TARM SETUP QUESTION

[jimde]

I will be installing my new tarm solo 60 in a insulated outbuilding with 1200 sq/ft of infloor tubing. My boiler is 150' from my house which is 2300 sq/FT with propane forced air. My furnace is about 6 feet lower than my boiler. I was going to order my thermopex at 1.25 inch but wanted some input from you boiler boyz. I am not a plumber and I dont want to screw this up. Is 1.25 big enough. I was able to obtain two 350 gallon hot water storage tanks which will be my storage that I will keep in the heated outbuilding. Looking for advice on my setup. What pumps will work without running me broke. How large of a expansion tank for 700 gallons of pressurized storage. GO PACKERS BUT STILL LOVE BRETT

 

[jebatty]

I suggest you do some homework on planning a hydronic system. Your questions all are fair, but you would be well served by doing some reading to develop basic knowledge of how a system should be planned to meet your needs. If you don't feel able to do that, then you should consider hiring a HVAC contractor experienced in hydronic system design and installation. The following comments may or may not be helpful, depending on how much you know.

As to 1.25" pex, the answer is yes/no/maybe. Do a heat load calc to determine how many btu's you need/want to move at the target delta-T. This will tell you how many gpm's need to move through your line. 1.25" pipe generally is rated at 17 gpm maximum. If you need to move more water, then you need larger pipe. Next do a pump head calc at the required gpm's on the system the Tarm will be feeding. Pick a circ that can supply the required gpm's at about the middle of the pump curve for the circ. Generally, you want to plan your system to require lower rather than higher pump head. Larger pipe = lower pump head than smaller pipe at the same gpm's. Pump head increases by a little less than the square of the flow increase. Circs that can provide the needed gpm flow at low head are usually less expensive to buy/operate than circs that can provide the needed gpm flow at high head.

I believe Tarm/Bioheat has recommendations on maximum length of pipe at various pipe sizes. You probably should follow those recommendations at a minimum.

 

[jimde]

Thank you for your valuable input. The problem I have is there seems to be such a difference of opinion between OWB men and gassifier men. The hydronics people around here ( northeastern wisconsin) are unexprienced,but yet intrigued by gasification.

 

[Singed Eyebrows]

Hi Jimde; Wisconsin has some sort of code/law that if you run under 15 psi your system does not need to be monitored. This is told to me by the people manufacturing my 720 gallon pressure storage. They are in Wisconsin also. I'll be running at about 12 psi at full expansion according to Amtrol. My tank is a 500 liter full acceptance replacable bladder tank with 10 psi precharge. Even if I need to go to 12 I'll still be under. I could not get the particulars of this law. It appears to apply to every pressure vessel though. I decided to not take a chance & do it right. 132 gallons of acceptance will translate to about 2 psi increase over fill pressure as I'm told. It appears that even running an open tank in the attic will not avoid this as your boiler is a pressure vessel & it might run past 15 psi although this could probably be brought down under though with some modification. Randy

 

[jebatty]

It appears that even running an open tank in the attic will not avoid this [15 psi pressure limit] as your boiler is a pressure vessel & it might run past 15 psi although this could probably be brought down under though with some modification. Randy

A boiler pressure vessel designed with an open expansion tank in the attic cannot exceed the psi developed by the height of the water column. No amount of modification to the boiler will change that.

An open tank in the attic will result in system pressure equal to the vertical distance between the top of the water column and a lower point where pressure is measured divided by 2.4. Example: one story house on a slab with 8' ceiling, assume open tank overflow 4' above the ceiling, assume boiler at floor level: psi = 12 / 2.4 = 5 psi. Assume 2 story house with basement, 10' ceilings on both stories, 8' bsmt ceiling, open tank overflow 4' above the ceiling in the attic: psi = 32 / 2.4 = 13.3 psi. At a total height of 36', you are over 15 psi (no matter what modification you make to the boiler).

That's one reason why most hydronic expansion tanks with a bladder come pre-pressurized at 12 psi, which translates to moving water up to 29 feet, which is adequate for most single family home hot water applications, with the boiler in the basement. If your application is, for example, single story 9' ceiling, boiler at floor level, and radiant floor heat, you need practically 0 pressure to move water through the system.

