Statics Pressures

[eberrong]

How can I find the acceptable static pressures for the supply and return for my air handler? I have a Bryant FA4ANF060 air handler. I checked the manual but it is not in there.

[lvieira]

Working as a Bryant Distributor the MAXIMUM static pressure should be .5. That being said in theory the supply and return should both be at a .25 but in reality 1/3 should be with the return and 2/3 with the supply.

Hope this helps.

[dash]

With factory installed filter,dry coil,and a 3 element electric heater:

1975 cfm @.5

1895 @.6

Both above are for the total of the supply and return ESP.

Deduct .06 to .07 from the above for the wet coil in cooling.

These are for Clean Coil and Blower,ie like new.

[dan sw fl]

TOTAL ESP = ~ 0.60"
A.H.U. _____ _____ 0.60

Diffuser _________ 0.06
Coil or
Heater element ___ 0.14
Filter ___________ 0.12
Sub-total ________ 0.32

Duct Total _______ 0.28_ _ _ _ _ ( AHU - sub-total )
Duct Supply ______ 0.19
Duct Return ______ 0.09

[bigbird]

Hay lvieira, do you know ward brady, san jose?
He`s my u.s. air salesmen.

[dash]

Originally posted by dan sw fl
TOTAL ESP = ~ 0.60"
A.H.U. _____ _____ 0.60

Diffuser _________ 0.06
Coil or
Heater element ___ 0.14
Filter ___________ 0.12
Sub-total ________ 0.32

Duct Total _______ 0.28_ _ _ _ _ ( AHU - sub-total )
Duct Supply ______ 0.19
Duct Return ______ 0.09



Factory filter and a heater, may or may not be included ,in mfr. fan data,read the footnotes.

In this case they were included,so if used,as noted, would not be deducted,

[lvieira]

hey bigbird I do know Ward, infact he was just in my office this morning =) good guy!!!

[sskzekeman]

Originally posted by lvieira
Working as a Bryant Distributor the MAXIMUM static pressure should be .5. That being said in theory the supply and return should both be at a .25 but in reality 1/3 should be with the return and 2/3 with the supply.

Hope this helps.

What would be wrong with say a -.35 suction and a .15 supply?? Still adds to .5. I know it suggests that the returns are inadequate in size, but what else is wrong?

[docholiday]

the return would be noisy and the supply would have a low velocity and probably not good distribution.

[toomanytoys]

I just moved my filter manometer connections around and I have a .35 reading on the return duct as well.

[eberrong]

A HVAC tech measured my system today and got 0.5" return and 0.25" supply for a total of 0.75"

This was done during cooling and the 2 filters are located in filter grills in the house (not in the air handler).

The tech mentioned that he may recommend to add returns to all of the bedrooms. Currently, there is one in the family room and one in the master bdrm. Does this make sense? I would think you would need more return in the central area of the house.

He is going to run a Manual J & D. That won't tell him where to locate additional returns will it?

What kind of CFM am I getting at this static pressure?

[dash]

With a standard PSC motor in an air handler,it's less then you need to get the full btus the system can produce.

Post the model numbers and we can tell you more.

[dash]

Return ESP higher then supply;

I don;t share concern about the example ,.15 supply and .35 return ,causing air flow problems or noise.If the return grille is undersized ,that will cause noise .

Though if it's metal duct the return may be noisey,don't doubt it,but we so little metal ,I havn't seen it.

.35 on the reurn of a horizontial air handler,may cause water to "blow-off" the coil,in some cases.

We have system with supply ESP lowr then .15 and have found no air distribution problems or had compliants from home owners.

[eberrong]

Originally posted by dash
With a standard PSC motor in an air handler,it's less then you need to get the full btus the system can produce.

Post the model numbers and we can tell you more.

Bryant FA4ANF060 air handler

Are you asking for the model number of the blower motor itself?

[udarrell]

Originally posted by eberrong
A HVAC tech measured my system today and got 0.5" return and 0.25" supply for a total of 0.75"

This was done during cooling and the 2 filters are located in filter grills in the house (not in the air handler).

The tech mentioned that he may recommend to add returns to all of the bedrooms. Currently, there is one in the family room and one in the master bdrm. Does this make sense? I would think you would need more return in the central area of the house.

He is going to run a Manual J & D. That won't tell him where to locate additional returns will it?

What kind of CFM am I getting at this static pressure?
Residential customer knowledge should increase our service calls, not reduce them. They will want the sub-operating system brought to its optimum performance. This will also improve our Public Relations with those consumers.

The room by room manual J will reveal how many BTUs per Hour each room will need and then the required balances of - velocities, duct sizes, & static pressures etc.

To figure ballpark required duct size CFM from required btuh of each room. This is using 450-cfm dry coil per 12,000-btuh (one ton) 12,000 / 450 = 26.66-Btuh per CFM.

If you can measure the air velocity coming from a duct, here is a rough ballpark formula to get the ballpark CFM:
CFM = (velocity in (FPM) Feet per Minute times the square footage of the duct area)

All HVAC work including ductwork should always be done by experienced licensed contractors! Never mess with situations that can take your lives & the lives of your family due to one critical code violation!

http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_syste ms.html
- udarrell

[dash]

FA4ANF060 is a five ton air handler,but could be matched with a 4 or 5 ton outdoor unit.

