The recent thread on hydraulic separators made me realize that the propane tank storage system I'm designing might be just that, an oversized hydro separator.
I'm building a house that's very well insulated and almost airtight. Very low heating load and 250 sq. ft. of Low-E glass facing SSW on a hill.I have a new Tarm Solo 40 that will always be putting out more heat than the house will be calling for, even on the coldest, windiest nights. The Solo 30 might have been more appropriate but the 40 is in the basement so there I am. So my situation is different than most and what I'm thinking about doing won't work for many of us.
I came up with a couple 500 gallon propane tanks and started watching very closely all the various schemes for directing boiler water to the tanks and then switching valves manually, electrically or thermostatically back and forth and I don't know what else to take heat to the house and so on. With Nofossil's 'Simplest' sticky for inspiration I wondered if the boiler and storage couldn't be coupled together even more closely so the boiler always fed into the storage tank. I wanted to come up with a way to connect the heating loads of the house so they always drew from the tank too but that when the boiler was firing the supply water could go directly to the loads 'through' the tank. I keep coming back to a 2" pipe welded through the top of the tank; boiler connected to one end and the heating loads to the other end. Inside the tank this pipe would be swiss-cheesed with lots of holes or slots facing up to the top to promote stratification. A corresponding pipe would be mirror-imaged across the bottom for the return lines. If the boiler is supplying more than the house is calling for it charges the tanks. If the house is calling for more flow than the boiler is supplying then the loads are supplied by the tank. If the flows are about equal, the supply water will come into the tank and flow right across to the loads in the house. The returns flows would cross the bottom in a similar way back to the boiler.
So I have now worked into Siegenthaler's book to where I understand the basics of primary/secondary distribution. And now I think that my little scheme might help things by decoupling the boiler circulator circuit from the rest of the system so that the various loads coming in and out and all that changing head in the system won't affect the boiler circuit itself.
And isn't this just what hydraulic seperators are about?
Was it Hot Rod that suggested that a hydro seperator/buffer tank combo would be perfect for low mass boilers? So why would an even bigger one not be better for a gassifier?
I've seen european schematics that seemed to suggest this might be done over there but the connection details are too simplified to know if that is what they are doing.
The biggest issue for this kind of simplest system that I see is the flow through the boiler when it is not running but the house is calling and drawing from the tank. Pretty much the same issue as Nofossil's system. If the flow resistance through the boiler circuit is a lot more than the large perforated pipes through the tank then this might be trivial but it won't be zero. A motorized ball valve of some sort in the boiler supply line to the tank would stop that flow if it became a problem.
I'm not trying to get my system running this winter season so I have lots of time to learn and improve my system design. This forum has become one of my top 2 or 3 reasons for the invention of the internet. I hope some of you pros and amateur hydronics experts out there might give me your opinions on this way of looking at pressurized storage.
Anybody out there doing this. What problems? What would you do differently next time?
Again, this might only be appropriate for people with low load houses that will never need more than a fraction of the boiler output. I don't have the intuitive understanding of BTU flow that a lot of you have from much experience.
Appreciate any and all input.
I'm building a house that's very well insulated and almost airtight. Very low heating load and 250 sq. ft. of Low-E glass facing SSW on a hill.I have a new Tarm Solo 40 that will always be putting out more heat than the house will be calling for, even on the coldest, windiest nights. The Solo 30 might have been more appropriate but the 40 is in the basement so there I am. So my situation is different than most and what I'm thinking about doing won't work for many of us.
I came up with a couple 500 gallon propane tanks and started watching very closely all the various schemes for directing boiler water to the tanks and then switching valves manually, electrically or thermostatically back and forth and I don't know what else to take heat to the house and so on. With Nofossil's 'Simplest' sticky for inspiration I wondered if the boiler and storage couldn't be coupled together even more closely so the boiler always fed into the storage tank. I wanted to come up with a way to connect the heating loads of the house so they always drew from the tank too but that when the boiler was firing the supply water could go directly to the loads 'through' the tank. I keep coming back to a 2" pipe welded through the top of the tank; boiler connected to one end and the heating loads to the other end. Inside the tank this pipe would be swiss-cheesed with lots of holes or slots facing up to the top to promote stratification. A corresponding pipe would be mirror-imaged across the bottom for the return lines. If the boiler is supplying more than the house is calling for it charges the tanks. If the house is calling for more flow than the boiler is supplying then the loads are supplied by the tank. If the flows are about equal, the supply water will come into the tank and flow right across to the loads in the house. The returns flows would cross the bottom in a similar way back to the boiler.
So I have now worked into Siegenthaler's book to where I understand the basics of primary/secondary distribution. And now I think that my little scheme might help things by decoupling the boiler circulator circuit from the rest of the system so that the various loads coming in and out and all that changing head in the system won't affect the boiler circuit itself.
And isn't this just what hydraulic seperators are about?
Was it Hot Rod that suggested that a hydro seperator/buffer tank combo would be perfect for low mass boilers? So why would an even bigger one not be better for a gassifier?
I've seen european schematics that seemed to suggest this might be done over there but the connection details are too simplified to know if that is what they are doing.
The biggest issue for this kind of simplest system that I see is the flow through the boiler when it is not running but the house is calling and drawing from the tank. Pretty much the same issue as Nofossil's system. If the flow resistance through the boiler circuit is a lot more than the large perforated pipes through the tank then this might be trivial but it won't be zero. A motorized ball valve of some sort in the boiler supply line to the tank would stop that flow if it became a problem.
I'm not trying to get my system running this winter season so I have lots of time to learn and improve my system design. This forum has become one of my top 2 or 3 reasons for the invention of the internet. I hope some of you pros and amateur hydronics experts out there might give me your opinions on this way of looking at pressurized storage.
Anybody out there doing this. What problems? What would you do differently next time?
Again, this might only be appropriate for people with low load houses that will never need more than a fraction of the boiler output. I don't have the intuitive understanding of BTU flow that a lot of you have from much experience.
Appreciate any and all input.
![[Hearth.com] The attack of the 1000 gallon hydraulic separator!](/talk/data/attachments/14/14058-4d769b76050ccb22cfdac4945e3ba6a3.jpg?hash=HmuSsSXfaP)
