In this episode with BENOÎT MONGEAU we talk about the components of combustion and what to consider when testing combustion on a fuel burning appliance.
- Tech Tips
Dan Holohan speaks to Bryan about his background and journey, pumping away, classic hydronics, and the difference between search and research.
Once you are done listening please head over to heatinghelp.com
Here are a few of Dan’s great books
There are many acceptable methods for making a wire splice and you need to consider many different factors when making a splice. Here are a few considerations.
Here are a few options for splicing wires depending on application –
Splicing any high voltage conductor in an “open” manner or in way that is not specifically rated. In most cases get a UL rated connector and make the connection inside a UL / NEMA rated rated box or assembly.
Making a splice by just twisting wires together and putting electrical tape on top. Just don’t.
Using wire nuts and creating a big ball of wires and running electrical tape over them until it looks like a giant blob of tape.
Use wire nuts on low voltage or control wire in dry and accessible conditions but twist them so the wires stay neat and lay half of the conductors in one direction and the other half in the other direction and tape up in a neat fashion.
The same type of configuration with 3M Scotchlok crimp connectors for better moisture resistance than wire nuts.
In some mildly damp conditions you may be able to use self fusing silicone tape for a more water resistant layer than electrical tape.
Use butt end connectors on stranded wire or if using small gauge single conductor wire (like 18ga stat wire) you can double the end of the wire over before making a crimp. When making a crimp ensure that that the actual crimp is made on the side of the connector OPPOSITE the seam. Once you make a butt end connector pull HARD on it totect and ensure that no bare wire is exposed outside of the insulator.
Use heat shrink butt connectors and stagger the connections to reduce the bulge. Heat the connectors to seal them, then run a piece heat shrink over them all. I found this 4:1 shrink ratio, marine grade heat shrink that should do a great job or water proofing. Heat shrink can be a real life saver and you can use a heat gun or a small butane torch to heat it up. Coincidentally they also make little, portable butane soldering irons as well.
When making a soldered splice make sure to use rosin core solder and wipe off the rosin flux before covering the splice to help prevent corrosion. Remember to run the heat shrink over the cable and the individual conductors BEFORE you start making the splices to prevent sadness and yelling.
The best options are to just run a new wire or make the connections inside of a rate box with proper connectors. Sometimes the best way is the simplest way.
Watts law states that Watts = Volts x Amps. If a particular motor need to do 1 horsepower of work at 120 Volts it will draw about 6.22 amps. And yes in an inductive load like a motor it’s not quite as simple as VxA=P but we are keeping it simple here.
A motor designed to do the same amount of work (1HP) at 240v will draw half the Amps (3.11).
This does not make the second motor “more efficient” because the power company charges by the Kilowatt NOT by the amp.
) If you take a load that is designed for a particular voltage and you DROP the voltage it will also decrease the wattage according to Watts law (Watts = Volts x Amps) as well as decrease the amperage according to Ohm’s law (so long as the resistance remains the same).
Let’s say you take a 5KW heat strip that is rated as 5Kw at 240v and you instead connect it to 120v.
It would then only produce 1.25 kw and draw 1/4 the amps, this is because while we may call it a “5 Kilowatt heater” it is actually just a fixed resistor designed to do 5 kilowatts per hour of work in the form of heat at 240 Volts. Cut the Volts in half you also cut the amps in half the and you decrease the amount of work done down to 1/4.
I have spent the last few days checking run capacitors on various systems with several different meters and this is what I found.
#1 – Comparing Start wire amps against Run + Common under the clamp together is meaningless as a practical test.
I used this test on 3 different systems with 3 different meters and came to the same conclusion, whether the capacitor is way too large, way too small or the right size, made no repeatable difference in the reading no matter how we read it.
Even if this is a valid test (which I cannot confirm at this time) the difference is within the uncertainty tolerance of the meter so it’s not useful for field testing.
#2 – The under load test does work (If your meter works)
reading the amps at the herm (compressor start wire) terminal multiplying by 2652 and dividing by the start voltage (herm to c) on the capacitor does work consistently on the compressor and the fan motor however some meters are less accurate at lower amperage readings so that may make a slight difference.
#3 – Power Factor works as a test but it’s a small change
I tested several systems with the Testo 770-3 in power factor mode by installing too large and too small capacitors. The power factor did decrease in all cases when the incorrect size was installed but in some cases the difference was very slight (from 1 to .99 with a 15 mfd too small run capacitor in one case). This means that while it is a valid and useful test it may not be sensitive enough to act as verfication that a capacitor is slightly outside of allowable specs.
