Help to decide multiple choice for Air Distribution!!! 1

[thien2002]

I have a warehouse building in this space:

L= 108.75 FT
W= 80 FT
H Wall= 19 FT
H Susp. Roof = 10 FT
Area Floor= 8700SFT
Vol. Fan Level= 165300 CFT
Vol. Susp. Roof= 43500 CFT
Space below 14' Temp. = 55-65F
Space Above 14' Temp. = 65-71F
Differential Temp. = 10F
Hot Water Supply = 160F
Hot Water Return = 150F
Boiler = 160F

We are losing Heat from floor to 14'. Our Return Air Louver is at on top at 22'H and our Supply Duct is at approx. 20'H. Apparently there is a short circulation due to stratification and shorter cycle. There are several options:

A) Lower the Return Air Louver to about 3'H above floor, and increase Boiler Capacity since Boiler only operates at 160F while Design indicates 180F.

B) Purchase 2 new Fans at 16' blades @ cost = $4000 ea. from Big Ass Fans to de-stratify.

C) Rearrange Air Distribution by lowering diffusers to about 3-5' and lower the Return Air Louver to about 3'H above floor.

I think option A) is the best but I don't know if Energy cost to crank boiler up to 20F would be the energy cost issues. Please consult. Thank you!

 

[Accystan]

What is your heat loss? There's no point in increasing boiler output or jacking up the temp. if the present heat requirement can be satisfied by the existing boiler set up.

The anti-stratification fans are perhaps the cheapest way to go. Rather than two huge "Big Ass" fans at $4,000 what about 6 or 8 of the commercial grade fans at $100 each?

Diffusers are not designed to get air (or heat) down. They are specifically designed to move the air, horizontally, across a ceiling (typically) such that the air hugs the ceiling (the so called Coanda effect) and entrains room air into the primary airstream and hence does not create drafts. Since you don't have a ceiling you won't quite get the full effect but either way, for the most part diffusers distribute air horizontally which is not what you want. Install some grilles or diffusers which are specifically designed (and adjustable) to squirt the air down (nozzles?).

Dropping the RA grille(s) to low level would also help a lot.

 

[thien2002]

The diffusers are at 45 angle down hung in the middle of the warehouse suspended roof. I think you are right about getting 6-8 commercial fans. I am also concerned about the energy it's going to consume of all 6-8 commercial fans. In the Summer, this warehouse usually has a problem when we are opening the Exhaust Fans, the Air travel from the opening vanes straight to the exhaust Fans (4), the vanes might cause also problem since they are not completely seal and they might be heat loss, I plan to cover the air vanes inlet areas with cover fabrics or insulated material covers. I think nozzle diffusers would also be an option according to you, nozzle can shoot the air to lower ground. Thank you.

 

[wilg]

Go with first part of A.

 

[ChrisConley]

I know this isn't part of your original question, but what is the Btu rating of your existing boiler, and what is the water flow rate of the system?

You mention increasing the boiler capacity and increasing the discharge water temperature to 180, that will only work if you also maintain the return temperature at 150 by increasing flow, adding/changing the pump.

If you do that, you'd want to take a look at all of the coils and heat exchangers on the loop to see what 180/150 will do with them.

 

[thien2002]

Dear Chris,

I figure out the problem was residue in the fire tube. Sensors at the pilot tube. We fix that and it seems to work alright. Thank you so much. I am ready to post my next question on necessary to use the plate heat exchanger, if you have time, please help.