BadgerBoilerMN
Hydronic Heating Designer
Again thanks everyone for the help and advice.
Two days ago the heating tech from a large heating contractor came over to look things over. He spent over an hour looking over the boiler setup and took measurements of all the rooms in the house. I had asked for him to come over and do a Munual J so as to see exactly where we were. He didn't think a manual J would be much more accurate than the shorter method he wanted to use. He said that in older homes like mine ,1860, that the manual J was kinda a wag as there was so many variables. I agreed and received the heat load estimate yesterday. The home is a 1860 built mansart roof of about 2300 sq/ft. I have 166 feet of baseboard all being regular except the kitchen which is 30 feet of Hicap.All exterior walls have had blown in celious (sp) insulation, with some gaps. Two floors and attic with 3-4 inch of rock wool. Windows are, for the most part, older double hung but all have dead glass interior inserts and others are all thermopane with kitchen being all Anderson. There is 166 feet of baseboard all being regular except the kitchen which is 30 feet of Hicap Three quarter full basement unheated. I think his estimate is on the high side but he came in at 91,460 BTU heat loss at 0 deg. With that heat loss he thought the Alpine 150 was probably slightly oversized but the next one down, the 105 would be too small considering we also have SuporStor SSU45 being heated by the boiler. I think I will do some calculations on a few rooms myself using some simplified manual j type math I have found here to see if we agree. It does seem quite high to me. I did use the 25btu/cu ft quickie. Based on the square footage and cieling heights of 8.5 ft. I came out slightly more than half of what he calculated.
Dana, I get my gas from "National Grid" and do not see anything on the bill about an average outdoor temp. I will give them a call and see if its available.
Also
As always, thanks for the help
Tom
This is crazy. First, a proper room-by-room Manual 'J' 8 is, by no stretch of the imagination, WAG. To suggest otherwise is insulting. If the a "heating tech" suggests otherwise, he is too ignorant, or lazy, to do his job. If he is "just" a heating tech, his supervisor should be providing him with the tools, be it software, or office staff, to do a professional job. We have replaced dozens of old cast iron, low-efficiency boilers, with new condensing boilers, in very old homes. We start with a proper heat load and do not inflate the calculated heat load for domestic hot water (bad practice), "big" pipes, cubic feet or any other such nonsense. If we happen to under-size a boiler (none yet) when design conditions were exceeded (temperatures dropped below 25 year averages), yes, the thermostat may drop off a couple of degrees for a matter of hours, and no, no one will die. However, for the next 25 years our customer will spend less on fuel and be more comfortable. It is very likely that the boiler will last longer and require fewer repair parts.
With all due respect. I am still not convinced past fuel usage is an accurate reflection of future building loads (the past winter here in Minnesota vs the previous year a prime example) and the industry as a whole rejects this as well. ASHRAE preferring a 25 year cycle to develop their design conditions data.
http://minnesota.publicradio.org/co.../2012/08/most_90_degree_days_in_metro_s.shtml
http://www.thefreelibrary.com/Updat...ic+data+for+design+and+standards.-a0250825197
ASHRAE outdoor design conditions represent long term average temperatures (not the mean extreme) that will not be exceeded more than a few hours per season. Over-sizing a boiler, or the pipe and pumps connected thereto, is detrimental to energy use, comfort, and equipment durability. Short-cycling and elevated operating temperatures are symptomatic of poor hydronic design, which often starts with and over-sized boiler. An over-sized HVAC system will have both a higher initial cost and a higher cost of operation. The frequent starting and stopping of short cycling can also lead to premature failure of the equipment. The ASHRAE tabulated temperature data is adequate for calculating peak heating and cooling loads, and should not be increased as an additional safety factor.
We use Wrightsoft to calculate heating/cooling loads and design radiant heating, warm air heaiting/cooling and ventilation packages. When designing system each room, and wall, may be modeled. Infiltration can also be modeled per detailed method. But with a properly administered blower door test, even this educated guess work is turned in to more-than-reasonable loads calculation accuracy.
By the way, no one can do this for free, at least not for long. Even the subsidized power companies usually charge a token sum for home energy audits, which may include a blower door, thermal imaging, insulation measurement or a combination thereof.
I spent 12 hours last Friday (referred by Lochinvar) on a Knight condensing boiler installed in 2008. After a dozen technicians looked over the troubled boiler (years of various error codes) my diagnosis was; poor installation. I have not done the heat load yet, but having done a few on these old four-square homes, I am guessing the boiler is over-sized. What I know for sure is that the boiler suffered over 25,000 ignition cycles in less than 7 heating season (no DHW loads). I found the supply sensor hanging in free-air, having been pulled out of the dry-well provided, and found a primary loop without the benefit of a pump. Oh, yes, the 200sf finished basement micro-zone (I will estimate the load <2000Btuh) was calling the 105mBtuh boiler, which was of course bumping off the bottom of its 20,160Btuh minimum-fire output. So much for modulating output, eh?
The only way to make the boiler run at all, was to leave the supply sensor in free-air to fool the boiler into firing when there was no "apparent" load/demand. Lochinvar was taking a beating for the ill-informed contractor that installed the boiler and the various technician; one of which worked for a company who's name started with "Air", please people; this should be your first clue.