Garn hydronic design

[Antman]

That was some of my feeling also on the pressurized topic - but I didn't really know so was waiting to see if you'd get more input on it.

And, to put it in 'For Dummies' talk on another thought on it - I was also thinking your water wouldn't stay in your boiler (& system) with the rest of the system so far above it. I could envision it running out of the top of the boiler.

I think with that much underground I would heavily consider spraying in trench - depending on what kind of a deal you can get from a local spray foam guy. Usually the cost/foot might come down a bit with more footage to do.

Also one more on your DHW comment - DHW is a very small part of a heating load compared to what your other HXs & houses will be using. So I would expect you could heat your DHW pretty well no matter what else you do. I can heat our DHW for a month with resistance electric for what it would cost to heat our house for only one day the same way. Unless of course you are rather off the charts with your DHW use.

If I can find 300' rolls of 2" barrier uponor or equivalent 1.6" ID I probably will trench and foam. It would take quite a bit longer but I have the patience and manpower to see it through. I am confident we have a water tight solution with bluemax if it comes to that. Otherwise, I may just have to bite the bullet and buy logstor preinsulated dualpex 1-1/2" (1.6" ID). Admittedly, logstor would be much easier to install and perhaps last longer and minimize the aging of the PUF with their special membrane under the HDPE jacket.

Bluemax is a barrier to radon but I couldn't find a way to compare diffusion coefficients between radon and cyclopentane which is the gas in Logstor PUF that equilibrates with atmospheric air in the absence of a proper barrier. I'm not sure what the insulating gas would be in the PUF I can resource. All I know for sure is radon is an element and cyclopentane is a C5H10 molecule so perhaps an elemental radon barrier such as bluemax would also be a barrier to a larger cyclopentane molecule assuming molecules are generally larger than elements. Unless someone can provide a definitive reference, I'd just have to assume any PUF I have sprayed would likely age and lose 15% of its initial insulation value. I think spraying thicker than logstor's thickness could offset this loss in R value. What is important is ensuring water tight underground lines which I will have to demonstrate to everyone using XPS with bluemax-impregnated fiber when I get the time.

 

[Antman]

That was some of my feeling also on the pressurized topic - but I didn't really know so was waiting to see if you'd get more input on it.
more complicated but seems worth if for less corrosion

And, to put it in 'For Dummies' talk on another thought on it - I was also thinking your water wouldn't stay in your boiler (& system) with the rest of the system so far above it. I could envision it running out of the top of the boiler.
Again, worth it as the highest point in the system will be 21' above the Garn slab

I think with that much underground I would heavily consider spraying in trench - depending on what kind of a deal you can get from a local spray foam guy. Usually the cost/foot might come down a bit with more footage to do.
really comes down to availability of 2" 1.6 ID in minimum of 250', may have to take a hit on the logstor 2-1/2" dualpex

Also one more on your DHW comment - DHW is a very small part of a heating load compared to what your other HXs & houses will be using. So I would expect you could heat your DHW pretty well no matter what else you do. I can heat our DHW for a month with resistance electric for what it would cost to heat our house for only one day the same way. Unless of course you are rather off the charts with your DHW use.

is there a difference b/w resistance electric and local utility electric? Wouldn't necessarily apply at this time until we get house 1 done and start on house 2 later which has electric DHW. House 1 has 3 50 gal LP DHW tanks. Kids take hot baths every night in large jacuzzi tubs and wife and I take reasonably long showers each day, kids will probably take longer showers as they grow up. Hot water taps run left open frequently as we do not have hot water recirc in place at this time...

 

[Antman]

That was some of my feeling also on the pressurized topic - but I didn't really know so was waiting to see if you'd get more input on it.
more complicated but seems worth if for less corrosion

And, to put it in 'For Dummies' talk on another thought on it - I was also thinking your water wouldn't stay in your boiler (& system) with the rest of the system so far above it. I could envision it running out of the top of the boiler.
Again, worth it as the highest point in the system will be 21' above the Garn slab

I think with that much underground I would heavily consider spraying in trench - depending on what kind of a deal you can get from a local spray foam guy. Usually the cost/foot might come down a bit with more footage to do.
really comes down to availability of 2" 1.6 ID in minimum of 250', may have to take a hit on the logstor 2-1/2" dualpex

Also one more on your DHW comment - DHW is a very small part of a heating load compared to what your other HXs & houses will be using. So I would expect you could heat your DHW pretty well no matter what else you do. I can heat our DHW for a month with resistance electric for what it would cost to heat our house for only one day the same way. Unless of course you are rather off the charts with your DHW use.

is there a difference b/w resistance electric and local utility electric? Wouldn't necessarily apply at this time until we get house 1 done and start on house 2 later which has electric DHW. House 1 has 3 50 gal LP DHW tanks. Kids take hot baths every night in large jacuzzi tubs and wife and I take reasonably long showers each day, kids will probably take longer showers as they grow up. Hot water taps run left open frequently as we do not have hot water recirc in place at this time...

