# Building a House for the GARN



## Father John (Dec 21, 2007)

Having made the decision to heat the radiant floors of our monastery with a Garn boiler, we began the preparations today by digging the footers for a boiler room addition and the trench to connect this addition to the current kitchen basement.

It is too bad we didn't hear about the Garn and its impressive size earlier this year, when I thought we had finished the landscaping of the area around the kitchen. We had had the naive idea that any wood boiler system could fit in the kitchen basement, but since we think the Garn will satisfy our heating needs for many years to come, it seemed worth doing it right and building it its own structure.

The building will be 16'x32' and attached to one end of the garage, but separated by an 8" concrete firewall and fire-rated steel door. The garage itself can be reached by way of a covered walk, so going out to tend the boiler shouldn't be too much of a penance.

Our generator was put at the end of the garage for the same reason, which is a great pity since I will have to redo the nice concrete pad and conduits somewhere else.


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## Father John (Dec 21, 2007)

Here are a couple of photos of the actual foundation trenches and the trench for the lines to the basement.


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## Eric Johnson (Dec 21, 2007)

Father John, I'd like to introduce you to Pook, our resident energy visionary and jazz critic.

I remain amazed that you can heat such a large building with a 144K btu oil boiler, since I'm heating somewhat less space with a somewhat bigger boiler. But I went to your website today and saw the construction photos, so obviously you've designed energy efficiency into the buildings. And the climate in Southwest Virginia is considerably milder than what we see up here along the northern border. So I'm looking forward to seeing your progress.

Are you doing this work yourself? If so, do you have help. Judging from the website photos, I'm sure you guys will do a first class job.


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## Father John (Dec 21, 2007)

We are doing the work ourselves, with occasional assistance when we really get in over our heads. Today a loan of a Kubota mini-excavator was all the help needed digging, so much easier than the old fashioned way.

The truth is since we got all the heat turned on a couple of years ago, we haven't had a real winter. Last winter was extremely mild, except for a brief period in early spring, so I really don't think that one 144k btu boiler will suffice when winter truly returns. On the other hand, we have over 1500 yards of concrete in this building, as well as several million pounds of aerated concrete block and limestone, so if we are careful to turn the heat on early enough in fall, and not let it get cool, the thermal mass of the building is rather enormous. In the ice storm earlier this year we lost power for a week (the erstwhile generator was not yet hooked up), and the temperatures dropped into the teens and twenties, and most zones in the building lost only 7-10 degrees over that time.

On the other hand... getting those ten degrees back into the building after power returned was an exercise in patience.


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## Eric Johnson (Dec 21, 2007)

Well then you're probably a good candidate for the Garn, because getting all that water up to temp is going to take some sustained firing. But once you get the ball rolling......

Any solar?


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## brad068 (Dec 21, 2007)

Father John,  

 I 'm glad to see that you chose the Garn.  You will not be disappointed.  These units are awesome.  I constructed one of them myself after seeing two older units (over 20 years old) and one new unit in operation.  They're big, they're expensive, but they're simple.  You will love the induced draft.  Don't let them crude cold war downdraft gasifiers rain on your parade. You made the right choice.


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## Father John (Dec 21, 2007)

Well, in spite of an inch or two of snow in the night, which was unexpected, we got the footer poured today for the Garn room. Next item on the list will be to put in a pair of 1 1/2" PEX lines and insulate the same to carry the hot water from the Garn to the current boiler loop. Does anyone know if the already insulated lines available (like Ecoflex) are truly waterproof?

The question of solar panels is intriguing. I would be interested to know if they are a DIY project, or do they have to be bought? It seems that the Garn would be perfect to store heated water from solar panels during the summer for domestic use, rather than having to light a fire.


