1st Gas Bill with New Vitodens

Mike T., Swampeast MO

Fortunately the reading on my statement IS 100 ccf off from the actual meter--guess they didn't calibrate the radio sending unit properly to the meter.

Vitodens used about 0.16 therms per degree day during this period. Not cold and heat loss has been below the lowest possible modulation ability for about 2/3 of the period. This should be the worst-case (efficiency wise) for the Vitodens.

Didn't use the old cast iron boiler in a similar period for many years due to extreme cost of operation.

In the coldest period last year when the old boiler should have been at it's best efficiency, it used about 0.36 therms per degree day.

That's around a 55% reduction when comparing worst new operation to best old!

At $1.1753 per therm, the savings are substantial! By February or so I rather suspect that the gas company will be coming to inspect the meter!

jerry scharf_2

not sure about that lowest efficiency comment

Mike,

With the outdoor reset, the return water is the coolest it will be. I would expect the Vito's efficiency to drop slightly as the season gets colder.

Other than that, the numbers are great. So many times other things change besides the boiler, and it's hard to compare the units in a similar situation.

Best of all you get to have heat in the shoulder seasons now!

keep up the posts, I'm loving it.

jerry

Mike T., Swampeast MO

Always had heat in the shoulder seasons, but it was forced air electric coming from the ceilings--UUGH!

Really is a fair comparison as the boiler is the only change. TRVs, constant circulation, reset and WWSD were already in use and the Vitodens is operating with a nearly identical reset curve.

Will make a 24-hour head-to-head test when weather is cold and also late in the season after the Vitodens is fully "acclimated".

Only time will tell regarding any change of efficiency with colder weather. Return temps will be somewhat higher but even supply only goes above 140° at design temp (141° @ 8°). Surely the cycling when loss is low takes some sort of toll on efficiency.

Question for you Jerry (or anyone else):

How should I set my differential pressure bypass valve? With the old boiler and B&G circulator I adjusted "by ear" and then set for fewest/longest cycles in an hour of steady temp. This was a VERY sensitive adjustment and there was ALWAYS some bypass unless you opened quite a number of TRVs wide. Pressure differential was so low that I couldn't get a reading off of the gauge built in to the valve.

With the Vitodens, I'm having a bit of a problem. First, it has a small differential pressure bypass built in and I do hear it operating when the system is under an extremely low load. Always some circulation out in the mains from the small radiant floor loops, so it's really impossible to "dead head". Two approximately 30' 3/8" loops connected into ½" tubes which then connect to the mains; two approximately 25' 3/8" loops taken off of branch lines to rads.

Have been playing with the big (1¼") outboard bypass the last couple of days. Still an EXTREMELY sensitive adjustment. Left it with a fair amount of bypass (by ear) overnight (it was nearly 60° yesterday afternoon) and noticed that the radiant floors weren't up to temperature this morning with temps continuing to fall through today.

Could still hear bypass with outside temp around 45° and burner firing about 50% of the time ("burst mode") as I call it. Adjusted again until bypass noise just disappeared. Used a strong light and to my surprise saw an indication on the differential gauge of about 1.5 psi.

Does 1.5 psi (3.5') differential sound reasonable for a Vitodens internal circulator operating a TRVd system?

eleft_4

Mike,


How large and how tight is the area you are heating and for how many days?

Explain, the cost per BTU per therm vs oil @ 1.89 per gal.

My assumption here is, highly efficient thoroughbred units may not cost less in the long run.

al

Mike T., Swampeast MO

About 3,250 sf not counting basement or attic. Basement averages 1/2 exposure. (On grade at front, fully above grade at rear with an even taper.)

Attic has separate heating system--all electric up there. Electric bill in attic for same period was $61 including fridge, cooking, DHW, heating, laundry, etc. 8" of cellulose plus 1" of styrofoam insulation between 2nd floor and attic. Eaves have about 16" of cellulose--tapering out to the edge of course... New "bump out" for master bath has 6" of rigid insulation.

Walls (balloon frame 3 1/2" stud) insulated with standard kraft-faced fiberglass. Window weight pockets insulated with 3/4" styrofoam against the outside casing and very well caulked. Exterior sided with asbestos/cement tile--40# felt underneath. Solid shiplap 7/8" (originally 1" I guess) cypress sheathing. While I'm sure it was originally tight, there are now about 1/4" gaps.

Original but completely restored windows (51 not counting 4 attic "roof windows"). Weatherstripped with spring bronze in jambs and pile weatherstrip between stop mold and lower sash of the double hung. Triple-track aluminum storms.

