Can I add storage & would it be worth it?

[Roundgunner]

Is it possible and beneficial to add storage to this setup? I'm thinking about a old hot water tank on each oil loop.



If so where would you put it?

 

[mustash29]

Yours is outside (XT series?). Mine will be in the house (Elite 100).

Yours is roughly 2x mine, both in BTU and water jacket size.

My plan is very similar to the "big house" side of your set up, but with zone valves instead of pumps and a large buffer / storage tank where your (red and teal) manifolds are. This location will be an atmospheric tank, and will require more water treatment chemical due to the increased volume of water. Essentially making the boiler think it has a huge tank of it's own. Once the boiler comes up to temp and the LK loads it will charge the tank. As the tank heats, more BTU's will be available to the house HX's.

Good: Facilitates batch burns, especially helpful for shoulder seasons.

Bad: Since the Empyre's are designed to cycle on / off, too long of an idle cycle may cause the refractory to cool too far and prevent re-ignition when the blower turns on. If the boiler goes out, bridges, fails to re-light itself, runs out of wood, etc you will still have the boiler pump running, so it may rob BTU's from the tank and blow them up the flue. Some have rigged up a timer or low flue temp shutdown device.

Something small would be considered a buffer tank. You could put a buffer in each house. They would go in the pressurized loops of the (oil) system(s). They could be sized differently based on the heat load each house sees. You would most likely need to up-size whatever expansion tank(s)s are already there.

You could do one large or 2 separate atmospheric tanks, one in each house as well. They would go in the non-pressurized boiler loops. Properly sized for the whole load (one tank) or different loads (if using 2 separate tanks). I think for a 200K boiler and 2 houses, 1000 gal minimum would be necessary.

Atmospheric tanks will require water treatment if that same water will be pumping through the boiler. Chemistry control will be crucial since atmospheric tanks will contain more dissolved O2 due to the larger surface area of the air to water interface.

My plan:

Empyre Elite 100 w/ danfoss, pumped to an atmospheric tank. The boiler will be on a floor that is 3.5 feet higher than the tanks floor, so all air will vent out the boiler vent / float guage. Cap off the float guage hole. Plumb the overflow port @ the float guage to a stainless Crown Mega Stor 40 gal indirect that has a pinhole in the heat coil. Essentially the tank and boiler will be flooded 24/7 and the 1/2 dead indirect will serve as a head tank / cistern tank to take care of the expansion & contraction as the sysyem undergoes temp swings.

Taco ZVC 406 zone valve controller is the main brain. On a call for heat: The storage pump will suck from tank to warm the HX. The load pump and corresponding zone valve will satisify the load demand via the oil boiler headers. The cooler zone returns will be re-heated by the HX. 80 gal indirect will have priority, and be plumbed with a Nyletherm for summer use.

The "TT" contacts of the ZVC 406 will go to the storage aquastat, then to the oil boilers Honeywell 8124 tripple aquastat. If storage is hot, oil burner will be locked out via storage aquastat. If storage is cold, oil burner will fire and storage pump will be locked out. 8124 low limit will either be set to minimum 100 or disabled via interrupting the "blue wire".

Tank choices:
- New oil tanks, multiple 275's or 330's. Made of 12 ga mild steel. Only a few thousandths thinner than the 1/8" Empyre water jacket. That is all I can fit in my 14 x 14 basement without major cost and without knocking a wall out to get them in there.

- (broken link removed to http://www.newhorizonstore.com/Products/96-tank-hot-water-storage.aspx) Pricey for 500 gal. Made of 1/8 mild steel plate, same as the Empyre boiler jacket.

- Stainless steel or mild steel IBC tote tank. A refurbished, used, 550 gal stainless IBC can be had for 1/2 the cost of the New Horizons tank. Mild steel is 1/3 the cost. This would require knocking studs out of a load bearing wall to install. I don't forsee that happening.

 

[mustash29]

The IBC tanks are 10 ga.

 

[velvetfoot]

How about the square tank that Tom in Maine sells? They assemble.

 

[Roundgunner]

I was thinking that 50-60 gal on the pressure loops would keep the temp from dropping enough to trigger the oil even if 3-4 zones call at once.

 

[arbutus]

Interesting. If I understand correctly, your desire is primarily to prevent the oil boiler from firing during a call for heat, rather than to obtain maximum efficiency out of every stick of wood. Could you use an additional aquastat, or the aquastat controlling the gold pumps (may need relays or use Normally Closed side) to only allow the oil boilers to fire if the wood is actually off?

 

[Roundgunner]

Yes my main concern is to burn little oil. I would be happy to not chase as much wood either.
The supply manifold has an aquastat that shuts down the gold pumps that are always on if the supply manifold goes below 140. The Empyer is supposed to cycle on and off as needed to keep boiler between 170 and 180. I need to have the oil on automatic standby because if the house temp drops below 71 MIL will be wearing a hat, gloves wrapped in a blanket and on the phone with my wife acting like the world is ending.
My wife reacts in predictable fashion.

 

[mustash29]

What kind of data do you have handy? Didn't you just install this system last fall? How did the Empyre perform in general? How much wood did you go through? How well seasoned was it? How much space are you heating? What heat loads are you dealing with? How much oil? How often were the oil burners kicking on in auto backup?

