Brazing


Brazing is the process of joining two metals together without the wick effect that solder has.


It consists of two similar metals or dissimilar metals being joined by a brazing rod that melts before the metal being joined will. This will help assist in the bonding process. You can butt the two pieces together and braze them and it will be stronger than a soldered joint. The copper pipes can get red and silver solder will already be melted at this point.


Now a few other terms we must be aware of:


Liquidous temperature is the lowest temperature at which a metal is liquid. Solidus temperature is the highest temperature at which the metal is completely solid.


The temperature at which metal melts is called its melting point.


Brazing uses a higher temperature to melt the rods than soldering. Gas torches such as MAPP gas or oxy acetylene could be used depending on the environment and the size of pipe. MAPP gas works well in non-windy areas for up to ¾ inch pipe. Anything larger than that would push the limits of the heat.


In brazing, the components that make up the rods is determined by the metals you want to join. For the HVACR industry, we typically use silver solder containing different percentages of silver. This will determine the fluidity of the rod on the metal being joined, the cleanliness of the joint for aesthetics, and the strength of the joint.


Flux can come in various forms such as a paste or a coating on the rods. In the example for the HVACR purposes we will use 15% silver solder. An example composition of 15% Silver Solder is: 15% Silver, 80% Copper, 5% Phosphorous. In joining copper to copper, none of these phosphorus/silver/copper rods need flux or would even benefit from it. The phosphorus allows the rod to self-flux on copper. So, if you use the silver solder it has phosphorus in it and does not need flux. It is the flux!


Example: Two pipes cleaned and placed inside a coupling. Heat the pipes until the 15 percent silver solder melts and spreads smoothly along the metal joint between the pipe and the coupling. Then do the other pipe at the joint at the coupling as well. Then stop and allow to cool. Or use a wet rag to cool it down.

Round 2 terminal capacitor

Close-up of a silver metal capacitor with two terminals and printed label.

Round 3 Terminal Dual Capacitor

Silver BOJACK 40/5 µF 450V dual run capacitor with three terminals on top

Oval Capacitor

Silver Titan cylindrical electrical capacitor with two terminals on top
Metallic 9-volt battery with two snap terminals on top, isolated on a white background

Oval Dual Capacitor

Start Capacitor - Black

Brown cardboard tube with crumpled white paper or foil inside

Start Capacitor - Brown

Anthony Coker

Technical Services Manager North Georgia District

May 2, 2022

The Unknown Soldier

Wondering why the VFD is called the Unknown Soldier? It is because it does a lot of work and goes unrecognized. It is one of those things that does its work behind the scenes and doesn’t get recognized until it stops working. Well we are going to give the recognition to this one and maybe by doing so it will have a long and productive life!


VFD


Maintenance of the VFD is critical and can be detrimental when not maintained at specified intervals. The dust can cause overheating and possible damage to the VFD as well causing a shortened life span to the device.


All this information can be found on HVAC Partners under VFD-08SI


VFD Maintenance


If installed in an appropriate environment, the VFD requires very little maintenance.


Table 1 lists the routine maintenance intervals recommended by Carrier

Table 1 - Maintenance Intervals

Heat Sink Cleaning


The heat sink fins accumulate dust from the cooling air. Check the heat sink annually and if the dust is heaver than usual increase the frequently of cleaning.


Use the following procedure to clean the heat sink on the (AHC550 VFD)

1. Turn off power and (lock out/tag out) unit for your safety and others.

2. To remove the drive cover. Remove the captive screw. (See Figure 1)

Figure 1 – Remove Cover on the (ACH550 VFD)

3. Press together the retaining clips on the top cover and lift. (See Figure 2)

Figure 2 – Remove Cover on the (ACH550 VFD)

4. Blow clean compressed air (not humid) or dry nitrogen from bottom to top while simultaneously using a vacuum cleaner at the air outlet to recover the dust.


5. Replace the cooling fan.


6. Replace the drive cover.


7. Restore power.


Use the following procedure to clean the heat sink on (ACS320 VFD)



1. Turn off power and (lock out/tag out) unit.
2. To release the top cover, insert a small straight blade screwdriver into the slot and press it in to release. (See Figure 3)

Figure 3– Remove Cover on the (ACS320 VFD)

3. Blow clean compressed air (not humid air) or dry nitrogen from top of ACS320 while simultaneously using a vacuum cleaner at the base to recover the dust.


4. Replace the top cover.


5. Restore power.

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