CAUTION Wood pressurized boilers are designed to operate with a minimum pressure, as pressure raises the boiling point of water. You don't want to operate below a pressure which results in the water boiling in the boiler. I'm going to assume, but I don't actually know, that minimum system pressure of 12 psi is adequate to prevent boiling. At 12 psi, the boiling point is about 240F.

 

[Singed Eyebrows]

Hi Jim; Thanks for the info. My thought was that the pressure of the water colume could be regulated if it went over 15 psi, this might be impractical though. I'm only going to raise water 12 feet so the 10 psi charge should be ok & 190 is the max I will run. My large expansion tank is the one reccomended by Atmos so they apparently don't want a lot of pressure increase during expansion. Thanks Jim, Randy

 

[jimde]

Would either of you be able to tell me how large of a expansion tank I will need for 750 gallons of pressurized storage. I am slowly trying to gather all components for my system. THANK YOU

 

[jebatty]

You have to add the gal of storage, plus gal in the boiler, plus gal in the system. If you have 4% of that total, that should be OK. But be sure the acceptance volume of the tank is that 4%, not total volume. Some use 5% rather than 4%, but probably a little overkill.

 

[Singed Eyebrows]

Jims calculations will work well & for most members, end of story. They will probably not keep you under 15 psi though. I will try to find out more about Wis pressure vessel rules for you. Out east a few states have some tough ASME standards for pressure vessels & members are not just disregarding these. You are going to run the same size storage as I will & I'll have 132 gallons of acceptance. As jim says make sure you don't confuse tank size with acceptance. 132 gallons acceptance would be a good start & you could add some more if needed. You have other options as Nofossil has posted & even pressuring a plain tank. 132 gallons acceptance won't be cheap in new expansion tanks. Good luck, Randy

 

[jebatty]

...will probably not keep you under 15 psi though.

Very true. I have 1000 gal storage, plus about 55 gal in the Tarm, plus quite limited plumbing. When my tank is at 65F, I have practically 0 psi. When the tank is 190F, psi is in the 20-25 range. I have the Extrol SX-160V pressure tank, advertised at maximum acceptance of 46 gal. I did reduce the pre-charge pressure to 8 psi, thinking that it might increase the acceptance volume a little. At 25 psi, one of my system 30 psi relief valves starts to weep a bit. I may have to add an additional expansion tank.

I'm surprised at the WI rule you mention. We have a rental house with an LP hot water boiler, and my HVAC tech said to keep the pressure at 20 psi. Go figure that with a 15 psi rule!

 

[jimde]

If I draw a detailed drawing of my building layouts and where the boiler and tanks are located would I be able to send it in to TARM or BIOHEAT and have them desgn my plumbing setup. I could include the results of my heat calc, size of my furnace, sq/ft of heated space and elevations.

 

[Gooserider]

If I draw a detailed drawing of my building layouts and where the boiler and tanks are located would I be able to send it in to TARM or BIOHEAT and have them desgn my plumbing setup. I could include the results of my heat calc, size of my furnace, sq/ft of heated space and elevations.

Don't know, you could ask them for sure...

We could also try taking a shot at it here. I doubt that we'd be willing / able to do loop layouts and such detail work, but certainly we could probably work out a nice block diagram of how to do the overall system.

Another option or two that might be worth considering is that some of the pex and other supply places will do design work for you in exchange for a commitment to purchase the supplies from them.... Also some of the boiler and plumbing outfits have software that can be downloaded or requested, which will let you do most of the stuff yourself - obviously that software will be written to suggest that company's products, but in most cases you could substitute alternatives without to much difficulty.

A last option, is that John Siegenthaler at Hydronicpros.com (The "Siggy" we frequently refer to) sells a lot of different software packages along with his books, which are heavily relied on by the pros in the industry. His stuff is a bit pricey for one time use, but he does offer limited function trial downloads of some of his products that I understand may be enough to get through the job for a homeowner...

Gooserider

 

[jimde]

I want to start aquiring my interior plumbing parts. Will 1.25 inch copper be a wise choice for plumbing the two pressurized storage tanks in tandom. I appreciate any help or comments.

