Posted by Sherman in Idaho [72.47.153.105] on Tuesday, November 26, 2013 at 23:08:15 :
In Reply to: OT outdoor water furnace posted by junoir copey [100.43.114.58] on Tuesday, November 26, 2013 at 08:38:15 :
I'm glad you saved the old cast iron radiators rather than scrapping them. Scrap yards give $1 per section for them, which is enough to motivate the tweakers. I know one case where they stole them out of the house they were renting and scrapped them. I have two buildings with hot-water radiator systems; my home with a small boiler and a commercial building with a 1.3 million BTU/hr boiler.
I'm not a certified expert but I know something about them. First of all, you do not want to turn down the water temperature. Most systems run at around 180-190 degrees.
There are two ways to control these things. The simple way, for smaller systems, is to turn the burner and the circulating pump on and off at the same time, controlled by a single thermostat in the house.
The more complicated way, for larger systems, is to keep the pump running as long as the water is above some specified temperature, and cycle the burner on and off as needed to keep the temperature in that range. In that system, you have a thermostat in each room, that controls a valve to let the water go through that room's radiator or not. The main reason to use one versus the other is whether you want to regulate each room individually or not.
On my big building I installed a PLC that I programmed to do lots of fancy things like varying the pump speed to save electricity, monitoring the outside air and return water temperature to prevent freezing when the heat is off, and a system to calculate, based on inside and outside air temperature, when to fire up the boiler at night to bring the building up to temperature just as the workers arrive.
It's hard to tell just what you have in your system, but if it's a typical home system, you should be able to set the thermostat to whatever temperature you want and have it hold it there, even with the iron radiators. The difference is they have a lot more thermal mass than your old ones, which means when warming up the house from a cold soak, the temperature will likely overshoot by quite a bit after the thermostat shuts off the boiler. The "anticipator" adjustment on the thermostat is supposed to help compensate for this. You might try adjusting it, but they don't really "anticipate" enough for a cast iron radiator system. Or just turn the thermostat down.
You've got a good system that is way better than anything made today.