Alaska_Range wrote:the general consensus is that it is always more efficient to move fluid rather than air.
Alaska_Range wrote:Thanks everyone for the responses. I've been away from the computer for a few days but grilling the other local coal boilers. I think I'm back to leaning towards the boiler. Berlin's comment re: the air damper...duh...I kind of forgot about that aspect, being able to really clamp down on the fire by controlling the O2.
Living off the grid is a necessity not a luxury for me. I've done it for 12 years in my last home. Its amazing how well you can live without using a lot of electricity. You do a lot of conservation and using alternative systems like propane refrigerators, on demand hot water, etc and the simple things like compact florescents. My last system had four 6-volt batteries wired in a 12 volt system with an inverter/charger. I primarily relied on a 3000 watt honda generator (still running after over 10yrs) for my power to charge the system. On average I ran it 9hrs per week to provide all my electrical needs. It equated to an electrical bill of about 10-15 gals of gas a month...pretty good these days.
Back to burning coal...I believe I've figured out how to arrange a system with 120v zone control valves (avoid the transformer drain) and wire them in conjunction with the circ pump so that it only comes on when a zone control valve opens or when I need to dump excess heat to the garage slab. I keep it as a simple open loop system by installing a make up reservoir above the highest point in the system and letting it vent through it. I will also likely route the drain from the PRV into the firebox, others around here have had success with it...a good way to cool down a overheated fire. All this combined with a thermal air supply damper an I think I've got a good thing going.
In the end the only real electrical draw is the circ pump and only when called for. I may splurge and spring for an autostart function on the next generator...they automatically start when the battey voltage drops below a given set point. After reading other "off grid" pubs I think the general consensus is that it is always more efficient to move fluid rather than air.
I'll be sure to keep the forum posted on my progress. Thanks again for the input and feel free to send more.
Sting wrote:maybe consider reviving the art of gravity flow hot water distribution