 

[Gooserider]

I want to start aquiring my interior plumbing parts. Will 1.25 inch copper be a wise choice for plumbing the two pressurized storage tanks in tandom. I appreciate any help or comments.

It might be, however you really need to do the number crunching to be sure... If you do the search, you can find all the math formulas that you need to figure out pump choices, plumbing sizes and so on...

For much of the system, what you will want is a detailed heat loss calculation for your loads - essentially so that you can see how much heat each circuit in your setup will need to be able to provide. If you look at the "tidbits" sticky at the top of the area list, you will find a link to a tech paper from TACO that gives a pretty straightforward process for figuring out the house side of the system.

For the boiler - storage section, however, what you really want is the ability to pull heat out of the boiler and transfer it into storage as fast as the boiler can make it. While you MUST keep the boiler above condensation temps as much as possible, the cooler you can run it while staying above that point, the more efficiently you will get heat transfer from the boiler HX tubes into the water. Also the greater the difference between the boiler in and out temps, the better. Both rules imply that within reason, the larger the pipes in the entire boiler-storage loop the better. The question is what is "within reason", and that is something you have to crunch the numbers to be sure about... The other limiting issue to some degree is what size are the fittings on your boiler and tanks - it doesn't help to have big pipes going into small fittings, so that can be a factor. Most of the boilers have ports that are more than large enough, but the tanks people get are more variable, so that may be worth figuring out first...

Gooserider

 

[jimde]

Would you do me a favor and go to Hamilton Engineering website. Under products you will find " storage tanks" with a drawing link on the bottom. I have the HET350 tanks. I believe you will find this very interesting and understand my situation. Thank You

 

[Gooserider]

Would you do me a favor and go to Hamilton Engineering website. Under products you will find " storage tanks" with a drawing link on the bottom. I have the HET350 tanks. I believe you will find this very interesting and understand my situation. Thank You

You didn't post a link, but I found this page which I hope is the right one... If so, it looks like you have 2.5" ports on the tanks as I'm reading the chart. That's probably much bigger than you need, but I'm not sure 1.25 is quite big enough... While I occasionally crunch numbers out of my own curiosity, I prefer to leave that part as an "exercise for the student"

You have the boiler and tank specs plus (hopefully) some idea of your piping layout and thus pipe lengths, and I gave you a pointer to the equations... Assume you have no house load, and want to dump 100% of the output of your boiler into storage. Solve for pump size and volume needed to move the maximum rated output of your boiler to the storage tanks... You will almost certainly come up with several solutions, using either a larger, more power hungry pump and smaller / cheaper pipes, or a smaller, more efficient pump, and larger / more expensive pipes... You have to pick the balance you prefer between up front material costs, and long term operatng costs... One of the "fun" parts about this stuff is that there is usually no single "right" answer, instead you have to deal with a series of compromises in order to get acceptable performance at an acceptable price - you are the only one that can really make those choices...

Gooserider

 

[jimde]

Thank you for taking the time to check on this. You are correct, the fittings are 2.5". I will probably decrease them down to 1.5". I am going to try to avoid the larger and less efficient pumps. I hope having these manufactured pressure vessels is worth what I had to do to get them.

 

[hayrack]

1 1/2 fittings are tough to find and are expensive especially when you use copper. 1 1/4 is very standard in the industry. Your mixing valve will most likely be 1 1/4 along with other valves and fixtures. Most supply and return manifolds will end up being 1 1/4 also. I think there are plenty of people using 1 1/4 for similar installs.

 

[RobC]

I just did some 1.25" and 1.5" copper work. The up charge between pipe sizes is about 30% and the fittings are 50% ( $4 goes to $6 ea for example ). Commercial plumbing outlets have any sizes you want and many fitting configurations not normally seen that are very useful. The Termovar mixing valve is indeed 1.25" however when you look inside it's about 1". I'm not sure of the hydraulic theory involved but having a point restriction in one spot, just upstream of a circulator, has little effect on the systems overall performance. Some of these devices are looking for a pressure drop to make them work correctly.
Rob

 

[jebatty]

Will 1.25 inch copper be a wise choice for plumbing the two pressurized storage tanks in tandom [boiler is Tarm Solo 60].