Thanks for the interest -- 23 days of riding, 25 days total. Shortest mileage day was 23 and longest was 97. Average/day was 65 miles. Temperatures ranged between a low of 28F (two mornings) and a high of 94F. The trip was solo, self-supported. Bicycle plus packs, gear, food, water was about 105 pounds. An amazing adventure for a 66 year old guy. This link covers a quick summary of most of the trip: Rolling

I am narrowing down on a destination for another trip in 2016.

For anyone who doesn't ride out there, that is one hell of an impressive ride! I'm in pretty good shape, and I cannot fathom how I could ever pull that off without riding many years almost daily.

 

[Antman]

That ID indeed is important, glad you noticed that.

Keep in mind that although the Garn WHS2000 carries a 325,000 btuh maximum output, it probably is unrealistic to expect to see that for extended periods of time. My rule of thumb for gasification wood boilers is that average output over a burn is about 70% of rated output. Also keep in mind the Garn is best operated in batch burn mode: burn a load (or a couple of loads), let the fire go out, clean the ash and dead coals, and then the Garn is ready for another batch burn.

A couple of years ago I did extended and intensive data logging on a Garn WHS3200, rated at 700,000 btuh. Over an 18 hour period I was able to keep the Garn fueled at the rate of 100 lbs of wood per hour, and by the end of the period the Garn had to be allowed to burn out because the firebox bed was loaded with coals and additional wood could not be added. Also, actual output over the 18 hour period was measured at 500,000 btuh, which is almost exactly 70% of the rated output.

Also keep in mind that if you need consistently very hot water, 160F minimum, even as low as 140F minimum, your Garn will need to be fired pretty consistently to provide that hot water. That also would be true of other gasification boilers. If you can use water down to 120F or lower, then you have a lot more flexibility in firing your boiler. Of course, heat loads play a big role in this.

So 70% 0f 325MBH is 227.5MBH. In the Garn Design Manual I see 1.28ID and a 30F dT at 15GPM can deliver 225MBH which could be performed with 1-1/4" logstor. The problem is that there are not a lot of WTAHX from which to choose and I believe most of them have 20F or less dT. Is anyone aware of WTAHX with 30F dT? If not, I guess I'm still looking at 1-1/2" logstor.

 

[Antman]

I really appreciate everyone's feedback and support!

Thank you, thank you, thank you!

It is helping me clarify some of my own preconceived notions I have developed after reading the Garn Design Manual. I'm looking forward to reading the books from Dan H. I'm hoping to get more clear how 3/4" lines and/or the 8000gal tank car could work. I can't see how enough BTU's could get underground to satisfy the 150MBH load with all WTAHX calling for heat at the same time. Is the buffer tank the key to 3/4" lines working and, if so, I suppose it has to be adjacent to house 1 and not the Garn barn? If it could go by the Garn barn that is doable but I can't realistically think of a way to put an 8000 gal tank car next to house 1. And, once all 8000gal are up to 160F, am I correct in thinking it extends my time between burns four-fold?

Please forgive my lack of experience drawing diagrams, but could you mentor me on how the 3/4" design needs to be altered?

 

[maple1]

is there a difference b/w resistance electric and local utility electric? Wouldn't necessarily apply at this time until we get house 1 done and start on house 2 later which has electric DHW. House 1 has 3 50 gal LP DHW tanks. Kids take hot baths every night in large jacuzzi tubs and wife and I take reasonably long showers each day, kids will probably take longer showers as they grow up. Hot water taps run left open frequently as we do not have hot water recirc in place at this time...

No. Well, sorta. Resistance electric heat uses local utility electric to heat water via elements. As opposed to say a heat pump, which uses utility electric to heat via refrigeration techniques.

My DHW tank heats my DHW in the summer the same way as my backup electric boiler heats my house when there is no wood fire going on. Only difference is the DHW tank uses one 4500w element at a time, whereas the electric boiler has 4 of them going, as needed.

