Sq ft equal to BTU output?

Brad White_30

is, as Mike T. alluded, dependent on whether the boiler is hot water or steam. As Mike said, a square foot of steam radiation (at 215F or 2 psig) is 240 BTU's per hour -in a 70 degree room to be precise.

We use EDR as a suffix to denote radiation versus floor area -if we think of it :)

Mike is also right in that the numbers might be reversed. Steam is usually given as a SF EDR number and water in BTUH.

Your 265,500 BTUH steam number is about 1106 SF EDR if at 240 per.

When the same radiation is used with hot water (at 180 degrees entering, 160 leaving so 170 average) the 240 number drops to 150 BTUH per SF EDR.

Something is odd here and it may be really simple. Usually the hot water rating of a given boiler in BTU's per hour (BTUH) is more than for steam. Reason is with steam, the top portion of the boiler is left dry as a place for steam to form. With hot water the surface is fully wetted around the combustion passages so you get more capacity. You may well get a 15% hot water capacity bonus depending on the boiler.

The bigger question (nameplate disection aside): What is the heat loss of your house?

How many SF of radiation do you have connected to the system?

You really should calculate both and know them by heart :)

Only then can you select the appropriate higher efficiency unit, steam or hot water.

If it is hot water, the boiler is selected for the heat loss. If steam it is selected for the connected radiation plus piping allowance. That is the short story.

Hope this helps.

Brad

larry_15

Sq ft equal to BTU,s

Hey Guys,

I need a formual to covert sq ft to btu output can anyone help?

I have an old american standard boiler I'm trying to put a quote together and hoping to put in a higher efficency boiler in it's place. I have two rating 1400 sq ft water and 265,500 steam I figured someone here could help me thanks.

larry

Mike T., Swampeast MO

You might have that in reverse. The square foot rating refers to square feet (in EDR or Equivalence of Direct Radition) of radiators--not square footage of a home.

One square foot EDR of normal low pressure steam is good for 240 btu/hr.

Is this a steam or water system?

larry_15

EDR

Hey,

I didn't even think of taking a heat loss cal. I'm getting to use of people trying to get the info from me with out really thinking about it. I will tell them I need to to do a calulation frist thanks for reminding me to do the correct thing frist guys.

larry

Brad White_30

Go Get 'Em, Larry

Kick a**, take names and get a good solid heat loss. You will forever be glad to know what your home can do.

"If you cannot measure it, you cannot manage it".

Keep us posted.

Brad