Static Pressure

Static Pressure

PostBy: Carbon12 On: Thu Dec 05, 2013 10:18 am

Any of you HVAC Gurus have any thoughts about how to lower the static pressure on my air handler? I have a hot water coil installed in the plenum of my oil fired furnace with heat pump A coil below. Hot water from coal fired Keystoker KA 6 boiler. I was taking external static pressure in the fan box post air filter and before the coils and determined it to be higher than it should. If I take the reusable electrostatic air filter out of the filter box the static pressure gets better. I'm thinking my return air may be inadequate. Coils are clean. I installed the hot water coil this past fall. New to me home. Not sure what the static pressure was before I installed the hot water coil. I'm hoping I don't need to get a bigger hot water coil. The coil I installed is, dimensionally, slightly larger than the supply plenum. Any thoughts???
Carbon12
 
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace

Re: Static Pressure

PostBy: Rigar On: Thu Dec 05, 2013 6:06 pm

is it feasable to slow down your blower?
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Static Pressure

PostBy: Carbon12 On: Thu Dec 05, 2013 6:16 pm

I do believe its a 4 speed blower. I'd have to check the specs. 3 speed for sure.
Carbon12
 
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace


Re: Static Pressure

PostBy: McGiever On: Thu Dec 05, 2013 6:28 pm

What is the order of all componets?

Have you given any thought to "cuttin' in" some additional cold air returns?
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Static Pressure

PostBy: Rigar On: Thu Dec 05, 2013 8:12 pm

more cold air supply OR possibly modify you bonnet...for a larger (thicker ) filter
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Static Pressure

PostBy: Carbon12 On: Thu Dec 05, 2013 9:48 pm

The order, starting at the main return trunk is: air filter, blower fan, oil burner heat exchanger, A coil for heat pump, hot water coil from coal boiler at top of plenum and then main supply trunk. I'm thinking more return air. The furnace manual I found states that if airflow is greater than 1800 CFM the bottom of the air handler should be used or TWOS SIDES of the cabinet should be used for return air. Whoever installed it only used one side return and the fan is theoretically supposed to be blowing 2000+ CFM with both heat and cooling. I suspect the supply and return ducts are way undersized as well. Furnace manual states Max external static pressure of .5 WC. My external static pressure is .9 WC.
Carbon12
 
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace

Re: Static Pressure

PostBy: Rigar On: Fri Dec 06, 2013 5:54 am

ok...its early so i apologize if this dont make sence (coffees brewing !)

...is the pressure too high...or too low???
2000 cfm requires very large ductwork for optimum performance...
with that said...i woud calculate what the capacity of your existing ductwork is....and try to regulate fan speed accordingly.
If removing the air filter improved your goal...i would try to increase the size of the filter. (its probly 1 inch thick??- modify for a 2 or even 4 inch thick)
the extra thickness provides more surface area...and less restriction.(and a bit longer life as well)
it doesnt seem the blower is starved tho...(heres where i dont quite understand your post)
aside from pressure-....is it loud(at the vents?)...is the house comfortable and even temps in most rooms??
CA returns should be adequate for the HA side...not sure if larger cold air will help...but it can never hurt to have more.
...just remember- dont ever put a cold air return in the bathroom !! :lol:
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Static Pressure

PostBy: Rigar On: Fri Dec 06, 2013 6:23 am

...almost forgot-
.. are you measuring correctly ( I ask with all due respect)
..Total External Static Pressure. (TESP) requires you to mesure pressures in two places...before and after blower...fyi
...also...i would measure pressure at supply trunk (after all coils)....and determine air flow back to the vents
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Static Pressure

PostBy: Rigar On: Fri Dec 06, 2013 6:24 am

...almost forgot-
.. are you measuring correctly ( I ask with all due respect)
..Total External Static Pressure. (TESP) requires you to mesure pressures in two places...before and after blower...fyi
...also...i would measure pressure at supply trunk (after all coils)....and determine air flow back to the vents
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Static Pressure

PostBy: Carbon12 On: Fri Dec 06, 2013 11:06 am

Yup, measured pressure after filter just before blower and through the fan and limit opening after fan before the coils. I think the furnace is way over sized. Oil is fired at 189,000 BTU/hr gross house is nowhere near that big or loose. I'm going to try and figure out how to lower the fan speed and see what happens. I'll probably have someone come in who can do all the proper calculations correctly. House has been comfortable, so far, even with some nights down in the teens. No noise at registers. System seems to be working fine. I wouldn't have noticed the problem if I hadn't gone looking for it! :lol:

The blower does have 4 speeds. The instructions state that at the firing rate of the oil burner the fan should run on high for both heating and cooling. If I'm not using the oil burner, lowering the fan rate shouldn't be a problem.
Carbon12
 
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace

Re: Static Pressure

PostBy: McGiever On: Fri Dec 06, 2013 4:24 pm

If lowering the fan speed you will then have longer blower cycle times...not saying that is a bad thing.
Lower speed = Lower btu/H output. So, at some point there may not be enough output to supply enough heat for the load.
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Static Pressure

PostBy: Carbon12 On: Fri Dec 06, 2013 4:53 pm

Too few CFM blowing over hot air coil and enough heat won't be available. Too many CFM over the hot air coil and heat won't be efficiently extracted. Gotta find that sweet spot. I guess I'll find my answer when it's 20 below 0 and the wind is howling. If the coal boiler/hot air coil combo doesn't keep up for what ever reason, I can always fire up the oil burner :mad: Right now I have the aqua stat set at 160/190 with a diff of 15. Seems to be working fine and coal consumption seems right. I know hot air coils transmit more heat with higher water temps at the cost of higher standby losses. If it's witch nipple cold out,...there won't be much stand by time and I'll crank the aqua stat up a few notches. Learn while you burn Lightning once told me :D
Carbon12
 
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace

Re: Static Pressure

PostBy: Carbon12 On: Fri Dec 06, 2013 5:37 pm

Ok. Just opened up the fan junction box and changed the fan speed. The installers should have wired it for high speed as per the firing rate of the oil burner as per the furnace instructions. They wired it for medium high. I stepped it down and wired it for medium low. Didn't do the external static pressure test yet. HOWEVER,...the temps, according to the IR thermometer, at the supply registers are up from 110 degrees at medium high fan speed to 125 degrees at medium low fan speed! :D :D :D I'll take that,....I think. Will let y'all know what the static pressure is running later.
Carbon12
 
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace

Re: Static Pressure

PostBy: McGiever On: Sat Dec 07, 2013 1:08 am

Higher temps at register w/ less CFM is not more btu/H output.

And you need to remember to change motor speed for A/C again next summer.
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Static Pressure

PostBy: Lightning On: Sat Dec 07, 2013 1:22 am

McGiever wrote:Higher temps at register w/ less CFM is not more btu/H output.

I agree,
You can add 30 degrees to 1000 cubic feet of 70 degree air to make it 100 degrees
OR
You can add 60 degrees to 500 cubic feet of 70 degree air to make it 130 degrees..

The overall heat added to the house is the same :)
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut/Stove Size Mix