One fireplace--unused--damper is currently inoperable and about 1/4 open. 14 doors to the outside (am counting French doors as 2) and including two single garage doors. I tend to make my doors fit quite tight.

For an old (1903) house, I'd call it reasonbly tight. Compared to SIP or other extremely tight new construction, I'd call it "loose".

31 days in billing period. Degree days as reported by "Weather Underground" website.

Will have to research cost of BTU per thrm vs oil a bit later. Heating oil is not available in this area so I have to hit the books/web.

eleft_4

Mike,

Our envelopes are set up alike. I have 1320 sq ft cathedral throughout.

The heating systems are apples and oranges, older W/M 368 with AFG upgraded to 70mmaqn fired @ .60x60* - 140 psi = .77 Pre & post purge. House is all radiant, W/M IHWH 30 gal.

Burner fired 254.5 hrs in 102 days using 199.2 gal = .78 gph

That's $3.69 per day.....should I complain about old non condensing oil CI tech "efficiency"?

al

Mike T., Swampeast MO

Envelope Similar

Do you have a North exposure 30' to eave, 46' to ridge with 23% in glass and a view?

Unknown

Mike,

Do you allow the homeowner to touch the Comfortroll™?



To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

jerry scharf_2

I'm sure Mike does

It's his house!

jerry

eleft_4

Mike ,



How is the therm vs. gal calculations going?

al

Mike T., Swampeast MO

Cost Comparison of the Fuel is Easy

With gas at $1.1753/therm of 100,000 btu and oil at $1.89 for a gallon having about 140,000 btu, the cost for a therm of oil is $1.3499

$1.18 for gas compared to $1.34 for oil.

Trying to speculate how much fuel it would have taken to heat this house with oil is the hard part.

An extremely high percentage of the BTU content of the gas consumed by the Vitodens is going into the structure. In the very same system an extremely high percentage of the BTU content of the gas consumed by the old boiler was going up the flue.

Granted, the old boiler was extremely oversized and this certainly reduced efficiency. But it also had the benefit of modern controls--TRVs, constant circulation, outdoor reset and warm-weather shutdown.

About all I can say regarding the fuel oil is that if I had a properly sized, well-tuned, traditional oil burner that my actual fuel cost would have been higher even if it were as frugal with the BTUs as the Vitodens. Since such is impossible with current oil burning technology (at least not available in the U.S.) I suspect that the cost with oil would have been nearly the same as with the old gas boiler. Overall system efficiency would have a some increase, but it would have been eaten by the higher cost of the fuel.

Burner fired 254.5 hrs in 102 days using 199.2 gal = .78 gph

That's only about 2.49 firing hours per day average during the period. Considering you're using the boiler for DHW, surely there wasn't much cold weather in that period.

Am using the Vitodens for space heating only. Even though the TRVs make my system a bit atypical, am trying to demonstrate the savings ability of condensing/modulating with older hot water, standing iron systems.

While the shells may be similar, it's just not possible for me to draw a comparison to a newer (I suspect) home in a completely different climate with full radiant floor heat.

Mike T., Swampeast MO

Even if it weren't my house I'd certainly give the homeowner access to the Comfortrol™! After all, it's DESIGNED to be operated by the homeowner!

But the homeowner shouldn't be monkeying with anything in the "installer setup" section--that's where you configure the boiler to work with the system hardware.

eleft_4

Mike,


It's a 1961 that I gutted out to the sheathing sealed up all infiltration i possibly could to get ready for the radiant heat. Replaced all windows and doors with Anderson R 30 ceilings and R15 walls
As for the weather, I can't get the degree days, we usually get down to or below freezing at night it has ranged 30's to highs in the 50's days. I've seen my thermometer at 12
It's dark here before 5 pm so the temp. drops rapidly after 3 pm

My V/S inj radiant is on call for heat all the time. Delta T between 10 - 12 from panel supply manifold to return manifold. That's between 90 and set high at 125. Ratio .9 WWSD 80. (need a flat curve)
Boiler high 170 with a 10 differential.

Merry Christmas

al

scott337

1st OIL BILL

Switched from Keyspan last year because they suck. Did it over the summer and added an indirect for my DHW. My gas bill was from Oct-March 2004 the following: $240, $300, $450, $480, $480, $200, $120. My new gas bill is $20.00 a month (still cooking with gas) but just filled my oil tank for the first time since the switch over for $270.00 for 200 gallons. On my way to more money for Xmas.....
Screw Keyspan!!!!!!