Figuring out EDR, help!

JeanneB

We had a new steam boiler installed when we bought our home last year, we replaced the original 90+ year old oil burner with a Burnham gas-powered burner. I'm trying to figure out if our plumber advised us to get the correct model for our house. I do not remember him figuring out the EDR. After measuring all of the radiators I came up with a number of 445.27 and multiplied it by 1.33 (pick-up factor) to get 592.2. That is where I'm stuck, I know our new boiler's DOE is 144,000 BTU and the Net IBR for steam is listed at 108,000. Can anyone tell me what this all means?

STEAM DOCTOR

correct

Assuming that you measured the edr properly you would need 142,130 doe and 106,864 net ibr. edr x 240=net ibr x 1.33 = doe gross output

DanHolohan

Jeanne,

EDR means "Equivalent Direct Radiation." For steam each square foot of EDR will put out 240 Btus per hour. You've got the right size. Did something happen to make you think the boiler was the wrong size? 

JeanneB

high bills

Thanks for your reply, I'm really getting alot out of your book. We had pretty high gas bills for the month of December and January (~$475/month) I first got an energy audit which was helpful but saw your book on a site when I was looking into radiators and thought it would be great to figure out our steam system. It's been frustrating with clanking, hissing and very uneven heat. I did adjust our Pressuretrol last night from a Main setting of 5 and a Diff setting of 3 to a main of 1 1/2 and a diff of 1 psi and the clanking and hissing were gone! I'm just planning on checking everything out that I can based on your book to get the most out of our system.

BobC

Good news

Jeanne



I'm glad reducing the pressure solved a lot of your problems.



If you can post some pictures of your boiler and the piping that comes and goes from it perhaps we can suggest some other things ypu can do to make the system work better - and cheaper.



Bob

Brad White

That is good news...

That your boiler was correctly sized, I think your sizing is pretty much on the money, they do not get closer than that, and that is a good thing. Nice to get immediate gratification on your adjustments, too. Amazing when you think about how many systems run the way yours did for years and everyone accepted the way things were as normal.



As for your high bills, can you tell me the therms you burned per month and what your geographic location is? I can back-calculate to get a range for what your consumption might be. (The dollar cost varies month to month, but the therms of gas are what I need- you can apply the cost later.)

JeanneB

Therms

I just got an energy report from the gas company for 12/23/10-1/25/11 and we used 296 therms and it calculated that we used 37% more gas than neighbors with comparable sized homes.

JeanneB

Location

Also, we're just south of Boston.

Brad White

Some Numbers

Hi Jeanne-

I live in Newton so know the area. I obtained heating degree days (HDD) for three locations, Quincy, Braintree and Weymouth 1282, 1208 and 1319 HDD respectively. Average is about 1270 HDD for the date range you gave.



From this, the therms you used and some assumptions on efficiency, I came up with a heat loss of about 75,300 BTUH and this assumes 75% system efficiency, to have you burn that many therms (296). I also assumed that you keep the place at 68F when it is 6 degrees outside as a design temperature.



If I assumed a system efficiency of 60%, a heat loss of 60,000 would have you spending the same therms of gas, you can see how sliding one factor affects the other. I chose 75 percent because your boiler is fairly new.



Anything over 75%, maybe 80%, is getting optimistic in my experience but if you were running at 80%, your therm usage would support a heat loss of about 80,400 BTUH.



I am thinking your 75,300 BTUH number is close enough for discussion.



Your radiation as noted could support a heat loss of about 107,000 BTUH so you are about 42% over-radiated. Not a bad thing, just a point of reference.



That 42% surplus is in line with what improvement insulation and storm windows might make, assuming the old radiators were matched to the heat loss originally.



My point in all of this is that your gas usage, from what I see, does not seem that much out of line. Anything can stand some improvement though.



How big is the house? In my experience, a heat loss of that magnitude in our climate might be between 1850 and 2150 SF more or less? Just a benchmark, a way to compare. Is the house in the shade or sunny in winter? That too has bearing on the consumption.



Brad

JeanneB

Can you advise

Me on my EDR problem as discussed earlier? So I went around and believe I calculated my EDR correctly but I certainly could be wrong. With the numbers i put in my first question it appeared that we had a perfectly sized boiler. We have had pretty high gas bills and due to some other issues with our system we called in a plumber today that was recommended on your site. They were great, very knowledgable but they calculated our EDR to be 88,000 and feel that our boiler is almost twice as big as it needs to be. I'm guessing they know more about calculating EDR than I do but it's such a big difference in calculations I'm not sure what to do. Would appreciate your thoughts.

Mike Kusiak_2

EDR or heat loss?