You do have more hot water usage than we do. Up until last summer, we had 2 adults & 3 teenagers. No baths but showers every day (usually). But overall, with checking out power bills & heat useage, our space heating demand is about 30x what our DHW demand is, in kwh. Roughly estimating.

 

[Antman]

I'm kind of wondering about those heat loads.

150,000 btu/hr seems like a lot for a place that doesn't get colder than 20f.

From my burning habits here the past couple of years, I think I'm in the area of somewhere between 500,000 & 600,000 btu per day. It was -18c here this morning (0°f). It is now -12c (10°f). I'm in a 20 year old 2700 sq.ft two storey (plus 1500 sq.ft. basement), on an open hilltop.

Unless I missed something along the way...

House 1 is 10 years old and friend of the family is one of the bigger insulation guys in the area. He came by last winter on one of those 20F days and looked at the windows and walked through the attic. Said the place was well insulated and stated that the wood windows were very good because he couldn't feed any cold air coming through.

I did the heat loss calculation twice, once using slant fin, and again using the Taco hydronic design software. I input the data from the house plans as accurately as I could and came up with 150MBH using slant fin and I think 135MBH using Taco software. I guess I just used the higher number because it more closely matched the output ratings on the LP furnaces:

BTUH output on 2.5 ton LP furnace with the 14x20 supply plenum listed at 30,000, 80% efficiency
BTUH output on 4 ton LP furnace with the 17x20 supply plenum listed at 48,000, 80% efficiency
BTUH output on 5 ton LP furnace with the 20x20 supply plenum listed at 80,000, 80% efficiency, (i.e. 100,000 BTUH input)

30,000 + 48,000 + 80,000 = 158,000 BTUH output when all furnaces calling for heat

The biggest factor is probably the 10' ceiling downstairs and 9' ceilings upstairs. I am also in the middle of 40 acres up on a hill so winds steal a lot of the heat by (?convection)

This is the little lumberjack and my Chesapeake Bay Retriever winding up a day on the Garn Barn.

 

[maple1]

I really appreciate everyone's feedback and support!

Thank you, thank you, thank you!

It is helping me clarify some of my own preconceived notions I have developed after reading the Garn Design Manual. I'm looking forward to reading the books from Dan H. I'm hoping to get more clear how 3/4" lines and/or the 8000gal tank car could work. I can't see how enough BTU's could get underground to satisfy the 150MBH load with all WTAHX calling for heat at the same time. Is the buffer tank the key to 3/4" lines working and, if so, I suppose it has to be adjacent to house 1 and not the Garn barn? If it could go by the Garn barn that is doable but I can't realistically think of a way to put an 8000 gal tank car next to house 1. And, once all 8000gal are up to 160F, am I correct in thinking it extends my time between burns four-fold?

Please forgive my lack of experience drawing diagrams, but could you mentor me on how the 3/4" design needs to be altered?

I don't know what the implication for 3/4" lines was. But if it was for the underground, I would forget about that - you could never move enough water for your loads.

And sure, going to huge excessive storage like that would extend time between burns. But it would also seriously increase the load on the Garn when it needs charged again, and from what I have read about the Garn, it might not cope very well - needing periods of shut down for cleaning out the ash. If you were looking at needing longer periods of continuous burning (as opposed to batch burning in periods of a load or two), you might be better served by a different boiler of the downdraft variety. But sounds like it's too late for that kind of a major component change.

 

[jebatty]

My brain is a bit dense this morning, but I don't see how 3/4" pex @ 4 gal/min will work, and Leon is going to have to explain that with a diagram, math, pump head, circulator specs, etc. for me to see how it could work.

 

[maple1]

House 1 is 10 years old and friend of the family is one of the bigger insulation guys in the area. He came by last winter on one of those 20F days and looked at the windows and walked through the attic. Said the place was well insulated and stated that the wood windows were very good because he couldn't feed any cold air coming through.

