Froling S3 Turbo Install with 850 Gallons of Storage - OffGridICF

[OffGridICF]

Howdy Everyone!

After reading lots and lots of excellent posts here (Thanks to all for sharing your experience!) I am finally making some progress on the installation of a 30kW Froling S3 Turbo with about 800 gallons of storage. Our new house is built with ICFs to the roof (R-23) and SIPs for the roof panels (R-50+). It is partially earth bermed to reduce exposure to the outside air temperature. The calculated heat load is less than 400,000 BTU per day for an average January day so hopefully only one firing of the boiler per day will be required on most days. The primary heat source will be the wood boiler plumbed to radiant tubing in the concrete floor. The upper level will use panel radiators. Both the floor and radiators will be mixed from storage with outdoor reset mixing valves. Domestic hot water will be from a propane tank type water heater where the incoming cold water can be preheated from storage by a heat exchanger. Backup heat may be provided by a propane boiler in the future.

We live off grid so power consumption is a big concern. Our power comes from a large PV array and is supplemented by a backup generator. Winter days are very short and often cloudy, made worse by the surrounding topography which limits the direct sun on the array to about two hours in December. All of the radiant loops will be on one circulator with a second for the radiators and a third for the domestic hot water preheat. There is also a fourth circulator from the boiler to storage. These are all ECM versions to save power and they will only run as necessary. I'll be uploading some diagrams and asking for suggestions and feedback soon.

In the meantime, rather than continue to hijack a thread by @chew72 where I had asked him some questions, I'll answer questions from @hyfire here.

How long burn time do you get per load in the boiler? What is the internal firebox volume?

The boiler is a Froling S3 Turbo. The firebox on the 30kW holds 37 gallons (about 5 cubic feet) according to the online specs. The burn time for softwood should be about 3-4 hours (4-5.5 with hardwood) with an output of 30kW or about 102,000 BTU/hour.

What is your expansion volume tank size?

Based on 850 gallons of water, a starting point of 40F at 12psi and an ending point of 190F at 28psi the Watts expansion tank sizing tool gave a required acceptance volume of 26.6 gallons with a tank volume of 105.4 gallons. I have ordered an SHXT110V and SHXT90V to be plumbed in parallel for a total of 106 gallons with an acceptance of 42.6 gallons.

Initially, the plan was to use a 119 gallon scrap propane tank configured as a compression tank. After reading lots of comments here I decided to order a diaphragm type expansion tank since there is no way to place the compression tank at the highest point in the system and I had already ordered parts for air elimination instead of air management with a scoop before I understood the trade-offs.

Expansion tank threads, some with links to volume calculators:

https://www.hearth.com/talk/threads/help-please-quick-sizing-of-expansion-tank-for-windhager-262-pellet-boiler-240-gallons-pressurized-storage.193265/
https://www.hearth.com/talk/threads/expansion-tank-size.193931/
https://www.hearth.com/talk/threads/pressure-problems.164658/page-2
https://www.hearth.com/talk/threads/do-i-need-more-expansion.143864/
https://www.hearth.com/talk/threads/open-expansion-tank-questions.136412/page-2

 

[hyfire]

Thanks for the detailed explanation, my only thing that you might look into is replacing the panel radiators with some highly efficient fan coil units which take only a few watts of power. There is a guy on youtube who installed one , I will post up the link.

 

[OffGridICF]

Thanks for the detailed explanation, my only thing that you might look into is replacing the panel radiators with some highly efficient fan coil units which take only a few watts of power. There is a guy on youtube who installed one , I will post up the link.

Thanks for the suggestion, I'll check out the link when you post it. The rads I got are from Jaga which sound similar. They look more like a car radiator inside. Rather than pay them a lot more for their fan units, I just ordered the wider core version where I can lay my own computer muffin fans on top of the core for increased heat output, especially at lower water temperatures. I'll add a cheap temperature controller to complete the package. They should work well down to 120F - 140F to get the most out of storage without being huge.

 

[hyfire]

Here it is

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[hyfire]

Doing some research looks like these are Made in China by a company called PHNIX. No idea if they are CSA or UL listed even.

 

[OffGridICF]

Doing some research looks like these are Made in China by a company called PHNIX. No idea if they are CSA or UL listed even.