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## Nofossil (Dec 21, 2007)

Father John said:
			
		

> Well, in spite of an inch or two of snow in the night, which was unexpected, we got the footer poured today for the Garn room. Next item on the list will be to put in a pair of 1 1/2" PEX lines and insulate the same to carry the hot water from the Garn to the current boiler loop. Does anyone know if the already insulated lines available (like Ecoflex) are truly waterproof?
> 
> The question of solar panels is intriguing. I would be interested to know if they are a DIY project, or do they have to be bought? It seems that the Garn would be perfect to store heated water from solar panels during the summer for domestic use, rather than having to light a fire.



I've done some experimenting with solar heat and hot water storage. It can be a DIY project, especially for people who aren't afraid of projects. I think you qualify. I've got some details on my site - link is in my signature below.


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## Father John (Dec 21, 2007)

Nofossil, how are your commercial glazed copper panels made? That is the part I was wondering about being DIY. Is it a copper loop sandwiched between layers of glass and sealed, like a thermal pane window?

The Garn is going to be backed up to the south wall of the boiler room, with its fire chamber door facing north. Can I use the exterior face of that south wall to mount a large panel? Will it thermosiphon and circulate back into the Garn tank?


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## Nofossil (Dec 21, 2007)

Father John said:
			
		

> Nofossil, how are your commercial glazed copper panels made? That is the part I was wondering about being DIY. Is it a copper loop sandwiched between layers of glass and sealed, like a thermal pane window?
> 
> The Garn is going to be backed up to the south wall of the boiler room, with its fire chamber door facing north. Can I use the exterior face of that south wall to mount a large panel? Will it thermosiphon and circulate back into the Garn tank?



They're not that impressive in terms of construction or complexity, except for the collector surface itself. 

The glass is single pane tempered glass, and based on my experience double pane would not be necessary. The box is made of light gauge aluminum with aluminum extrusions to provide a little rigidity and a place for screws to grab on to. There's about 2" of fiberglass insulation behind the collector surface, and a little around the sides of the box.

The collector surface is a copper sheet with several small tubes formed into it. There's a 1/2" header at each end that the tubes are brazed into. Given the price of copper, I'd explore other alternatives - perhaps aluminum tubing and aluminum sheet. You'd have to find someone who can weld fittings onto it, but it would be vastly cheaper than copper and just as effective. It would take some thought and perhaps experimentation to find the best way to thermally couple the tubing and the sheet.

Temperatures in the collector box reach 225 or so if water flow is stopped, so material selection takes some thought. Plastic fittings are a bad idea. I think metal panels with an external wooden frame would work.

The best situation is to have the top of the panels below the storage tank. In that case, you don't need any pumps or controls at all - thermosiphoning is your friend. If the panel and tank overlap, thermosiphoning can still work, but it's a bit more dicey. You have to get an ultra low backpressure check valve to prevent reverse thermosiphoning from cooling off your storage at night. The higher the panels are relative to the storage, the less effective thermosiphoning is.

You can use a thermostatically controlled pump if you have to.

I use mine only in the warmer months, so I don't need antifreeze. In your situation, you might build a simple shell-and-tube HX (like the sidearm) to keep the boiler water and the solar panel fluid separate.

Good luck with this project. I'm very impressed with everything you've done so far.


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## Eric Johnson (Dec 21, 2007)

When I was in Guadalajara Mexico a few years back, my dad was volunteering at an orphanage that had huge solar collectors on the roof--all ruined in a freak freeze some years earlier. He was trying to rehab them so that the orphanage could have some free hot water again. The design was one that I decided to use on my in-tank heat exchanger, which I hope to have running this weekend. Basically, if you took the header assembly pictured below and sandwiched it between two sheets of corrugated steel roofing painted black, you'd be pretty close to the elements on those solar heaters, which I think worked pretty well when they worked. They operated mostly through convection, though I believe there was a pump and a storage tank involved.

