Steam coils...HELP

Unknown

CFM times Delta T (air, in °F) divided by 800.

That gives pounds per hour steam.

PPH= Sq Ft EDR divided by 4

Noel

Paul Mitchell

Steam coils...HELP

Replacing a boiler that has two Flexitube coil set ups in old air handlers. Company that produced them was Aerofin in Newark. Date on tag 1925. Looks like each air handler has two coils on top of each other...I need the EDR to size the boiler. Looking in my every darn radiator book but no luck so far. They are 29" x 36" x 5". Any help asap would be much apprec iated.
Paul








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Paul Mitchell

OK Noel

Just a question on that. Believe it or not the company is still in business but i need to go measure the coils to get an idea of btu output. So in your deal lets use an example... 1500 cfm times 70 divided by 800=131.25
Then 131.25 times 4 coils= 525. 525 times 240 =126,000 Does this sound right? Now to get cfm on old belt drive I am going to measure the wheel and there you go I should get a cfm rating.
Paul

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Paul Mitchell

Noel Question in above post



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Unknown

Looks Ok to me

I'm going to go through it again, though, just in case.

Noel

Paul Mitchell

Noel heres the deal

I measured the blower wheel and looking in a Lau book on blowers the CFM is approx. 3000...Now I need 3000 x 70 = 210,000...210,000 divided by 800 equals...262.5
262.5 according to you is PPH. So I would then have to multiply that by 4 to get EDR. That would be 1050 sq ft EDR. Something is not right because the house is big but I have two units this size plus radiators and it would be a total edr of 2550...House isnt that big. I looked at the coils and they are not that big either.
Thanks Paul

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Unknown

CFM sounds high for the house

What size ducts are they? Is that the measured temp rise? Air isn't my strong suit, Anybody else here good with air?

Noel

tim smith_2

cfm

You say you looked in the Lau book for cfm, what is your blower rpm. Then check the lau book based on that rpm. Tim

Paul Mitchell

I know it sounds high

I am winging it based on the wheel size but it is 50+ years old. I am thinking that the cfm is more around 1200-1400 tops. Looking at hydronic coil air handlers we sell. Ducts are huge and old and the blower motor is only 1/3 hp. LLets say 30 degree temp rise?
Paul

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Paul Mitchell

New info

Spoke with the rep from the coil manufacturer. He figured cfm based on suface area. Now he says the coils can put out a min. of 196,000 btuh. Way too much heat for this house. I need to size the boiler correctly what do you guys suggest. they are copper coils...
Paul...............Should I be doing a heat load at this point and size to what the home needs and not the coil ratings?

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Unknown

If......

If they take any raw outside air in, you ought not consider water. Steam has the advantage of being empty during boiler outages.

Otherwise.... Water to the coils and a heat loss survey to determine load demand, and partial reset to lengthen the cycle without blowing cold air.

How has it been working in the past? Did they like it? Sure has room for improvement....

Noel

Paul Mitchell

Fine I assume

No complaints for the most part. We are leaving the steam coils but I need to size the new boiler. 445.26 sqftEDR for cast iron in home. Need to figure what to add to that based on these coils or load of the house.
Paul

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Unknown

That's the issue

These, on steam, will chew through a lot of steam when they run. If you don't meet the demand, the shortage of steam might not be where you would like it. That's my fear of undersizing.

When they both run together, you'll see that demand.

Noel

RickR

Cart Before The Horse

First, do a heat load calc (many programs available from suppliers etc or you can do it manually) pay particular attention to improvements in windows, insulation, etc. Very likely your heat load is less than it was originally.
Then ask what do the Air Handlers serve? Fresh air make up,
basic heat or what.
Then figure how many BTUs they need to acomplish the task. If it is make up air (doubtful unless it is a mansion) the Delta T is much greater (like 70) than for heat. Anyhow
BTU/Hr = CFM x Delta T x 1.08.
Again,if this is make-up air you would add this amount to your basic heat load. If it is just space heatng it would be part of your load & no addition is necesary.

Paul Mitchell

Good deal guys

Been on the phone with the manufacturer rep, on here with you guys, and my own research. The rep. came up with the final deal. Going to get the boiler. I will take some pics...I appreciate all the help, more than I can express on line. Owe you all a beer and a shot.
Iwill keep you posted.
Paul

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