Highlander wrote:Hello fellow Coalburners
It is the same PLC, a Crouzet M2, that I used with the first Harman stove, but the program has grown substantially and includes reset control, proportional / integral control mode, a coal useage counter, a reverse anticipator fucntion, and a scrollable display for water temp, outside temp, manual control mode, Summer / Winter mode and a coal useage counter. The PLC can read 0-10V signals with 8 bits of precision, not great by todays standards, but plenty for this level of process control.
I have a fairly decent background in PLCs with PID control and analog I/O, mostly Allen-Bradley SLC and some DeviceNet. You've pretty much done what I've been thinking about all along - integrate modern controls with old-tech coal burning to bring it into the 21st Century. That is a really impressive setup and very well thought out. I was thinking about using a Cubloc PLC and doing something a bit similar on my Keystoker next year.
During the summer months I burned about 12# per day for hot water. I estimate using between 4 and 5 tons for the year. With propane at $3 / gallon, it should have payback in 2 years for an investment of about $5000. Not too shabby.
How much heat does the boiler add to the house? Is the house air-conditioned? Is the boiler room separate, insulated, and/or ventilated from the rest of the house? I'd be concerned about the residual heat from the boiler idling with no hot water demand most of the day adding a lot of heat to the house that must then be removed via the A/C system, especially in a modern, well insulated home. I imagine in a old home with damp, fieldstone basement or similar, that added warmth would be welcome in the summer, but in a modern home, I'm not so sure.