I think the trend, which I would endorse, is to buy manufactured collectors, most of which tend to be evacuated tube designs, and DIY the rest of the setup. The panels are around $800 each, and I'm told and evac. tubes are capable of extracting a remarkable amount of heat even on cloudy days. I suspect that you're in prime solar country in southern VA. And they're a perfect compliment to a wood gasification system seup, I think. Of course, free wood is cheaper than solar panels, so it may not be an issue. But if you are concerned about carbon emissions, then it's hard to discount solar.


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## Father John (Dec 22, 2007)

Where do you find these evacuated tube collectors for sale? It is a pity copper is so expensive, since I really haven't the skill or ability to deal with aluminum. I could find someone who can, but then I don't know what that would cost.

We would be interested in an eventual solar component to our setup, not because we risk ever running out of wood, but because anything that makes our time and labor go further may be well justified. We try to grow our own food, and in general provide for most of our daily needs from this property, so a one-time project like solar collectors would be worthwhile if there was a recurrent savings in work for the future.

Although I can picture nofossil's collector box, I am not sure what the collector surface looks like. How are the tubes formed into the sheet? I am imagining they are a similar layout to Eric's assembly (that's a fine piece of work by the way), overlaying the sheet, but I am not sure that is correct.

To get below the Garn storage tank much would require laying the collector nearly flat on the ground, which would presumably lower it by only so much as the Garn is tall. Perhaps this would be enough.


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## Nofossil (Dec 22, 2007)

Father John said:
			
		

> Where do you find these evacuated tube collectors for sale? It is a pity copper is so expensive, since I really haven't the skill or ability to deal with aluminum. I could find someone who can, but then I don't know what that would cost.
> 
> We would be interested in an eventual solar component to our setup, not because we risk ever running out of wood, but because anything that makes our time and labor go further may be well justified. We try to grow our own food, and in general provide for most of our daily needs from this property, so a one-time project like solar collectors would be worthwhile if there was a recurrent savings in work for the future.
> 
> ...



I've experimented with a very inexpensive collector surface - a solar swimming pool heater. It's 4' x 20', and made of extruded plastic. Just lying on the ground in Vermont, it supplies water at 130 degrees. With a simple glazed enclosure, you could probably do much better, though at some point it might get too hot and degrade the plastic. I've got pictures here.

Nearly flat on the ground is fine for summer sun. You'd want a little angle to flush bubbles out, but you don't need much.


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## brad068 (Dec 22, 2007)

I'm hoping to hook up my solar hot water system into my homemade garn boiler. I removed a complete system from a home that a young new couple bought. It has 4, 4'x10' panels that are about 200lbs each. I got the trellis frame the two piece fiberglass storage tank, 4 circulators, 3 finned copper tube hx, a high eff. electric water heater (maybe backup), and the control box. The name on the control box is Independent Energy Inc. East Greenwich, R.I. C-100 system manager. I was wondering what the initial cost of this system was and how old it is. The expansion tank had a code on it ending in 81 I think. 

My goal is to plumb this into my garn tank and hopefully generate enough heat to carry me through the summer to heat my DHW and maybe prolong firings in the heating season. My concern is how much heat will the panels generate in terms of temp range.


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## Nofossil (Dec 22, 2007)

Garnification said:
			
		

> I'm hoping to hook up my solar hot water system into my homemade garn boiler. I removed a complete system from a home that a young new couple bought. It has 4, 4'x10' panels that are about 200lbs each. I got the trellis frame the two piece fiberglass storage tank, 4 circulators, 3 finned copper tube hx, a high eff. electric water heater (maybe backup), and the control box. The name on the control box is Independent Energy Inc. East Greenwich, R.I. C-100 system manager. I was wondering what the initial cost of this system was and how old it is. The expansion tank had a code on it ending in 81 I think.
> 
> My goal is to plumb this into my garn tank and hopefully generate enough heat to carry me through the summer to heat my DHW and maybe prolong firings in the heating season. My concern is how much heat will the panels generate in terms of temp range.



