After working with the components, I changed the wood boiler layout a bit. This is really the 14th version of the piping layout.
The wood boiler plumbing is installed and set up for air testing before filling with water.
The main difference between the first and second plumbing configuration (or 13th and 14th) is that the old hot water tank is on the wood boiler side instead of on the gas boiler side. It occurred to me that the gas boiler piping should be kept free of any possible sediment in the old water tank so I put the hot water from the wood boiler into the tank instead of into the heat exchanger.
The pipes from the wood boiler are connected to the side ports of the water heater. I installed a pressure relief valve and an expansion tank on the tank even though the wood boiler piping should not be under pressure. The storage tank is far enough from the open piping on the wood boiler that it is possible that pressure could build up in the hot water tank. I thought it was easy enough to install these safety measures.
The make up water inlet was easier to connect from the utility room too–so the fresh cold water will enter the wood boiler loop from the storage tank on the return side of the heat exchanger.
This change means that the water from the top of the hot water tank will feed the heat exchanger and return past the water inlet, the expansion tank and back into the water tank. This loop has the pump on it and a Honeywell aquastat. When the water pumping into the heat exchanger from the water storage tank is hot enough, it will circulate through the heating system. When it is not hot, the aquastat will send a signal to the Taco relay to turn on the gas boiler.
This setup is also different because the radiant heat water will always pass through the gas boiler side of the heat exchanger. The pipes are not far away but the diversion might remove heat from the gas boiler’s hot water. I might have to install another zone valve to stop circulation to the heat exchanger when the storage tank is not hot.