storage tank

[wolfkiller]

I was planing on using a couple old oil tanks for water storage. Now that I have heard of problems with that how about plastic. I found a 2000 gal plastic tank. I am thinking of having it sprayed with foam and burying it in the back yard. Is there any problems with a molded plastic tank?

 

[BrownianHeatingTech]

I was planing on using a couple old oil tanks for water storage. Now that I have heard of problems with that how about plastic. I found a 2000 gal plastic tank. I am thinking of having it sprayed with foam and burying it in the back yard. Is there any problems with a molded plastic tank?

Most plastics are not designed to handle these sorts of temperatures. Put 180-200 degree water into a typical plastic, and it softens to the point that it will leak.

Joe

 

[wolfkiller]

This is a very heavy plastic tank made for under ground use. It was made by Greer tank here in Fairbanks. I will give them a call and ask about what kind of temps it can handle. Thanks for the reply.

 

[MarcM]

Find out specifically what kind of plastic it is. Polyethylene won't do it. Polypropylene might. In any case I'd go with the safer EPDM lined option.

 

[serafisa]

Wolfkiller

What have you heard about the problems with using oil tanks for heat storage? I've seen a couple of references to problems but no details. Are the problems based on corrosion? I've got two tanks I was thinking about using, but now maybe not... 550 gallons doesn't seem like enough with an EKO 40.

 

[Eric Johnson]

Welcome to the Boiler Room, dogfarm. Do you have an EKO 40 now, or are you planning to get one?

Steel oil tanks are kind of a Catch 22: They aren't designed to hold the pressure they'll see in a pressurized system, and if you try to use them as unpressurized storage, you'll have corrosion problems with the oxygen present in the water. You could treat the water, but there's no good way (that I can think of) to get a decent heat exchanger into the tank. You'd need something external like a flat plate hx, but it would be tricky, I think, to engineer something that would work in series with more than one tank. I'm not saying it can't be done--just that there are probably easier/cheaper solutions.

 

[serafisa]

Thanks for the info Eric.

I'm into my second season with the EKO 40. Last year I got it started mid-winter and I found out what not enough dry wood feels like. Quite a training exercise! Zenon from New Horizons and Dave at Cozy Heat (where I bought the unit) both counselled me on the magic of dry wood. I bought a log load and had it drying on small piles all summer. Things are much better this season.

I just ran into the bypass flap sticking problem and called Dave who turned me on to this site. What a wealth of information!! Now I'm fiddling with the air flows and I think I've got it running more efficiently - loads seem to last longer.

My thought on the heat storage unit was to cut two round holes out of the top of each tank and suspend a couple of spiral 20" diameter 3/4" copper tube heat exchangers, passing the copper tubing through a couple of grommets set in holes in the cut out part of the tank. The cutouts would be edged with some kind of gasket material (EPDM?) and refastened to the tank. With two tanks, I'd only end up with 500 gallons effective volume, and they don't make effective use of the space available. So maybe I'm better off building a tank using some of the ideas here.

 

[Eric Johnson]

Lots of tank info here--lots of good ideas.

I solved my bypass damper sticking problem by turning around the handle on the firebox (i.e., undermined the safety feature). This allows you to open the firebox door when the bypass damper is closed, and you can easily pop the damper loose with a stick or the cleaning tool just by giving it a good poke. I've never come close to singing any body hair by opening the firebox door with the bypass damper closed, so I don't really consider it a safety issue--at least not in my setup.

Really dry wood makes a huge difference in performance, as you say. I've found that you can burn somewhat moister wood once you get a good fire going, but you need good, dry wood for a clean light-off. Otherwise, you're looking at a thin stream of blue smoke until she gets up to temp. I've found that pine cones, dried bark and yellow birch bark work on cold starts.

 

[jebatty]

Yes and no on used fuel oil tanks. I use three 275 gallon tanks in series, non-pressurized. I got all three for $125.

Why bother with coil hx? Use a flat plate hx, does take a second pump, but sooo easy and highly efficient. I have a 2-5 degree temp drop between boiler water in to hx and hot water out to storage. And they are inexpensive ($200-250 for 5 x 12 x 30 plate on ebay).

My tanks are in series: from hx hot water in to top of tank 1, out at bottom to top of tank 2, out at bottom to top of tank 3, out at bottom to hx. Tanks 1 and 2 are sealed, and tank 3 is open to vent, so all 3 tanks will equalize. Slight pressure, around 1 psi, does build in tanks 1 and 2 due to circ pump pushing water in and thermal expansion/water vapor, but pressure also helps to push water out to next tank.

