Add more returns or supplies to lower static pressure?

[firecontrol]

Using Infinity 58MVB60 air handler installed the static pressure showed by Infinity thermostat display is 0.9 – 1.0. It seems a bit high.
The air duct (supplies) sizes I have calculated for the 600 – 700 CFM by using well know HVAC Calc software tool.

I removed the air filter insert from an air purifier GAPA body, keeping the filter compartment open letting easier for the air to get into the air handler.
I was surprised that the static pressure went up by 0.1

It is an old house and the ducts installation was a real pain.
But I want to get the pressure down to appropriate 0.5 level or so.

My question is should I add more returns or more supplies?

Are we to assume that you installed this system yourself?

If you didn't, then you should be calling the installing contractor back if you have concerns about the TSP the control is showing.

Either way you've just found out first hand one of the first basic rules of air flow in ductwork. Velocity increases static pressure.

[perrybucsdad]

Donate it to your local tech school/college.

Great idea!!

Either way you've just found out first hand one of the first basic rules of air flow in ductwork. Velocity increases static pressure.

and so we should also conclude that dead animals in the duct work can decrease static pressure?

[perrybucsdad]

If your supply static rises when you add return, your supply duct is also restricted.

So what does this mean if you add more return but your supply side does not get effected at all? Still some sort of blockage in the supply side (like a dead animal )?

[beenthere]

If its a VS blower. They don't always increase when you decrease the return.

[perrybucsdad]

If its a VS blower. They don't always increase when you decrease the return.

, I didn't decrease the return, I increased it (or are you talking about the pressure?) When I say I increased it, I mean I added more air to it by opening the blower door.

Also, when you say VS blower, do you mean a blower that a tech can jumper to adjust the blower speed or something that is controlled through some sort of circuitry that will increase or decrease the speed. In my case, the blower has to be jumpered (or whatever you guys call it).

Personally, I think there is something in the supply side either before or after the cooling coil. I have a call into a different servicing company that will do the annual maint on the unit. My Dad really recommended them as he has used them numerous times for when he builds his YMCA Dream homes. I'm thinking something is up there and hopefully they can fix that when they do their maint. Either that or the cockamamie way they have all the supply lines coming off the main trunk right after it leaves the furnace is the problem. Either way, I'm not sure how much that will cost, but it should pay for itself with added comfort and hopefully reduced bills.

[beenthere]

I was talking pressure.

VS blower are adjusted by jumpers/dip switches.

[firecontrol]

and so we should also conclude that dead animals in the duct work can decrease static pressure?

No...... dead ones would increase static pressure along with increasing a few other things in the home but let's not go there.

[perrybucsdad]

No...... dead ones would increase static pressure along with increasing a few other things in the home but let's not go there.

Okay, but they will decrease airflow after the dead animal.

Does it increase the static pressure because the air has nowhere to go?

[firecontrol]

Okay, but they will decrease airflow after the dead animal.

Does it increase the static pressure because the air has nowhere to go?

Yes in varying amounts depending on all the different variables.

It increases the static pressure (between the air mover and the animal) because there is something causing resistance to air flow.

Air flows through ductwork basically the same way water flows through a garden hose. Go outside and experiment.

[perrybucsdad]

It increases the static pressure (between the air mover and the animal) because there is something causing resistance to air flow.

Okay.. that gives me a visual. So am I right to assume that if I turn the water supply down (reducing the water flow) that would decrease pressure in the hose, and would account for lower pressure (same as if you had a filthy air filter or air starved system)?

[firecontrol]

Now you're getting the general idea.

[sskzekeman]

Using Infinity 58MVB60 air handler installed the static pressure showed by Infinity thermostat display is 0.9 – 1.0. It seems a bit high.
The air duct (supplies) sizes I have calculated for the 600 – 700 CFM by using well know HVAC Calc software tool.

I removed the air filter insert from an air purifier GAPA body, keeping the filter compartment open letting easier for the air to get into the air handler.
I was surprised that the static pressure went up by 0.1

It is an old house and the ducts installation was a real pain.
But I want to get the pressure down to appropriate 0.5 level or so.

My question is should I add more returns or more supplies?

Where is this reading or readings taken? Is it the ESP or is it the pressure in the duct downsream of the blower. If it is the latter then the .1" increase is not surprising. You blow more air, then the static pressure in that duct will increase and since you opened the input, the suction side negative pressure will numerically decrease, resulting in a net lowering of the ESP.
Finallly, I am not convinced you have to do anything. What is your problem with the current system that would be lead you to make a correction? Is it noise or power?