Finally getting static pressure checked

[key1cc]

Why would you want to do that if you paid good money for a TWO stage furnace??



How many sq ft is the home, and where are you out of?

I'm in central NJ and the house is 2 story 2800 sq. ft. double pane windows, 30 years old.
Key1

[key1cc]

I spoke with my installer today and he indicated that he had to order some sophisticated equipment to do my static pressure...and it has not come in yet.
I'm not getting a warm and fuzzy feeling with this installer as I suspect this may be his first static pressure check.

I hope he knows which direction to point the "pitot tube" (or whatever it is called).... in the direction of the air flow?

Key1

[beenthere]

They come with directions.

[key1cc]

Well, your trunks are a little small for a 100,000 BTU 90%er.
Your total static is going to be too high.

have bad news....then good news...then more bad news.

1st, my installer backed out of running my static pressure as I thought he would. Said he could not come anytime in the near future due to heat wave emergencies hear in NJ.
The good news is I work at a fairly large company an I see HVAC guys there occaisionally working on the cooling systems. I spoke to one today and asked him what he thought of my situation. He indicated he was in residential but now he is commercial only, but he has done tons of static pressure measurments...and for $$xxx dollars he would stop by after work and run it for me. I agreed.

He used something called a magnehelic gauage connected by tubing to a bent small metal tube with a magnet.

He said his sister had a Trane and they came with holes so he new where to check. I showed him the pictures from this thread to be sure (thanks cmajerus for your pics in post 10 of this thread).

We turned the unit on cooling and waited a few minutes I heard the blower crank up after about 1 minute to hi speed and it stayed on that speed.

His first readings was with my 3-week old merv-8 pleated filter in and he got a positive reading of 0.55 and a negative reading of 0.48. He checked several times to be sure. He said he finds it that high or higher all the time in residential and that my motor has to run all out so I am using far more energy than that of a 75 watt light bulb that Trane sales guys like to pitch.

Next we put in the original filter that came with the unit (never used) and the negative pressure dropped to 0.32 but the positive pressure went up to 0.62.

He was a nice guy and left me the gauge set up to check the impact of any changes I make and said that he has plenty from work and it gives him an excuse to order a newer one. Maybe he felt guilty for charging me what he did for a few minutes of actual work. Either way I am grateful.

Since my upstairs is 10 degrees hotter than downstairs in 100F degree weather, I closed 3 downstairs supply registers in the room with the thermostat to try and force more cool air upstairs. This had no measurable effect on the static pressure. I next tried closing a damper close to the furnace on one of the 3 trunk lines leaving the plenum. The positive static shot up by over 0.15 units so I quikly opened it back up.

I'm now at a lost on how to get the upstairs cool and how to get the static pressure down.

Any help would be aprreciated.

Key1

[beenthere]

At 1.03" TESP, you don't have much longer on that air filter. before it gets to a static that is harmfull to the VS blower.

Somewhere after 1.2" its life becomes shortened.

[cmajerus]

your welcome. Did he take a reading with the filter removed? I would like to see a reading around .55-.65 with a new pleated filter. No higher that .7 or you will have the issues your pushing right now.

[beenthere]

The filters only 3 weeks old.
He needs supply and return duct remediation.

[key1cc]

Key1

[beenthere]

Can you post some pics of your supply trunk, along with sizes.
And the same would be nice for the return.

The supply could be as easy as adding a helper duct.

[cmajerus]

Hate to say it but the only way your going to solve that is by having your ductwork sized properly to your cfm demands. the readings you have prove the suspected undersized ducts.

[key1cc]

pics are on the way..
Key1

[key1cc]

Here are some additional photos.

Here are some pics.

The furnace is a standard upflow type with a coil mounted on top and a plenum at the very top.

The plenum is 17 iches tall and 20 inches wide and has 3 rectangular trunks coming out.

the one coming out the front is 12 x 8

The one coming out the back of the plenum is 9.5 x8 (looks like room to expand to 17x8).

and the one coming out the top of the plenum is 12x9.

Key1

[key1cc]

Can you post some pics of your supply trunk, along with sizes.
And the same would be nice for the return.

The supply could be as easy as adding a helper duct.

....Also the return trunk going into the furnace is 24" x 10".

Key1