Real Rating BTU

Phil May · Post by **Phil May** » Wed. Dec. 14, 2011 2:18 pm

What is the real output for a 520 or a 700. My house uses all of a 103,000 oil boiler on cold and windy days. I have an ahs C70 that is rated 220,000 on wood or 265,000 on coal it wont even keep up with the 103 oil boiler. I want to add a 2400sqft shop with 16' ceiling. The shop has radiant heat in the concrete and is insulated under the slab with 2" blue foam and over r-25 in walls and r-45 ceiling. It also has a 20'x14' sliding insulated door and a 12'x14' and 16'x14' insulated overhead doors. After considering this I am skeptical that a 520 can do the job. I live outside Genesee Pa. at 2300' possably the coldest place in the lower 49 states with constant wind. When I calculate total load it comes to 151,000 BTU +domestic HW. I know that it is way to low for bad days. Any recomendations.
Thanks
Phil May

Post by **Rob R.** » Wed. Dec. 14, 2011 3:21 pm

Hi Phil, I also live in a very windy area, in the very Northeast corner of New York State. Infiltration losses from the wind are my biggest challenge, but I have significantly reduced the heat loss of my house by replacing the windows on the wall that gets the most wind, and caulking/sealing the rest of the house the best I could. I recommend that you do the same.

As for the boilers, you can reliably get 200,000 BTU's out of a 520, but the stack temperature will be higher than if you did the same job with a 700. I got the 200k number by allowing 12,500 btu’s per lb for anthracite, 20 lbs per hour for the stoker in a 520, and 80% efficiency. Yes it is true that the stoker in a DF520 can burn 25 lbs per hour, but in my experience if the coal burns a little slower than average, it is tough to get a proper burn at that setting. I have no experience running a 700, so I don't know how well it would run at maximum feed.

One thing I do have firsthand experience with is installing an EFM 520 in a house that was previously heated with a 105k BTU oil boiler. It is my dad’s house, and the oil boiler used to run about 15 hours per day when it was zero and the wind was roaring. The EFM has no problem holding the house at 72 degrees on 4 teeth of feed (50% output) in the same conditions, and it runs about the same amount per day. I could increase the feed rate so the stoker didn’t have to run as much, but a -20 day doesn’t happen often enough to justify changing the settings.

Enough about my projects…lets hear about yours. Where do you plan to install the stoker boiler? Do you use a lot of domestic hot water? Why do you say the AHS hand-fired boiler can’t keep up with your oil unit? Would you be willing to fire up the oil boiler to help shoulder the load on exceptionally cold days?

Phil May · Post by **Phil May** » Wed. Dec. 14, 2011 4:57 pm

My house has 3 pane windows and 6" fiberglass and 1/2" reflective foil, house wrap and vynayl siding. The 103 smith cast iron sectional boiler would run 24-7 on cold windy conditions using over 250 gallons/month. In the same conditions the ahs needs wood every hour and still cant get the water to 170. With nut coal it will use over 300lb a day without ever getting to 180. I have removed the oil boiler and just heat with the C70 using mostly wood and some bit coal on cold nights so the fire does not burn down to far before I refill. I am wanting to go to an EFM stoker so I can go to bed at night and not worry about getting up to a cold house. I want one big enough for the shop also. I have a 10'x10' boiler room now I am thinking of a 520 or possably 2-520s. I have also considered usuing the oil boiler for domestic hot water in summer as I am not sure a 520 iding all summer would be very economical. I have been hand feeding and babysitting a wood/coal stove for way to many years and want something with less care. We use the normal amount of domestic water with just 2 of us living here. I will use hot water to wash equipment and cars on days the heating system can handle it. One thing I have noticed is how the pot rotates on the 700 kind of interesting. I have considered building my own unit with an Efm burner. I feel that I can build one that is easier to clean and would hold more water. The main thing is I want to be sure what ever I put in can handle the load.
Thanks

Post by **Rob R.** » Wed. Dec. 14, 2011 6:23 pm

The house sounds well-built...what kind of design & square footage? Lots of glass? You certainly have some heat going somewhere.

I used to run hand-fed boiler as well. It ate wood like it was going out of style. In real bad weather I had to reload it every 2-3 hours. Now my EFM does the same job with no fuss.

What do you have for a chimney?

Post by **stoker-man** » Wed. Dec. 14, 2011 6:55 pm

Somewhere in the efm forum is a thread about the 520 installation and how it heated our warehouse. The warehouse was 7000 sq. ft. with 30 foot high ceilings and absolutely no insulation. It was drafty and most of the wall space was leaky glass windows from 90 years ago. We heated that space easily with the 520 and used 9 tons of coal. The heat loss was calculated at 400,000 BTUH.

CapeCoaler · Post by **CapeCoaler** » Wed. Dec. 14, 2011 8:41 pm

The wind is key...
Tighten up the house, cutting heat loss to infiltration...
Based on your numbers you are in the 90-140k per hour range...
This new shop should be tight and not suck up too many btu...
A proper heat loss calc will show if the 520 or 700 is a better choice...
Got a pool or hot tub for a summer heat load...