Those fan units look like a good option but the heat output of the one in the video is a lot more than I need. You can find more on the Jaga Strada radiators I got here: https://jaga.com/ex/radiators/strada/

They offer an optional fan module (DBE or DBH) that fits inside the housing: https://jaga.com/ex/options/dbh-upgrade-set/ that looks like this:

These are low water volume radiators. Their spec sheets list the BTU output of each model with and without the DBE (dynamic boost effect). All of mine are Type 15 (6.6" out from wall) except one Type 20 (8.6" out from wall). Here's one of the part numbers if anyone is interested: [STRW.03509015 = 35 cm (14") high, 90 cm (35.5") long, 17 cm (6.6") width, Type 15]. That one outputs 2872 BTU/hr with 0.29 gpm flow or with DBE, 4492 BTU/hr with 0.45 gpm assuming incoming water at 140F, 20F delta-T and 65F ambient. I got Danfoss valves and operators to go on them so each room can have its own temperature setting without the power required by electric zone valves. The radiators will be connected to an Alpha2 circulator that will probably be set in a constant pressure mode. I'll have to figure out some control method to turn it off and on as necessary.

 

[OffGridICF]

Here are the drawings for the system, any comments, concerns or suggestions will be much appreciated!

Since most of the parts are not available locally, the drawings try to capture all the various pieces that will be required to get everything installed. The first page is an overview with the details on the following pages. The auxiliary propane boiler details are not included. It will only operate on the upper half of the left-most storage tank and will have a differential bypass valve on it's supply output to prevent ghost flow through it from the wood fired boiler. The overall scheme closely follows the design from @Newfiestang .

There will be more heat loss from the 4 smaller storage tanks than 1 or 2 larger tanks but since I got a great deal on these I'll just try to add more insulation around them.

 

[OffGridICF]

The boiler was moved into the house with pallet forks on the tractor. After that, I made a custom lifting frame on wheels to move it around inside. I also made some 'roller skates' for the tanks to move them into position.

 

[hyfire]

Here are the drawings for the system, any comments, concerns or suggestions will be much appreciated!

Since most of the parts are not available locally, the drawings try to capture all the various pieces that will be required to get everything installed. The first page is an overview with the details on the following pages. The auxiliary propane boiler details are not included. It will only operate on the upper half of the left-most storage tank and will have a differential bypass valve on it's supply output to prevent ghost flow through it from the wood fired boiler. The overall scheme closely follows the design from @Newfiestang .

There will be more heat loss from the 4 smaller storage tanks than 1 or 2 larger tanks but since I got a great deal on these I'll just try to add more insulation around them.

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Do you know what material is inside those spring chrck valves. I had some with plastic internals and they got brittle and brokenin a short time. You might want to see whats inside.

 

[OffGridICF]

Do you know what material is inside those spring chrck valves. I had some with plastic internals and they got brittle and brokenin a short time. You might want to see whats inside.

Thanks for the heads up. It's rated for 212F and based on the photos looks like it's all brass except the seal. While checking that, I noticed it is not DZR brass and should not be used with water with high mineral content. It will probably be OK but I might swap it out for a different one with DZR brass. Changing it later will not be fun.

 

[PassionForFire&Water]

Will your expansion tank of 42 gal acceptance volume be enough for 850 gals?

I saw a pellet boiler yesterday with 400- gal thermal storage and expansion tank was 34 gal acceptance and the 30 psi relief valve started dripping at around 160F water temp

What drawing software do you use for those sexy schematics ????

 

[PassionForFire&Water]

The boiler was moved into the house with pallet forks on the tractor. After that, I made a custom lifting frame on wheels to move it around inside. I also made some 'roller skates' for the tanks to move them into position.

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It's early in the morning, but I don't understand how your "roller skates" work. Is there something magical under the 1/2" plates that supports it?

 

[OffGridICF]

Will your expansion tank of 42 gal acceptance volume be enough for 850 gals?

I saw a pellet boiler yesterday with 400- gal thermal storage and expansion tank was 34 gal acceptance and the 30 psi relief valve started dripping at around 160F water temp

I sure hope so ;-) The Watts calculator said the calculated total volume is 105.4 gal and acceptance volume is 26.6 gallons. Amtrol says total volume 80.55, acceptance volume 26.6 gal. Westank says tank volume 66 gal and recommends a tank with a volume of 66 gal and acceptance of 41 gal. The combination of a Watts ETSX-90 and ETSX-110 has a total volume of 106 gal and acceptance of 42.6 gal at 12 psi so it should be OK. The starting temp of 40F is a bit low, but probably close for the initial fill temp from our well. Changing it to 60F only changed the acceptance volume by 0.5 gal.

What drawing software do you use for those sexy schematics ????

Well, they are not nearly as sexy as newfiestang's since I don't have an AutoCAD license anymore. I tried using TurboCAD but finding models was very difficult since most of those items are now built for Revit/AutoCAD. Since I really mostly wanted to capture all the fittings for my shopping list, just using LibreOffice Draw was the simplest option. Making the components was the most time consuming but not too bad. Each one required taking a screen shot of the item, removing the background (and scaling in some cases) using Gimp then saving a png file. These png images can be easily inserted into Draw and adjusted to the right size. It's basically all imported pictures and lines but it worked pretty well. LibreOffice Draw and Gimp (photo editor) are both free programs that run under Windows and Linux.

