Understanding bypass systems

Everything about Bypass System for Control Panels

The Nex Flow Panel Cooler is a vortex tube operated air conditioning system used to cool electrical and electronic control cabinets. They have many advantages such as simplicity in installation, near zero maintenance, no condensate and more. But one major advantage for control cabinets in harsh environments is that when operating they keep control cabinets at a slightly positive pressure, therefore keeping out the factory atmosphere. Panel Coolers are utilized especially in environments that are very dirty, dusty, hot and moist, or corrosive. This ability to keep the control panels at a slightly positive pressure becomes very important. However, this is only the case while the Panel Cooler is actually operating.

On-off control

One of the ways to minimize compressed air use with a Panel Cooler or any vortex cooling system is to have some sort of an on-off control system. One method is to use a thermostat coupled with a solenoid valve to turn the compressed air on when the cooling is needed, or turn the air off when it is not required. However, when the Panel Cooler is off, it no longer keeps the control panel at that slight positive pressure. It is at this point where the factory environment can encroach into the control cabinet and possible to have a negative impact on the internal components.

Single VS Multiple Panel Coolers

If there are two or more Panel Coolers on a control cabinet, normally one runs continually and the other one (or ones(s)) cycle on and off as required for cooling. That is enough to keep the control panel, even if very large, at the slightly positive pressure enough to keep out an unfriendly environment. But when only one Panel Cooler is used then some creativity is needed.

One of the tricks of the trade in factories such as highly humid bottling facilities, even with standard air conditioners, is to take a small compressed air line and pipe a very small amount of compressed air constantly into the cabinet to keep out the humidity that could harm the controls. A typical Standard air conditioners go on and off, so the humidity needs to be addressed. Similarly in very corrosive and dirty environments, a tiny amount of compressed air piped into the panel solves the potential expensive repair of the internal parts of an electrical or electronic enclosure.

So what are the options when using a single Panel Cooler? One vortex cooler supplier uses a thermostat and solenoid package for on-off control but they drill a small hole into the solenoid valve so that in the “off” position, a small amount of compressed air continues to flow through the cooling unit.  There is not enough flow to effectively cool in the off position but enough flow to keep the cabinet at a higher pressure than the environment.

There are two disadvantages with this method.  

First, it may not be legal in some jurisdictions because drilling a hole in the solenoid valve may take away its electrical approval rating. This may result in all sorts of problems from insurance coverage to legal should something go wrong.  

Second, there is no control over how much of this air can go into the cabinet. For very large cabinets, it may not be enough air to make any difference in pressure, and for small cabinets there may be too much air flow that it wastes energy.

Overcoming the disadvantages

To overcome the above disadvantages – Nex Flow has designed a special by-pass system.

The by-pass system works with all panel coolers both Nex Flow and non-Nex Flow units. It consists of a control valve that is connected between the compressed air supply (after filtration) at the inlet to the solenoid valve that controls the on-off operation of the vortex cooling system.  There is a small tube emanating from the control valve that is connected to a three-way fitting that connects to the outlet of the solenoid valve. One inlet is for the tube, a second inlet connects to the outlet of the solenoid, and the other connection goes to the line that takes the compressed air to the cooling unit.

This overcomes both the previous disadvantages mentioned. The solenoid valve is not tampered with so no electrical approvals are jeopardized and eliminating any potential insurance or legal issues.

The control valve on the inlet side of the solenoid valve has a small knob to set the amount of by-pass compressed air used. It can be set to a very small flow rate for small control panels to save energy and a higher flow rate for larger control panels to insure there is enough air flow to maintain a higher pressure than the environment. Control remains completely in the hands of factory personnel and not with a tampered solenoid valve.

The Panel Cooler by-pass system is also made of all 316 stainless steel so it can be used in all types of environments and with all ranges of Panel Coolers offered by Nex Flow (and their competitors) including NEMA 4X (IP 66) environments. The system is simple to install, easy to use and versatile.

In relatively benign factory environments, a by-pass system may not be necessary. Furthermore, if the Panel Coolers operate continuously they are obviously not required. To determine if having a by-pass system would be beneficial, you simply have to access the plant environment. In corrosive atmospheres or highly humid atmospheres the benefit is quite clear cut. However, regardless of the environment, when used, they have been proven as an effective way to keep the internals of a control clean and dry.

If there is more than one Panel Cooler, as mentioned earlier, normally one is always operating.  However, if the plant atmosphere is really harsh, it might still be useful to have a By-Pass System on at least one cooling unit assuming the control panel is completely shut down during a plant shutdown.

As with all Panel Cooler installations, it is important to have proper filtration to remove any loose water or oil to keep the system clean and dry.