The only issue is removing the water vapor that builds in tanks 1 and 2, as they heat first. The water vapor creates a vapor space in the top of the tank, water capacity drops, and tank 3 needs extra expansion space (tank 3 is left about 1/4 empty for expansion). So, have to do an equalizing line across the tops of the three tanks, with a valve just slightly open, to let the water vapor escape to tank 3, which is vented.

Corrosion on the open system is an issue, but how much I don't know. I have not treated the water. I do use a high temp filter, 50 micron, and change it once/week. It does accumulate a rusty slime, so corrosion is taking place. I figure that at some time a pinhole drip will develop, which will be a sign that the tank is ready to be replaced.

The steel fuel oil tanks were a first effort at storage, as I needed something and the price was right. I installed my gasifier late last summer. I'm not sure that I would recommend this as a long term solution without further attention to the corrosion issue.

My plan is to move to pressurized storage with a 1000 gal used LP tank. I just got a fair price on one from the local LP company, a retired tank in good condition for $850 delivered. When that tank is put in service I will treat the water, and then with a closed system it should be OK.

BTW, for plumbing between the hx and the tanks, I'm using 3/4" hot water hose rated at 200F, with hose barbs for the connections. This runs about $50 for 50 feet. It is flexible and can easily snake it for any run. After nearly a full season of heating I have not noticed any problem developing with the hose. I plan to continue to use the hose for connections to the new LP tank storage. If anyone has contrary experience, let me know.

 

[Eric Johnson]

Great explanation, Jim. I'd forgotten that you were doing it that way, but it's good to see the idea in practical use.

 

[Stlshrk]

Great site guys!

I am in the process of designing my system (for install this summer) and am looking into doing it with a heat storage tank setup. I have the furnaces narrowed down to the tarm, woodgun, eko, greenwood, and wooddoctor converter. Honestly leaning towards the woodgun, but I get more info in email, reading, and snail mail daily.

My system will use forced air for the house (and expand a zone to the basement once finished, but that is a separate project(s)), a suspended space heater in my detached garage, and a water to water heat exchanger so that the electric potable hot water heater only has to run in the summer. My questions (actually there are many) around the heat storage tank are these.

1- How do you prevent the storage tank from causing a large system heat up lag if the system has been off for a number of days? Basically I would want to heat the house first and send excess to the storage tank, rather than take an entire burn cycle where the house would only warm slowly as the storage tank does.

2- Any cons to using a pressurized primary loop with this storage tank vice and unpressurized with glycol? I don't know of anyone local using a pressurized system but it seems like a more efficent way to go and better for the gasifier unit.

3- Should the system circulate constantly to avoid slugging? or does this not matter when using a storage tank? or for that matter with a gassifier?

Thanks for any input!

 

[Eric Johnson]

Welcome to the Boiler Room, NSOTK. We have many threads talking about all the boilers you mentioned, so I'd say you came to the right place.

On your first question, I think the best approach is to have a bypass piped into your system so that you can heat the house directly when necessary, and then heat the tank when the house zones are satisfied. You can do that manually with ball valves, or automatically with a three-way zone valve and aquastat. Or both. One advantage of the manual approach is that you can play around with it infinitely, which some of us like to do. It's another toy. Or if you're a complete controls geek, rig up your computer to run things.

Lots of people use pressurized storage. The most common vessel is a 500- or 1000-gallon propane tank, preferably acquired for less than $1 a gallon, though the price of scrap steel is driving that benchmark up. One thing you need with that much pressurized storage is a pretty big expansion tank, and they're not cheap. Or, you can make one out of a hot water heater. There's a how-to link in one of the two stickies at the top of the main forum page.

I don't know what slugging is, but my pump stops and starts on a regular basis, depending on system water temps. There's no problem that I'm aware of with that. You don't want the water circulating while the boiler is getting up to temp, for example.

 

[slowzuki]

You found the right place!

1) Zone the house as priority is one option. There are literally dozens of ways to achieve this, would need a bit more info. For me, my boiler circ is basically there to pump to the storage as my boiler is way oversized. If the house calls for heat it just robs a bit of the flow from the feed to the storage. When the boiler circ is off, the house robs heat from the storage only.

2) Most gasifiers are pressurized. It is a lot easier to prevent corrosion in a sealed system that to try to treat for it in an open system. That said there are very effective open systems out there. I setout to use glycol but I've just about been convinced not to use it. There are a lot of cons to using it.

3) Circulation, the boiler itself should not circulate continuously since it won't likely be running all the time. Your heating loops can be designed to circulate continuously if you want. There are many ways to do it. Traditionally in north america we use high temp radiators or hotwater baseboard and use bang-on bang-off thermostats with zone valves or pumped zoning. Recently the euro method of using continuous circulation and adjustable water temps has begun to make headway as radiant slabs need low temps and don't always work well being turned on and off.

