Fireplace Boiler in Action

On Christmas Eve it was cold outside and we finally made a fire in the fireplace boiler.

First Fire in Fireplace Boiler

First Fire in Fireplace Boiler

The fireplace outside air draft worked perfectly, and the glass door makes a spectacular fire show. The fireplace water got very hot but there was no internal pressure. It turned out that I had the water supply turned off–so it may have been cavitating with not enough water flow.

Temp and Pressure first fire

Temp and Pressure first fire

After I turned the water supply on I could hear the storage system filling with water and assumed the stove system was also filling. So for New Year’s we fired up the stove again. But the water in the pipes did not seem to get warm while the stove water got very hot.

Unfortunately the logic for sending the warmed water to storage in the utility room is flawed. The first problem was that the zone valve would not open. I realized that it was not getting power and finally that the Grundfos clip on aquastat would not work–since I double checked the stats and it turns on (closes the switch) at 95 not off, and off at 120 degrees while I would still want the the hot water to circulate to the storage system.

For the second fire, I replaced the Grundfos with the storage tank’s Honeywell 6006 aquastat. But the pipe never seemed to get hot enough to turn the storage zone valve on. I had it set at 120 degrees with a 30 degree differential so that the valve would come on at 120 degrees and higher and would turn off again at 90 degrees. Then I just tried leaving the storage zone valve open manually but the water still did not get warm in the pipes.

Fire in the fireplace boiler

Second fire in the fireplace boiler with Honeywell aquastat

The pressure did build in the stove the second time. In fact as it reached 20 psi and the temperature in the stove approached 200, the check valve above the hot water pipe began to tap. Leading me to believe that the water was not pumping through the stove correctly. It was worrisome that the pressure regulator might go off, but it did not. Did the flapper type check valve slow the hot water cycle down?


Pressure and Temp build as fire burns–Check valve at rear of stove

My conclusion is that the single 006 pump at the boiler is not strong enough to get the water through the stove and also to storage. So the warmed water is not moving through the stove to the piping system. My solution will be to replace the zone valve with a second 006 pump that will be controlled by the aquastat. When the water in the primary loop is warm enough, the secondary pump will come on and pump the water through the storage loop.

If I look at this system as a primary/secondary loop system, then the current piping would be incorrect, as there are not close tees to the secondary loop. So it may be that the piping will have to change too. And if the check valve continues to tap, it may need to come out. Trial and error will eventually work out the issues with the system.

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