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I made a couple of changes here on my NG WM GV4 S2 boiler. Specifically in a effort to counter short cycle times due to micro zoning I have manually opened 3 zone valves. When the living area upstairs zone calls for heat, the bathroom, family room and spare bedroom also get heat. Burn times have gone from 3 minutes to 4 minutes & 30 seconds. Not great but markedly better. A side effect of the open zone valves is a reverse flow through the Runtal baseboard in the bathroom and spare bedroom when the circulator is off. The one circulator seems to be able to handle all 4 zones although there is a circ in the boiler which may provide some assist. I'm temped to manually open the master bedroom zone valve as well.
One possible downside to all this is a greater quantity of water that needs to be brought up to non-condensing 130F water. As many of you know the thermostatic mixing valve was prone to failure on these boilers, I can't really tell if it's working or not.
I'm not sure but I think indirect check valve may be not working because the indirect calls for heat much more often (like every 3 or 4 hours). It suggests there is reverse flow from there as well. I think I'm ok with that. I'd rather burn a little more fuel then need to replace the boiler. I'd really appreciate some feedback on this, thanks.