Phil May · Post by **Phil May** » Thu. Dec. 15, 2011 2:20 pm

I came up with 151,000 BTU + 36 gallon Domestic water heater. How much can that use? I used AHS calculator from their web page. I have a very tall 8" square masonry chimney that is built with 8" blocks and the cores are filled with vermiculite. It has lots of draft it will suck a piece of news paper up from the ash clean out door. The house is 2544sq' with 3 floors. The basement and 1st floor are30'x32' the 2nd floor is 18'x32' + a 6'x8' dormer it is built under the rafters with a 8'wide 8' high center section. I like the house at 72. The garage is 32'x36'x10' high I keep at 50. Yes my wife reminds me often that the garage is bigger than the house. The house figured out to 48192BTU and the garage 23500BTU the new shop figured 60000BTU which seems low I would like to at least be able to have 65 degrees in case I want to paint something. I have 2 other small outbuildings that wold need 19000BTU. The only thing I can do to the house is add more under the siding if I ever replace it. It really sound like a 520 can do the job? Is it economical to run it all summer just for domestic HW. I have been doing this with wood only because I have had lots of wood and I am cheap. I just want to be sure that I am not going to be cold after spending 8-9k on a new furnace. My Basement and garage have radiant in the concrete. The new shop can go either Radiant or convection. What is the right temp differential to schedule to water through the mixing valves for the floors. I have adjusted it hotter and colder without much difference. If you get it cold enough the pump will run continously. Thanks for all the insight.

Post by **Rob R.** » Thu. Dec. 15, 2011 3:01 pm

Phil, I assume the radiant floors in your basement and garage are well insulated & drained? Ground water can really suck the BTU's out of a radiant slab.

It sounds like you have done your homework, and your numbers seem reasonable to me. I know 60,000 btu's/hr seems low for the shop...but the rule for a radiant slab with tubing on 12" spacing is 25 BTU's per square foot of floor space. If the shop is 2400 sq. ft, than 60,000 BTU's is right in line. The indirect hot water heater probably requires 75-100,000 BTU's per hour to achieve max output. If you have it set as a priority zone, it isn't entirely in "addition" to the heating load.

I think your biggest sources of heat loss are likely the overhead/sliding doors in the garage & shop. Do your best to make sure they are well-sealed.

Phil May wrote:It really sound like a 520 can do the job? Is it economical to run it all summer just for domestic HW.

In warm weather my 520 uses 20-25 lbs of coal per day to provide DHW for a family of three. With the current price of fuel oil, it is cheaper for me to run the 520 for DHW than the oil boiler. As for the total capacity...I wouldn't be scared to put that load on my 520, but that is because I already own it. It would be a good idea for you to talk to an EFM dealer that has experience with both units. Even better, get the dealer to visit your property and evaluate it before making a recommendation.

Phil May wrote:I have a very tall 8" square masonry chimney that is built with 8" blocks and the cores are filled with vermiculite. It has lots of draft it will suck a piece of news paper up from the ash clean out door.

How big is the thimble? A 520 has an 8" flue outlet, a 700 is 9". I would use no less than 8" on either one if you were going to be running it hard.

Phil May · Post by **Phil May** » Thu. Dec. 15, 2011 3:27 pm

Yes I have 2' blue foam with vapor barrier under the floors along with clean stone and good drainage. The chimney has 8" thimble. It sound like you live in similar conditions as me. Everything north of Oswego with the wind is comparable. People that live in sheltered areas don't understand the effect of being out and exposed like we are here.

Post by **Rob R.** » Thu. Dec. 15, 2011 4:13 pm

Phil, have you talked to an EFM dealer to see what they think? Are you planning to do a boiler swap this winter?

Also, please check your PM's (flashing envelope at top of page).

Phil May · Post by **Phil May** » Thu. Dec. 15, 2011 4:24 pm

I am not going to swap till summer. I would not know how to act if I slep al night without filling the stove. I do some work for a dairy farm that has either a 700 or 900 that heats all the hot water for a 1300 cow operation along with some heat for the building. It is very impressive.

lsayre · Post by **lsayre** » Thu. Dec. 15, 2011 6:12 pm

You would have to burn roughly 600 lbs. of coal per day to achieve an output of 260,000 BTUH for 24 hours.

I would figure about 50,000 BTU's per day for hot water. ~5 lbs. of coal.

Post by **stoker-man** » Thu. Dec. 15, 2011 8:09 pm

The best that the forum members can offer is that they are heating higher loads successfully with the 520. The fact that it heated the efm warehouse was amazing enough as it was. Regarding your chimney draft that can lift Marilyn Monroe's skirt, you might need two draft regulators to keep the draft at negative .004

CapeCoaler · Post by **CapeCoaler** » Fri. Dec. 16, 2011 12:27 am

Used/Refurbished Boilers will cut the cost of new...

Phil May · Post by **Phil May** » Fri. Dec. 16, 2011 11:14 am

Thanks for all the input I am leaning toward a 520 mainly because of the ability to throttle it down in summer for domestic HW and the Possability of adding another indirect to wash equipment with on warm days. If it cant do the job I can always add another in series or another form of heat to supplement on the extremly bad days. Stoker are you saying that I have to much draft. I did not realize that could be a problem.