Old Boiler Efficiency?

rep

I’ve got an old Kewanee Type R Model 1736 Firetube gas boiler. The boiler is rated at 700 (what?) with 41 square feet and 3.42 HP.

My calculations timing the gas meter while it fires say it burns 250 CF/HR.

It’s a one-pipe system of 285 SF/EDR or 68,300 BTUH for the radiators plus 4 CF of mains and risers heating a small
30’ x 40’ two story building.

1.What is the SF/EDR of the 4 CF of mains and risers?
2.What is a rough estimate of Input (270,000 BTUH?) and Gross Output?

Thanks for the help.

Big Ed

Output


The net btu rating = (Efficancy of boiler) x (Gross input.)

Below chart for btuh output for bare hozontal pipe.

A guess 275,000 btuh x 65% + 178,750 btuh net output..

Steamhead (in transit)

That boiler's way oversized

the 700 is its rating in square feet EDR!

As such, it's not very efficient due to the fact that it's probably short-cycling.

If I were you I'd replace it.

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rep

That's what I suspected

> the 700 is its rating in square feet EDR!

>

> As

> such, it's not very efficient due to the fact

> that it's probably short-cycling.

>

> If I were

> you I'd replace it.

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 367&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

rep

Thanks guys,

that's what I suspected.

What would a new unit cost w/o install? What type of efficency increase can I expect? This unit only runs 6 to 7 weeks per year and is supplemented by a pellet stove.

The boiler doesn't leak, all the vents are new, replacing the insulation with 1" fiberglass and all the controls are relatively new. A new boiler would seem like getting rid of my wife because she eats too much and the cost of food is rising (luckily not the case).

I'd like to get it running as efficiently as possible, put her/it on a diet so to speak. Is it likely to be overfiring? Looks like a wok that could feed China. Probably set up by the guy who had it set to cutout at 6 psi. Can the burner be adjusted so not so much heat rushes past the firetubes w/o being absorbed by the water? How would one calculate that?

Sanks

rep

Would the 65% efficiency

guess include the losses from the bare pipe as per the chart?

rep

Is the 700 SF/EDR rating

Input, Gross Output or Net Output?

Boilerpro_3

Old Kewanees......

can fire very efficiently, if properly set up. Most I see are at least 80% and often higher, some around 85 to 87. However, the massive amount of water in them means they take forever to warm up. All that energy that goes into warming them up is lost. Also it sounds like the unit is waaaay tooooo big! So your real world efficiency is terrible.
There are tons of type R's and other Kewanees in my area (Kewanee is only about an hour and a half away) and they last forever. However, as I have always said, that type of boiler is great for industrial applications... constant load and high firing efficiency.... but they have no place in space heating systems unless step fired or modulated input.


Boilerpro

rep

Could you please

explain "step fired or modulated input".

What about the 700 SF/EDR rating, is it Input, Gross Output or Net Output?

Thanks

Boilerpro_3

Usually

the edr rating is output. Alot of commerical boilers use power burners than vary the input according to the pressure in the boiler. This way the aren't banging on and off so often, and get a nice boast in efficiency. Another way to deal with this problem is to have a two stage or more burner and controls determine when to move from one firing rate to another. Also, this same concept can be used for multiple boilers.... You only fire one as needed and then the second comes on under heavy loads. Here's a smaller stage fired Slantfin steam boiler install with two modules for a commercial structure.

rep

Would the following calculation

represent the amount the burner could be over firing?

700 SF/EDR Gross Output x 240 BTUH per SF/EDR (steam) = 168,000 BTUH Rated Gross Output at 80% efficiency.

168,000 BTUH divided by .8 = 210,000 BTUH Rated Input

Current Firing Rate of 270,000 BTUH – 210,000 BTUH Rated Input = 60,000 BTUH amount of over firing?

rep

Anybody?

How about a hint if I'm going in the right direction?

Would the following calculation represent the amount the burner could be over firing?

700 SF/EDR Gross Output x 240 BTUH per SF/EDR (steam) = 168,000 BTUH Rated Gross Output at 80% efficiency.

168,000 BTUH divided by .8 = 210,000 BTUH Rated Input

Current Firing Rate of 270,000 BTUH – 210,000 BTUH Rated Input = 60,000 BTUH amount of over firing?