Based on your drawing, what appears to be happening is that when multiple zones call for heat, the HX on that loop is undersized, so the pressurized loop does not get fully re-heated when going through the HX, so the oil burner lockout aquastat gets too cold and the oil dragon roars.

If the lockout setting is set too high, it will be too sensitive and awaken the dragon too frequently. Lowering that setting will allow the pumps and wood more time to react to the calls for heat. Could you move those aquastats to a different location to change the response timing of them?

Adding modest sized buffer tanks (and larger expansion tanks) to each pressurized loop would seem to help. Feed the colder returns to the HX, then to the bottom of the tank. Top hot would discharge toward the oil dragon. That would give some mixing time.

 

[mustash29]

[quote=".....The supply manifold has an aquastat that shuts down the gold pumps that are always on if the supply manifold goes below 140.....[/quote]

If the supply manifold is getting too low and killing the gold pumps, the wood boiler is not reacting fast enough so you need more wood boiler pumping power, or you need to lower that setting to allow more reaction time for the temps to recover.

 

[mustash29]

Essentially what you have going on here is when your supply manifold goes below 140, the gold pumps are locked out, which is killing any BTU input from the wood to the pressurized oil loops, so the dragons awake. I would think you need to keep those gold pumps running to keep the wood heat flowing toward the oil loops. The 140 bypass on the Empyre will protect it.

 

[Roundgunner]

The gold pumps shut off so the heat exchanger is not working in reverse (adding oil heated water to wood boiler) should the wood stove run out before I get home.

 

[Roundgunner]

This has lot of info you may like.
https://www.hearth.com/talk/threads/i-bought-and-installed-a-empyre-elite-ii-200-questions.119959/
the gold pumps only hut down if the OWB runs out of wood. I dont want to heat wood loop with oil. I went thru 12+ cord of crappy wood last year. This year I have over 20 with some on ground waiting to CSS.

 

[arbutus]

Again, can you tie the aquastat that controls the gold pumps to the oil boilers so that if the gold pumps are on, the oil boiler will not fire?
Or add another aquastat to perform this function?
Or does the wood boiler just take too long to get up to temp once it falls into the 140-150F range?

 

[Roundgunner]

Again, can you tie the aquastat that controls the gold pumps to the oil boilers so that if the gold pumps are on, the oil boiler will not fire?

I'm not sure if you can do that with this controller




but if I did that and the wood water was at 170 but the house was calling on 2 or 3 zones the heat exchanger cant always get the oil fired loop hot enough soon enough, I don't think I want to force it to stay off, I want to make it never want to come on. That is why I thought having more volume of water in the oil loop would be beneficial.

Or does the wood boiler just take too long to get up to temp once it falls into the 140-150F range?

The wood boiler very seldom gets below 170 -165. If it does it just needs wood and it will come up quickly, I think 1 per miniute or so, after it gets wood. The oil loop on the other hand will go down to 140 pretty quickly if 2 Zones are calling and it takes a while to recover. I'm going to put in a 100 plate HE to replace the 50, if I do a small storage or volume increase that would be the time.

 

[mustash29]

It seems your piping arrangement is sort of backwards on both houses. Colder returns from your loads return back to the oil boiler inlet header, cooling it off. Then the flow goes out toward the loads again sort of bypassing the HX. If multiple zones call at the same time, your distribution loop goes cold.

If those cooler returns rejoined the header, then went into the HX, then to the oil boiler, then back out to the loads.....this way you would have cooler water hitting the HX, more delta T on the HX and more BTU flow across the HX plates.

Based on the numbers in your install thread, those HX's appear to have about a 10 deg approach.

 

[mustash29]

I don't know what these go for new, but this seems like a good deal for 120 gal. Non-ASME so I think that means 125 psi rating instead of 150 psi but not sure.

(broken link removed to http://providence.craigslist.org/mat/4558691157.html) 120 Gallon In Direct Storage Tank - $400 (Newport, RI)
I have an RJA120 Lochinvar storage tank I would like to get rid of, brand new in box....NON ASME

(broken link removed to http://www.lochinvar.com/products/Default.aspx?type=ProductLine&lineid=106)

 

[AaronM]

Forgive me if this sounds a little crazy, but for smaller storage (under 200 gallons) what about several used 50gal electric water heaters plumbed in series? Or would this fail in terms of temperature/pressure tolerance?

 

[mustash29]

That would be fine, as long as there are adequate temperature / pressure relief valves installed. Typical DHW heaters have a 150 psi rating, hydro test to 300. The oil boiler loops should never see > 30 psi due to it's relief valve.

 

[Bob Rohr]

That would be fine, as long as there are adequate temperature / pressure relief valves installed. Typical DHW heaters have a 150 psi rating, hydro test to 300. The oil boiler loops should never see > 30 psi due to it's relief valve.

Usually reverse return is a better piping methods, or some variation of.

Here is an example of parallel reverse return. This assures equal draw from both tanks loading or unloading. With WH tanks you have good connection points to do this.

Use the drain ports at the bottom and the top H&C connections.

Piped this way you get around the flow issue of just having 3/4" connections, with tanks in series.

 

[AaronM]

Thank you both, I am opting for this after sourcing five 50 gallon electrics in the classifieds, some free, some nearly free. Very narrow staircase to the basement, so this should be manageable. I fear it might not be enough storage, but someone home at least every 8 hours to fill the wood boiler.

Will update when finally installed