I did the heat loss calculation twice, once using slant fin, and again using the Taco hydronic design software. I input the data from the house plans as accurately as I could and came up with 150MBH using slant fin and I think 135MBH using Taco software. I guess I just used the higher number because it more closely matched the output ratings on the LP furnaces:

BTUH output on 2.5 ton LP furnace with the 14x20 supply plenum listed at 30,000, 80% efficiency
BTUH output on 4 ton LP furnace with the 17x20 supply plenum listed at 48,000, 80% efficiency
BTUH output on 5 ton LP furnace with the 20x20 supply plenum listed at 80,000, 80% efficiency, (i.e. 100,000 BTUH input)

30,000 + 48,000 + 80,000 = 158,000 BTUH output when all furnaces calling for heat

The biggest factor is probably the 10' ceiling downstairs and 9' ceilings upstairs. I am also in the middle of 40 acres up on a hill so winds steal a lot of the heat by (?convection)

So House 1 has 3 furnaces? I might think about putting some sort of run-time meters (hour meters?) on them if possible to see how much they are actually running, say during the course of a typical month of winter. 150,000btu/hr is a huge heat load. Not saying it's not right - just seems very big. Haven't seen the house, either, though.

 

[Antman]

No. Well, sorta. Resistance electric heat uses local utility electric to heat water via elements. As opposed to say a heat pump, which uses utility electric to heat via refrigeration techniques.

My DHW tank heats my DHW in the summer the same way as my backup electric boiler heats my house when there is no wood fire going on. Only difference is the DHW tank uses one 4500w element at a time, whereas the electric boiler has 4 of them going, as needed.

You do have more hot water usage than we do. Up until last summer, we had 2 adults & 3 teenagers. No baths but showers every day (usually). But overall, with checking out power bills & heat useage, our space heating demand is about 30x what our DHW demand is, in kwh. Roughly estimating.

So in my case, 150MBH/30 = 5MBH or 5,000 btuh which is consistent with page 7 of the Garn Design Manual for one DHW tank, but I have 3 50gal tanks so maybe I'd fall somewhere between 5,000-15,000 btuh range?

 

[Antman]

I don't know what the implication for 3/4" lines was. But if it was for the underground, I would forget about that - you could never move enough water for your loads.

And sure, going to huge excessive storage like that would extend time between burns. But it would also seriously increase the load on the Garn when it needs charged again, and from what I have read about the Garn, it might not cope very well - needing periods of shut down for cleaning out the ash. If you were looking at needing longer periods of continuous burning (as opposed to batch burning in periods of a load or two), you might be better served by a different boiler of the downdraft variety. But sounds like it's too late for that kind of a major component change.

Yes, I actually don't mind firing multiple times per day if required. Just hoping to minimize loading any way possible in case I have to rely on someone else to do it.

 

[Antman]

So House 1 has 3 furnaces? I might think about putting some sort of run-time meters (hour meters?) on them if possible to see how much they are actually running, say during the course of a typical month of winter. 150,000btu/hr is a huge heat load. Not saying it's not right - just seems very big. Haven't seen the house, either, though.

I posted a pic of the lay of the land. Run time meter is a great idea. Now is a perfect time to do it. Thank you.

 

[maple1]

So in my case, 150MBH/30 = 5MBH or 5,000 btuh which is consistent with page 7 of the Garn Design Manual for one DHW tank, but I have 3 50gal tanks so maybe I'd fall somewhere between 5,000-15,000 btuh range?

Having that many tanks isn't directly correlated to how much DHW is used. Similar to having 150,000 btuh of furnace capacity might not mean you need that much - how active they actually are for the loads they are meeting is the teller of the tale. Since you are at the right place in the designing stage for it - I would seriously try to accurately monitor how much time all of your heating devices actually spend heating.

 

[Antman]

Having that many tanks isn't directly correlated to how much DHW is used. Similar to having 150,000 btuh of furnace capacity might not mean you need that much - how active they actually are for the loads they are meeting is the teller of the tale. Since you are at the right place in the designing stage for it - I would seriously try to accurately monitor how much time all of your heating devices actually spend heating.

understood. I'm all for knowing if maybe I don't need those 1-1/2" logstor dualpex after all. do you have a website for the device, if not I'll call my brother in law who is in HVAC

 

[leon]

I really appreciate everyone's feedback and support!

Thank you, thank you, thank you!

It is helping me clarify some of my own preconceived notions I have developed after reading the Garn Design Manual. I'm looking forward to reading the books from Dan H. I'm hoping to get more clear how 3/4" lines and/or the 8000gal tank car could work. I can't see how enough BTU's could get underground to satisfy the 150MBH load with all WTAHX calling for heat at the same time. Is the buffer tank the key to 3/4" lines working and, if so, I suppose it has to be adjacent to house 1 and not the Garn barn? If it could go by the Garn barn that is doable but I can't realistically think of a way to put an 8000 gal tank car next to house 1. And, once all 8000gal are up to 160F, am I correct in thinking it extends my time between burns four-fold?

