Have to decide on storage tanks

[Paver56]

I posted last week that I was having trouble with my local L&I inspector. Well I have not recieced an official answer yet but he seemed to like the idea of a non pressurized storage tanks better than using the propane tanks I had planned on. I took delivery of my Froling yesterday. It will be a while til I am able to get it intalled but it is very exciting. My question is whether an non pressurized storage system with heat exchangers is as efficient as two vertical pressurized propane tanks? It will cost more for the non pressurized tanks but in my situation, it will be a lot less work and probably make the inspector a lot happier. I received a quote on a 957 gallon tank with 4 heat exchangers. I would just like to know if I will be as happy with this setup as I would be if I went with the propane tanks. Any info or opinions would be appreciated. I would like to make a decision soon. Thanks!

 

[DaveBP]

Another way to do non-pressurized is to plumb the propane tanks exactly as if they were in a pressurized system and run a pipe from the tanks up at least several feet higher than the highest point in the hot water circulation through the baseboard or whatever your system is composed of. Upstairs closet is common in Europe. At that point you install the (preferably stainless steel) expansion tank that is vented to the roof. That way, no pressure is built up but enough static pressure exists at the bottom near the boiler to keep cavitation in the near-boiler circulators under control. This sort of vented system tends to be looked down upon here is the States but is apparently common is Europe.

This way you do without all the heat exchangers and circulators and their attendant losses. It might allow some air to infiltrate the system, though. I would think it makes careful water treatment mandatory but one of our Scandanavian contributors to the forum says that neither he nor any one he knows of uses chemicals in their water when using this type of vented system. They do use stainless steel expansion tanks, at least in the photos I've seen.

 

[Singed Eyebrows]

I run no more than about 12 psi(fully expanded) in my system now. I believe a tall pipe going up to the attic to an open tank will give around this pressure, Randy

 

[flyingcow]

Why 4 heat exchangers? In the tank i have there are two. One for DHW and the other for heat. Works very good. It was installed per Tarm diagrams.

 

[peakbagger]

I am biased as I just picked up a 535 gallon tank kit from Tom in Maine (American Solartechnics). I havent installed it yet but it was nice being able to bring all the components down the basement stairs without any rigging. The kit is very complete and the instructions look to be great. I have a solar hot water system for my potable water so only needed on coil.