LsFarm wrote:Hi 26, I use a water/water plate-type heat exchanger.. this way I have two different water systems.. the exterior one has some antifreeze in it, just incase of a power outage for weeks and no fuel for the generators.
I put the heat exchanger in the return from the baseboard zones, so it preheats the return water, and I reset the propane boiler to a lower temp than the coal water temp.. so the propane burner won't come on.
A 40-plate exchanger is around $200, is simple to plumb in, and works great..
I then have a second plate exchanger that the cold water that supplies the Domestic hot water heater goes through, preheating water to the Domestic tank/heater... I don't use any propane for DHW unless there is no demand for over 18 hours..
I enjoy Gregs' advice and think it is always sound he has been kind and a big help for me
- but may I climb once again on my soap box against 1 inch pex and say " use something larger" (1-1/4 or better 1-1/2) - that requires a less expensive, lower pressure, lower watt draw pump - to move a greater volume of energy bearing water at far lower pump head. In the long run - a hi watt draw pump, pushing into a hi head load, to move the same amount of energy - will consume more amps and cost more to operate - than a correctly sized, low power pump, installed with a larger diameter line - and the lower pressure water will transfer energy from boiler to load more effectively.
You will likely circulate the boiler to load loop 24/7 for frost protection and quick load response so antifreeze and the related drama and draw backs of AF can be unnecessary. If worried about power loss frost/freeze/burst protection - pitch everything to a low point in the outhouse, and provide for quick drain to daylight for the liquid above ground level - then you only have a few gallons to drain off the loop to get below the ground frost line. When power it restored - refill and degass the liquid on the first fire. With a coal boiler and a semi insulated outhouse you have a few hours to anguish before you need to make such a desperate move, and you will be draining you house water very soon also. A back up gen set is a better option than boiler burst protection chemicals, but thats my view only and if your gone for extended time during power outage chemical may save an outhouse appliance, but what about the house???????? By then things are going north there too!
Since your circulating that loop that much, do not scrimp on its installation. If not done right, that loop will make any boiler look bad!
BTW how many wires can you run in a 3/4 conduit? - and folks think I am a control freek