Tag: BTU

Let’s get through all of the jargon and try to get to the point as quickly as possible. All of these ratings are a calculation of how much energy you have to put into a system in order to get a BTU of heating or cooling out.

Simple…

But the problem is that cooling and heat pump equipment has a bunch of variables that impact the numbers so they are all a little different.

Here is a quick summary

EER (energy efficiency ratio) = BTUh of output ÷ Watts of Energy Input 

The nice thing with EER is you can measure it real-time if you know the watts being used and the BTU’s being produced. No conversions needed, no fancy math. Measured EER is an easy snapshot but rated EER is another matter as it is only based on RATED conditions. It doesn’t take into account seasonal temperature or runtime variations.

COP (coefficient of performance) = BTUh output ÷ BTUh of Energy Input 

In other words COP is the same as EER but you convert the input to BTUh from watts by multiplying watts by 3.413. Also easy with one more bit of math added in. The same issue in that it is snapshot of performance or based on only one set of operating conditions.

SEER (Seasonal Energy Efficiency Ratio) = BTUh output ÷ Watts of Energy Input / Averaged over an entire cooling season 

So SEER is just like EER but theoretically would be the average EER if you measured it all through the cooling season and then averaged it. The PROBLEM is that isn’t the same everywhere… so it is still based on a set of conditions that are meant to replicate an average.

HSPF (Heating seasonal performance factor) = BTUh output ÷ Watts of Energy Input / Averaged over an entire heating season 

This makes HSPF exactly like the SEER but the winter (heating season) version where the EER is calculated and then averaged out. The same challenge exists in that not all places have the same set of operating conditions.

The solution lies in understanding each efficiency measure as well as the requirements of the particular market you work in to provide your customers with the best possible products to serve their needs. If you live in a market with very high outdoor temps like Phoenix you want to look at the extended performance data on the equipment you see and find systems that continue t perform well at high temperatures.

If you are installing a heat pump in Maine the same is true but reverse it.

Ratings are great… being situationally aware is greater.

— Bryan

 

 

I got in one of these tiny torches the other day to experiment with brazing aluminum in tight spots and one of the techs walked in and asked “what type of torch is that” to which I answered “It’s oxy/acetylene”, he picked it up and looked at it a bit then asked “Does that get hot enough to braze copper?”

It’s actually a tough question to answer simply

When we say does something get “hot enough” we often mean that the TEMPERATURE is high enough to melt solder or brazing rod, but heat is both an intensity (temperature) and a quantity (BTUs), so while this tiny torch is certainly high enough temperature to melt a rod, it may or may not be enough BTUs to heat up the base metal being joined.

The temperature of the flame is primarily dictated by the fuel or fuels being burned as well as the oxygen mixture. The BTUs depending on the pressure being used and the size/type of the tip.

Most torch manufacturers will list the size of the (copper) pipe that the tip is rated for as well as the proper oxygen and acetylene pressures for the task.

So, heat is both a quantity (BTU) and an intensity (Temperature) and when we say how hot or how cold it really depends on what you mean.  But to answer the question… Yes ,you can braze copper with the tiny torch, so long as it is small tubing.

— Bryan


We all learned how to read the tonnage off of a model number within a few weeks of beginning in the trade. What you may (or may not) have learned is that just because something has an 036 in the model number does not mean it actually produces 36,000 btu/hr even during RATED conditions let alone real world conditions.

Some of you may be used to pulling up an AHRI rating to find the true capacity of a system match. This is a good start and often you will find out that the the system produces slightly less to up 4,000 btu/hr less than the nominal rating. Here is the AHRI ratings for the system I have on my home.

You will notice that the 2-ton matches actually produces 24,000 btu/hr at the rated conditions, which are REALLY WARM temps inside and out by the way. However the 4-ton match produces 46,000 btu/hr at the same conditions.

Here is an example of some real world capacity readings I took on my Carrier VNA8 4-ton system with the Testo Smart Probes app and two 605i thermo-hygrometers.


This is a 4 ton unit with a proper charge (right at 11.6 subcool like the Infinity stat calls for) a 0.45 TESP and it’s been running for 30 minutes at high stage. You might be tempted to think something is wrong with the measurement or the unit, but we need to look closer.


You will notice pretty quick that my indoor temperature is low (68.3db)with a low indoor RH (54%) which equates to a 57 degree wet bulb indoor return.

Also, the outdoor temperature is only 72 degrees DB. In order to tell if 41,000 btu/hr is within range or not we will need to look in detail at the manufacturers expanded performance data located in the product data.

Here is the expanded data for this particular match and we lucked out. My air handler, condenser and suction line size are the match that the rating is based on. In some cases you will need to use a multiplier based on an alternate match or smaller copper sizes which can further reduce the rated capacity and possibly the efficiency as well like in the case of the FE4ANF003 or 002 below.

Now let’s zoom in on the performance data that applies to our actual conditions and see how we did.

The highlighted figure is the closest this chart comes to our actual conditions, though our indoor dry bulb is actually significantly lower than the 75 degree DB on the chart. So now the real world 41,223 btu/hr actually stacks up pretty well with the 42,870 btu/hr on the chart.

All of this to say that when sizing equipment and when testing capacity there is a LOT more to it than just the nominal tonnage in the model #. The only real way to know is to dig into the manufacturer product data and really understand that piece of equipment of equipment.

— Bryan

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