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Originally Posted by amana_heatingandair

Hi I heard about static pressures in class, but was never utilized. I feel like i am missing something huge. Is there a manual for newbees on static pressure measuring, where to measure, and what kinds of measurments we are supposed to see for different issues like blocked return etc....? Great topic

Welcome to HVAC-TALK. If you have scanned a few of the other posts in this "OPEN" (anyone can view) Tech-Tech forum, you probably have noticed we don't post manuals or technical information. This Tech-Tech forum is just a means for guys like you to work on getting Pro membership without getting too technical.

If you get your post count up to 15, and apply for PRO membership, it will allow you into the "LOCKED" Pro side of this forum where we openly talk and post technical information.

The other very important thing to do, is fill out your profile on this forum (under Forum Actions), including an email address (Stomp! Stomp!), so we can read a little about you.

So to answer your question, there is a lot of info/references on this subject that we would love to pass onto you, but can't until you get pro membership.

Again welcome, and look forward to seeing you on the other side.

Hi I heard about static pressures in class, but was never utilized. I feel like i am missing something huge. Is there a manual for newbees on static pressure measuring, where to measure, and what kinds of measurments we are supposed to see for different issues like blocked return etc....? Great topic

Originally Posted by tedkidd

:-)



You might want both. Nice to know sp of filter, just like nice to know coil.

So, drilling into the fan compartment, ok. But if coil directly atop furnace, what? Definitely not comfortable drilling coil box. There some trick to this?

I cut a piece of 3/8 copper tubing and sleeve the bit only allowing the tip to make the hole, the copper stops the bit from penetrating any further and do any damage.

I remove the limit, apply a piece of foil tape over the opening, and take my reading there if there isn't any room between the coil and the furnace.

Teddkid, I don't know how you deal with the weather in Rochester. I went to RIT back in 1999-2001. The lake effect snow and wind up there is killer. I realized why they had tunnels underground on campus to get around!

Originally Posted by ch4man

i drill a boat load of holes when testing. i use a 3/6" - 1/2" step bit. as for as the hole above standard furnace and below a-coil. keep an eye on the drain port. there should be no part of the coil below that.

some times even that isnt enough, such as cases coils. then the back of the furnace cabinet gets stabbed. if everywhere seems impossible a final option woulg be to replace any screw in the faceplate with a #10 panel screw and use the 1/8" diameter 12" pitot tube that dwyer sells. 1/8" tubing fits in a hole left by a # 10 screw

Awesome, Thanks!!!

... on the bit, I know I need to get one of those. Just keep flaking it.

Originally Posted by tedkidd

:-)



You might want both. Nice to know sp of filter, just like nice to know coil.


















So, drilling into the fan compartment, ok. But if coil directly atop furnace, what? Definitely not comfortable drilling coil box. There some trick to this?

i drill a boat load of holes when testing. i use a 3/6" - 1/2" step bit. as for as the hole above standard furnace and below a-coil. keep an eye on the drain port. there should be no part of the coil below that.

some times even that isnt enough, such as cases coils. then the back of the furnace cabinet gets stabbed. if everywhere seems impossible a final option woulg be to replace any screw in the faceplate with a #10 panel screw and use the 1/8" diameter 12" pitot tube that dwyer sells. 1/8" tubing fits in a hole left by a # 10 screw

Originally Posted by tedkidd

:-)

So, drilling into the fan compartment, ok. But if coil directly atop furnace, what? Definitely not comfortable drilling coil box. There some trick to this?

I've drilled right at the edge where the plenum meets the furnace casing.

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Originally Posted by DeHeatify

So if it's included am I to be taking the measurement from upstream or downstream of the filter? I have wondered this before...

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Originally Posted by ch4man

can i borrow your ductblaster?

yeah ive read about those too.

:-)

Originally Posted by DeHeatify

So if my manual says this. Do I take the measurements before or after the filter?

Attachment 333041

You might want both. Nice to know sp of filter, just like nice to know coil.

So, drilling into the fan compartment, ok. But if coil directly atop furnace, what? Definitely not comfortable drilling coil box. There some trick to this?