Are you sure the contractor measured the EDR of the radiation and not the heat loss of the house? 88,000 BTU is pretty close to what Brad reverse calculated your heat loss to be. In any case your boiler is not double the proper size even if 88,000 BTU represented the actual EDR, since the IBR steam rating of the new boiler is 108,000 BTU. The oversize would only be 22% which is not extreme. I would not be thinking of replacing your brand new boiler yet!

Brad White

Second Opinions

are always good. If you can send photos of your radiators from an oblique angle with the heights, we can get a good idea. Rod, a fantastic participant here, has a form to fill out which makes this really easy. We can take a look and get you a second (third, fourth, fifth...) opinion. 



Can it hurt?

JeanneB

Thanks

I'll get to it and get back to you.

BobC

Installing a new boiler will not cure other problems.

Steam boilers are rated in both Net IBR output and sq ft of steam. double check your measurements to see if and why you might be off. It will take forever to get payback by replacing an oversized boiler with a smaller one. One key is to make sure everything else in the system is correct; this includes the venting, the thermostat,  and the piping



I have a steam boiler that is grossly oversized by about 2.7 to 1 and I heat the house relatively cheaply. I have insulated all of my basement piping, have insulation in the attic, and replaced the worst windows on the second floor. This winter has been more expensive than last because it's been windier (i live one block away from Quincy Bay). The other key is to make the building tight by stoping all air infiltration and insulating.



Bob

Mark N

Oversized?

Bob from what I recall from a previous posting of your, you keep your thermostat at a really low setting something like 60 degrees. There is no doubt you will burn less fuel the lower you set your thermostat. First of all I don' t think Jeanne's gas usage was all that extreme considering the weather. She used 296 therms, subtract out the gas she used for things other than heating. Maybe she used 260 for heating for that month over the 33 day billing cycle. Her usage comes out to 7.87 therms a day. Her boiler is 175,000 btuh. That comes out to 4.5hrs a day of run time for the boiler. That is quite good considering how cold it was.

BobC

settings

Over the years I've insulated pipes, made sure all the piping is sloped correctly and started to run the system at 12oz cutout with a 4oz cut in. I'm currently firing at 1.1 gal/hr vs the 1.65 gal/hr on the nameplate. The hose is about 1150 sq ft and i have 190 sq ft of EDR. I'm about a block from the Atlantic ocean and it's been a windy winter. I've also retired so I have to be somewhat prudent with the oil. i see no reason to enrich the commodity traders and the oil executives.



The heat comes up to 63 at 7am and to 64 as the sun sets, it sets back to 59 at night. I do use a small electric heater in the evening as I read or watch TV. that way I can stay comfortable and not have to raise the temperature of the whole house. I've gone through 295 gallons of oil and probably won't buy more till this summer.



If the boiler died tomorrow I'd switch over to gas but until then I'll play my string out. That is when I'll be able to correct my oversized boiler problem. Natural gas  in the Boston area is about $1.90 a therm right now, i won't change things just for the sake of switching to gas because there is no payback in that unless I'm faced with replacing a failed boiler - let's face it my Burnham V75 is 15 yrs old now, it's not going to last a whole lot longer.



Bob 

Mark N

Amazing

You've only used 295 gallons for the winter. Some people are going through that in a month. You state your boiler is only 15 years old. Who knows it might last for another 15 or 20 years. I had my boiler replaced a little over 2 years ago and it was at least 75 years old and ran fine except it was an oil pig.

BobC

To be full forthcoming

I have to tell you that I am able to isolate the first floor from the second by closing hall doors on the first floor, that means the second floor stays about 5-6 degrees cooler during the day. At night its all opened up so the cat can get to her food and water.



The whole point is to get all parts of the system working correctly so you can wring out all available efficiency. When i worked as a design engineer we used to call it "Getting the best bang for the buck". I'll go down a path as long as there is something to be had but not to the point of diminishing returns. Whe i reach that point I find a different tack.



Also I served in Korea when I was in the army so if it's a little cool it doesn't bother me.



have a great night,



Bob

Brad White

Bob

You mentioned you were a design engineer (retired) and live in Quincy- might we have worked together over the years? I was at  Scorziello Associates, Francis Associates, Shooshanian, BR+A and now TMP. Years 1977 to present. It is a small community so just curious.



Brad

BobC

A lifetime

I worked at Analog Devices, Hyperion Industries, DSK, and finally the post office (as a MPE technician) for my last 8 years. Most of the first 35 years was military work. The last 8 years was not easy but it was worth it because it let me retire at 62.



The majority of my life was in power supply work (as a technician, engineer and manager), anything from 3v at 5,000 amps (linear!!) to a 26kv radar power supplies. My last meaning full input to that world was developing a solid state replacement for a cranky royer that drove a display unit for airfields (and carriers) all over the world. that made a 26 year old design viable again. Some of those are still on service as we speak.



Bob