PM in High rise hydronic heating and chilled water piping supports

Are there any published standards or guidelines which discuss methods for supporting and anchoring vertical pipe risers in high-rise buildings to allow for expansion and contraction in the piping systems?

Any assistance would be most appreciated.

Heat Pump Compressor Diagnosis - Building Fire

@ September 17, 2013 11:30 AM in Heat Pump Compressor Diagnosis - Building Fire

Some HVAC package unit compressors were exposed to high heat during a fire in an adjacent structure. Concerns have been raised that the HVAC equipment was damaged due to the heat. One technician raised the concern that the equipment needs to be replaced due to possible acid formation in the oil. The equipment looks completely fine. There are no charred or melted parts. We plan on taking oil samples to check for acidity.

Questions:

1.If high levels of acid are found, then will the units require replacement, or could the refrigerant and oil be removed and flushed from the system, and replaced?
2. If acid is found, will the compressors or any other components require replacement or adjustment?

Any help or advice would be appreciated.

Fire Damaged Package Heat Pump Unit

@ July 26, 2013 3:06 PM in Fire Damaged Package Heat Pump Unit

Thanks for the feedback Techman. My impression is that you are correct, but there is a technician on the project who is raising the concern, and it may be valid. Any thoughts would be appreciated.

Fire Damaged Package Heat Pump Unit

@ July 25, 2013 11:44 AM in Fire Damaged Package Heat Pump Unit

I am working on a building which was exposed to a fire in an adjacent structure. The HVAC equipment looks fine. No visual signs of burned parts, no warping of metal or plastics, wiring looks fine, no soot accumulation on or inside of the unit, condenser and evaporator coils and fins look fine. The machines use R22 refrigerant.
The question has been raised as to whether high temperatures from the fire could have caused issues with the refrigerant and oil. What temperature would damage the machine? What is the best method for testing if the refrigerant is still re-usable, and if not, what procedures need to be followed to evacuate and clean the refrigerant circuit for refrigerant replacement?
Any thoughts would be most appreciated.

Fire Damaged Package Heat Pump Unit

@ July 25, 2013 10:58 AM in Fire Damaged Package Heat Pump Unit

I am working on a building which was exposed to a fire in an adjacent structure. The HVAC equipment looks fine. No visual signs of burned parts, no warping of metal or plastics, wiring looks fine, no soot accumulation on or inside of the unit, condenser and evaporator coils and fins look fine. The machines use R22 refrigerant.
The question has been raised as to whether high temperatures from the fire could have caused issues with the refrigerant and oil. What temperature would damage the machine? What is the best method for testing if the refrigerant is still re-usable, and if not, what procedures need to be followed to evacuate and clean the refrigerant circuit for refrigerant replacement?
Any thoughts would be most appreciated.

Missing Information

@ July 11, 2013 10:56 PM in Conduction along length of copper water filled pipe

The 1" pipe goes to a water softener, then continues on the the building water supply. Cold water will periodically flow through the pipe, but I am analyzing the system during off hours when there will not be any flow in the system.

The pipe is connected to a domestic water heater, and provides cold water to it. Just upstream from the connection is a recirculating hot water pipe which tees into the cold water line. I am assuming as a worst case that the recirculating water back to the heater is at 140 degrees F.

I will put together a diagram if it still does not make sense.

Conduction along length of copper water filled pipe

@ July 11, 2013 11:05 AM in Conduction along length of copper water filled pipe

I am looking for assistance in doing some calculations to determine certain factors associated with an uninsulated water filled pipe. The pipe is 1" copper pipe. It starts off at ambient temperature. Say 60 degrees F. 3 feet away, along the length of the pipe is a tee connection which delivers 140 degree water to the piping system. Assume that 100% of the 140 degree water flows along the other run of the tee, away from the cold water leg, and that there is no flow through the cold water leg. The 3 ft pipe run is horizontal.

How do I calculate the rate of heat transfer to the cold water pipe?
What will the maximum temperature become at the piping along the cold water pipe, 3 ft from the tee?
How long will it take to reach this temperature?