Went on a call about a month ago, gas pack had been through 3 ECM blower motors in 7 years they called us bc the company that changed the motors said they will only warranty the same piece 3 times in the 10 year warranty period, went out and opened the blower compartment door and the 18" flex was completely disconected from unit. How the other tech didn't see this when changing the blower 3 times is beyond me. Fixed the duct and put new motor in and the next day the customer called and asked what we did bc the unit was keeping the house cool and not running all the time like it had. There was not sp on the return duct causing the motor to overamp and burn up the ECM motor. Had it been a psc it would have pulled less amps.

You should always take static pressure readings when you suspect airflow problems. Signs of airflow problems could be furnace tripping on high limit, low suction pressures, icing evaporator. Most furnaces will have the design Total External Static Pressure (TESP) listed on the nameplate. If your total TESP is more than what the manufacture specifies, your duct work it too restrictive and the fan will not deliver the designed airflow. Your TESP measurement should include filter pressure drop. Measure the discharge static in the supply plenum far enough downstream to minimize turbulence. Measure the return static downstream of the filter and before the fan.
TESP will not tell you how many CFMs the fan is delivering only that the duct resistance it too high to deliver the design CFM. Most situations you might find that the return is too restrictive. There are many causes of too much restriction in the duct but thats another discussion. You might also find that the pressure is too low. Too low of a TESP can cause problems with some equipment. Mainly, to low of a pressure can cause fans to over amp and with some units can cause fans not to perform.

Originally Posted by DeHeatify

see this is where the problem with manufacture data..no standards. I have learned to take esp readings from after the filter and before the a/c coil. and was confirmed here....yet I download my service manual and it shows this:

Attachment 333451

aaaand I'm confused again......

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Yeah, standardization would be nice.

Originally Posted by DeHeatify

see this is where the problem with manufacture data..no standards. I have learned to take esp readings from after the filter and before the a/c coil. and was confirmed here....yet I download my service manual and it shows this:
aaaand I'm confused again......

My G50UH service manual says this in the notes of blower performance data: Also see Filter Air Resistance table.

Which means if you place the probe before the filter as they show in your picture, you still need to account for the PD of the filter based on the Filter Air Resistance chart in the manual.

Either way works.

Originally Posted by beenthere

Between filter and furnace.

see this is where the problem with manufacture data..no standards. I have learned to take esp readings from after the filter and before the a/c coil. and was confirmed here....yet I download my service manual and it shows this:

Attachment 333451

aaaand I'm confused again......

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davidr

It is not the same.

Originally Posted by beenthere

Between filter and furnace.

Good. That's where I've been taking them.

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Originally Posted by DeHeatify

So if my manual says this. Do I take the measurements before or after the filter?

Attachment 333041

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Between filter and furnace.

Originally Posted by tipsrfine

It is more than likely that what BT said about not having a straight piece of duct to test. Based on everything I've read (although there is always disagreement) using a ductblaster as a active (powered) flow hood is the more accurate method for testing air flow in residential systems. The following study indicates they a vastly more accurate than other flow hoods. http://epb.lbl.gov/publications/pdf/lbnl-49697.pdf

We did some through research of our own comparing real air balancing hoods to a powered capture hood.

Most readings on the average were within 5 CFM of each other.

If you really read that report in detail and don't take it for face value the results are skewed.

Originally Posted by energy star

NCI classes are not recognized by the Air Balance Council. Not saying you need that, but if you want to be an actual independent balancer certified to submit reports to clients requested by the state, or a commercial project by a builder, NCI is meaningless. Too many classes and companies in our industry creating these certifications with the only goal being a new source of revenue for them.

Why would it matter if NCI is recognized by AABC? They are another balancing organization.

There are a lot of architects and engineers accepting NCI certification on their projects. On some projects it is actually being spec'd.

If they accept a submittal package for the NCI certification, then NCI certification is absolutely valid for that architect or engineer.

So if my manual says this. Do I take the measurements before or after the filter?

Attachment 333041

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can i borrow your ductblaster?

yeah ive read about those too.

oh well, this is only one system. ive decided to forget about for a while. but am still looking for example from other techs and ideas/info from the TAB guys.

peace out