Quick calculation of additional EDR

DickC

I have an old building which has had the original heating system modified, more than half of the building has been converted to FHW.  The remainder is 13 radiators with a total EDR of 1,0013 sq/ft of steam.  They are using a Mills boiler firing 13 gph, a little overkill to say the least.  Looking to install a new boiler which I have siazed, however there is an 8" main approximately 100' long which these radiators feed off of.  I come up with approximately 35 cubic feet in the main which is well insulated, trying to figure additional EDR to add.  Any ideas?

moneypitfeeder

more info

I'm just a homeowner, but I think the guys here might need more info. From your post it sounds like you're wondering which pickup factor to use to calculate the boiler size? If that's the case first look around the building, do the areas that used to be heated by steam still have piping going to them and are capped off somewhere or was the main to those sections cut and plugged? Are you planning to insulate the main completely so the basement doesn't feel like the tropics? The standard pickup factor is 1.33 but if you've got a bunch of stray piping going to no where and you want to account for that then you could use 1.5 per LASH, btw do you have a copy of lost art? So rad X 1.33 or 1.5, then X 240 then match to the D.O.E. rating in MBH or "gross rating". Does that help any or have I completely misunderstood what your looking for? Hope you find what you need.

Steamhead

Has that main

had a lot of radiation removed, or is it pretty much serving all the radiation it did when installed? 

DickC

EDR solution

As I said in the post, approximately half of the building if not more was removed from the steam system and changed to FHW.  The remaining 13 radiators are being heated with the original boiler using an 8" main.  The EDR for the existing radiation claculated to approximately 1,000 sq'.  My concern was the 8" main, with the connected load, a smaller main would have been factored in the pickup and piping.  The 8" main is well insulated and they did not want to disturb it.  I found the factors I needed in the Burnham Heating Helper which had a chart up to 8" for insulated pipe.  Ended up adding 40 sq' and sized boiler accordingly.

Thanks

Steamhead

Oh, OK

your original post said there was 1,0013 square feet, which must have been a typo. If that figure were accurate, an 8-inch main would probably be the correct size. I had thought there were other mains originally feeding the part of the building that was converted.



But with only 1,000 square feet, a 3-inch main is sufficient. So you're way oversized.



Not sure which boiler you chose, but the Weil-McLain 80 series is popular in that size range. The 4-section model has a rating of 1238 square feet, with a 1.33 pickup factor.



To use a 1.5 pickup factor, you'd convert EDR to BTUH, giving you 240,000 BTUH. Adding 50% to this gives us 360,000 BTUH. The 4-80 has a Gross output of 396,000 BTUH, so that size should still work OK on a 1,000- square foot job with a 1.5 pickup factor.



The question will be, is 1.5 sufficient for such a grossly oversized main? I really don't know, as far as I know we've never had something like this come up on the Wall. The insulation will help a lot. And the oversizing means you can run the system at Vapor pressures- a few ounces at most. Use a Vaporstat instead of a Pressuretrol as your operating high limit, and vent the heck out of the main.



Let us know how you make out.

DickC

Sorry for typo

Was obviously typing to fast when I posted the load, it is 1,013.  As I described, with fudge factors included, I was able to calculate the load for the main at an extra 40 sq'.  I'm recommending a Peerless SC-06 which provides 1,267 sq'.  The information is available to calculate the EDR for the main and found it in the Helper.  Thanks.