Any assistance would be much appreciated  

Reverse

@ October 9, 2012 1:20 PM in Shell and tube heat exchanger failure

I agree, but I am dealing with an existing system which is already set up with the central plant water flowing through the tubes for each system,

Shell and tube heat exchanger failure

@ October 4, 2012 11:44 PM in Shell and tube heat exchanger failure

I am working on a building which has a mechanical equipment room which is supplied with 175 psi water at 315 degrees F, from a central plant a few blocks away. The high temperature hot water loop in the mechanical room circulates this hot water through the tube side of three shell and tube heat exchangers. One is for domestic water, one is for building heating, and the third is for swimming pool heating. The tubes in the domestic water heat exchanger have repeatedly failed/leaked. Examination indicates that there is likely velocity erosion in the tubes. Water through the tubes is controlled by a motorized valve which shuts off water flow when the shell side of the system is satisfied. I do not believe that there are currently and bypasses in the system.

My guess is that when the tube side of the pool and/or the heating hot water heat exchangers is off (valves closed), the system is trying to push all of the central plant hot water through the tubes of the domestic hot water heater, creating excessive velocity, and ultimately erosion.

Does this make sense?
If so, how should I modify the system to prevent this? (I believe that the central plant system is very large, and is controlling many other buildings - so I suspect that the flow from the central plant cannot be modulated in response to the changes in the building)
If this is correct, why would the domestic hot water heater tubes be the only ones failing (the other heat exchangers would see high velocities when the domestic water heater system is satisfied)?

Any thoughts or recommendations would be appreciated.

Pipe leaks

@ April 17, 2012 9:42 PM in Buried copper piping leaks

Was the branch coming off the top or the bottom of the main? The branch was coming off of the top of the main.

Was the elbow pointed parallel to the main, or at a right angle? The elbow was at right angles to the main.

Where was the crack in relation to the flow line? In other words, at the beginning of the fluid entrance to the el, or at the end? The crack was at right at the heel (bend) of the elbow. Perpendicular the direction of flow. 

You describe a "coil". Is this a fan coil unit, or an in cementitous radiant floor coil? The coil is at a varaible air volume box which is in a separate vault below the slab.

How long is the 1" branch, and how is it anchored to avoid movement? The 1" branch is insulated, and does not appear to be anchored, except it may be embedded in concrete near the box vault.

Your options of expansion joints are fairly limited. You can do the long legged U tube, or the radi type, but can not use a mechanical joint (trombone with O rings) nor should you use a corrugated type of flex connector below grade. And you definitely can't use any type of mechanical joint below concrete, unless access in the future is guaranteed, i.e. an access panel at the actual device.

As I previously noted, in order for an expansion joint to work correctly, the pipe must be anchored such that the growth potential is direct towards the expansion joint.

Lastly, the only way to determine wether the failure was stress or erosion is to split the pipe and fitting length wise and look for signs of erosion. Remember that horses always walk up stream.

Reaming

@ April 17, 2012 6:23 PM in Buried copper piping leaks

Thanks. But in this case I do not see internal pipe erosion or velocity as a factor.

Reaming

@ April 17, 2012 6:23 PM in Buried copper piping leaks

Thanks. But in this case I do not see internal pipe erosion or velocity as a factor.

Loop

@ April 16, 2012 10:48 PM in Buried copper piping leaks

I was thinking of adding some sort of flexible connection at each of the 1" tees. Any suggestions as to what I might use?

Velocity

@ April 16, 2012 10:45 PM in Buried copper piping leaks

I looked at potential velocity erosion as a factor, but I do not believe it to be the case. Velocities in this system are low - in the 3 ft per second range. The failure was at the heel of the 1" elbow. Crack about 1/4 of the way around the circumference.

Buried copper piping leaks

@ April 15, 2012 2:49 PM in Buried copper piping leaks

I am troubleshooting an existing building which is experiencing pipe leaks in a buried copper heating hot water distribution system. The piping is insulated and buried in sand a foot or so below a concrete slab. The main pipe run is 2", and appears to run 100 ft straight, without any provisions for expansion or movement (except perhaps some movement within the insulation - which is a rigid foam). There are a series of 2"x2"x1" tees in the pipe, with 1" feeds to heating coils. The failure was at a 1" elbow which is connected to the tee prior to running to the heating coil. I have calculated that the 100 ft run of pipe will expand approximately 1.5 inches (at a 120 degree delta tee). My initial thought is stress related to this. Any thoughts or opinions would be much appreciated.     

Arizona structure

@ November 16, 2011 12:26 PM in Temperature within a mechanically ventilated structure

122 degrees F is the maximum desired temperature within the structure.

Arizona structure

@ November 16, 2011 12:26 PM in Temperature within a mechanically ventilated structure

122 degrees F is the maximum desired temperature within the structure.

Arizona structure

@ November 16, 2011 12:26 PM in Temperature within a mechanically ventilated structure

122 degrees F is the maximum desired temperature within the structure.