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Author Topic: Adding storage questions  (Read 3662 times)

DonE911

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Adding storage questions
« on: January 10, 2018, 05:21:14 AM »

I have a natures comfort ncb80 which is only 80 gallons. It has been doing a fine job heating the living levels of our home and other than crappy pumps and a sticky aquastat I have no complaints. I have ordered a grundfos alpha to replace the constantly breaking broeder pump and a new aquastat is on the list.  This coming year I intend to add a HX to the basement that is now a shop/office/laundry space with a half bath. I also intend to heat a small outdoor shop that is really just an oversized uninsulated shed.  I live in the north GA mountains so my heating needs are not as extreme as you folks living up north, but the wife likes it 72 inside all winter long.

Up to this point the boiler has only been used in the winter, but I intend to begin using it year round to heat DHW.

I am sure that with the added heated space and only 80 gallons my run intervals will no longer be in the 12 hour range and I think I should be adding some extra storage.

I have a spare 300 gallon LP tank sitting in the pasture doing nothing, so I'd like to use it as hot water storage. I will build a small insulated enclosure next to the boiler, but I am unsure how I should plumb it into the loop and where I should install my inlet and exit pipes. I have a space on the boiler for a second pump, but I am not sure if circulating water from the boiler to the storage and back to the boiler is good or if from the boiler to the storage and then out to the house and back to boiler is a better option.

Thoughts and opinions ??
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wreckit87

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Re: Adding storage questions
« Reply #1 on: January 10, 2018, 07:11:50 AM »

Few things-

First, if you add the shop space, will you be using the second set of ports on the boiler to feed it, or will that come off the house loop?

Second, keep in mind that the space will still need the same amount of BTU to heat and extra water is still going to require the same amount of wood to give off the same amount of BTU. I'm not familiar with the NCB80, but it does appear to have a pretty big firebox which is great, but generally one would install storage to elongate draw periods. If your firebox only holds enough wood to last 12 hours as is (which is quite short for a 15 CU FT firebox in your climate), the added 300 gallons will give you a longer draw period but will shorten your burn intervals. Say you feed it every 12 hours now. With the added storage and load you may be able to get 16 hours worth of draw, but you'll have to fill the stove 2-3 times in the other 8 hours to charge the storage back up. Do you have the time to change your fill intervals? We had a customer years back that bought a small (like 60 gallon) Tarm indoor unit for her place which if I recall, was in the neighborhood of 5,000 sq ft. The firebox on this thing is scary small, like 5 cu ft. It was empty every 2-3 hours. So she added 1000 gallons of storage which would hold her place for the 10 hours a day she was gone, but the other 14 hours she was setting alarms to feed the boiler every 2 hours to charge the storage so it could idle all day while she was gone. Your situation is obviously less extreme, but I hope it makes sense. Last I heard she was still doing this. Do you really need the storage?

As for the piping, the way I would pipe it is with a constant circulation from the bottom of the storage tank to the return of the boiler, and supply of the boiler to the top of the tank. Then draw your supply water to the house from the top of the opposite side of the tank, and return to the bottom. This would also act as a hydraulic separator and settle any dirt and debris in the system to the bottom of the tank.

This is merely my opinion, as I haven't done a ton of storage setups, but the handful I have done, these are my observations. Maybe I'm just nuts
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hondaracer2oo4

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Re: Adding storage questions
« Reply #2 on: January 10, 2018, 07:30:52 AM »

Like Darin said, your btu needs won't change with an increase in gallons of storage. With only 300 gallons of storage the boiler will just cycle for longer when it goes from low set point to high set point. People who batch burn and store the heat in large water stores, think 1000 gallons or more burn wide open for hours on end refilling te firebox as needed until the water store is up to 180. Then they use low temp emitters such as radiant to hear with because they can utilize water temps down to 120 or so. Water to air hx can't utilize water at much lower temps then 150-160. So that means if you have water to air hx that you can utilize only about half the amount of the storage time that someone with low temp emitters can. Sounds like your going to need a bigger boiler if you want t to add on and have 12 hour burn times.
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E Yoder

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Re: Adding storage questions
« Reply #3 on: January 10, 2018, 01:15:35 PM »

Good advice ^^^
And I like the fact that if it's plumbed the way wreckit described and the flow rates are not too high it could stratify in the storage tank and feed hot water longer.
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Sprinter

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Re: Adding storage questions
« Reply #4 on: January 10, 2018, 06:31:58 PM »

Extra storage is just like a battery. More btu , means more woood. You can’t have yer cake and eat it too, in this situation
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DonE911

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Re: Adding storage questions
« Reply #5 on: January 13, 2018, 08:57:58 AM »

Thank you to all that have posted and sorry I am slow to return to this thread.

The NCB80 has a large firebox. I have visited with some one in my area that has a wood boiler that if I recall was a central boiler.... held 200ish  gallons and has a smaller firebox than I do.   I do understand that regardless of the storage I have to feed it BTU's.