You should get more than enough heat - more than you'll be able to store, so you'll have to think about dumping excess heat. I've boiled water in my panels when flow got blocked. My system routinely produced 175 degree water. You'll also want a tempering valve so that you don't get scalding water at the tap.


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## Nofossil (Dec 22, 2007)

Father John said:
			
		

> Where do you find these evacuated tube collectors for sale? It is a pity copper is so expensive, since I really haven't the skill or ability to deal with aluminum. I could find someone who can, but then I don't know what that would cost.
> 
> We would be interested in an eventual solar component to our setup, not because we risk ever running out of wood, but because anything that makes our time and labor go further may be well justified. We try to grow our own food, and in general provide for most of our daily needs from this property, so a one-time project like solar collectors would be worthwhile if there was a recurrent savings in work for the future.
> 
> ...



Another comment on solar panels and themosiphoning:

If your hot water needs are anywhere near as modest as your heating needs, it may be worthwhile thinking about another approach. Could you install a hot water tank adjacent to but higher than the Garn? It could then be heated from the Garn via convection, and it would give you more leeway on solar panel positioning. A smaller tank will also give you usable hot water much more quickly and more often, and could have its own backup heat source.

For instance, a 120 gallon hot water tank heated to 120 degrees is much more useful than a 2000 gallon tank heated to 95 degrees. If that smaller tank were heated with oil, electricity, or propane as a backup heat source, then you'd have hot water all the time while taking advantage of each heat source automatically.


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## Eric Johnson (Dec 22, 2007)

Here's just one online source for evacuated solar panels that includes pricing. I think if you're serious about solar, you should begin a thread in the Green Room forum. There are a couple of people who hang around there who have quite a bit of experience with solar and some pretty good ideas. Not that I disagree with anything nofossil has said (so far). If you have a gasification boiler, it seems to me, solar is less of a practical decision and more of a philosophical commitment to alternative energy, if that makes sense. In my case, it would be one more thing to play with.

http://www.siliconsolar.com/Evacuated-Tube-Solar-Collectors-p-16145.html

BTW, my parents recently bought a house in a city near their tree farm so that they can spend the harshest part of the Wisconsin winters in civilized surroundings. The house has a couple of huge solar collectors on the roof, and my dad reports that on cold, sunny days (i.e., below freezing) the house stays at 70 degrees without any help from the furnace. Imagine the impact on the energy/pollution equation if every house had a system like that.


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## Father John (Dec 24, 2007)

Since this solar project will probably remain an experiment for a while, nofossil's pool heater appeals to me as an inexpensive way to begin trying things out. After the boiler room is built I will see about setting up one of those just outside the building. 

Meanwhile, is there a consensus on the best way to insulate the PEX lines between an outdoor boiler room and the house? Or does everyone buy the pre-insulated corrugated product?

Merry Christmas to all.


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## Eric Johnson (Dec 24, 2007)

There are many ways to do it, ranging from total DIY arrangements to turn-key systems ready to drop into the ground. My piping all runs through building space, so I don't have any experience with buried pipe.

You might want to start a new thread with a descriptive title and see who drops in.


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## Tony H (Dec 25, 2007)

Father John - Nice looking project!  The pre-insulated corrugated stuff looked a little questionable to me so I used a product called Logstor you can see some info about it at Cozyheat.net. On the other hand I am in northern Illinois where the ground is frozen much deeper than your location so it may not be worth the additional costs.


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## Father John (Dec 26, 2007)

Thanks for the info and name of Logstor. Even though our climate is milder, we have the same risk of getting moisture in the lines, ruining the insulation. If I can't find a product like Logstor we can afford, I may have to insulate my own lines and install inside some of the PVC we have leftover from our project.


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## Father John (Jan 11, 2008)

A couple of days ago I got the first couple of block courses laid, and was able to rake out the gravel for the slab in the new Garn boiler room. I had to spend an inordinate amount of time moving our generator, tearing up the concrete pad, and rerouting all the conduits, but it was necessary to make sure the floor in the boiler room is all the same level.

