Posted by daestrom on October 19, 2005, 11:27 pm
Well, here in upstate NY, we have the heat on now (in the 50's outside) and
it will be on until late April. So we get several months of good 'solid'
heating with the house closed up. You're right, the exact amount isn't
perfect because of a varying amount of lighting (as the length of days
change), and all sorts of other variables. But some of this can be 'fudged'
if you calculate your degree-days from a slightly different 'house
temperature'. It's within a couple of significant digits, and considering
the 'granularity' of temperatures, gas readings, etc... it isn't bad.
I've toyed with the idea of factoring in the average daily wind speed, but
the speed at the weather reporting station is not the same as my house. But
maybe some snowy winter Sunday, after football season, I'll see if there is
any sort of correlation I can draw between the average monthly wind speed,
temperature, and NG usage. I know in my mind that there is one there, but
not sure I can 'see' it in the data noise. ;-)
Yeah, you won't 'see' anything closer than a couple of months. Has to do
with how often your gas meter is read. Of course, if you wanted to read it
yourself once a week or something.... (but that's going too far, even for me
Hey, thanks for that info. I have a pilotless stove/oven, dryer, and
furnace. But the HW heater has an ordinary pilot. Yeah, $/day just for
pilot lights is a bit when it's warm outside. Of course in winter, some of
that heat still makes its way into the water/house. But some of it
(hopefully the CO2 and water vapor at least) still goes up the chimney.
I've been looking a while for a 'condensing' high-efficiency HW heater. My
furnace is already a condensing model. My HW heater is a 'power-vent' type
with a mechanical blower to exhaust out the foundation wall (no chimney),
but when it runs it 'sucks' (pun intended) a lot of warmed air from the
house and discharges it outside with the HW burner fumes. Seems like a
condensing model would still vent horizontal (wouldn't have to put in a
chimney), and draw a lot less air. Oh well, maybe that will be *next
year*'s project ;-)
Posted by Solar Flare on October 19, 2005, 11:55 pm
Yeah, that power vent stuff drives me crazy. The fan not only draws power it
sucks more heat out the vent than is needed just so they could use cheap venting
by cooling the gases down with house air. I have a make up air vent beside it
but that just leaks more air into the house.
Too bad somebody doesn't make a vent heat exchanger for a hot water preheat
system since the gases are power vented anyway. Condensation may be a problem
but with the amount of house air they mix with it it may not or a drip pan may
be in order.
We seem to be caught in a technology changeover. We don't need or want the heat
to self draught the chimney but we blow it out the wall vent anyway and need to
cool it because it is too hot.
Posted by daestrom on October 21, 2005, 1:39 am
Yeah, but at least it only blows warm air out when the HW heater is running.
A chimney draws all day/night.
Posted by Solar Flare on October 21, 2005, 1:51 am
Not so sure about that one. The vent is on the top of the water heater and the
intake is still at the bottm. The heat from the core of the tank is exposed and
tends to create a draft the same as a regular chimney. I am sure not to the
same extent though, due to the smaller size pipe and possibly less themal mass
of the walls on the pipe sloped upward. The slope would be much less also.
Posted by daestrom on October 21, 2005, 7:14 pm
It draws air through the heater, but the air doesn't work it's way out of
the house. In my case at least, the outside vent is located low in the
house (heater is in basement), so if anything, I get cold air drawn *into*
the house when the unit is off. But that's a matter of stopping all the
other 'holes' that let warm air out the top of the house.
One of the drawbacks of gas-fired tank-type heaters is that when the burner
is off, there is still a small, constant draft of air up through the tube in
the center of the heater. And that tends to cool the water back down,
increasing the 'standby' losses. If it has a constant pilot, that flame
helps to keep the air in the vertical tube from cooling the water off too
much (i.e. the main burner doesn't fire as often), but then you have the
waste of that pilot flame all summer long.
Now, if they made a mechanical draft, condensing unit, with electronic
ignition, *that* would be something. But it probably would cost $000 and
never pay for itself :-(