Most techs and installers know that drains need to be pitched. I use the rule of thumb that drain lines should generally be pitched 1/4″ per foot of horizontal run. One thing that can easily be forgotten in pitching wall penetrations when drilling. It’s as simple as drilling with a slight upward angle if drilling from the outside or slightly downward from the inside. The goal is to have the outdoor side lower than indoors both to assist in draining system condensate and to prevent exterior moisture from running into the building. You will also want to make sure that the drain doesn’t get run on top of copper, or go up and down for any other reason. This is especially common in Ductless systems with flexible drains. Keep that pitch moving the right direction from start to finish and all will be well. — Bray.

 

As a technician you most likely know some customers who still have an oldie thermostat (you know, those old mercury bulb things, like the round Honeywell CT87 and such).  Keep in mind those usually have an adjustable heat anticipator.  If you’re newer in the field  you may not have seen or worked with those very much, or even not at all.  They can seem confusing at first (why is it set with amperage? What amperage? How am I actually adjusting this???) but actually are quite simple to work with.

 

First of all, I hear you thinking “do you actually need to adjust that?  I mean, is it going to make that much of a difference?”  Honestly, in most cases, no, it won’t make a big difference.  But it’s no reason to ignore it.  And when it actually does make a difference, you will want to know how to adjust it properly.

 

Here’s a hypothetical story: you just changed a system, let’s say converted from a 30 year old oil furnace to a brand new condensing gas furnace.  The homeowner just loves their old, simple, ‘’I-just-have-to-turn-it-up-or-down’’ thermostat and won’t upgrade it to a modern digital one.  And hey, it still works fine, so why bother.  Then, a few days later, you get this service call:  ‘’that new furnace you guys just put in, it doesn’t work right!  It keeps starting and stopping every 5 minutes! (or) It stays on for too long and overshoots the set temperature by a whole degree!’’  (and the line everybody loves to hear): ‘’It didn’t do that with my old furnace!  It’s that new one, you sold me defective garbage equipment!!!’’

 

Okay, it doesn’t happen like that all the time, but I’m sure you’ve heard of similar stories.  Now, to focus on the problem.  I’m writing this tip about heat anticipators, but please don’t assume that’s going to be the issue whenever you get this kind of service call.  I am merely reminding you that it is one of the many possible problems.  So let’s say everything else is normal, no faults occurring during furnace cycles, no airflow issues, proper system sizing, etc.  There’s a chance a very poorly adjusted heat anticipator will make a significant difference in cycle time.  After all, it’s what it’s designed to do.

 

In short, the anticipator is simply a resistor built in the thermostat that is in series with the heat call low voltage circuit, i.e. the “W” terminal.  That resistor generates a tiny amount of heat to preheat the bi-metal and end the furnace cycle a little bit earlier, anticipating the residual heat from the furnace and fan off delay to cover the gap in temperature and avoid overheating the space.  Now, even though it’s a resistor, you don’t set it by ohms.  You set it by amperage.  The amperage drawn by the heat control circuit.

 

Now it takes a little bit of effort to get that measurement properly, but it is quite simple.  First of all, you need to remove the anticipator itself from the circuit when checking the control’s amp draw!  All this means is you need to remove the thermostat from the circuit by twisting together the R and W wires at the thermostat.  This will, obviously, give you a constant call for heat.

 

Now the amperage you need to measure is typically very low, no more than half an amp in most cases, sometimes much lower.  So, in order to get a more precise reading (unless you have a super sweet meter that gives you precise readings in the tenths to hundredths of an amp range, this would be done in series instead of with a clamp) you should proceed as follows:  get a nice very long piece of thermostat wire, which you will repeatedly wrap around your meter clamp, so it goes through it 10 times.  Then connect that wire to your W wire from the thermostat on one end and to the W terminal on your furnace control on the other end.  Simply put, just extend the W wire so that you have enough to wrap it around the clamp ten times.  Then turn the power on and let the furnace cycle begin.  Wait until all the relays and components are energized (on a typical gas furnace you will see the greatest amp draw coming when the gas valve is energized), then take your reading.  Divide it by 10, and you have your heat anticipator adjustment value.  Simple as that.  For example, you might read (completely arbitrarily) 2.40 Amps on your meter with ten wraps of wire.  Which means the control actually draws 0.24 Amps, so you will need to set your heat anticipator to 0.24.  It is recommended to insert the tip of a pen or something similar in the slot to gently slide the needle to the desired setting.  And this procedure, by the way, is still explained in modern install manuals.

Honeywell also gives a basic guideline for different heat types

 

To further adjust cycle times if the actual setting doesn’t seem to work quite right, you may change it accordingly: higher amperage setting = longer cycle time lower setting = shorter run time.  I wouldn’t stray too much from the ‘’proper’’ setting, however.

 

 

— Ben Mongeau

We had a really great conversation on the HVAC School Facebook Group about some belt tension best practices and it turns out that even a lot of really smart and experienced techs are not aware of all the factors related to belt tensioning.

Myth #1 is that amperage is used to set belt tension. Now don’t get me wrong, checking amperage before and after changing belt tension is an excellent practice to ensure you are not binding the bearings from over tension, it does not tell you whether or not the belt is at optimum tension.

I think Browning summarizes it best in this statement from their Browning tool box technician app

Ideal tension is the lowest tension at which the belt will not slip under peak load conditions

Getting a belt too tight shortens the life of the belt and bearings and can cause high amperage. Leaving a belt too loose will shorten the belt life and result in loss of airflow and noise.

Many techs confuse the sheave adjustment, designed to alter the pulley ratio and the airflow with the belt tension adjustment. These are not the same thing and serve separate purposes.

The adjustable sheave allows the pulley faces to adjust closer or further from one another, resulting in a belt that rides closer to the hub when looser (halves further apart) or closer to the edge when tighter  (halves further separated) THIS ADJUSTMENT IS FOR FAN SPEED ONLY NOT TENSIONING

A properly tensioned belt should not slip significantly when starting, it should not be noisy and it should not bounce around. If you tighten the belt check the amps before and after and the motor should not overamp.

The correct tension method is to get the belt close to the correct tension by feel with a deflection of 1/64 of an inch for every 1″ of distance between the two pulley centers. You can then use an app or a chart like THIS ONE to find the proper force to generate this deflection.

You would then use a belt deflection tool like the one shown above to test the deflection force required and adjust accordingly. The video below demonstrates this.

I like what Jeremy Smith stated in the group “Belt tension has less impact on motor amperage than pitch diameter of the sheave and how that affects total airflow. Use the Emerson tool and the app (or paper chart if you’re all stone age) Record tension and other data (sheave diameter, center to center length, rpm and proper tension) on the blower housing.”

Check those belts during commissioning, maintenance and service and change them as needed.

— Bryan

Scroll to top
Translate »

Daily Tech Tip

Get the (near) daily Tech Tip email right in your inbox!
Email address
Name