Mike Haasl wrote:If you run out of heat before morning, you'd need more water. If you still have heat in the water in the morning but the greenhouse is too cold, you need to increase your heat delivery. Thus more gpm and more cfm and hopefully not a bigger radiator.
Or at least I think that's a logical progression.....
Side note, as a test you may be able to put a box fan on the outlet of the radiator and suck air through instead of pushing it. But you'd still need to remove the inlet box since that would restrict it significantly...
Gilbert Fritz wrote:Mike, if I attached the box fan pulling air through the front of the radiator, and left the little duct fan in place, I would boost the airflow considerably, right? That way I could test more airflow without pulling everything apart.
Gilbert Fritz wrote:After many, many threads on here kicking ideas around for greenhouse plans that never came to anything, I've now got a 9' by 16' partially buried hoop house in the back yard, with 420 gallons of water in flat wooden tanks lined with EPDM pond liner. The water is pumped through an old car radiator which is connected to ductwork and a fan. The idea is that the water will absorb heat during the day and then release it at night, damping out all the temperature swings and pulling the house back toward the average temperature. I'll be raising vegetables and some Mediterranean perennials in it; right now I've got cool weather vegetable starts going.
So, the above is the idea. Reality is sometimes a little different. Yesterday a cold front moved in, and it has been almost twenty-four hours since the greenhouse had any thermal gain, and the thermal mass is not fully charged. Outside the temperature is 32 F. Inside it is 42 F. I'd prefer if it stayed at 50 F. What will happen in the next few days when the temperature drops to 20 F outside, still with no thermal gain?
I'm hoping that at a certain point the tanks of water and the radiator put a "floor" under the drop in temperature. If this does not happen, one of two things may be wrong. Either there isn't enough heat storage, or that the fan is inadequate to move the heat out of the tanks fast enough. In the one case, I need a bigger fan, in the other, more tanks. I suspect that the fan may be undersized. Of course, I could solve either problem with more insulation. Also, the thermal mass is not fully charged yet. One thing that hampers me in figuring out what the system is doing is that I don't have a floating thermometer in the tank.
The fan is this one: https://suncourt.com/products/inductor-corded-in-line-duct-fan-db6gtc?_pos=1&_sid=2c50db266&_ss=r I had it laying around.
The north side of the hoop house has bubble wrap insulation installed between the plastic and the hoops. The whole structure is dug into a slope. Pictures coming shortly to help you understand the system.