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.
I wonder how often the solar heater will provide needed heat to the home.
if may not be cost effective
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.
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
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?
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
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
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
Auto heater cores is something that has been considered..
Jimmie
The OP may be well served, to set up a separate hot water heat system. I knew some folks who used a car radiator and a fan indoors. Outdoors they had a wood stove with pipe loop inside the stove. Hot and return pipes under ground, and circulating pump. One of a kind, the people and the heater.
Christopher A. Young Learn more about Jesus
I did the reverse of that using cold groundwater to help cooling in the summer. I used an old automobile radiator placed in the air stream in addition to an A-coil that was part of a regular central cookling system. I don't see why the OP couldn't try an auto radiator and save a lot of $$$ over buying something else.
Too small to do much good. Try auto radiator.
Christopher A. Young Learn more about Jesus
Auto heater cores is something that has been considered..
Jimmie
a large automotive heater core may fit the bill.
Personally, I'd go at it a little differently. Since this solar assist is not the PRIMARY heat source, I'd install the solar hydronic loop in the RETURN air to the furnace - and to avoid excessive restriction I would put it in PARALLEL with the existing return air duct . Properly designed, the heat exchanger could have very little more restriction than the open return, and a system of dampers could restrict the airflow on either side to extract the maximum heat from the solar loop.
Because the delta T is higher on the return side than on the heated side, you would get more heat ( in absolute BTUs) out of the solar assist than if it was being used on the outlet side.
Even a couple of heater cores.
How many BTUs do you get out of an automotive heater? SOME heater 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..
The unit has a slot for an electrotatic airfilter that is not being used, my son plans on test various designs by building them so the will slide in place of the filter. He may well be able to find a radiator that would fit. He was talking about taking a look at the heater core out of a school bus one day this week to see how it may fit.
Jimmie
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?
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.
I think the OP is already planning on putting it on the return side. He said he had a filter unit that was not being used and he could put the heat exchanger there. On the return side is the only place that makes sense to me.
- and to avoid excessive restriction I
You'd always get maximum heat extraction with the most airflow through the heat exchanger, so why the need for a system of dampers to vary the flow?
Agree, which is why I don't think it makes any sense to put it anywhere else. But first thing I'd do is figure out how many BTUs of heat are really available on a typical day. And he could only expect to recover some portion of those, clearly nowhere near 100%. Having some numbers he'd have an idea if it would be worth it.
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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