Hot water to forced air

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My son has a home that he added a solar water heater to a few years ago. Works great , too great. The unit far exceeds his demand for hot water. He wants to add some coils to his forced air HVAC system so he can use the solar heated water to heat his home. He was expecting there to be a coil he could place in his HVAC system but cant find what he is looking for or knows what to ask/google for. Any help would be greatly appreciated.
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I wonder how often the solar heater will provide needed heat to the home.
if may not be cost effective
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Another factor is a forced air system frequently already has a heat exchanger in it, the AC evaporator. Adding another obstacle for the air to go through will create more resistance for the blower. It might create enough so that it burns it out the blower motor. Or the added resistance reduces the cooling performance in summer, etc. Overall, doesn't sound like a great idea to me.
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wrote:

ROFL...
Not just cutting it into the duct work and adding it to what is already there, but modifying the trunk where the AC coil is located with some dampers and adding a place for the hot water heat exchanger would do just fine without burning out any fan motors as it blows the air past the AC coil just fine without burning out now...
It sounds to me like the OP's idea will have a high initial cost and would be quite a while before any sort of ROI is realized...
~~ Evan
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Clueless as usual. Re-routing the air through another path via dampers, etc, creates significant additonal drag as well. And I would not be surprised to find that the addional resistance is MORE than just putting another coil in the existing loop. Any of those add to the load on the blower.
Want to tell us again how it's illegal to vent nitrogen into the atmosphere from an AC system and how it must be recovered as you claimed? Or how a homeowner with reasonable skills is gonna die if they dare to cut and re-glue a simple PVC pipe?
Clueless, totally clueless.

Gee, you really think so?
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On Jan 4, 9:06pm, snipped-for-privacy@snyder.on.ca wrote:

You do realize there is a difference between a modern ECM blower motor on a furnace and a vacuum cleaner that is cavitating, don't you? An ECM motor tries to maintain constant airflow. Put more resistance on it and it uses more power to push the air harder. They are typically spec'd for a maximum pressure. If you put more resistance in a duct system, be it another heat exchanger or a clogged filter, you INCREASE the power used and at some point you decrease the life of the motor.
Also, furnaces have a min airflow reqt to keep the heat exchanger within it's correct operating range. Put more resistance in the duct work and you could exceed that limit as well.
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On 1/5/2012 8:14 AM, snipped-for-privacy@optonline.net wrote:

If you close too many registers, the heat exchanger will overheat and the high limit safety will shut down the furnace.
TDD
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Apparently you've never seen an ECM blower on a modern furnace. The controller maintains a constant volume of air, ie X CFM. Put more resistance in the ducts and the motor used MORE energy to move the same amount of air. Moving the same amount of air with a restriction takes more energy because of the increase in pressure. Capiche?
Funny, aren't you the one always ranting about how the UK is way ahead in energy technology? No ECM blowers over there?
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On 1/5/2012 2:00 PM, snipped-for-privacy@optonline.net wrote:

Years ago, me and my late friend whom I did a lot of HVAC work with, installed a new system equipped with the new ECM fan motor. I hadn't read the literature on the system because I was only peripherally involved with the installation of the new package unit. The customer called complaining something was wrong with the new system because there was little air movement and the blower wasn't working very well. I checked and the fan didn't seem to be blowing very hard and it took it a while to start blowing. A call to the factory rep at the distributor gave me the answer. The darn thing was supposed to do that! The ECM fan motor is supposed to run slowly all the time to keep air circulating in the home. When the system calls for heat or cool, the fan speed ramps up slowly and winds down to a continuous low speed when the set temperature is reached. Darn newfangled energy saving doohickeys. o_O
TDD
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Apparently the America bashing genius here that rants about how advanced the UK is heating technology isn't familiar with ECM blowers which have been around for over a decade here.

You really think so?

As I recall, the issue was placing another heat exchanger which offers more resistance to air flow in a heating system. That is NOT zero air flow.

No energy efficient ECM blowers in the UK, eh?
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On Fri, 6 Jan 2012 05:17:26 -0800 (PST), " snipped-for-privacy@optonline.net"

"variable speed" and controlled by mass air dlow or temperature differential (heat gain). My furnace has an ECM blower and the controller needs to be SET to a particular speed - so it runs like a programmed multispeed fan, not a variable speed. This requires, when setting up the system, that the tech reads the temp and pressure on both sides of the furnace, does some calculations, and sets the speed accordingly. This results in a different speed for AC and Heat.
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On Jan 6, 4:01pm, snipped-for-privacy@snyder.on.ca wrote:

I have a variable ECM blower too. And guess what? It too has switches that set the target air speed. That says nothing about what happens to power as you restrict the airflow.
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On Thu, 5 Jan 2012 06:14:43 -0800 (PST), " snipped-for-privacy@optonline.net"

Well, your experience is different than mine. I've ALWAYS found that a blocked filter lowers the load on the fan.

it - no problem - but the furnace may end up "high limited"
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You need the word "hydrionic" which will help out. Beyond that, I'm not a lot of help.
I think using solar to help heat the house is a great idea. Best wishes, hope you can make it work for you.
Christopher A. Young Learn more about Jesus www.lds.org .
My son has a home that he added a solar water heater to a few years ago. Works great , too great. The unit far exceeds his demand for hot water. He wants to add some coils to his forced air HVAC system so he can use the solar heated water to heat his home. He was expecting there to be a coil he could place in his HVAC system but cant find what he is looking for or knows what to ask/google for. Any help would be greatly appreciated.
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On 1/4/2012 12:53 PM, JIMMIE wrote:

We call that a "Hydro-Air" system. The hot water coils are inside the air handler along with the cooling coils. I think he could make his solar system assist the boiler, but I don't think I'd rube the air handler to do it. Possibly if he T'd the solar loop into the boiler loop where the go into the air handler, and set up some solenoid valves, so whenever the thermostat called for heat, an aquastat on the solar system would open it's solenoids as long as the water temperature was hot enough. It would also have to turn on a circulating pump for the solar loop. When the temperature isn't hot enough, the aquastat would close a circuit, opening the solenoids from the boiler loop and it's pump, and fire the boiler. The problem with doing something like this, is that the only guy who will know how to service it, is the one who built it. If anything malfunctions, he could be without heat for a while
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My son is an engineer who has a lot of "farm boy horse sense" and pretty good about figuring out anything. He has already considered that adding another coil may restrict the air flow too much. Not knowing any info on the heat exchanger it wasnt an idea he had completely tossed. This system wouldnt be the only source of heat just an augmentation to to decrease his power bill hopefully. I think he would be happy if it just heats his "great room". It is beginning to sound like this is going to be a separate system that just heats the main part of the house.
Jimmie
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This system wouldnt be the only source of heat just

thats the way to go, seperate system to just heat one room.
the question is how much will that room need heat when the solar collector has excess heat to supply?
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wrote:

Auto heater cores is something that has been considered..
Jimmie
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Too small to do much good. Try auto radiator.
Christopher A. Young Learn more about Jesus www.lds.org .
Auto heater cores is something that has been considered..
Jimmie
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On Wed, 4 Jan 2012 19:01:59 -0500, "Stormin Mormon"

cores would be too small, but many are about 100 square inches and 2 1/2 inches thick. The advantage is they are DESIGNED for roughly 3/4" hose, and the flow rates involved, while radiators are designed for roughly 2 inch hoses and the much higher flow rates. 2 heater cores from something like an old impala or Chevy Suburban would likely be more than adequate.
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