Search:

When using Static Pressure as the target measurement for desired volume the formula becomes SP2 = SP1 x (CFM2/CFM1) squared

A calibrated capture hood is the easiest and most convienient method of measurement since you don't need to use a "correction factor" for the Ak (free area factor) which would be required using a...

In keeping with the general "rule of thumb" that 400 - 500 cfm expected per ton of cooling then, 430 cfm return would be low, or about 21% of the estimated 2,000 total cfm for a 5 ton unit (unless...

Depends on if the unit is single fan or dual fan. (supply fan only or supply and return fans)
Also, if dual fan, what minimum OA and minimum EA design is at full mechanical cooling.
If single fan,...

For TRANE VAV's, the K-Factors is actually the volume in CFM that the box should deliver at 1.00 inch of pressure drop.
How-ever, these are based on ideal installed conditions which are not always...

I had a rank odor coming through my house duct system.
Traced it out and found a dead. half-rotten rat in the main duct.
The smell would knock a dog off a gut-wagon.

TAB = Testing, Adjusting and Balancing
(never thought about TAB = music tabulation) good one tho!

Check out this one and reply what cha think.

http://www.youtube.com/watch?v=O9mEKMz2Pvo

For the most part, adding restriction to the available air flow will also lower the current draw. This also depends on what TYPE of fan wheel you have.
If "Vaneaxial fans" are used, adding...

CV values of valves are also typically based on straight water without any additives such as glycol or rust inhibitors, etc.
If additives are used then there is a correction factor required.
If you...

The CV value of valves are typically the volume of water in (GPM) the valve will provide at a 1.0 psi drop at full open.

Have you checked the possibility of an air bound coil?
Air becoming trapped at coil high points can cause water flow to be sluggish.
Try venting the system at high points until you burp it.

You could put electric strip heat in the ducts but you would have to add in the electrical cost of running the fan. They work like toasters.
Electric heat is 100% efficient. Only trouble with that...

I/R readings are best I find for verifying temperature differentials.
Even if the actual temperatures tested are "off"...they will be "off" by the same amount of error giving you a good indication...

...dryer than a Popcorn Fart.

... is the cats meow. I've seen conditions in early mornings where OSA temps are 55 - 60 degrees with RH levels at 90% or higher. (dense fog from dew lifting off the ground and surface water...

....the amount of CFM a box will deliver at 1 inch of differentialpressure.

.....you are just simply using temperature/color shade as the medium of determination.

....work on a differential pressure based curve...I'm thinking that outside air intake ducting will typically offer less resistence then it's return air ducting. There-fore, to move the same amount...

....that capacity loss will always be found when using glycol in a system.
The loss when the mixture is above 30 - 40 % is greatly increased.
Good ol' plain water (no additives like floride,...

20 years experience; industrial/commercial/light commercial projects; have own equipment and transportation; looking for temporary balancing work and willing to relocate for a couple months....

....will not work well under extreme load conditions unless it has been accurately and adequately balanced. Comfort levels may or may not be adversely affected under light load conditions. This is...

....by sequencing the variable damper to full closed, how does the occupied spaces satisfy minimumoutside air requirements?
Just curious....

.... is called a "hurricane louver." I think what you want is something that offers the total air mass flow you require at a low inlet velocity to keep from drawing the snow in with fresh air.
I've...

.....there's over 6,500 construction jobs bidding in Texas right now worth 2.2 billion.
(just remember to tip yer hat to the ladies while your there)

..... welcome HVAC TALK newest member olc ! :)

...guess I'd better throw my 10" manometer away then huh?

.... is in need of a certified balancer (air & water) with my own equipment I might be able to break away a few weeks or so this winter.....

....that the sensed outside air temperature was 10 degrees below the actual measured at any given point in time.
That probably doesn't help matters when free cooling is being allowed at 10 degrees...

....across the unit to compare with mfg. fan curve.
I've seen correct voltage connected to wrong motor winding leads before. which resulted in the same conditions as what you describe here. Low...

..... try taking a wet bulb/dry bulb reading at the supply air duct branches serving the areas with the concern.
Compare these readings to samples taken within the air ducts of areas that are fine....

Is the supply and return ducts connected solid to the unit or was flex (canvas) used.
Hard ducted units can generate vibration and harmonics, and harmonics can create additional vibrations and...

Rather than to go real deep into it, I was making a generalized statement as to high amp draw vs. reverse rotation of a fan. In most cases, a fan running backwards will deliver substantially less air...

....... build up a good reputation and bank account and don't expect to show a solid profit for a least 2 - 3 years.
Hire qualified techs and expect to work lots of hours until you get things up and...

....... told the M.C. his pump was in backwards and he said "go get an electrician to swap leads then, thats HIS problem."
I said, " No sir- you don't understand...rotation is fine... your pumps are...

...... from the high 80 to 90 percent, to the present 67 percent. They are installing enthalpy control which will help too. This morning was 60 degess with a heavy fog bank that didn't burn off til...

....... in the efficiency of the coil performance can be realized in the removal of latent heat, that the current 70 - 75% humidity levels will reduce to 40 - 50%. That would be sweet.
Could anyone...

..........concerning the high humidity levels in the building (typically 70 - 75%) they have finally decided to change all chilled coils to counter-flow arrangements.
The biggest wrench in the works...

........ WD-40 is not really a very good penatrating fluid.
I use PB Blaster from the car parts store (it eats the rust away). Try it once and you'll be sold on it. :)

........ will still move air in the right direction: there will be alot less of it and current draw will be very high.
If you have air being supplied through the return duct system.........something...

.............. I don't use my thumb for a rule.
For you guys that do "comfort balancing" as part of a service call or a design build concept where an independant balancer is not required, the rule...

IMO (regarding mechanical systems) the only stupid questions are the ones that don't get asked.

The RTU's could be repiped at their present connected side of the coils, as they are fed by risers...

...... the supply air sensor is duct mounted about 25 feet downstream.
Hot water preheat coils are before the chilled coils.

..... are being addressed first.
The economizer setpoint has been 67 degrees which is a bit high for Northern New England. We've had quite a few weeks of "dog days" with outside temps of 65 - 70...

A recent concern has been flagged by me in regards to a chilled water system I balanced that has several large coils piped in a "parallel flow" arrangement as opposed to the typically found...

........ it is a matter of having the curve for the size valve and its model/make.
Keep in mind tho' that hydronic system balancing is based upon a system "full load" consideration. If its a hot...

......... replaced with electrical conduit at an Elementary School air handler. (GC snapped a few pics of that one)

An entire living space above the ceiling of a public library.
cable T.V.;...

....... specs usually call for special corrosion resistent materials when located near or on coastal properties.

again, access to the systems is sometimes a valuable reference in such cases where controls want to charge for something thats required for your work (hardware and software).
If specs are vague on...

....... has about 180 VAV,s with reheat coils. The boxes and RTU's are TRANE and the control system is Circon.
A large percent of the vav terminals have had problems at the little drive motors...