AquaTherm Furnace - No Hot Water Issue

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!
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Why would you want to heat hot water?
Maybe THAT is part of your problem...
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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 conjecture:
+----------+ | | | 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
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Fred Marshall wrote:

If the [ommited] diagram is right, that raises another question: Aren't you supposed to avoid situations where the water system that drives the houshold heat is sharing/interchanging water with the potable water supply?
--Goedjn
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Since there appears to be some confusion on this unit, this post is meant to clairify:
Aqua Therm is made by First Company, and utilizes a Hot Water Coil fed from the dwellings hot water heater. This hot water coil is not "radiant" heat as one respondant hypothicated, but rather incorporated in a Forced Air Unit. A blower forces air through the hot water coil and out the supply ducting. A "Taco" pump pumps the water through. The SAME water that is used for the buildings hot water is used for space heating. The hot water from the hot water heater is fed through he coil, and the return feeds back into the cold water supply inlet to the hot water heater. Obviously there are check valves.
In answer to another posters musings, there is no problem with the heated water being used double duty for Space Heating and for potable water supply. Copper pipe is used for building plumbing, and for coil heating applications. Absolutely nothing harmful is introduced to the water, it is simply circulating through more pipe. That is all. In an extremely simplistic example, it is as if we were simply placing a fan across the hot water pipe coming off David's hot water heater and making use of its heat to help heat the space. There in lies the rub, and David's problem: If we force air over the hot pipe, the pipe will give up some of its heat. The water then is not as hot as it was.
In answer to David's question, there is not a lot he can do. When the heating unit is in operation, hot water from the water heater is circulated though the coil. Air is forced over the coil, taking heat from the water which is then returned to the water heater. The water heater must cycle to re-heat the water.
David can increase the temperature of his hot water heater. In doing so, he will increase the heat output of the heater (Aquatherm), and gain some residual benefit of an increase in the buildings hot water. He might consider putting scald guards at his fixtures if he ups the temp too much. This will naturally raise David's utility bills, as the Heater will run longer.
He can also consider changing the water heater to a larger unit, and one with the greatest recovery rate he can afford.
Since your hot water is being circulated in a coilIn article

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Well, the AquaTherm unit information I gleaned from the web seemed different. But no matter....
One thing that happens when hot water is circulated might be unexpected. Nothing happens until you start to seriously draw hot water and then things change. This situation sounds like that's what's happening.
Example: I had a house with a hot water pump / loop so that hot water would be more quickly available at the furthest point in the house from the water heater. We noticed that the water would rather quickly become less than really hot while taking a shower. If the circulating pump were turned off, this didn't happen. Why?
The circulating system takes hot water out of the tank as normal and routes it through the house. The return pipe feeds water into the water heater cold water inlet side. When there's no hot water being used, this keeps the water in the pipes hot and doesn't much affect the water heater. However, when there is hot water being consumed, things change. Instead of cold water coming in the bottom of the tank and hot water coming out the top as usual, hot water mixes with cold water coming into the bottom of the tank. This causes more mixing inside the water tank than normal and quickly enough the entire tank goes to a lower temperature. This is in contrast to the normal situation where there being a rather sharp temperature gradient between cold water at the bottom and hot water at the top. So, this can be annoying.
There are a couple of solutions: One can attach a hot water heater thermostat to the water heater inlet pipe that controls the circulating pump. The idea is to stop circulating if the inlet water is cold. Something like that....
Another approach is to put two hot water heaters in series and only circulate water from the heater on the outlet side of the pair. This way, there's no cold water mixing in the outlet side heater until the inlet side heater runs out of hot water. The outlet side heater can be small because it's only other purpose is to circulate hot water - which shouldn't take much energy if the pipes are insulated. The inlet side heater is not subject to the kind of mixing that occurs with one heater plus a circulation pump.
Now, if the energy loss in circulation goes up then the outlet side heater would need to be larger and this wouldn't be such a good solution because mixing would occur. However, it's probably better than not having two tanks because really cold water isn't brought into this "mixing tank" right away.
Fred
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things
would
water
off,
routes
the
top
quickly
to
pipe
the
side
circulation
tanks
away.
Why not simply put a $5 check valve into the loop?
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of
gradient
way,
because
heater
because
There's no backflow in the loop because the pump is always running. So, I don't see what a check valve will do. The problem is added mixing in the heater tank when there's consumption.
Fred
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replying to David, eric wrote:

I live in a condo and have an AquaTherm furnace and my problem is I only get hot water if I turn on the heat. It is not much of a problem in the colder weather but in the summer I have to put the heat on in order to get hot water. I live in Las Vegas (105 to 110 in the summer)
Thank for any and all help
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replying to eric, PolarVortex wrote:

hot
weather
live in

Hi. A lot of folks especially in the US are not aware of these systems. I have one in my condo as well in Ohio and faced a similar issue that you described. It turns out that these systems have two check valves. The valves only allow water to flow in one direction. If these fail the water starts flowing in reverse and that is why you get lukewarm water when the system is not on. I suggest replacing both the check valves to fix this problem. You can pick up the check vales for around $12/each online and call a plumber to replace them or do it yourself if you can handle pipe fitting/soldering. If your system was installed without the check valves, you should install one at the hot water intake and one at the hot water outlet going back into the hot water heater.
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PolarVortex wrote:

What kind of condo is it? Condo board supposes to take care of things like that in my case. Our xondo building has one big system for all units. I don't live in condo. That is rental unit I keep in downtown.
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