Professional Member*
I see only 27 days < 25'F for low temp.
4,125 HDD Oct 15 2011 - April 12 2012
Differential temperature > 43'F for about 160 hours.
Differential Temp = T-stat setpoint [68] - Outside Air Temp
http://www.wunderground.com/history/...q_statename=NA
Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities
Regular Guest
From *removed link to HVAC Forum*
Applying Brad's formula:
BTHU = (Annual Fuel usage/0.6)*(house temp-design temp)*efficiency*fuel heat value)/HDDx24
Where:
68 house temp that we set to
9 design temp from gov data
0.79 efficiency from energy audit
138690 fuel heat value for #2 diesel
775 fuel usage from energy audit/oil company logs
4753 Heating Degree DaysHDD from gov
yields = 73,197 BTU loss per hour
Professional Member*
The efficiency number from the energy audit is what is skewing the numbers. That is combustion efficiency not system efficiency. At 2000 sq. in Groton, around 40,000 sounds about right. The Slant Fin program works and has a fudge factor included in it.
Professional Member*
Annual Fuel Usage / 0.6 ... Now T H A T'S one helluva Fudge Factor !Originally Posted by Edgeman
1/ 0.6 = 1.6667 ...NOTHING like adding 67% to the Appropriate result _ 43,918 BTU/Hr
Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities
God Speed, Jim. We'll miss you - 2-26-23
But it will never under size a unit. ROFL
Professional Member*
No, but it may very well get one operating times that MANY would Not be real pleased with.
OR a calculated 100,000 * 1.66 ... 166,000 .:. you can have at least 2 units.
Are mechanical contractors now selling 2 for 1 [ BOGO ] like you see in the grocery store?
I'll plan on the _GET ONE_ when my neighbor does the _BUY ONE_ portion.
Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities
God Speed, Jim. We'll miss you - 2-26-23
No, but it may very well get one operating times that MANY would Not be real pleased with.
OR a calculated 100,000 * 1.66 ... 166,000 .:. you can have at least 2 units.
Are mechanical contractors now selling 2 for 1 [ BOGO ] like you see in the grocery store?
I'll plan on the _GET ONE_ when my neighbor does the _BUY ONE_ portion.
Do you even have boilers in Florida. LOL
Seems many contractors still like to use the finger sizing rule. Stand across the street. hold your hands in front of your face at arms length. How ever many fingers it takes to cover the house, is how many sections the boiler needs to be. Not too many houses a 10 section won't heat. LOL
Professional Member*
HELL Yes, we have boilers. However, I much much more prefer BBQ to those damn old oil fryers.
Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities
Professional Member*
That 79% efficiency number is probably closer to 60%, use that instead.
The .6 you have after annual fuel usage can be adjusted based on solar gains and other incidental gains according to Brad. If you change it from .6 to .75 the heat loss comes much closer to reality.
My condensed version of 55 x gallons used = heat loss works for Long Island, your house is maybe 60 miles from mine.
They don't make an oil fired boiler small enough for the majority of homes on Long Island. The heat loss on your house is around 40,000 (I have a 1900 sq. ft. ranch too).
Regular Guest
I need to get a min 90% AFUE to get the $750 rebate. Quotes for the TT Prestige Primax Excellence or a mod-con with an indirect is so expensive $$$ I am considering to buy a mod-con with a conventional 50 gallon tank to cut the cost. Thoughts?
Professional Member*
The latter will create venting issues, your not supposed to vent "orphaned" water heaters into a masonry chimney. People always get hung up on the rebate money, get a conventional gas boiler with an indirect water heater if you don't want to spend the extra money.
Regular Guest
Well then it becomes a cost problem because I may then have to line my Chimney stack for the lower temp gas venting which would be a prohibitive $1. Mod-cons have come down in price over the years so that it doesn't pay to get a conventional broiler when you switch from oil to gas with all the cost and incentives. The Navien looks like the lowest price point to effect the changeover.
Last edited by Chris_Worthington; 02-25-2013 at 12:14 PM. Reason: Pricing Removed
Professional Member*
A conventional gas boiler would need a chimney liner as well. FYI
Regular Guest
That's what I'm citing as an added expense that makes going the mod-con route a better choice because you don't have to use your stack.
Professional Member*
Good, because to play the game effectively you have to know the rules.
I vote for a Triangle Tube Solo 60 with the appropriately sized indirect coupled to it, but everyone likes something different.
Regular Guest
R, I really appreciate your input. I'm going to nix the Navien CH210 Combi idea. The initial contractor came in with that and I asked him to rework the proposal with a AFUE 90+ boiler with an indirect and he suggested a Wiel-McLean GV90+5 with a Aqua Plus 55. I suggested a GV90+4 and a Aqua Plus 45. The boiler has a cast iron heat exchanger. Also considering a TT prestige Trimax Solo 110 with an indirect but they are more $$. Th eSolo 60 may be at the threshold when mating with the 45 gal indirect. Another contractor is coming by this week to talk about the Viessmann Vitodens 100.
Professional Member*
The TT60 would drive a 45 gallon indirect just fine for a four person household (we don't have any big Jacuzzi's in that ranch do we?). I happen to be a big fan of the Vitodens 100 and we usually couple them to a 32 gallon indirect. The mod/cons are pricey but we have to put a lot of different components together to make a heating system.
Regular Guest
Looks like I'm looking at the TT CC125s (aluminum heat exchanger) with the TT Smart 40 Indirect Hot Water Heater vs. Weil McLain GV90+4 with the Weil McLain AquaPlus 45 Indirect hot water tank which is 5% cheaper. The GV90+$ has a cast iron heat exchanger. Will this have a longer life? Which one would you choose. The contractors are suggesting the the TT Prestige 60 is too borderline with the indirect tanks. Thoughts?
God Speed, Jim. We'll miss you - 2-26-23
If you get the 60, just get a smaller indirect. no problem then.
Regular Guest
I currently have a propane stovetop which uses maybe 30 gals a year @ $4.33 currently.or $130 per year. I also have an electric clothes drier. Should i bother piping natural gas to change the stovetop and perhaps have a gas drier if ever my electric drier dies? It cost $500 to run the gas lines on the outside of the house to hook up the stovetop and have the ability for the gas drier later. Is it worth it? Not sure what the equivalent cost are but if natural gas is 1/6th of the price of propane then the payoff is 5 years. Should I bother or keep the propane? My Maytag electric drier never dies.
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