rethinking tank reversal

[Bob Rohr]

The small 80 gallon tanks acts as a hydro separator and some buffer capacity for the boiler.

It allows heat to go to the loads fairly quickly, then the 500 gallon tank comes on line as the boiler has the capacity to load it.

Ideally you would want to unload the 500 back to the 80 gallon or directly to the load. This dual pump with a 3 way diverting valve allows you to shuffle between the tanks without breaking up the stratifiaction.

That could not be accomplished with just the 4 way reverser in my original plan.

hr

 

[mikefrommaine]

I take it the 500 gallon tank is pressurized? What control logic would you propose to control the 3 way and pumps?

And if both tanks are pressurized what advantage do you see in this scheme vs just having a single 500 gallon tank as the buffer/seperator and pulling heat out the top when the loads call for it. Less of a delay to get usable heat?

 

[ewdudley]

I take it the 500 gallon tank is pressurized? What control logic would you propose to control the 3 way and pumps?

And if both tanks are pressurized what advantage do you see in this scheme vs just having a single 500 gallon tank as the buffer/seperator and pulling heat out the top when the loads call for it. Less of a delay to get usable heat?

Kinda what I was asking myself. Rethinking the conventional approach is important for finding better ways of doing things, but for a pressurized system what advantage could be served by adding a $2900 buffer tank between the boiler and storage, and then adding enough valves, pumps, and controls to get the thing back out of the way?

As far as getting hot water sooner goes, hot water will stay at the top of storage and becomes available as soon as you please after the boiler comes on line. There are many systems that over-pump the load circuits and they would mix away the hot water until storage comes up to temperature, so I suppose smaller separate buffer would help in such cases. But even so it would be simpler to eliminate the mixing problem to begin with.

 

[Bob Rohr]

Kinda what I was asking myself. Rethinking the conventional approach is important for finding better ways of doing things, but for a pressurized system what advantage could be served by adding a $2900 buffer tank between the boiler and storage, and then adding enough valves, pumps, and controls to get the thing back out of the way?

As far as getting hot water sooner goes, hot water will stay at the top of storage and becomes available as soon as you please after the boiler comes on line. There are many systems that over-pump the load circuits and they would mix away the hot water until storage comes up to temperature, so I suppose smaller separate buffer would help in such cases. But even so it would be simpler to eliminate the mixing problem to begin with.

It's my hobby, I tinker with hydronics and solar when I not working. Granted I get bargin prices on components, as well as freight damaged returns, so changing every season is more for the hobby aspect.

In a perfect world I would not have any storage, stoke the beast to the load.... maybe when I retire Until then I would like the boiler to go to the load as quickly as possible, then warm storage for the over load, or nightime use. With radiant slabs I can almost "flywheel" thru the evening hours, so large storage is not a key goal.

The 80 gallon is my buffer to give the thermostatic valve a reference. Thermostatics don't behave well without some buffer to work against, so the design engineers tell me. Which is why some brands require balance valves. So the tank serves that purpose, as well as separating the pumps, hydrauliclly speaking. If the pumps were different sizes that would be a reason to separate them. The tank also serves as my central air elimination, and acts as a dirt separator. The multi ports give me thermostat wells at different levels. And it has 2" of spray foam all around so loss is very minimal. The price you mentioned is list, by the way, contractors get a good multiplier off of list. It should be priced close to any insulated, glass lined storage vessel.

Control wise, I think the Resol MX will handle the various on/ off differential functions. If not a PLC could be designed to easily control the system.

I agree the 500 could serve all these functions, be ideal to mount it in a vertical position and have all the correct taps installed. Insulating 500 gallons is a must, lots of surface area.

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[Mark Holden]

It seems to me a single large stratified tank could do everything, with less complexity and heat loss [than a large + additional tank].
But it sounds like you have been working on these things for longer than me!