Piping for Storage??

[strmh]

Working on my EKO 60 install.....

I put up a 60'x40' shop with an attached boiler room. The boiler is 210' from the house. I plan to heat both the shop and house with the EKO.

Due to space limitations in my basement, I'm going to locate the storage (1000 gal) in my boiler room.

I've read about piping schemes, but I can't seem to get storage piping thru my head.

I've got most of the copper run from the boiler...circ pump, danfoss, air scoop, etc...are all in place. I'm to the point where I have to connect to the house supply/return and also tie in the storage.

Now.....my primary concern is first, keeping the supply to the house up to temp, then heating the shop, and finally storage.

How do I divert to storage when nothing else is calling for heat? Which then leads me to wondering how do I pull from storage when needed?

Also..in the sequential flow of piping from boiler, should I tee for storage before I connect to the underground run to the house, or after?

Any chance someone can explain (in layman's terms) how this works? For the most part, I "think" I understand the basic piping; it's the control logic that has me baffled....

Thanks for any input.

 

[Nofossil]

There are a bunch of plumbing schemes. Here's a variant of the 'simplest pressurized storage' approach that was designed for a situation similar to yours.

 

[in hot water]

This 2 piece article shows piping and explains controls for a couple different piping arrangements. (large file)


www.hpacmag.sartech.ca/archives/2009/3_April.pdf

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[strmh]

Thanks to you both for the information.

The article looks like a good read for sure.

Nofossil, in your diagram....if the load circ isn't running, will the water automatically cycle thru the storage?

Right now, I have a Taco 0010 as my one and only circulator. It looks like I should have a separate circ to deliver the hot water to the house?

In my house, I have zone pumps versus valves (as in your diagram).....should that make a difference?

I take it that the thermostat on storage will initiate the load circulator provided storage is up to temp?

Sorry for all the questions, but the help is appreciated!

 

[Nofossil]

Thanks to you both for the information.

The article looks like a good read for sure.

Nofossil, in your diagram....if the load circ isn't running, will the water automatically cycle thru the storage?

Right now, I have a Taco 0010 as my one and only circulator. It looks like I should have a separate circ to deliver the hot water to the house?

In my house, I have zone pumps versus valves (as in your diagram).....should that make a difference?

I take it that the thermostat on storage will initiate the load circulator provided storage is up to temp?

Sorry for all the questions, but the help is appreciated!

The 'simplest pressurized storage' approach depends on at least approximate matching of circulator flow rates to the heat loads and heat source(s). I'd strongly circulators that have multiple speed settings to help you balance flows.

You will need a circulator for the boiler itself, and that should flow enough to extract the heat output of the boiler at an acceptable temperature rise. You'll also need one or more circulators to create flow through the zones. Again, those should be sized to flow rates that deliver the desired output at acceptable temperature drops. Typically, all zones together should have less flow than the boiler, since the boiler usually puts out more heat than the zones can absorb. If that's the case, the extra boiler flow automatically goes into storage.

If the zones are flowing more than the boiler (because the boiler is recirculating to maintain inlet temp, for instance) some of the flow to the zones will be drawn from the top of storage.

Since you have a circ on each zone, you may not need an additional load circulator. The possible problem is that if you have a fossil boiler in the house, the zone circs might pull water through that boiler instead of from the outside storage/boiler combination. A load circ would create a positive pressure on the supply side of the load circs and prevent that from happening.

My sticky describes the control logic in more detail.

 

[Nofossil]

The easiest way to think about flow in this approach is that there are two loops:

LOOP #1: Clockwise from the boiler to the top of storage, downwards through storage, and back to the boiler inlet. Flow in this loop is based on the BTU output of the boiler, and varies based on the amount of recirculation required to maintain inlet temperature on the boiler. Some systems (like mine) also vary the speed of the boiler circulator to better match the flow rate to the boiler output.

LOOP #2: Clockwise from the top of storage through the loads, back to the bottom of storage, and upwards through storage to the top again. Flow in this loop is based on the number of zones calling for heat and the flow rate required for each zone.

These two loops overlap at the storage tank(s). If the flow rates match exactly, then there is no flow through storage - the boiler is supplying the heating zones directly.

Any time the boiler flows more than the load loop needs, the extra goes into storage.

Any time the loads need more than the boiler can supply, the extra comes from storage.

There are fancier ways to do this. Probably the most sophisticated is primary/secondary loops, although there are also approaches that use diverter valves, mixing valves, differential controls and other techniques.

The weakness of the 'simplest pressurized storage' approach is that you have to pay attention to flow rates and head loss in doing your initial system design. If the load circ(s) are too big and there's too much head loss in the flow path through storage, you could get ghost flow through the wood boiler when it's not running.

 

[chuck172]

strmh,
You can check out BioHeat's PT-1 schematic
.http://www.woodboilers.com/userfiles/file/Solo Innova Plumbing.pdf
They use a Termovar valve to divert hot water back to storage while the heating loads are being met.

 

[patch53]

Hello nofossil, I was just looking at your "simple" storage diagram and have a question. When you say "the two loops overlap at the storage tank" what exactly do you mean?

This system would be very similar to what I would have after adding a pressurized tank. I don't understand how the hot water is actually "pulled" from the storage tank if it is being "pushed" into the tank from the wood boiler constantly. It seems the only way you could actually pull water from the storage would be if the pump to the house loads was stronger than the push coming from the wood boiler, otherwise all the water would just come from the wood boiler loop.

If the water from the wood boiler loop is only say 160F or so, you would only want the hot water from the storage to be used correct?

What am I missing here?

thx, Pat

 

[in hot water]

A couple suggestions if I may for nofossils drawing.

It's best to "pump away" from the expansion tank as it establishes the point of no pressure change PONPC. Tee the tank either one large one, or all 3 shown, into the blue return line just under the storage. Then all pumps are pumping away making air removal easier and the pump head is added to the system.

The boiler circuit through the piping and tanks probably has a very low pressure drop (all wide open vessels.) The highest pressure drop is probably the 3 way valve in throttle position. The Cv of the valve would tell you that. A low or medium head circ with low head and high gpm maybe a flat curve circ would maybe fit the bill.

The pressure drop through the distribution piping and emitters is probably higher than the boiler circuit, it may, or may not require a different pump or pump speed.

When the boiler pump and distribution pumps are running at the same time these pumps are in series. So you double the head of the circs. It may be a good idea to install a PAB pressure activated bypass valve to "shed" some of that head if only one zone is calling. It may be over pumped by quite a bit in that case.

If you take the pump curve for the selected pump, and lay a system curve over it you can see where the OP operating point is on the pump curve.

It's hard to define how much flow goes into the tank under various zone conditions. Another option would be a delta P pump on the distribution as it would change it's output based on which zones are calling, although it would still be in series with the boiler pump. An autoflow valve could be installed also to assure the zones get exactly the flow rates they require at any given time, one pump or two.

Every piping layout has pros and cons. Simple is good if you can account for your flows and the system balances out without excessive velocities which can result from pumps in series. It sounds like nofossil has a handle on his piping and layout from actual use, and has it fine tuned to his application. I don't know that you could rubber stamp that piping schematic to any job as the distribution circuit dictates what is going on to a large degree. You can define and calculate most of the circuit, without flowmeters I'm not sure what flows into the tank and when.

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