It's early in the morning, but I don't understand how your "roller skates" work. Is there something magical under the 1/2" plates that supports it?

Yep, totally magic. The initial idea was for something with wheels on both sides and cross arms that could be locked together after lifting up the tank. After a lot of thinking, it turned out that the cross arms are not needed if the skates have a little lip that catches on the tank's foot plate like this:

With the tank rocked up onto two legs the skates can slip onto two feet. The next two are a little more tricky but not bad for these tanks. The skates went on the 250 gal tank while held up by the tractor. A small floor jack and the foam + OSB insulators made it pretty easy to remove the skates and adjust the tank position. Casters with a higher weight limit than required are a very good idea. These are mostly trashed now since wrestling the tank around can put a lot more than 25% of the load on a single caster. Attempting this with larger tanks or with them further off the floor could be even more dangerous due to the tipping hazard.

 

[OffGridICF]

There are a number of posts in this forum on re-purposing scrap propane tanks for hot water storage. There are obviously some risks involved in cutting and welding if any propane remains in the tank, there are risks associated with large amounts of pressurized hot water if a weld fails not to mention the risk of pressure testing with air alone instead of a little air in a tank mostly full of water. Some areas or insurance companies may also require ASME certification (fortunately, no certification is required in my area).

After reading a lot of these posts, I still decided to modify the tanks I got from a local propane company. They were all made in the 1950s and had been out of service for a while. They sat by my barn for a couple of years with the fill ports open to the air. I used a propane torch near the open port to make sure there was no propane remaining (The Internet said this is safe since the tank won't explode if it is not sealed, it will just vent flame ;-). No flames ensued. Next, holes were drilled and the tanks were pressure washed inside and out. An extra pressure washer wand with a bend in it made this easier. After that, fittings and legs were welded in place, a rust removal solution was used followed by more pressure washing then the tanks were moved into the new house.

Some casters were mounted upside down on timbers to make it easier to roll the tanks. This was handy for marking the layout using a strip of paper folded in fourths to locate the legs 90 degrees apart. It also made it much easier to weld the olets on the ends.

Lots of rust flakes came out while pressure washing. The rust removal solution helped but the dirt separator will still get a workout until all the residue clears. It looks like a lot of rust but the tanks were made with 1/4" thick steel so there should still be plenty left.

All the tanks got 3/4" olets added to the ends for vent and drain connections. They also got 2" olets as near as possible to the ends (top and bottom when standing upright) for the primary water flow. These enter and exit almost horizontally and are increased from the 1 1/4" plumbing to 2" to improve stratification. I used olets instead of merchant couplings (half couplers) because the thicker steel seemed less likely to deform during welding. The olets were welded in with an open root (small gap) to make sure there was complete weld penetration into the joint. I learned how to TIG weld and got some practice welding the feet to the legs before attempting the olets. The welding is not as pretty as that by @warno but it came out OK and there were no leaks. Some usable volume will be lost since the ports are not at the absolute top and bottom of the tanks but it's not a lot.

Use a carbide holesaw if you need to drill more than 2 holes. If you use a carbide burr in a cheap die grinder to clean up the holes, make sure the collet stays tight or you might be fishing the burr out of the tank with a long piece of wire... Maybe more than once...

Even after grinding down to shiny steel some areas still caused problems with porosity when welding. It could have been contamination in the steel, maybe some residual oil from drilling coming out of the tank or maybe some residual zinc if the tanks were galvanized. It took a lot of extra time and effort to grind out the bad areas and redo them. I thought the following would be good enough after cleaning with acetone but that was not always true.

Here's a 2" olet after the root pass. More of the area under the olet shoulder will be built up with a couple of more passes which will also fill in the slight undercut seen in a few places.

The legs are made from angle iron with 6" x 6" x 3/8" plates on the bottom as feet. The 250 gal tank got legs made from 3" x 3" x 1/4" angle iron and the 173 gal tanks got legs made from 2 1/2" x 2 1/2" x 1/4" angle iron. These were not engineered in any way but I expect they are strong enough since it is only 15" from the bottom of the weld on the tank to the foot.

Each tank was leak tested at 70psi by filling with water to within a few inches of full then adding the air through a Schrader valve on top. All the original ports were plugged including the gauge block which had to be welded closed since it was not threaded.

The 250 gal tank probably weighs less than 500# empty. The addition of water will add around 2000#. This 2500# works out to about 625# per leg or 17psi with 6" square feet. The tanks are placed on a piece of 1/2" OSB over 1" of 25psi EPS foam for thermal insulation from the floor. The OSB kept the foam from being torn up while getting the tanks set in place. Metal shims were added as needed to keep the tanks from rocking. You can see the pads under the feet in this photo where the tanks have all been placed in their final locations.