The rule of thumb on pipe gpm's is 1"= 8 gpm, 1.25" = 14 gpm, and 1.5" = 22 gpm. While the Solo 60 is rated at about 200,000 btu's, actual output, based on my experience with the Solo 40, is that, except for relatively brief peak burns or very high delta-T's, it will be unusual for you to achieve that output. I would expect your normal range of output to be 65-85% of rated capacity over a typical burn.

You say the storage will be in your out-building with the Tarm, so pipe length between the Tarm and storage will be very short. If you use 1.25" black steel pipe between the Tarm and the storage, assume total pipe equivalent length of 50', head loss is a little less than 3' at 14 gpm and a little less than 4' at 17 gpm. At these low head's you can use an inexpensive, low power consumption circulator without difficulty. A Taco 007 will move 17 gpm at 4' head and cost about $50 and use 80 watts. I mention Taco only because I have the circ charts stored on my computer for Taco, and it is easy for me to refer to them. Other brand circ should be satisfactory also.

Using a delta-T= 20F, 14 gpm = 140,000 btu, and 17 gpm = 170,000. Double this at delta-T = 40F. IMO, based on these assumptions, 1.25" plumbing between the Tarm and storage is very adequate. If you do have an occasional boiler idle, it will be brief and of little consequence. If you plan for consistent delta-T of less than 20F, then you need to move more water, which you can do with a higher capacity circ.

Plumbing between the out-building storage and the house, and plumbing within the house, is a different matter, and depends greatly on your heat loss calc for the house. Assuming 350' pipe equivalent length between the out-building and the manifold in the house, 1.25" pipe will have a little over 18' of head loss at 14 gpm, which is 140,000 btu at delta-T = 20F. A Taco 0011 may handle this, and a 0013 will more than handle this. Based on these assumptions, if your heat loss calc is 140,000 btu or less, 1.25" pipe should be OK.

If your house is low temp radiant, and you don't need water at 160F or greater, then you may be in an even better situation, because you can move higher temp water from storage and mix down at the house, the result being lower flow rates between storage and the house.

IMO your biggest decision is the plumbing between the out-building storage and the house, and you absolutely need to do a heat loss calc for the house to determine how many btu's, at what temp, and at what flow rate are required. With your distance, you do not want to be in a position of under-piping this pipe run based on your need; but on the other hand, it is very expensive to over-pipe if you don't need the capacity.

From your posts it sounds to me like you are winging it, but winging less and less as you learn more and more, just like many of the rest of us. With the Solo 40 I initially plumbed with 3/4" out of ignorance, and then replaced with 1". Fortunately, my plumbing run was short and the re-do was only a couple of hundred $$. 1" is plenty adequate for the Solo 40 in my situation, and yes, I do have an occasional idle at high return from stratified storage temps, but as mentioned, I regard that of no consequence.

 

[jimde]

Wow ,thats some good info. I am starting to grasp the importance of proper heat calculations. I am still waiting for the results. Without sounding like a idiot can I assume that the delta T is established after the heat calc reaveals how many btu,s per hour are needed to supply the home. Could this be the order of importance.
1 Obtain heat calc for proper BTU
2 Figure pipe from boiler to tank
3 Figure pipe from tank to home ( thermopex) for proper flow for required GPM
4. Calculate head loss due to pipe distance and diameter
5 Size circulators for proper flow
6 Establish Delta T

I hope you all dont get impatient with me as I proceed. Please put my list in the proper order.

 

[RobC]

Jim thank you for the explanation of rated output, realistic output and corresponding pipe size.
You mentioned your 3/4" to 1" pipe swap. I had this same issue with and OWB that I use to have. I got the old 1" will work fine deal. My problem was the lines ran under driveway, garage, etc. and no way to replace them. I was able to live with it but it wasn't great.

Thanks for jumping in, Rob

 

[Gooserider]

Wow ,thats some good info. I am starting to grasp the importance of proper heat calculations. I am still waiting for the results. Without sounding like a idiot can I assume that the delta T is established after the heat calc reaveals how many btu,s per hour are needed to supply the home. Could this be the order of importance.
1 Obtain heat calc for proper BTU
2 Figure pipe from boiler to tank
3 Figure pipe from tank to home ( thermopex) for proper flow for required GPM
4. Calculate head loss due to pipe distance and diameter
5 Size circulators for proper flow
6 Establish Delta T

I hope you all dont get impatient with me as I proceed. Please put my list in the proper order.