Please forgive my lack of experience drawing diagrams, but could you mentor me on how the 3/4" design needs to be altered?

=================================================================================================


Each and every gallon of hot water has only so many BTuH it can deliver.

Based on a 20 degree temperature drop one gallon per minute of flow will transport 10,000 BTuH

SO 4 GPM will deliver 40,000 BTuH to your heating loads Per Loop

The suplus tank car could go in your carriage shed next to the Garn boiler you have to plan on having 38 feet to park it and have a pair of concrete hemispere supports cast in the floor to support it.

BUT saying that there is no reason you could not use good hardwood cribbing 12 by 12 by 12 to create a long enough crib to support the tank car body minus the trucks and axles. if you bought it with the trucks and axles it would double the price and you dont want that!

Hiring a house mover to set that up will save you time and money aggravation as they have all the goodies-NO a large tractor will not do it!!

You may need a separate slab if you have a shallow thickness of concrete in the floor- I have to go now-many errands for boiler install. BUT the hardwood cribbing may be all you need for this if you pursue that route.

You have to think of the tank or tanks as 10,000 gallons of thermal mass and only thermal mass. Your going to have that amount of gallons to make hot water and hold hot water for you.

The firing rate of your garn is going to depend on your heating load after you have the water heated to the temperature you want.

Your going to have to empty the ashes to keep up a hot fire and keep it burning hot and then you may end up increasing the water high limit temperature even more to keep up.

So much of this is going to depend on your first season of use to create the right amount of hot water for your heating loads and having system bypass loops are going to save you energy as a portion of the water will return to the garn boiler hotter than the low limit temperature and raise the boilers water temperature and hopefully reduce cycling.

I would want to install circuit setters in each heating loop to return at least one gallon per minute back to the return loop uphill to the garn boiler to start with and you can always open them up for full flow to the heating load if three gallons a minute of hot water is not enough.

Ideally you want the smallest water to air heat exchangers in your ducts as they are nothing but energy hogs and will strip the water of its heat value quickly.

 

[Antman]

=================================================================================================


Each and every gallon of hot water has only so many BTuH it can deliver.

Based on a 20 degree temperature drop one gallon per minute of flow will transport 10,000 BTuH

SO 4 GPM will deliver 40,000 BTuH to your heating loads Per Loop

The suplus tank car could go in your carriage shed next to the Garn boiler you have to plan
on having 38 feet to park it and have a pair of concrete hemispere supports cast in the floor to support it.
BUT saying that there is no reason you could not use good hardwood cribbing 12 by 12 by 12 to create a crib to support the tank car body minus the trucks and axles. if you bought it with the trucks and axles it would double the price and you dont want that!

You may need a separate slab if you have a shallow thickness of concrete in the floor- I have to go now-many errands for boiler install.

The slab is 40'x20' with 10' ceiling so it would probably be too tight to maneuver that much weight but another slab could conceivably go adjacent to the barn under a deck which is planned for after both houses are completed. Very interested to see how the 3/4" design could work...

 

[leon]

SO if you are pushing 4 gallons per minute through the 3/4 pex you are delivering 240 gallons per hour at 40,000 BTuH=2,400,000 per day per heating load making 4,800,000 in 24 hours theoretically.

The 4 GPM figure I used is for a "no water noise" in baseboard loops figure from the baseboard folks.

It is theoretically possible that the simple act of thermosyphoning may be enough to do this as you have 2,000 gallons of hot water in the garn and once it starts moving down hill with venting the line properly at the heating load using a boiler drain on the return line with a garden hose draped into a laundry sink you will not get all the air out on the first firing.

So a gallon of water weighs 8.34 pounds times 2,000 pounds is 16,680 pounds= (8 tons+680 pounds)

SO a single loop will have that water weight wanting to take advantage of the situation by simple gravity because water is lazy just like electricity it will go just about anywhere.


You seriously need to talk to a mechanical engineer about this and pay for an hour of his time and then you will have all your answers as a thermosyphon could work- remember water is pumped up hill and flows down hill naturally- our city water system has a very tall gravity drop and has worked this way for a hundred years now and it works very well.

Your looking at physics and head pressure at its finest hour with 2,000 gallons of water(8 plus tons) sitting above your heating load.