The ICF walls on both sides and the far end are R23 (half on each side of the concrete core) with OSB on them to protect the foam and provide a solid mounting surface. There is an additional R15 of Rockwool around the tanks and some fiberglass in the gaps with R38 between the tanks. More will go above and below after the plumbing is done and leak tested then they will be completely enclosed.

 

[hyfire]

The watts calulator is right on, but i would not take near the limit of the relief valve. I would do those calculations at 25 psi max.

 

[salecker]

Nice job
When i did my tanks i got what was called a flanged fitting here
It had a flatter area to weld to the tanks.
i tested everything i used in my system to 80 psi, filled with water then pressurized with air. Including my cast iron rads.
Then once built i tested the complete system to 80 PSI again, after it was filled with fluid and pressurized with air.

 

[OffGridICF]

The watts calulator is right on, but i would not take near the limit of the relief valve. I would do those calculations at 25 psi max.

Thanks for the feedback. I'm a little concerned at this point but not ready to order another tank yet. My wallet is still scorched from the recent flurry of orders ;-)

The Watts calculator run for 12psi - 28psi, 40F - 190F and 850 gal said the required acceptance was 26.6 gal. The two tanks on order will provide 42.6 gal which seems like about 60% more than required but this turns out to not be relevant (more below). The overall required tank volume of 105.4 gal is the limiting factor and the tanks will provide 106 gal which is very close at 28psi max.

The actual system volume will be closer to 825 gal and it will probably only be run to 185F so there's a little extra safety margin there. Also, only the storage and boiler loop will be at the max temperature. All the radiant loops will only be around 105F max and the radiators 140F max. There is very little volume in the water heater preheat loop. This will reduce the effective system volume to around 810 gal.

The initial fill pressure could also be reduced a little since the maximum height in the system is only 12'. The minimum pressure for 12' should be (elevation in feet / 2.31 feet per psi) + 4psi = 9.2psi, or rounded up to 10psi. The max pressure can then be reduced to 25psi as you suggested.

Re-running the calculator for those conditions, 10psi - 25psi, 40F - 185F and 810 gal, drops the required acceptance from 26.6 gal to 23.8 gal and the required tank volume from 105.4 gal to 91.1 gal which is a much more comfortable margin.

This whole expansion tank business was still a bit confusing to me. Digging deeper and using the Watts tool to generate a plot of max pressure vs. acceptance volume for a fixed expansion tank total volume of 106 gal, 40F - 190F, 12psi min was helpful. It turns out that the tanks on order will only accept 42.6 gal once the pressure reaches about 40psi, far above the 30psi PRV limit. I also ran the numbers for a 106 gal expansion tank, 40F - 185F, 10psi min for comparison. Both with 825 gal water total.

With the ability to make these changes if needed, it seems like the tanks on order should work OK. If necessary, another smaller tank can be added later. I'll add another tee and cap it off just in case.

 

[OffGridICF]

Some progress has been made on the plumbing. All four tanks are in place along with the boiler. The boiler is sitting on some 3" tall blocks to get it up off the floor a little.

All four tanks are now connected in series. The joints are sealed with Loctite 55 plus a little pipe dope. I'm waiting on another roll of the Loctite 55 - the initial roll of 164' didn't last too long with the 2" pipe and fittings. Soldering the 1 1/4" copper with a MAP gas torch was pretty easy after a thorough cleaning and fluxing. Soldering the valves in place made me a little nervous but all the info I found says they can take the heat. They were cooled with a wet rag after the solder solidified.

I ended up using copper in more places than expected in order to make things line up. I had figured on 3/4" insertion depth for most of the black iron pipes and fittings but it turned out to me more like 1/2". The 2" ports on one of the tanks were rotated a little relative to the legs which tightened up the spacing, too. All but the last tank vent are in place. They will stick out of the insulating enclosure to allow access.

The cold return was one of the most challenging bits to assemble. Assembling the 2" pipe would have been easier with an even bigger pipe wrench. It's all put together along with the check valves for the circulator loop returns. These are DZR brass rated for 250F with stainless springs and all brass internals except for the valve seat.

It will be on toward the boiler tomorrow after the new roll of Loctite 55 arrives. Drawing everything out in advance made the assembly much easier so far...

 

[hyfire]

What are you using to seal your pipe unions? I use loctite 510 flange sealant works great.

 

[OffGridICF]

What are you using to seal your pipe unions? I use loctite 510 flange sealant works great.

I just put a little Vaseline on the threads and the brass mating face then cranked it down. If they leak, I'll fall back to the Loctite 510 or Permatex 51531 which appears similar. I'll flush the system so that will provide a chance to check for leaks before it's drained and refilled.

Speaking of flushing the system, who should I talk to about water testing and any necessary chemicals? There are some references to woodboilersolutions.com in the forum but it appears that they are no longer in business.