You are starting on the right track... The initial step as far as I'm concerned is to break down the system into major parts, and figure out what different heat flows are needed... I define a heat flow as "different" if it could involve a different amount of heat from other flows, if it follows a different path, and if it doesn't have to take place at the same time as other flows...

In your setup you have a boiler, storage, and a house load, with the major flows being from the boiler to the storage tank, and from the storage tank to the house load.

For each flow, you need to figure out the BTU's involved, either how much has to be moved away from or to a given point. Your house load needs to have BTU's moved into it, the boiler needs to have BTU's moved out. These are separate calculations as in your steps two and three, but it doesn't really matter which one you do first.

There is a paper from TACO that goes into the details of calculating the pipe sizes and pumps needed. However they need to have a delta-T defined in order to start, so you need to move #6 up to second place on your list.

So for each of the boiler - storage, and storage-load loops, you need to:

1. Figure out the BTUs/hr that need to be moved. This is essentially your house demand, or about 75% of the rated boiler output.
2. Find your delta-T for each loop. If starting from scratch there are ways to maximize this, but if you are tieing into an existing system you are somewhat limited to what is already there. Unless you have reason to assume a different number, I would probably go with 20*F
3. Using the equation from the Taco paper, figure the GPM flow rate needed.
4. Using the GPM flow rate, figure out what pipe sizes are appropriate - use the charts in the Taco paper, and from other sources for materials / sizes they don't mention. Find the sizes that give 2-4 feet per second flow velocities. You will probably find several pipe sizes that work.
5. For each pipe size, determine the equivalent pipe circuit length, head loss, and appropriate circ.
6. Again for each pipe size make a rough estimate of costs to do the job using that size of pipe for fittings, circ, etc... Also look at the operating costs for the chosen circ (at the appropriate speed setting if using a multi-speed circ) - balance the tradeoff between increased initial install costs for a larger size pipe, vs. the reduced lifetime operating costs of the lower powered circ that you will need with the larger pipe...

Gooserider

 

[jimde]

Thanks for the reply, but how can I establish a deta T without the the system running and knowing what my water temps are at the desired flow? Or are you basing the delta 20 as a preferred industry standard? Im concerned about this because my boiler is rated at 198,000 btu and my current home has a 80,ooo btu furnace. As I stated before I could also plumb a water to air exchanger in my 700sq/tf attached garage to use up more btu. All this plus 1200ft of infloor tubing in the shop which I assume has a seperate delta T, and circ. Thats my hangup. Thank you all.

 

[Gooserider]

Thanks for the reply, but how can I establish a deta T without the the system running and knowing what my water temps are at the desired flow? Or are you basing the delta 20 as a preferred industry standard? Im concerned about this because my boiler is rated at 198,000 btu and my current home has a 80,ooo btu furnace. As I stated before I could also plumb a water to air exchanger in my 700sq/tf attached garage to use up more btu. All this plus 1200ft of infloor tubing in the shop which I assume has a seperate delta T, and circ. Thats my hangup. Thank you all.

It is possible to calculate the delta-T, and I've seen stuff on how to do it, but I don't have the links offhand... However picking the 20*F number will at least get you in the right ball park - if it's a bit more or less that won't be a big problem for the plumbing sizes...

I also wouldn't throw up extra heat exchangers just to "use up" BTU's - you want to save them for heating places where you WANT the heat...

As we said before, figure about 75% of the rated capacity on the furnace when planning the plumbing - IOW, size the boiler-storage loop based on a 20* delta-T and 150,000BTU heat supply.

While you are going to be better off with a precise heat-loss calculation, especially considering that many people get existing equipment put in that's oversized, if your current furnace seems to be a good match to your home's needs, then using 20* and 80,000 BTU's for the storage-house loop would work.

And yes, the storage - shop loop would be it's own calculation, with the important note that if the two loops share any common plumbing, then the shared portion should be sized based on the combined total of the two loads.

Gooserider