Today I worked on building the leads and corners, and hope to get many more block laid tomorrow. Since I will be using 1 1/2" Pex, which I think will be too stiff to bend up and keep near the inside wall, I am making a well in the floor, at the end of the trench, so I can always get to the Pex fittings.

When the Pex arrives next week the fun of threading it through the carrier pipe can begin.


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## Eric Johnson (Jan 11, 2008)

I found pex-al-pex, which is stiff like soft copper, to be a lot easier to work with than I expected. You can't make tight turns without expensive fittings, but it will snake where you want it to go and it's easy to pull long distances.


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## Tony H (Jan 12, 2008)

The standard required bending rate of normal pex is 6 times the outside diameter (nominal size plus +1/8") of the tubing.  So if you figure 7 times you should be safe. For example 1' pipe equals 6 3/4 Radii on the actual chart. There are some brands that claim better rates but this is the standard all are supposed to meet.

A couple of thoughts when pulling pipe thru another pipe gained from 20 years of trial and error.

Pull all inner pipes together that reside in a single tube and pull all like sizes if possible.

If you need some AC or controll wires pull them in a seperate tube. The black plastic "utility" pipe sold at most lumber yards works well for this as long as it's allowed by local code. (Well even if not allowed it still works well)

Pulling lube is your pal ! 
Sold in the electrical section use lots of it if you have a number of bends in your run and just because it seems ok to start with does not mean you won't wish you had put more lube on that first 50 feet when you hit those bends 100' later.

For the larger pex pipe and or longer runs consider using a pulling sleeve or whip  This is a wire mesh sleeve several inches long open on one end to insert the pipe and connected to a stranded cable loop on the other end to connect your pull rope as you pull the mesh tightens down on the cable or pipe so you can pull with alot of force like a come-a-long or a truck and have a secure connection that slides easily thru the pipe. 

It's a good idea to leave a well even if you don't need any connections there you might need a pull point or "hand hole" to assist the pipe thru that area.


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## Father John (Feb 12, 2008)

It has been taking me a good while to get the block walls laid for the new Garn room, especially since the weather has been back and forth this last month. It is hard to get a good solid week of outside work in this time of year. Still, there are just three block courses left to go before I can pour the bond beam and frame the roof.

At the same time I took advantage of a comfortable day last week to insulate the 1 1/2" Rehau pex lines to connect the Garn to the current boiler loop. I used Imcolock insulation with a 1" thick wall, kindly provided by our friends at Nomaco. Since I was working alone I had to come up with a way to control the 100 ft long lines so I could slip the black corrugated carrier pipe over them. I accomplished this by taping one end of the insulated pex to a fence post, then I attached the pull rope (which I previously had slipped through the corrugated pipe with a fish tape) to the other end of the pex. Then I tied the free end of the rope to a tree after pulling tight. The corrugated pipe easily slipped down the taut rope and over the pex. The assembly was then dropped into the trench and shoved through the holes in the walls at each end.

The Garn is due to arrive any day this week, so I really better hurry with the block.


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## Eric Johnson (Feb 12, 2008)

Looks great!

That's one thing I like about working alone--it forces you to come up with some pretty creative approachs to things like insulating pex lines.

Pretty nice looking boiler room so far.


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## Tony H (Feb 12, 2008)

Father John - The pipe solution looks nice, I take it from the picture the feed and return pipes are each in a different sleeve. That looks like a very nice clean and reasonable solution. I and some of the others around here would love some part numbers and estimated costs if you get some time. The installation seems to take longer than expected I am in the about same spot except I have the boiler in place and just got the shed built and the pipe buried.  Just started working on the plumbing layout and connections. Nice to see your progress, just like me you will have heat in time for summer. ;-)


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## brad068 (Feb 12, 2008)

I see room in the pipe for some foil/bubble wrap too. Can't have to much insulation. High E did this same principle with foam sleeve first then a couple wraps of 2' wide foil/bubble.


