HVAC Technician Training | HVAC Troubleshooting | HVAC Education

They have one inlet...sometimes. Sometimes they have two.

They have one outlet...sometimes. Sometimes they have two.
                        Well now, that's clear as mud.

Ok, the porting (inlets and outlets in laymen's terms) is determined by what type of three way valve it is; either a mixing valve, or a diverting valve.
Mixing valves have two inlets and one outlet. Diverting valves have one inlet, and two outlets.

The common port is normally marked AB, and the other two ports are marked A and B.
Either valve can be used to vary either flow or temperature, depending on how its piped.

As with a two way valve, the three way valve generally shuts off against the direction of flow to stop water hammer and allow smoother control.
And I almost forgot; they're either open, closed, or somewhere in between.

Next article we'll talk about how to pipe them.

Here's the basics on two way valves-

• They have one inlet and one outlet.
• They're either open, closed, or somewhere in between.

As far as the internals go; some are single seat, others are double seat. Some are globe, some are ball, some are gate, and some are butterfly.
Here's what you need to know about them-
They need to be piped correctly meaning, the inlet needs to be the inlet, and the outlet needs to be the outlet. They generally (almost always) close against the flow of water to prevent water hammer caused by water pressure slamming the valve shut. This is especially important with single seated valves.

What’s to know about valves? They’re either open, or they’re closed. Right?

Fact is, there’s a lot to know about valves, and being valve savvy is one of the things that makes a master technician.

What are valves used for in our industry?  You name it, valves are used to control it:

• Steam for heating
• Steam for humidification
• Hot water
• Chilled water
• Condenser (cooling tower) water

How many kinds of valves are there? Let’s see, five….plus a few variations.

• Two way
• Three way Mixing
• Three way Diverting
• Modulating
• Non modulating

In the next few articles we’ll talk about porting and piping, applications and of course, troubleshooting.

                                                                                     Stay Tuned

The other day I was surfing the web looking for some information on a defrost control. Much of the search engine's top spots were populated with the typical garbage we're all familiar with.

You know the sites I'm talking about; the sites where the writer doesn't know their ass from their elbow but have decided to 'educate' the world with their blathering anyhow.

Normally I skip over these sites, but today I took a gander at them. Why? I wanted to see the misinformation the average homeowner is being bombarded with. Again, why? Why would I care? Simple; you need to know your enemy. Why are these sites the enemy?

Because when a trained professional (you) interacts with their customer they need to be ready to dispel the bad information the homeowner may pick up online.

Here is an example of one of the entries I found:

                     "...the defrost board on your (brand X) heat pump can develop ice on it throughout the winter..."

Really? That's interesting! I've never known a defrost board to "develop ice". Let's read some more of this HVAC wizard's insight into our industry-

"...if the defrost board has too much ice on it, you can fix the problem yourself........you can do it yourself with little hassle and minimal knowledge of the subject...."

Wow! This is good news for the home owner! He can save a huge amount of money by not paying an expert (you) to resolve the problem. I can't wait to see what they recommend.

"...fill a bucket with hot water from your sink and go to the defrost panel on the back of your heat pump. Pour the hot water on the ice to melt it..."

If you're like me, you were shaking your head and laughing as you read the authors advice.If you're really like me, your next reaction was a sick feeling, sick because if some unsuspecting homeowner actually used this advice they would likely be electrocuted and killed.

At least the author gave some useful advice at the end of the article...although if the home owner followed his previous advice, it's probably too late.

"call a certified HVAC technician to take a look at your heat pump if these solutions are not working for you. They will be able to properly diagnose your unit and make an appropriate repair.

If the end user is wise enough to call an expert first, be sure to warn them against blindly following advice found on the internet. Why? (There are a lot of 'whys' in this article...)

Because after they get your quote for the repair, they may look to the internet for advice on an alternate money saving solution, and worse, they may follow it.

Patrick

You are invited  to "Infrared Thermal Imaging for HVAC" Presented by John Cannamela of Infrared Survey and ZenHVAC at the 75th annual RSES conference on November 17th, in Charleston South Carolina. The four-hour session will target all audience levels and will cover the use of infrared cameras for heating and cooling system diagnostics. Cannamela will discuss basic infrared camera use and how to apply thermography to specific system applications such as chillers, steam systems, boilers, computer room systems, duct systems and more.

Nate ID 5406-0002

After attending John's session, take the survey and let us know what you think!