Pumping away help!

[Eastcoast]

Hello I'm trying to do a little change up on my system before the cold weather starts! First off the reason is because I can hear water rushing through my pipes a lot and yes I tried probably 12 times or more and different ways to bleed it and still same problem! I have a Kerr tw2000 wood boiler and a NY thermal oil boiler. They are connected to each other when the wood boiler drops below 150⁰ the oil boiler takes over. there is also a coil in the oil boiler for my domestic hot water. I will include a few pictures to give an idea how it's set up. My system has 2 circulating pumps one beside my wood boiler on the return line and one beside my oil boiler also on the return line and it is the primary pump! also there is a big steel expansion tank beside my wood boiler on the supply line and a diaphragm expansion tank beside my oil boiler on the supple line! So I'm wondering should I place my circulating pump that is beside my oil boiler the (main circulator) on the supply line instead of the return line? And then I'm wondering can I just use one expansion tank for my hole system instead of 2 as long as I got a big enough one for my system? or should I still use 2? I'm thinking maybe them could be some of my problems! Thanks in advance.

 

[E Yoder]

I'm no expert on pressurized boilers. But pumping away from the expansion tank is very important and often ignored, especially on older boilers.
Dan Holohan has an excellent book on the pumping away principle.