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## Father John (Feb 12, 2008)

I didn't give a list of costs, since our project is quite unusual. We have been able to call upon help from friends at Nomaco in the past, so the Imcolock was free. The Rehau pex was also free, again thanks to some very generous friends who have helped out many time before in our project. I do know what this would cost if all products were purchased, and I still would have been able to assemble the needed materials and install for less than a quarter of the usual price for the different pre-insulated brands go for.

The supply and return lines are each in separate sleeves, and the ends are sealed with PUR foam, so are completely waterproof with no air movement. The polyolefin insulation we used gives us an R-value of about 6. Without a consistent air gap I figured the foil radiant barrier wouldn't be worth the effort.

Even though I was not looking forward to messing with big pex and pulling it through the carrier pipe, that turned out to be the easiest part of the job. Cutting the hole in the kitchen basement wall was actually the hardest work, since we couldn't afford to hire a core-drill, and I ended up using our ICS chainsaw to cut a rectangular hole. Spending time deep in a trench with a +100 cc saw burning 25:1 mix left me feeling rather queasy for some time afterwards.


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## Tony H (Feb 12, 2008)

You got to admit they are very nice saws but I still wouldn't want to spend too much time down in the trench with one.  When I cored a 5" hole in my basement wall it took me 5 hours .... boy was that fun at least I had no fumes to deal with.


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## Eric Johnson (Feb 12, 2008)

Will you have space in the new building for any firewood?


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## Father John (Feb 12, 2008)

I would have liked to make the boiler room bigger to store more wood, but had to compromise because we feared a bigger addition would not be as aesthetically pleasing in that spot. We decided instead to retain many of the hundreds of crates the limestone veneer came in, and we have been for the last months storing and stacking firewood in one of our nearby pole barns. The firewood is now palletized and we can move it with the forklift or the farm tractor. We should easily be able to store in the boiler room about 2 cords at a time. I think it will be a nice system, since I can go down one of the old roads in the forest carrying empty pallets on the front and back of the tractor, and fill them up as the wood is cut. It is easy to move the pallets around in the boiler room with our pallet jack, so handling should be reduced to the minimum.


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## Eric Johnson (Feb 12, 2008)

That sounds like a really good plan to me. You just don't want your fuel to get wet; MC makes a big difference with a gasifier, I've found.


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## brad068 (Feb 13, 2008)

Father John,

 With the foil/bubble wrap you will have a consistent air gap (because of the air bubbles) plus reflective foil, with this wrap.  I'm curious, when you say "our ICS saw" What do you need this saw for?  I know many construction companies that don't have these saws, and I can't help but wonder.  Thats a $2000 saw!


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## Father John (Feb 13, 2008)

ICS has a line of saws called the Redzaw which was brought out only three or four years ago. At that time we were cutting a lot of the limestone for our church and tower here, and needed to make deeper cuts than a typical cut-off saw with 14" wheel could handle, ICS agreed to donate one of their early demonstrator Redzaws with a 14" bar, and they made use of our project in their promotion of the new tool.

At the time I was aware of pricing (now several years out of date) the Redzaw line was about 75% of the cost of a regular duty ICS saw. Since we have handled several million pounds of limestone, and poured a couple thousand yards of concrete, we have found plenty of jobs for this useful tool.

On the topic of bubblewrap, how much R value do you think it adds to an assembly? Obviously I don't know much about how that wrap works, and would be very interested in hearing how it is used by others. I presume you must use reflective tape on the joints.


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## Sting (Mar 1, 2008)

Aren't you concerned about trying to shove 

quick calc here.......

Like 16 GPM minimum ( maybe far more) down that one inch pex to carry the energy effectively away from that new big engine????


