[SustainableTompkins] water heating

Tue Jan 29 11:14:07 PST 2008

Hi Katie,

We have a fairly complicated wood furnace/solar preheater/static water 
storage tank/radiant slab setup in our house, significantly more complex 
than what you are thinking about. I used Steve Seamon at A1 plumbing. He 
didn't know tons about this stuff before we started, but we both learned 
a ton doing my system and he is now quite familiar with gravity feed, 
tempering valves,  termovar (auto-mixing valves), etc. He also happens 
to be a really nice guy and very interested in these alternative heating 
systems.

My only comment is to reinforce what Joel said about making sure you 
have adequate pressure relief safegaurds in the system. You do not want 
a tank of steam-pressurized water leaking inside living space. It is a 
serious safety hazard. Having said that I am a tinkerer at heart: I 
agree with Joel, this can be done safely. Just get someone to review the 
engineering design (especially the pressure relief).

Cheers,
David

Joel and Sarah Gagnon wrote:
> Hi Katie --
>
> You may have trouble finding such a person, given that it has been a long 
> time since the technology was prevalent. The installation, however, could 
> be handled easily enough by any competent plumber. There are just a couple 
> of things to get right for it to work properly.
>
> The tank needs to be mostly above the firebox (it could even be in a room 
> above the kitchen). Usually these tanks were vertical and sat on a stand to 
> raise them up above the floor. A stand could easily be fabricated for the 
> purpose. Keep in mind that if the tank is very close to the stove (as they 
> used to be), you will need to be careful about combustible materials. Most 
> older cook stoves need a clearance to combustible surfaces of about 3 feet 
> (which can be reduced by shielding).
>
> Size the piping to match the diameter in the firebox. The cold inlet comes 
> from the bottom of the tank  and goes to the bottom of the coil. The hot 
> comes out of the top of the coil and goes into the upper part of the tank, 
> typically a foot or so below the very top. Any shutoffs in the lines should 
> be full flow. Quarter-turn ball valves would be fine and are probably the 
> cheapest choice. Gate valves would have been used in the old days, but they 
> are uncommon now. Make sure the tank has a temperature and pressure relief 
> valve. It will add expense, but a pan beneath the tank with a drain to 
> safely deal with tank failure or discharge from the relief valve would 
> provide peace of mind, especially if the tank is above finished rooms.
>
> These tanks were uninsulated "back in the day", but there is no reason they 
> couldn't be insulated. An old or even a new water heater tank could be 
> used, and you could even have the tank have its own heat source so the 
> water could be heated when the stove is not in use. Alternatively, the tank 
> could be used as a pre-heater and tempering tank for an instantaneous heater.
>
> Joel
>
> At 07:39 AM 1/29/08 -0500, you wrote:
>   
>> Has anyone successfully hooked up their wood cookstove to a hot water
>> system?  My Oval cookstove has in/out hot water pipes that run through
>> the firebox, but I haven't found an installer who's ever done this kind
>> of a hookup.
>>
>> -- Katie Q-J
>>
>>
>>
>> Joel and Sarah Gagnon wrote:
>>     
>>> I have been using a solar batch heater for a few years now. It serves to
>>> preheat the water, which then goes to a very well insulated conventional
>>> electric tank heater. In the summer, the water is hot enough most of the
>>> time that the tank heater needs to add very little heat. Kitchen and
>>> bathroom sinks are on either side of a common wall, with the tank almost
>>> directly beneath them, so there is very little waste getting hot water to
>>> the tap.
>>>
>>> If I had more remote taps, I would locate the tank closest to the greatest
>>> use. An instantaneous electric heater (or even a small tank) at the remote
>>> tap would minimize water wastage, albeit at the expense of some wasted 
>>>       
>> heat
>>     
>>> (which does heat the house, after all).
>>>
>>> If the logistics worked, I think the water heating should be integrated
>>> with space heating using biofuels. I think of wood as stored solar. In the
>>> months of November through January, there is very little direct solar gain
>>> around here. Worse, the incoming water is colder, needing more heat to be
>>> warmed to service temperature. So, when you need it most, the sun isn't
>>> there. It is there, though, in indirect form in the wood I burn to heat 
>>>       
>> the
>>     
>>> house. Moreover, my use of the stored solar is inversely proportional to
>>> the available direct gain, making my wood stove the ideal complement to 
>>>       
>> the
>>     
>>> solar batch heater. The trick is to get them to work well together, which
>>> is difficult unless you luck out or plan a house around it.
>>>
>>> In the early 20th century, it was common to heat hot water with a tank
>>> connected to the kitchen range. A convective loop of pipe adjoined the
>>> firebox and circulated water from the stove to the adjoining tank. A
>>> similar heat-transfer coil could be wedded to a woodstove to convectively
>>> heat water in a nearby tank, provided the tank was somewhat higher than 
>>>       
>> the
>>     
>>> coil. Ideally, that tank could be the same tank as is heated by the sun in
>>> a batch heater, or, absent such a tank, it could be the tank of a
>>> conventional electric tank heater. Conceivably, the storage tank could be
>>> heated with propane of natural gas (or even oil), since the chimney is
>>> at  hand. The storage tank would most likely end up on the second floor
>>> with the woodstove on the first.
>>>
>>> This isn't the only possible arrangement, by a long shot, but it is
>>> something to think about. I agree with Margaret that the ultimate solution
>>> may lie in generating our electricity from renewable sources, but we are a
>>> long way from that. If you read Mark Jacobson's web article advocating 
>>>       
>> wind
>>     
>>> as the energy choice of choice, you may have remarked, as I did, that we
>>> could generate enough energy to replace all fossil fuel use in the US with
>>> a mere 500,000 5-megawatt wind turbines. We have the equivalent of 2000 of
>>> those so far. Only 498,000 to go!
>>>
>>> Joel
>>>
>>>   At 06:34 PM 1/27/08 -0500, you wrote:
>>>
>>>       
>>>> On Jan 27, 2008, at 6:22 PM, Ira Goldstein wrote:
>>>>
>>>>
>>>>         
>>>>>   Howzabout a middle way scenario in a dwelling with say a basement,
>>>>> 1st floor & second floor (or more): installing a single on-demand
>>>>> heater in a location somewhere kinda equidistant from the various
>>>>> points of use (maybe on the first floor) to eliminate an overly long
>>>>> run and wait time to any particular use location?
>>>>>
>>>>>           
>>>> That would be ideal. In most houses kitchens and bathrooms are in the
>>>> same general area. It would still take some retrofitting of hot water
>>>> piping and a gas line would be needed and it could be power vented
>>>> through a wall to the outside. Maybe hide it in a closet?
>>>>
>>>> I have day dreamed about doing this from time to time. And this
>>>> discussion has me thinking again. But I no complaints about the
>>>> AquaStar in the basement.
>>>>
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>>>       
>> --
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