Heat loss calc vs fuel usage

shoudabeenaplumba

I've tried various methods/programs/websites to get an accurate heat loss calc for my house.  The current boiler is 164k downfired to about 1.0 gph.  After 1/2 dozen (granted, they were free) different heat loss calculations I've come up with a minimum of 70k and a maximum of 90k.  I also installed an hour meter on my burner to give me a day-by-day account of fuel usage. 

On the coldest day of the year (-5)  my burner has run under 10 hours.  With 1.0gph @ 83% eff. I've got an average of about 48k/hour.  I figure a majority of this is when the sun is down, but still, that's pretty low.  I'm in NH, and this is a 4300sqft house.  I suppliment my heat with a wood stove, but even when I'm not burning during the Summer I still burn 1.5-2 gallons a day for hot water, so for heat I'm looking at even less than my average. Walls are 2x6 and the ceiling is r50, well built, well sealed, good windows,  but this is a big frigging house.  

Am I missing something in my equation?  I've checked the pressure and nozzle size against a chart and if anything I'm under 1.0 gph. 

toilburn

toilburn

two gallons a day for hot water in the summer is way too high

MikeT_Swampeast_MO

Large Household?

1.5 - 2 gallons of oil for DHW in the summer does seem rather high.  At about 50% efficiency from the high heating value of #2 fuel oil, with a rise in temperature of 100F, that's about 150-200 gallons of hot water per day.  Large family or something else for a lot of hot water use?



Heat loss calculations are extremely conservative.  They have zero consideration for occupancy loads or natural solar gain with air infiltrating consistently and constantly.  Everything in your house that consumes electricty produces heat that does in fact add to the heat lost in the winter.  Cooking can add significant heat and even humans give off heat.  The sun heats windows which on even extremely cold days can become radiators to the space and high quality windows, well installed and properly oriented can actually become net heat contributors by allowing more heat in on a typical day than they loose at night.  Heat loss calculations also assume that wind infiltration occurs from all directions simultaneously and steadily--both of which are impossible in the real world.



Even traditional paid heat loss calculation software will often include a phrase like, "This program produces a 'best case' calculation and you should round up when sizing for delivery and heat production."  Perhaps true for typical and shoddy forced air, but untrue for hydronics!



A boiler whose net output is 50% of a traditional heat loss calculation will likely have no problem maintaining your desired heat level in any reasonable conditions in at least reasonably insulated and tight homes.  Don't however expect to turn the thermostat down to minimum over a long weekend, come home in very cold weather and expect to be cozy warm anytime soon...

shoudabeenaplumba

Seven people living in my house

The oil for hot water usage is bugging me too.

Five girls and two boys.  Some of the girls will occasionally be caught taking 20 minute showers, plus my wife is one of those people who will take a shower after the pool, so all the kids do the same.  2.5gpm shower heads gives me about 120-150g/day + dishes and laundry, so I'm estimating 200g/day on hot water isn't out of our realm of being possible. 

80 degree rise x (200 gallon * 8.4lbs)  = 134400btu / (138k*.80) = 1.21 gallons of precious, precious heating oil.  I'm sure the trianco boiler isn't putting out that great of numbers, and there's a 70' run from one side of the house to the other, which I sure is eating up quite a few of my btus. I'm hoping to see a 20% reduction after the boiler change-out.

hot_rod

sounds like you need some SDHW

solar DHW to lighten the $$s you are spending for DHW. A 2- 3 collector system could provide 50- 60% SF (solar fraction) on a yearly basis, maybe 80% or more in the summer months.



hr

GarvinP

shower heads

I don't know how popular this will be with your girls but you might want to check out USAlandlord.com.



I have used these on our rental units and its the only ones I have ever found that DOESN'T get complaints.

Seems like low flow and good pressure.

Not the type that tenants complain that their heads burn and their feet are cold and that steam up the bath.

I like their facet aerators too. Using all has greatly cut down on water sewer fees as well as the HW gas bills.

shoudabeenaplumba

I've got a pretty poor setup for solar

Not a lot of open land, and the roof is not totally to the South.  I'll know later this year if its practical.  If my DHW bill goes down to 1g or below over the Summer then I doubt it would worth it.