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## Eric Johnson (Mar 1, 2008)

I think he said he's using 1 1/2-inch pex.


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## Sting (Mar 1, 2008)

oppps 

Sorry!


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## Father John (Mar 25, 2008)

Just a week before Easter I finally, at long last, got the roof put on the addition to house the new Garn boiler, and last Monday we moved the Garn into place. It turned out to be quite easy to move around with a pallet jack, since it is not nearly as heavy as it looks, although ours (a Garn 1500) is still every bit of 3500 lbs I think.

I have just about assembled all the parts needed to plumb the Garn into our system, as well as build the insulated enclosure around the tank, and will post more photos as the installation proceeds. Hopefully the plumbing and other work will be much quicker than my block-laying was.


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## Father John (Aug 21, 2008)

After spending much of the spring and summer working in the vineyard and garden, I have finally been able to finish plumbing the Garn into our radiant heating system, and am now building the enclosure to insulate around the tank. We filled it yesterday, and no leaks are apparent, so we will fire it in a couple of days and make sure there are still no leaks before we begin insulating.


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## Adios Pantalones (Aug 21, 2008)

Yowzer!  What a monstah!


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## Eric Johnson (Aug 21, 2008)

Thanks for the update, Father John. I've been wondering how it was going. Beautiful setup. The vineyard would take priority with me, too.


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## Mmaul (Aug 21, 2008)

I am glad you posted an updated I was wondering what happened to that church with the beautiful view.


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## Father John (Sep 12, 2008)

Here are a couple photos of the new installation. One shows the hx for the domestic hot water loop, and the other shows the two 1.5" pex lines from the Garn, their transition to copper, and the bypass so we can run the Garn in summer without heating the radiant injection loops.

The Garn is now fully piped and filled, and will be fired this very afternoon. More news to follow.


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## brad068 (Sep 13, 2008)

Father John,

  The directions that I got with my three plate heaters say not to install them horizonal. They want the plates to be vertical I suppose to help keep them clean.


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## Willman (Sep 14, 2008)

Is the Garn in the block enclosure ? Why two smoke pipes ?

Will


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## Father John (Sep 14, 2008)

The hx is from FlatPlate whose instructions show installations in both vertical and horizontal positions. Our water is filtered and treated on the boiler side, and filtered on the domestic side.

I perhaps should have labelled the photos better, but the last pictures show the kitchen basement plumbing, not the Garn enclosure, so the two flues are the backup oil-fired boilers.


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## oliver5528 (Sep 14, 2008)

Father John,
  My Hat is off to you.  Up here there are a lot of churches undecided on alterative heat. Keep the pictures coming!

JC


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## heaterman (Sep 14, 2008)

Hi Father John. I'm really curious to hear how fast the water temp in the Garn drops when you first fire up the floors. That cold concrete can soak up a huge amount of BTU's before it even starts to budge in temperature.  After the floors get stabilized you'll find that it will require much less heat to maintain the floor temp than it did to raise it in the first place. Night time temperature setback with thick slab radiant like you have there is often counterproductive.


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## Father John (Sep 22, 2008)

Hello Heaterman,

We will probably be turning on the radiant slabs in the fall before they have had a chance to cool down much, but I know you are exactly right about the uselessness of setbacks for such a thermal mass.

Right now, though, we are heating just the hx for the domestic hot water, and finding that about one fire in the Garn each week gives us plenty of hot water, and we may even be using more hot water than usual since it feels free. I will need to do some figuring to tell you better how much hot water is being used. For now all I know for sure is we have fired the Garn until the tank is nearly 200*, and it is still just above 120* a full week later.

Our Garn is well insulated with vermiculite, and framed in with steel studs on two sides, and AAC block on the other two sides, so the heat loss is extremely minimal. One nice thing about the vermiculite is that any mouse who wants to take up residence in the enclosure will think it is in quicksand, so the open top to the insulation is not the problem I thought it would be.


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