Measured total ESP of .75 in wc.

Well that's off the fan data chart,it can move 1895 cfms at .60 ESP .

.50 on the return is likely to have been blowing water of the coil.If they see the galvanized blower housing has a splattered white "powder" look on the outside ,that's from water blowing off the coil.

If I remember correctly your filters are at the grills,since the fan data ,includes the factory filter,that can be in the air handler,and it's not,you can reduec the .75 by .152 in wc @1800 cfms.

So that would get you down to the .60 and 1895 cfms.

But I'm a wet coil ,in the cooling mode needs to be accounted for ,so that raises the .60 ,by .063 at 1800 cfms,so now a total of .663 in wc.

You likely have a 10kw two element heater ,and the fan data includes resistance of a 3 element heater.So reduce the .663 in wc ,by .02 ,for a final of .643 in wc.

Since it off the chart,we can't say for sure ,but it can likely deliver 1750 cfms ,which is 350 cfms pers ton if it's a 5 ton outdoor unit,and ideal cfms for the humid Florida cooling climate.

If you go with and Infinity ,it will run at 1750 cfms per ton in high stage cool,most all the time that it's in high stage,of course it will run in low stage most of the time.

I'd have the ducts reworked to lower the return ESP to prevent water blow off,and if you add a better ,more restrictive filter ,the return duct ESP will need to be lowered to allow for the filter.With VS the higher the ESP the more it costs to run the indoor fan.VS fan should have no higher then .70 ESP ,and lower is better.

Since the air handler is older and not perfectly clean,the ESP may be greater with the new one ,as dirty coils and blowers reduce the amount of cfm that the air handler can produce.The fan data chart is accurate for 'like new " conditions.If due to dirt the air handler is producing less cfms than the fan chart shows,the ESP would be higher if it was clean and producing higher cfms.


How's the temperature difference between rooms ,in your home?Let them know if it more then 3 degres,so they can look at correcting duct sizes to reduce the temp. difference.



[Edited by dash on 09-21-2006 at 08:00 AM]

[eberrong]

Originally posted by dash
FA4ANF060 is a five ton air handler,but could be matched with a 4 or 5 ton outdoor unit.

Measured total ESP of .75 in wc.

Well that's off the fan data chart,it can move 1895 cfms at .60 ESP .

.50 on the return is likely to have been blowing water of the coil.If they see the galvanized blower housing has a splattered white "powder" look on the outside ,that's from water blowing off the coil.

If I remember correctly your filters are at the grills,since the fan data ,includes the factory filter,that can be in the air handler,and it's not,you can reduec the .75 by .152 in wc @1800 cfms.

So that would get you down to the .60 and 1895 cfms.

But I'm a wet coil ,in the cooling mode needs to be accounted for ,so that raises the .60 ,by .063 at 1800 cfms,so now a total of .663 in wc.

You likely have a 10kw two element heater ,and the fan data includes resistance of a 3 element heater.So reduce the .663 in wc ,by .02 ,for a final of .643 in wc.

Since it off the chart,we can't say for sure ,but it can likely deliver 1750 cfms ,which is 350 cfms pers ton if it's a 5 ton outdoor unit,and ideal cfms for the humid Florida cooling climate.

If you go with and Infinity ,it will run at 1750 cfms per ton in high stage cool,most all the time that it's in high stage,of course it will run in low stage most of the time.

I'd have the ducts reworked to lower the return ESP to prevent water blow off,and if you add a better ,more restrictive filter ,the return duct ESP will need to be lowered to allow for the filter.With VS the higher the ESP the more it costs to run the indoor fan.VS fan should have no higher then .70 ESP ,and lower is better.

Since the air handler is older and not perfectly clean,the ESP may be greater with the new one ,as dirty coils and blowers reduce the amount of cfm that the air handler can produce.The fan data chart is accurate for 'like new " conditions.If due to dirt the air handler is producing less cfms than the fan chart shows,the ESP would be higher if it was clean and producing higher cfms.


How's the temperature difference between rooms ,in your home?Let them know if it more then 30 degres,so they can look at correcting duct sizes to reduce the temp. difference.



I pointed out which rooms are warm all the time (all rooms furthest from air handler) to the tech. He recommended the Carrier Infinity system. He said that if you set the blower to run all the time, you can likely solve the "hot rooms" issue without going to the expense of zoning. He also said that I have a high humidity problem in the house, which the Infinity can solve also. He really has high hopes for the Infinity, I hope it can deliver.

I measured the humidity in the house with a radio shack hygrometer and get 44-48%RH. I calibrated it last night with the salt water and got only 63%. So I think I actually have 56-60%RH in the house. Correct?

[Gunslinger]

<<How's the temperature difference between rooms ,in your home?Let them know if it more then 30 degres,so they can look at correcting duct sizes to reduce the temp. difference.>>


You do mean 3* right??? Not 30*

[dash]

Originally posted by Gunslinger
<<How's the temperature difference between rooms ,in your home?Let them know if it more then 30 degres,so they can look at correcting duct sizes to reduce the temp. difference.>>


You do mean 3* right??? Not 30*

Yes 3°,thanks .

But if it's 30° difference still tell them!LOL!!!