You have 2K (8 tons) of hot water at an altitude of 30 feet above the point of use
you have the $15 3/4" dual pex laying in the ground, you have 8 tons of water weight wanting to blow outof the garn tank creating pressure against the tank walls with one or two outlets not including the by boiler pass loop if you have one-you should just to make life easier and raduce cycling as your heating load(s) will stop calling for heat at one time or another.

Water pressure at sea level is 14.21 PSI depending- SO you have all that hot water with all its heat wanting to escape and waddle off someplace other than where it is.

So you have 3/4 Pex that can push more than 4 gallons per minute(more like 50) without batting an eye and the pressure is only regulated with the pex pipes inside diameter, the Pex pipe length, the back pressure created by the resistance in the pipe and the heating loops, and the return piping to the tank.

I want you to think of a marble as Dan would say, If it came to a Tee where would it go? How fast would it get there? How does gravity work in this case its all down hill like a bad day.

Hooking up one heating load and then a second in the same loop does a couple of things for you.

The first heating load strips heat out of the water and leaves the neighborhood for parts unknown(not really) the cooler water wanders over to the next house and the heating load in that house strips even more heat out of the water than the water waddles out for parts known only to you and the dual 3/4 pex back up hill to the garn barn and Viola the water is pushed back into the garn to be heated once more for the job of transferring 10,000 BTUh per gallon,

The gallon of water waddles down hill at a rate of 4 gallons per minute with its brothers and sisters and then creeps up hill to the garn at 240 gallons per hour 5,760 gallons per day in one loop that runs from one house to the next and back to the garn barn to be reheated so it can deliver 10,000 BTuH and the work continues

SO you have 8 plus tons of water pushing 33 pounds of water through the single loop(if its regulated) and its wanting to get out of the way for the rest of the water family to get through there.

I really want you to talk to a mechanical engineer as yoiu can take advantage of this with a really small circulator at the garn and the mechanical advantage you will have is in the 8 tons of hot water just sitting there.

Be the marble.

Do not forget that 1 GPM is 60 GPH and 1,440 gallons per day in the scheme of things and if you heat the garn to
180 high limit, gravity and a thermosyphon and the 8 tons of water weight in that tank are your friend.
The water is pushing from the garn to the first house then to the second house and then back to the garn.


Talk to a mechanical engineer and pay him for an hour of his time explaining your system, the altitude of the garn above the heating load and how you are examining pipe size for pex etc., and then go from there and you should have an answer to your issues. and you just may be able to thermosyphon to deliver heat to your heating loads.

Just think of how lazy the water family will be if 8K of additional hot water(33 tons+-) is pushing its family down hill in that 3/4 pex and wanting to get there, wherever there is.

Think like the marble, think of the garn as a simple platform scale with a pail of marbles that will slide down a pipe, think of a pipe loop as a horse shoe and the marble has to follow the inside loop of the horse shoe if you roll it in the inside and its slick enough the marbles will roll right up and jump back in the bucket.

Its not the most eloquent expalanation but I am tired so....................

 

[maple1]

Leon, did you calc head loss for all that underground 3/4" pipe?

It won't work.

 

[leon]

Hey maple1,

I just crawled back inside from town, still waiting on plumbers.
I was thinking of 160-180 degree water high limit water temps

With the $15.00 Pex losing a degree for every 100 feet I did not think it
would amount to much- But I did not include the two heat loads stripping
the heat from the water.

 

[maple1]

I was talking more of the issue of just getting that much flow through that much 3/4" pipe over that much distance with a reasonably sized pump. All in all, this is a rather challenging project, but should be do-able with a proper amount of pre-thinking.

Had one more thought on the run-time monitoring related talk above. You might also get a verification or rough 'second opinion' on the heat load if you have a decent history of past fuel useage over the course of a winter. Or winters. Not sure how old they are & how long you've been there though.

 

[leon]

Hello maple1,

If I wanted to use the hydraulic pump as an example you
could pump fifty gallons per minute through a 3/4 inch hydraulic
hose it at 100 PSI. Hydraulic pumps are tested at 100 PSI and
1,200 RPM to get a base line flow rate at that pressure and RPM.

small sump pumps and drainage pumps operate at high speeds with no little to no resistance
to the discharge end of the hose/pipe

It would make a huge amount of noise but I digress.

