Heater for Small Greenhouse

[Jerry Delaney]

You are sure right there Ray. While the person who invents it may get rich, I wonder if all us who could make use of it would benefit. Our luck would be that the various gas companies would buy the patent and lock it away!!!

[orchids3]

Thats a good idea Ray but wouldnt two small heaters set at slightly differant temperatures accomplish the desired result? Of course installation expense would be more.

[Ray]

Picture a heater with multiple, small burners, rather than a single, large one.

The controller would have to monitor the trend in heating and cooling - a classic proportional design.

If it's only slightly cooler outside than inside, the temperature drop will be slow, so one burner comes on. If it continues to drop, a second one does, then a third, etc. is going down rapidly, all of the burners would be on. As the rate at which the temperature drop slows, one of the burners is turned off, and as that trend continues, more and more drop out, so that ultimately you get so something resembling a steady state, rather than the on-and-off of a typical heater/thermostat combo.

[Posey]

If one uses a vented Southern Burner heater, how far away from the greenhouse walls, the benches and the closest plant does it have to be kept???

[Jerry Delaney]

[QUOTE=Ray;70418]Someone needs to design a heater with a proportional controller and a burner that's super efficient at all fuel flow rates. Right now, most are simply on-and-off at full flame, which is wasteful.

Ray, I got to thinking (something I rarely do these days) about our comments concerning a modulating gas valve. Some years ago during my working days, we used air actuated steam valves and a proportional controller that used fuzzy logic to control the temperature of fermentation vessels during both sterilization and fermentation. These worked extremely well and controlled the temperature within a few degrees C. I did some looking around and found lots of info on modulating gas valves. Is this what you were referring to?

Modulating gas valves and systems invention

Rinnai Natural & LP Gas Heaters - New England & New York - Nelson & Small

[Ray]

Almost, Jerry.

That patent, and the Rinnai heaters, simply regulate the gas flow to a single burner. While that achieves the same thing I was speculating about, I suspect that a burner does not operate as efficiently at different gas flow rates, whereas a series of small burners operated at their optimal flows might be better.

I'll tell you what though, we'll definitely keep the Rinnai heater in mind for the future. Even the simpler modulation scheme is bound to save money, and I guarantee that their pipe-in-a-pipe flue system and separated combustion helps. I have those on my current GH heater, and switching to that from my old Modine cut my gas consumption by 40%!

Thanks for doing the digging!

[orchidexpress]

Ray has it down with his calculations!

Good Luck!

[terrys plants]

Originally Posted by HDCochran

My orchid collection has outgrown my orchidarium and I am building a small 12' x 12' greenhouse and will need about ~10,000 Btu/hr of heat to keep it warm enough next winter. I cannot find a ~10,000 Btu/hr vented propane heater. Does anyone know of a source? Alternatively, can anyone provide reliable information on any detrimental effects on orchids of using a vent-free propane heater? I've read arguments on both sides of this question.

i found a source of good heaters in boating supplies and sales.i used one for a while and there were no deire effects to the plants,unless it's to close the heater.heat rises so i kept it on the floor.good luck: