Measuring Humidity Levels

[summerblues]

As a maintenance person, all my units are fixed orifice, 1.5- 2 ton units, split systems.

To acurately measure the charge and determine superheat I know I should be
using a sling phychometer to determine wet bulb temp in an apartment.

Is there any way to fake it ?

For example if the weather report determines the humidity level in the area,
is there a standard rule you can use , for example outside humidity + 5 percent more of humidity to determine inside wet bulb, or is this just rediculus ?

[pstu]

There must be some professional quality instrument which will deliver humidity conveniently and accurately. I understand the sling psychrometer is traditional and accurate, but it sounds like a bit of effort to use.

I'm a homeowner who likes to monitor %RH using cheap thermometer gadgets from Walmart. Convenient but not all that accurate, I'm thinking you need something of quality about 10x more expensive.

Based on my humidity measurements, I can most definitely promise you that outside humidity +5% has no relation to what's going on inside my house.

Hope this helps -- Pstu

[hvaclover]

As a maintenance person, all my units are fixed orifice, 1.5- 2 ton units, split systems.

To acurately measure the charge and determine superheat I know I should be
using a sling phychometer to determine wet bulb temp in an apartment.

Is there any way to fake it ?

For example if the weather report determines the humidity level in the area,
is there a standard rule you can use , for example outside humidity + 5 percent more of humidity to determine inside wet bulb, or is this just rediculus ?

A sling is a pain to use for varying reasons. The biggest is you must take a whole bunch of reading and average it out if in a large area.

Try the Yellow Jacket site as well as Testo.
For 80 bucks you can buy an electronic hygrometer (fancy name for a RH meter)

No u can't fake it. You either use the relevent data required or you take a SWAG.

[BigJon3475]

(http://www.johnsnhweather.com/rh.html)

[Talen]

Wrap a wet paper towel around the end of your thermometer.Then put it in your return air grill.Try it, it works!

[BigJon3475]

How accurately?

[hvaclover]

How accurately?

Dig it.

[Shophound]

Get you one of these:

http://www.nationalcomfortinstitute.com/members/images/products/TestoSticksB.jpg

A temperature/humidity stick. The probe is small enough to insert easily into a supply plenum while doing capacity checks. Measures temperature, humidity, and converts to wet bulb. I have one on order from National Comfort Institute. It's made by Testo. Last night at my RSES chapter meeting a fellow tech showed me his and it is the bee's knees.

[hvaclover]

Get you one of these:

[IMG]http:// Last night at my RSES chapter meeting a fellow tech showed me his and it is the bee's knees.

ok i wont ...:D

[Shophound]

ok i wont ...:D

Sheesh...get your mind out of the gutter, dude. :D

[hvaclover]

Heh, yeah.:rolleyes:

[wconell]

Last night at my RSES chapter meeting a fellow tech showed me his and it is the bee's knees.

Bee's have knee's? :eek:
I shouldn't have slept thru biology!:confused:

[hvaclover]

Bee's have knee's? :eek:
I shouldn't have slept thru biology!:confused:

Yeah and crickets have ears in their shins!:p :p

[chillbilly]

I use a digital psychrometer to determine wet bulb temp, find the ODDB and then I use the slide chart to determine required superheat.

If not, I can use a psycrometric chart using IDB and RH or specific humidity levels to determine wet bulb temp.

[hvaclover]

I use a digital psychrometer to determine wet bulb temp, find the ODDB and then I use the slide chart to determine required superheat.

If not, I can use a psycrometric chart using IDB and RH or specific humidity levels to determine wet bulb temp.

i have a CPS Temp Seeker with humidity probe. It uses a psych chart too but it is hard to read.

I've got my eye on a digital Amprobe digital.

"til I do buy it it's either squinting at the chart w/magnifying glass or i do a Bruce Lee impersonation with my sling.

[BigJon3475]

I use a digital psychrometer to determine wet bulb temp, find the ODDB and then I use the slide chart to determine required superheat.

If not, I can use a psycrometric chart using IDB and RH or specific humidity levels to determine wet bulb temp.


Just need to know your station pressure and you can use this nifty little device.

http://www.johnsnhweather.com/rh.html

[dan sw fl]

There must be some professional quality instrument which will deliver humidity conveniently and accurately. I understand the sling psychrometer is traditional and accurate, but it sounds like a bit of effort to use.

Keep It Simple ( AND More Accurate)

http://www2.oregonscientific.com/shop/product.asp?cid=18&scid=70&pid=505
Oregon Scientiifc model EB313

Available at Lowe's in the garden section / outdoor thermostats.
TRY IT for ~ $25 ... You will like the simplicity !
(except maybe for the SLOW response time)

[elkhvac]

Wrap a wet paper towel around the end of your thermometer.Then put it in your return air grill.Try it, it works!

An old shoelace works very well also.

My digital yellow Jacket is much faster.:)

[teddy bear]

http://www.nkhome.com/ww/4000.html, http://www.nkhome.com/
This is an accurate meter with dew point, wb, air flow, etc. Very durable also. TB

[BigJon3475]

http://www.nkhome.com/ww/4000.html, http://www.nkhome.com/
This is an accurate meter with dew point, wb, air flow, etc. Very durable also. TB

For $330 my right arm will be like popeyes....

[dan sw fl]

Keep It Simple ( AND More Accurate)

http://www2.oregonscientific.com/shop/product.asp?cid=18&scid=70&pid=505
Oregon Scientiifc model EB313

Available at Lowe's in the garden section / outdoor thermostats.
TRY IT for ~ $25 ... You will like the simplicity !
(except maybe for the SLOW response time)

H.O. need something less accurate,
but gives a very good clue on equipment performance
and very cheap.

77'F Room Temp
54'F Container of Water
.. Container is not sweating .. % R.H. < 48%.
___________________
59'F Container is sweating .. % R.H. ~ 54%.

_______
My current readings ... 79'F room temperature ...
~ 52'F Dew point using "cool liquid container" = 42% Relative Humidity
which is the same as my two hygrometers ( 42% & 41%)

[allan38]

As a maintenance person, all my units are fixed orifice, 1.5- 2 ton units, split systems.

To acurately measure the charge and determine superheat I know I should be
using a sling phychometer to determine wet bulb temp in an apartment.

Is there any way to fake it ?

For example if the weather report determines the humidity level in the area,
is there a standard rule you can use , for example outside humidity + 5 percent more of humidity to determine inside wet bulb, or is this just rediculus ?

I use an amprobe digital psycrometer, much faster than the sling. Bought a sling a couple of seasons ago, used it 5 times. Bought the digital and wear it on my belt. Use it every call. It's convenient and fast. Worth every penny.

You can't use a simple rule of thumb based on the outdoor humidity. Too many variables are involved.

If the system is still working some then it may be removing humidity.
People produce humidity during normal living activities. If the building occupant has been cooking or taken a shower humidity will be much higher.

[hvaclover]

For $330 my right arm will be like popeyes....

ROFLMAO

You sure it's from the sling and not some thing else:cool: :D ?