Thank you so much for your videos I know you do not get millions of views but I promise you The people like me that are viewing these videos highly appreciate you thank you
I have a room we have just replaced a 4 ton rooftop unit , the old unit was burned out , now my grills are sweating , if I take the room temp WB and DB and read the DP , how can I apply these info to make corrections so we wont have this issue These are the info I think I have to obtain 1- room temp WB 2- Room Temp DB 3- return Air WB and DB 4- SUPPLY AIR TEMP AT GRILLS 5-RH OF ROOM 6- RH OF RETURN AIR 7- RH OS SUPPLY AIR
Thank you for doing this. I’m trying to wrap my mind around using wetbulb measurements for performance. Is or was wet bulb the standard along with dry bulb because wet bulb was easier to measure before digital psychrometer meters? Using the two points to determine RH for latent loads? Thansk
When referring to performance measurements, you will need to measure dry bulb temperature across the evap and wet bulb temperature across the evap. Then there are some formulas which will translate those temperature differences into BTU/h. The dry bulb performance indicates sensible heat removal while the wet bulb performance indicates latent heat removal. In my experience, it is difficult to get a really accurate field measurement of wet bulb discharge air temperature. You really need about five duct diameters of straight duct after the evap to do it well. Failing that, you need a special instrument to take a duct traverse and average the measurement. In manufacturer's published performance specs, you will see two specifications: sensible BTU/h and Total BTU/h. The difference between the two is the latent BTU/h which you need do a little subtraction to figure out for yourself. These same specs will often also show what the evaporator dry bulb temperature difference will be at these performance points. This is much easier to measure and as long as you have all the other points covered, you can be "field certain" that you are good to go. In the world of performance contracting, they are often much more concerned with total heat removal in real time than your average service tech. Due to the aforementioned challenge getting good supply air WB measurements, I often wonder how valuable this metric is.
The yellow, General unit that you were showing next to the sling , I purchased it on Amazon for about $84 and I’m pretty happy with it. The slim design makes it easy to wedge between return grill slats especially on ceiling mounted returns. It also makes it easy to forget and leave behind 😂
I've been using a pair of the Fieldpiece wireless psychrometers for a while. They're pretty slick in that you can read the results of both probes at once from a distance. The only problem is the flexible neck is a fairly large diameter, so it can be hard to get access to the supply and return air without drilling big holes.
HVAC student, here. Minute 9:10 you state that Target Superheat chart is for fixed metering devices only. I had understood that we can also use the superheat chart to verify that the TXV is working properly. Did I have the wrong concept?
A TXV is meant to maintain a constant superheat across a wide variety of operating conditions. On a fixed Metering Device, superheat will change as operating conditions change.
Why is dry bulb measured by outside air while wet bulb is taken inside? Isn't that apples and oranges? Of course outside will be higher wet or dry. Outside air is not conditioned and is not going to be run through the system. What am I missing?
Outdoor dry bulb air temp influences the head pressure which changes the flow rate of refrigerant into the evaporator on fixed metering device systems. You need to know that in order to analyze superheat with a fixed metering device. Indoor wet bulb is the factor which influences how quickly the refrigerant in the evaporator boils off.
Thank you so much for your videos I know you do not get millions of views but I promise you The people like me that are viewing these videos highly appreciate you thank you
I have a room we have just replaced a 4 ton rooftop unit , the old unit was burned out , now my grills are sweating , if I take the room temp WB and DB and read the DP , how can I apply these info to make corrections so we wont have this issue
These are the info I think I have to obtain
1- room temp WB
2- Room Temp DB
3- return Air WB and DB
4- SUPPLY AIR TEMP AT GRILLS
5-RH OF ROOM
6- RH OF RETURN AIR
7- RH OS SUPPLY AIR
Fluke = waste of money, i got two and they read totally different
Gotta keep em calibrated
Thank you for doing this. I’m trying to wrap my mind around using wetbulb measurements for performance. Is or was wet bulb the standard along with dry bulb
because wet bulb was easier to measure before digital psychrometer meters? Using the two points to determine RH for latent loads?
Thansk
When referring to performance measurements, you will need to measure dry bulb temperature across the evap and wet bulb temperature across the evap. Then there are some formulas which will translate those temperature differences into BTU/h. The dry bulb performance indicates sensible heat removal while the wet bulb performance indicates latent heat removal. In my experience, it is difficult to get a really accurate field measurement of wet bulb discharge air temperature. You really need about five duct diameters of straight duct after the evap to do it well. Failing that, you need a special instrument to take a duct traverse and average the measurement.
In manufacturer's published performance specs, you will see two specifications: sensible BTU/h and Total BTU/h. The difference between the two is the latent BTU/h which you need do a little subtraction to figure out for yourself. These same specs will often also show what the evaporator dry bulb temperature difference will be at these performance points. This is much easier to measure and as long as you have all the other points covered, you can be "field certain" that you are good to go.
In the world of performance contracting, they are often much more concerned with total heat removal in real time than your average service tech. Due to the aforementioned challenge getting good supply air WB measurements, I often wonder how valuable this metric is.
How to get the outdoor temperature in °C?
The yellow, General unit that you were showing next to the sling , I purchased it on Amazon for about $84 and I’m pretty happy with it. The slim design makes it easy to wedge between return grill slats especially on ceiling mounted returns. It also makes it easy to forget and leave behind 😂
Thanks for the feedback!
I've been using a pair of the Fieldpiece wireless psychrometers for a while. They're pretty slick in that you can read the results of both probes at once from a distance. The only problem is the flexible neck is a fairly large diameter, so it can be hard to get access to the supply and return air without drilling big holes.
Do these work reliably in refrigeration?
Refrigeration tries to remove as little moisture as possible. I'm not aware of a good use for psychrometers in typical refrigeration applications.
Thanks, great information. Keep going, we’re rocking down here in central Florida. Now with your knowledge on our side!
Great video , thanks for simplifying this information. 👍🏼
HVAC student, here. Minute 9:10 you state that Target Superheat chart is for fixed metering devices only. I had understood that we can also use the superheat chart to verify that the TXV is working properly. Did I have the wrong concept?
A TXV is meant to maintain a constant superheat across a wide variety of operating conditions. On a fixed Metering Device, superheat will change as operating conditions change.
@@hvacservicementor Wouldn't target superheat work for adjusting the txv?
Excellent overview! Thank you.
Hi! Is a digital psychrometer suitable to measure air conditions at the outlet of small cooling towers? Thanks :)
Hey I'm applying for a grant and need a mentor can you help?
Great video
Glad you enjoyed it
Why is dry bulb measured by outside air while wet bulb is taken inside? Isn't that apples and oranges? Of course outside will be higher wet or dry. Outside air is not conditioned and is not going to be run through the system. What am I missing?
Outdoor dry bulb air temp influences the head pressure which changes the flow rate of refrigerant into the evaporator on fixed metering device systems. You need to know that in order to analyze superheat with a fixed metering device. Indoor wet bulb is the factor which influences how quickly the refrigerant in the evaporator boils off.
@@hvacservicementor thanks for the quick reply! That makes sense. What is edl?
Great video. Thanks for sharing.
I like my UEI Psychometer, it's fragile but its got a nice big display and gets readings fast.