non-pressurized vs. pressurized

A different post has me considering something for spring. I have two buildings that are heated by the Garn using its non-pressurized storage (no additional exchangers). One building, the workshop in which the Garn is housed, is using radiant slab while one of the buildings is a home with a water-air exchanger in the plenum. My home has hydronic heat, with a flat-plate heat exchanger because it is a pressurized system so I needed an interface hence the FP. Could I run my house as a non-pressurized system (essentially removing the flat-plate) and if so what things should I consider before doing this, or should I abandon doing this? I understand that my existing boiler could not be used as a backup. It hasn't run since I hooked up the Garn anyway. I would want to make provisions to fairly easily re-hook up the existing fossil boiler (return the home to a pressurized system) if the need should arise. I also understand that purging/cleaning the existing water in the pressurized system would need to be done prior to this as well. What else?
Any opinions-help or whatever is always appreciated. Thank you.

"There's no school like the old school." It does sound interesting to go with a purely un-pressurized system. My main objective is to increase my storage time, and the only way I can see to do that is to be able to use the lowest water temperature needed for my heat emitters that can satisfy my BTU loss with the highest ΔT returning to storage after it is utilized up within the desired heated area. Also to minimize my underground heat loss (there has to be some) as much as I can. None of which I am currently doing. The advantage I see by not using the flat plate heat exchanger is two fold. It reduces my transfer loss of the HX itself and it seems the other advantage is it could allow the ability to send return water back to storage that has a higher ΔT than the HX is designed to do. Eliots buffer tank idea slammed the brakes on my original idea (which is good it helps me learn) which was to mix from the Garn either with setpoint or full ODR prior to going underground. This seems to fit my parameters because I have heat emitters that can utilize lower water temperatures than is currently being sent underground from the Garn especially when I bring storage up beyond my needed temperature. On one hand I like the additional volume of the buffer tank but I don't know which method would be better. With the buffer tank I would have to run higher temperatures through the underground to heat the buffer tank, but for shorter amounts of time. It has me at a crossroads. The one advantage that mixing prior to going underground with ODR gives me is that I would'nt worry about the underground freezing because of the nearly continous circulation, albeit at lower water temperatures than I currently have. With the buffer tank I think I would want some sort of timer for the underground (no-glycol) which just represents heat loss, but needed for peace of mind. I gotta stop obsessing about this or I may be sleeping on the couch. hh:

ALASKAPF185 said:

Boilers design for closed loop last longer, closed loop systems have much less corrosion and component failure, thus the 25-30 year warranty. This is the biggest difference. If you were to make a CI open loop, we usually see failure around 10 yrs and if not using special pumps they usually go much more often and sometimes barely circulate zones. Circulators are just that, they are not pumps, they work by creating pressure differentials not by pumping water like a sump pump. Temp probes will have large swings in turn on turn off temps. Safety devices like flow switches and thermisters don't last long.

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I would tend to agree with you, in a general sense, if the water chemistry was never analyzed. With that being said however, proper water chemistry in any boiler system, whether closed or open, should be analyzed on some sort of maintenance schedule to prolong the life of the boiler, the interconnecting distribution piping, and associated various components. With proper water chemistry maintenance, longevity between the two types of systems can be equalized.

Yes, perhaps he is. Good morning Eliot.