"David" wrote in message
om...
Hello, I have an AquaTherm furnace connected with a 40 gallon hot
water heater. When the furnace is on and using the hot water heater,
I get either no or only luke warm water in the house. Does anyone
have any idea what the problem is? Is my hot water heater going, or
is there any adjustment that I can make? Thanks in advance!

Well, it would be good to tell us a bit more about the configuration.
All I can imagine is a sort of strange setup that looks like this based on
pure conjectu

+----------+
| |
| Home |
| Heating |
| |----BTU
| |
+----------+ +----------+ | |
| | | |-----| |
|AquaTherm | | Water | +----------+
| | | Tank / |
| |----| Heater |
| |BTU | |
| | | | +----------+
| | | |-----| |
+----------+ +----------+ | |
^ | Hot Water|
| | Use |-----BTU
| | |
| | |
| | |
+----------+
Electricity
BTU or watt hours


The AquaTherm is set up for radiant heating based on circulating hot water.
The outdoor AquaTherm unit is used for heating the water.
There's a hot water heat exchanger and a pump that circulates water from the
firebox and a holding tank.
This *same* tank has been plumbed into the house as the hot water source.

When home heating is needed, the same water is circulated through the floors
in the house.
This removes heat from the water.

So, in really cold weather, the temperature reduction in circulating the
water through the house is noticeable when you draw water for household use.

The whole arrangement seems strange and yet intriguing.

If the water holding tank is also an electric water heater then the
AquaTherm outside wood burner apparently works in tandem with this other
source of energy. Presumably one could save on electricity by circulating
water through the AquaTherm. So that sounds like it could be a good thing.

Now, I don't know if one can expect a domestic water heater to support
radiant heating. They aren't made for that. Of course, there are heaters
that are made for that purpose but I don't know what their outlet
temperatures normally are - maybe the two are compatible. Maybe this is OK.

To make a point:
I have two hot water heaters in series and run the one on the inlet side
when there's going to be high demand for hot water in the house. When
demand is low, the inlet side heater is turned off and just looks like a
piece of pipe. When demand is going to be high, and the inlet heater is
turned on, then the heater on the outlet side looks like a pipe (although it
does add heat) until the inlet side heater runs out of hot water. At that
point, the inlet heater looks like a pipe and the outlet heater operates as
if the inlet heater isn't there (although the inlet heater is adding heat).
On occasion, I run out of hot water when running just one heater.

The point of this description is this: if hot water demands are reasonably
high then the heat stored in the water is easily diminished. There would be
no heat left to heat the house by circulation.
Similarly, if the house is being heated by circulation from the same tank,
there would be much less heat left to allow drawing hot water - particularly
in cold weather. So you would notice that the hot water source for
consumption would have a lower temperature.

A lot has to do with dynamics or transient changes in temperature. But, you
can estimate what will happen by analyzing the average heat requirements:
You can figure out how many BTUs are necessary to heat your house and
convert those to watt hours.
You can figure out how much normal hot water use would use power for your
water heater in watt hours.
You can figure out how much energy it would take to run the hot water heater
100% of the time.
You may be able to estimate how much energy the AquaTherm can deliver.
Presumably the AquaTherm can deliver enough energy to heat the house.
Presumably the water heater can deliver a whole lot more hot water than you
will normally use.
You can calculate how much heat can be taken out of a 100% running water
heater while keeping the water heater on all the time and keeping the water
temperature just at the power shutoff temperature.
You can calculate how much heat the AquaTherm needs to add in order for the
heat delivered to be such that the water temperature stays high.
You can compare the heat the AquaTherm would need to add with the amount of
heat the AquaTherm is capable of.

Water Heater Electric Energy = Wh+We where Wh is power to deliver
AquaTherm thermal energy = At - efficiency factor "ea"
Hot Water use thermal energy input = Wh
Hot Water excess thermal energy input= We (had by leaving the hot water
heater on all the time)
Hot Water thermal energy available to heat the house = We- efficiency factor
"eh"
Total water heater input energy if left on all the time = We + Wh
Home heating thermal energy load = Ht

Heat available for heating the house while keeping the hot water at high
temp limit:
(At - ea) + (We - eh)
can be set equal to heat needed to heat the house Ht

(At - ea) + (We - eh) = Ht

If Ht is ever higher than the energy available from both sources, then the
water temperature will drop and the house temperature will drop.
This is a steady state analysis based on averages. Actual water temperature
can vary if there's a large draw of hot water from the tank - as an example.

"Is the hot water heater going?" Well, maybe yes and maybe no. Another
analysis would ask, can the AquaTherm take care of everything by itself?

(At-ea)=Ht+Wh

If the left side of the "equation" is larger than the right side, then the
AquaTherm is capable of providing all the energy necessary for heating the
house and for providing hot water - on the average. In that case, the hot
water heater would not have to be turned on or to be working and the loss of
hot water would be perhaps similar to running the hot water until you ran
out - as with a working heater.

So, if the system ever worked in cold weather and if the demands for hot
water haven't gone up in the interim and if it all worked during the last
summer then it could be that the water heater failed some time ago and the
effect is showing up now in the winter.
If there's no acceptable cold weather experience, the system could be
underdesigned for what you're expecting.

First thing: testing the hot water heater should be pretty easy if you shut
off the AquaTherm and pump. Either you get hot water or you don't. Hot
water heater thermostats seem to fail often enough.

Caveat lector. For illustrative purposes only. Could have mistakes or
suggest things that aren't reasonable.....

Fred