The week of 3/5/2017 was “Business week” on the HVAC school podcast and we talked about a full range of business topics. Here are our business related episodes.
Why Maintenance Agreements Matter and How to Make Them Work w/ Ruth King
In this episode Ruth King shares some of her top insights on how to create a maintenance program if you don’t have and how to fix the one you have if it is broken (and how to know).
If you are interested in Ruth’s maintenance program course you can find out more HERE and be sure to use the offer code HVACRS (with all caps) to get a 10% discount on all her products.
Should I Start My Own Business? (and other solid advice) w/ Tersh Blissette
Tersh and Bryan were both techs working for other companies when they started their own businesses. This is a look back at what they got right, what they got wrong and the top things that have worked over the years.
Profitability and Money Leaks in HVAC w/ Ruth King
In this episode Ruth breaks down some of the main things an Air Conditioning contractor needs to consider when looking at their numbers and some of the major leaks that can lead to unprofitability.
You can see all of Ruth’s content and courses HERE and make sure to use the offer code HVACRS with all caps for a great discount.
Creating a Business That People Want to Work for w/ Bob Gee
This is an older episode but it contains great principals for leading an HVAC business as well as some really good sales practices.
I am now going to give an even easier test.
A properly funcitioning PSC (permanent split capacitor) or CSCR (Capacitor Start Capacitor Run) motor should have a power factor of very close to 1 if they have a properly sized and functional capacitor.
If you have a multimeter that can read power factor directly (like the Testo 770-3) you can measure the power factor by reading the voltage at the contactor and the amperage at the motor common (like usual). If you are at or close to 1 power factor then your capacitor is both functional and the right size.
In the image above I have a compressor that calls for a 35 MFD capacitor and the capacitor is running right at 35 in the under load test as well as the bench test. This is why the power factor is right at 1. I installed a run capacitor of 10 MFD larger and smaller and sure enough… the power factor dropped in both cases.
As a side note I was only seeing about a .3 amp difference between Start and run / common together when I oversized the capacitor so I may have missed the issue if I had just used that test alone.
Now, in order to see exactly WHAT is wrong with the capacitor, whether it is failing or improperly sized, you would need to do the under load test (start winding amps x 2652 / capacitor Volts) or bench test the cap and then check against motor data plates.
But as a regular service procedure this power factor feature is a time saver and gives you a unique insight into the operation of the motor.
P.S. – If you are interested in the 770-3 use the offer code “getschooled” at TruTechtools.com for an 8% discount
A quick note about UV lights. They work like sunlight in that they prevent and kill many types of bacteria and fungi when exposed to the light on surfaces. They do not generally do a great job of killing spores suspended in the air stream.
UV lights are great at killing yucky stuff on surfaces like coils, blower wheel and panels. They won’t “kill” everything in the airstream and they don’t capture anything.
Also, be careful what UV is allowed to shine on. It will deteriorate most wire insulation and can deteriorate and discolor many other plastics.
Finally, don’t look at a UV light for any amount of time. I once spent a very uncomfortable day in bed after damaging my eyes from looking at UV indirectly for only a few minutes.
UV can be great, but it’s not a fix all and always be carefully where the light is going.
When testing a run capacitor many techs pull the leads off and use the capacitance setting on their meter to test the capacitor. On a system that is not running there isn’t anything wrong with this test, but when you are CONSTANTLY checking capacitors as a matter of regular testing and maintenance that extra step of pulling the connectors off can be time consuming and in these cases it is also totally unnecessary. Testing the capacitors UNDER LOAD (while running) is a great way to confirm that the capacitor is doing it’s job under real load conditions which is also more accurate than taking the reading with the unit off.
First, if you are used to doing capacitor checks during the “cleaning” stage of a PM you are going to need to change your practices and do your tests during the “testing” phase. These readings will be made at the same time you are taking other amperage and voltage readings during the run test.
This method is a practical method and is a composite of two different test practices combined –
If you need a visual, here are some good videos on the topic. Note that some will use 2650, some 2652 and some 2653. It all depends on how many decimals of pi they are using in their calculation but all of them will result in an accurate enough conclusion for our use.
At first doing it this way may take a few minutes longer but in the long run you will go quicker, have fewer mistakes (forgetting to put the terminals back), have a better understanding of how the equipment is operating and get a more accurate reading.
Once you replace a capacitor always recheck your readings to ensure the new capacitor reads correctly under load.
It is also a good practice to check Capacitors you have removed with your capacitance setting on your meter as a reference point.
While this method is good, it is only as good as your tools and your math. When in doubt, double check… and always be in doubt.