I guess my thinking is I would rather burn hot for a longer period to heat more storage and do it less often
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hondaracer2oo4

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Re: Adding storage questions
« Reply #6 on: January 13, 2018, 02:42:13 PM »

Well unfortunately you are limited by the amount of wood thst you can put it. The onboard water jacket just delivers the btus to the house after each cycle of the boiler. Increasing the water jacket size will just have the boiler run for longer to cycle and idle for longer as the house eats off the btus. But the wood burned to produce the btus will be the same.
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willieG

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Re: Adding storage questions
« Reply #7 on: January 13, 2018, 04:54:42 PM »

there may be some gain (but I am not sure) in batch burning, if your extra storage was in your house? my thinking is your OWB is always losing a certain amount of heat  and if the mass storage was outside you would lose more heat? if your storage was inside the home the lost heat from that storage would not really be lost as it would "leak" into the home

you could maybe gain a few btu in a batch burn as we know we lose heat in start up and shut downs of the cycles of the OWB  as unburnt gasses and heat exit the chimney on both

how much gain you might really get I have no idea, may be minimal may be worth it?

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BoilerHouse

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Re: Adding storage questions
« Reply #8 on: January 14, 2018, 09:46:40 AM »

I use storage with my home built boiler. Commissioned in January 2010, I am now on year 8 with the current set up.  The boiler capacity is roughly 250 gals, and storage is 300 gals.  By OWB standards, my firebox is extremely small at just 8 cu ft, so storage is a must. Also my boiler is not set up with any sort of auto regulating damper, so I batch burn only, usually starting the fire mid afternoon with the water temp between 120 and 130 F, burning "full out" for 6 hours, then shutting it down for the night with water temps at 180 F.  Providing it is a "normal" January i.e. average daytime high of -5 C and night time low of -15 C, it seems to work quite well.  Last night at - 28 C it was cooler than normal.  I shut the fire down at midnight, and it is currently 11 am,  outside temp is - 14 C and water temp is 140 F. 
My storage is beside the boiler, both in a small separate building (10 ft x 10 ft x 6 ft H), 165 ft from the house.  The boiler building is fully insulated, and boiler and storage have 8 inches of insulation.  As Willie says, the best place for storage is inside the building you wish to heat, but that is not always possible.
The only pump I have on my system, which does both the house and garage (90 ft away) loops, pumps from the storage tank, through the boiler, to the house and garage and then returns to storage.  Advantages are, the pump is handling the "cooler" storage water, and when the boiler is fired, the higher temp heat is pumped directly to the house first.
I burn 6.5 to 7.5 cords per year to heat an older 1500 sq ft farm house and 700 sq ft shop (which is only minimally heated 80% of the time).  The wife likes the house T stat > 70 F.  I am sure the boiler/storage causes a heat loss, but I am sure I have a higher heat loss with 250 ft of the cheap 3 wrap underground pipe.   
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coolidge

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Re: Adding storage questions
« Reply #9 on: January 14, 2018, 10:48:12 AM »

I have an xtra 330 gallons of insulated storage in my basement that my boiler in tied too. As mentioned batch burning is great. My basement is the warmest part of my house.
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dukethebeagle

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Re: Adding storage questions
« Reply #10 on: January 16, 2018, 04:53:16 AM »

I have an xtra 330 gallons of insulated storage in my basement that my boiler in tied too. As mentioned batch burning is great. My basement is the warmest part of my house.
i second the last three post
i run 300 gallons in my basement
you don`t realize the benefits till u try storage.
a toasty basement means less cycling because the basement is usually the coolest part of the house
and batch burning cut down smoke,improves efficiency in homebuilt and cuts down cycling
i love it
but thats jmo
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smithbr

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Re: Adding storage questions
« Reply #11 on: January 16, 2018, 04:42:51 PM »

If I put in extra storage, that means my OWF will go longer between cycles, right?  So if I double the volume, I might nearly double the time between burns?  Hmm.  Don't think so.  We went up to six hours between cycles in the fall; if I double that, I'll be feeding it twice a week, but I'd bet I'll have to relight the fire for every burn.  It struggled to wake up as it was.  It gets even worse in April/May, as our house has a lot of glass to the SE/SW. 

If it weren't for "free" hot water,  I'd shut down the OWF in April.  Frankly, I wonder if the electrical load of the OWF isn't approaching the cost of using electricity for hot water, at least at that time of the year.  I might be better off to build a solar preheater for the electric hot water heater, and shut down the OWF at the end of March; PSV and mixing valves are in place, so it's just a bit of copper, valves, a reflector box, and some black paint.

I understand the storage economics for some, but for me, I don't see a benefit.
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wreckit87

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Re: Adding storage questions
« Reply #12 on: January 16, 2018, 05:29:47 PM »

If I put in extra storage, that means my OWF will go longer between cycles, right?  So if I double the volume, I might nearly double the time between burns?  Hmm.  Don't think so.  We went up to six hours between cycles in the fall; if I double that, I'll be feeding it twice a week, but I'd bet I'll have to relight the fire for every burn.  It struggled to wake up as it was.  It gets even worse in April/May, as our house has a lot of glass to the SE/SW. 

If it weren't for "free" hot water,  I'd shut down the OWF in April.  Frankly, I wonder if the electrical load of the OWF isn't approaching the cost of using electricity for hot water, at least at that time of the year.  I might be better off to build a solar preheater for the electric hot water heater, and shut down the OWF at the end of March; PSV and mixing valves are in place, so it's just a bit of copper, valves, a reflector box, and some black paint.

I understand the storage economics for some, but for me, I don't see a benefit.

I'm on the same page here. My house loop pump costs $20/mo to run. My water heater is propane, but judging by my propane usage the last 3 years, that water heater costs about $7/mo to run 6 months out of the year. Hell if I'm burning wood even for free hot water, much less spend an extra $13/mo in electricity AND having to deal with the boiler. No way Jose
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