I suppose you could use a centrifugal pump to push the water back up hill in an
insulated utility room in the home that is heated last and then the water could be
pushed uphill as is done in skyscrapers using a check valve cartridge like the ones in the
B+G NRF pumps I have the NRF 25 set at the number one speed for the heating loop
and the temperature balancing pump and they both pump about 17 G.P.M. with 3/4 piping
with little head loss as the baseboard is on one level with no restrictions and they are extremely
quiet as all the air is gone in my boilers- that will change tomorrow when they are removed
if the plumber shows up and the dual fuel coal stoker is installed but the air will not be
there for long once the loops are vented and the boiler drain on the module is shut off and what
little air is remaining will be what is in the boiler when the pump is running and the air vent line is
opened to the steel expansion tank.

I would be willing to say the 2,000 gallons he has in the Garn is a big start toward gravity circulation
for his heating needs with 3/4 inch pipe creating the head pressure for a thermosiphon condition
to occur almost naturally using simple valves to control it.
=======================================================================================
I do not know if using the Garn as nurse tank to either of the homes could be an option with a smaller tank connected
to the heating load in each home But the thermo-siphon method for heating is proven and simpler to plumb up and the
Garn barn is on the uphill side where it will be making all that hot water.

A float tank fed from the Garn may be all he needs to create the siphon and feed the single or double loop of 3/4 dual pex.
It would be easy enough to plumb in a steel stock tank and cover it with marine plywood and install a float valve and
let it flow downhill- car washes do this to have hot water on standby taking it from flash boiler and refilling the tank as
needed with hot water made by the flash boiler.

I hope he talks to a mechanical engineer about this issue and not an HVAC engineer as he has height and the rise and
run to take advantage of the 8 plus tons of water he is going to have in his Garn boiler and even more water if he buys
a surplus 8,000 gallon insulated tank car.

 

[Antman]

SO if you are pushing 4 gallons per minute through the 3/4 pex you are delivering 240 gallons per hour at 40,000 BTuH=2,400,000 per day per heating load making 4,800,000 in 24 hours theoretically.

The 4 GPM figure I used is for a "no water noise" in baseboard loops figure from the baseboard folks.

It is theoretically possible that the simple act of thermosyphoning may be enough to do this as you have 2,000 gallons of hot water in the garn and once it starts moving down hill with venting the line properly at the heating load using a boiler drain on the return line with a garden hose draped into a laundry sink you will not get all the air out on the first firing.

So a gallon of water weighs 8.34 pounds times 2,000 pounds is 16,680 pounds= (8 tons+680 pounds)

SO a single loop will have that water weight wanting to take advantage of the situation by simple gravity because water is lazy just like electricity it will go just about anywhere.


You seriously need to talk to a mechanical engineer about this and pay for an hour of his time and then you will have all your answers as a thermosyphon could work- remember water is pumped up hill and flows down hill naturally- our city water system has a very tall gravity drop and has worked this way for a hundred years now and it works very well.

Your looking at physics and head pressure at its finest hour with 2,000 gallons of water(8 plus tons) sitting above your heating load.

You have 2K (8 tons) of hot water at an altitude of 30 feet above the point of use

you have the $15 3/4" dual pex laying in the ground, you have 8 tons of water weight wanting to blow outof the garn tank creating pressure against the tank walls with one or two outlets not including the by boiler pass loop if you have one-you should just to make life easier and raduce cycling as your heating load(s) will stop calling for heat at one time or another.

Water pressure at sea level is 14.21 PSI depending- SO you have all that hot water with all its heat wanting to escape and waddle off someplace other than where it is.

So you have 3/4 Pex that can push more than 4 gallons per minute(more like 50) without batting an eye and the pressure is only regulated with the pex pipes inside diameter, the Pex pipe length, the back pressure created by the resistance in the pipe and the heating loops, and the return piping to the tank.

I want you to think of a marble as Dan would say, If it came to a Tee where would it go? How fast would it get there? How does gravity work in this case its all down hill like a bad day.

Hooking up one heating load and then a second in the same loop does a couple of things for you.

The first heating load strips heat out of the water and leaves the neighborhood for parts unknown(not really) the cooler water wanders over to the next house and the heating load in that house strips even more heat out of the water than the water waddles out for parts known only to you and the dual 3/4 pex back up hill to the garn barn and Viola the water is pushed back into the garn to be heated once more for the job of transferring 10,000 BTUh per gallon,

The gallon of water waddles down hill at a rate of 4 gallons per minute with its brothers and sisters and then creeps up hill to the garn at 240 gallons per hour 5,760 gallons per day in one loop that runs from one house to the next and back to the garn barn to be reheated so it can deliver 10,000 BTuH and the work continues

SO you have 8 plus tons of water pushing 33 pounds of water through the single loop(if its regulated) and its wanting to get out of the way for the rest of the water family to get through there.

