Double traps are no good. End of tip. Ok, here is some detail.

Anytime your drain goes up and down more than once you have a double trap UNLESS you place an air vent between the two traps that vents ABOVE the drain inlet.

The double trap causes drainage issues because air becomes trapped between the two traps and air is lighter than water. This causes the air to want to travel up as the water flows down resulting in NO DRAINAGE.

A vent allows the air to move instead of becoming trapped. This is why you vent a drain after the first trap if there is another trap or the potential of another trap.

This is also why you vent a drain after the first trap and before a common drain if you are connecting more than one drain. It helps prevent the possibility of a double trap and thus prevents a nasty backup.

In general just pitch the drain properly, install only one trap and don’t interconnect (unless required) and you will have no problem.

That was easy!

— Bryan

Photo by Brad Hicks at HVAC in SC

Right off the top let me state loud and clear. The tool does not make the tech.

Let that sink in before you move on.

A good tech has a solid understanding of WHY they are doing what they are doing, the basic math of the trade and enough experience to spot most problems with their senses before they reach for a tool at all.

However… there are some cases when you need a specialty tool. You need it so much that you cannot do your job without a good one (Leak detectors and micron gauges come to mind). In some rare cases, the cheap version of a tool and the high-end version are so different that you are at a real disadvantage if you don’t have the quality version.

There are multiple manufacturers who have come out with wireless pressure probe technology. Up until recently, I couldn’t get over the fact that you cannot use these probes for charging and recovery… why would you want a separate tool set in addition to your gauge manifold?

Well… I think I finally get it. Here are some reasons that others have given me that have me seeing the light.

Low Loss

One big advantage is you can use the probes to check a system charge with no hose losses. This is huge for systems with a critical charge (Think Ice Machines), when doing regular preventative maintenance and when hooking up to the system to check it during a service call unrelated to charge. Keeping all that charge in the system is a service to the customer and helps save expensive refrigerant. You can keep some 90 degree core depressing adaptors or some short hoses to help connect in tight spots .

Additional Readings

With smart probes you can now check additional temp and pressure readings without the need to move your hoses around when you do have a manifold attached. You can check liquid and discharge pressure simultaneously, check temp drop across a liquid line or superheat gains across the suction. All great data that the wireless smart probes can help with.

Hard to Get Readings

Now this one was the one that tipped the scales for me and it was brought to my attention by tech Joe Shearer (Thanks Joe). You can use the smart temp sensors (Testo 115i) to get readings on running systems in spots where wired probes can be almost impossible. Reading superheat inside a heat pump condensing unit during heat mode, reading temp differential across a reversing valve and taking discharge temp at the compressor are all examples where the smart temperature probes come in really handy.

The MeasureQuick App

Testo is one of the first tools that works along with the new MeasureQuick app for full system diagnosis unlike anything you have seen. This may feel like a pitch, but working with MeasureQuick as well as the great price make the Testo Smart Probes a very attractive option.

So I think you may want to think about smart probes and if they might help you….. Once you already are confident enough to understand why and how you would use them to be a better tech.

— Bryan

P.S. – If you are interested you may consider going HERE and looking at the Testo smart probes. If you do buy from TruTech tools use the offer code “getschooled” for 8% off your order.



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