Great site guys!

I am in the process of designing my system (for install this summer) and am looking into doing it with a heat storage tank setup. I have the furnaces narrowed down to the tarm, woodgun, eko, greenwood, and wooddoctor converter. Honestly leaning towards the woodgun, but I get more info in email, reading, and snail mail daily.

My system will use forced air for the house (and expand a zone to the basement once finished, but that is a separate project(s)), a suspended space heater in my detached garage, and a water to water heat exchanger so that the electric potable hot water heater only has to run in the summer. My questions (actually there are many) around the heat storage tank are these.

1- How do you prevent the storage tank from causing a large system heat up lag if the system has been off for a number of days? Basically I would want to heat the house first and send excess to the storage tank, rather than take an entire burn cycle where the house would only warm slowly as the storage tank does.

2- Any cons to using a pressurized primary loop with this storage tank vice and unpressurized with glycol? I don't know of anyone local using a pressurized system but it seems like a more efficent way to go and better for the gasifier unit.

3- Should the system circulate constantly to avoid slugging? or does this not matter when using a storage tank? or for that matter with a gassifier?

Thanks for any input!

 

[Stlshrk]

Thanks for the replys folks!

The propane tank as a vessel sounds like a good idea to me, in theory. I just need to wrap my skull around it the rest of the way. Am I correct in following that since it would be pressurized that the same water is shared between the furnace, storage tank, zones, expansion tank? Or should I look into using a primary/secondary (possibly even three water) loop model where the waters do not mix? Benefit? Or would that just be an additional heat exchange(s) an complexity that I wouldn't need?

slowzuki - How does your house send the call, so to speak, and rob from the storage? Do you use an additional pump? Some sort of metered valve? If only the valve is there less resistance in that loop to allow the, "robbery?" And is it controled by a thermostat or aquastat depending on your system?

Eric - your signature says that you have 1000 storage pending. Is that going to be a propane tank? If so are you going to be pumping that water from the tank or dropping a heat exchanger in it?

Another question, how much pressure are we generally talking about these systems running at? And I've seen air removal mentioned as well. Do the "bubblers" go at the high points or closer to the heat source?

Thanks again!

 

[Eric Johnson]

I have the tank about 75 percent done. I have the heat exchanger built. My boiler works so well without it that I've been putting off the tank hookup until the weather warms up. It's non-pressurized storage--basically a concrete cistern with a rubber pond liner.

Pressurized storage uses the same water as every other part of the system. No need for heat exchangers anywhere, except for your domestic hot water. The boiler system pressure should be around 15 psi. All standard pressure relief valves pop at 30 psi.

I always locate my air scoops on the supply side, as high as possible and as close to the pump as possible. Joe Brown recommends an 18-inch (minimum) horizontal run before the scoop. They cost about $10.

 

[BrownianHeatingTech]

The propane tank as a vessel sounds like a good idea to me, in theory. I just need to wrap my skull around it the rest of the way. Am I correct in following that since it would be pressurized that the same water is shared between the furnace, storage tank, zones, expansion tank? Or should I look into using a primary/secondary (possibly even three water) loop model where the waters do not mix? Benefit? Or would that just be an additional heat exchange(s) an complexity that I wouldn't need?

Although it adds a pump and heat exchanger, I do recommend using an external plate heat exchanger to separate the pressurized storage tank from the boiler. You don't need a burst pipe dumping 1000 gallons of water in your basement...

Another question, how much pressure are we generally talking about these systems running at? And I've seen air removal mentioned as well. Do the "bubblers" go at the high points or closer to the heat source?

Air vents are sometimes located at high points, depending on the system design. The "air removal" typically referred-to is the air separator, which is typically installed near the boiler or primary loop. Some systems may have more than one. These come it two basic flavors: the air scoop, which is cheap and does an "okay" job, and the microbubble remover, which costs a little bit more, but does a much better job.

As Eric mentioned, the air scoop type needs a minimum of 18" of straight pipe (that means no fittings - just a straight run of pipe) before the scoop, to allow the turbulence to even out so that the bubbles can rise to the top third of the pipe where the scoop actually works. That's not just a recommendation - it's an installation requirement, from the manufacturer.

The microbubble removers work on the entire area of the pipe, so they don't have that requirement (there are even models that can work on a vertical pipe). The most popular brand is probably Spirovent, although Watts, Caleffi, and several others make versions of this technology.

Joe

 

[Stlshrk]

I can see running the heat exchanger and additional pump to avoid a flood in the house. Thanks for the idea. I'll take all the good ones I can get!