I really want you to talk to a mechanical engineer as yoiu can take advantage of this with a really small circulator at the garn and the mechanical advantage you will have is in the 8 tons of hot water just sitting there.

Be the marble.

Do not forget that 1 GPM is 60 GPH and 1,440 gallons per day in the scheme of things and if you heat the garn to
180 high limit, gravity and a thermosyphon and the 8 tons of water weight in that tank are your friend.
The water is pushing from the garn to the first house then to the second house and then back to the garn.


Talk to a mechanical engineer and pay him for an hour of his time explaining your system, the altitude of the garn above the heating load and how you are examining pipe size for pex etc., and then go from there and you should have an answer to your issues. and you just may be able to thermosyphon to deliver heat to your heating loads.

Just think of how lazy the water family will be if 8K of additional hot water(33 tons+-) is pushing its family down hill in that 3/4 pex and wanting to get there, wherever there is.

Think like the marble, think of the garn as a simple platform scale with a pail of marbles that will slide down a pipe, think of a pipe loop as a horse shoe and the marble has to follow the inside loop of the horse shoe if you roll it in the inside and its slick enough the marbles will roll right up and jump back in the bucket.

Its not the most eloquent expalanation but I am tired so....................

I will try to locate a mechanical engineer to discuss thermosyphoning in this context in more detail. I'd like to clarify that the Garn Barn (GB) slab is only 3' above house 1 and house 2 grades, not 30'. I was hoping 30' was a typo in your analysis, but please forgive me if that wasn't clear. I've attached a diagram attempting to illustrate this further. I tried to draw to scale as much as possible. I can draw the houses larger if my writing is too small to be clear. Also, the highest point in the system for house 1 is 5' above the floor of the attic that is above the 2nd floor (23' above the level of the Garn Barn slab) where the 4 and 5 ton LP furnace supply plenums (17x20 and 20x20 WTAHX) are 5' above that floor.

Don't get me wrong, I'd absolutely LOVE to run the hot water from GB to house 1, and back past the GB all the way to house 2 prior to returning to the GB because house 2 only needs ~110F for radiant floor heating. This is how I originally though the system could be designed. I guess the downside to putting both homes in series, aside from the head loss issue, is that if one house is down, both houses likely would be down. Please correct me if I'm wrong, but I would think the most likely reason for the system to go down, assuming a leak-proof, pressure-checked, installation, would be a bad pump. That solution could be as simple as keeping 2 of each circulator/zone valve, one for backup if the corresponding operating unit fails.

Like maple1, I just can't see how to overcome this kind of head loss using small circulators and 1-1/4" or 1-1/2" logstor, much less 3/4" logstor. That's why I thought I'd need to break the install up into house 1 this year and house 2 next year. I guess I could possibly use larger circulators, but I was trying to use small ones if possible because I'm interested in minimizing power consumption in the event that I run the whole thing one day on solar.

As I understand, a reasonable estimate of head loss is:

Head loss = length of the longest loop * 1.5 (to account for resistance of fittings, HX's, bends in the pex, etc.) * 0.04 (all water with no glycol)

Head loss for house 1
560' * 1.5 * 0.04 = 34 feet of head (barn to highest and furthest points in house 1, and back to barn),
where 560' = [230' (GB to house 1) + 50' (distance from buried dualpex up into the attic and all the way over to the 17x20 and 20x20 WTAHX)]*2

Head loss for house 2
900' * 1.5 * 0.04 = 54 feet of head (GB to radiant supply manifolds, through any 300' loop, back to return manifold, and back to GB)

That is a rather large head loss for either circuit alone, much less combined:
34 + 54 = 88 feet of head

BTW, these head loss numbers seem to correlate with the Garn Design Manual. Referring to pages 13 and 14, a system designed with 20F dT's could flow hot water through 0.678" ID barrier pex (i.e. logstor 3/4") at 3GPM and 4.5GPM and deliver 30MBH (4 feet of head per 100') and 45MBH (6 feet of head per 100'), respectively.

At the 3GPM flow rate, a perfectly straight 560' pex pipe would see:

560' * (4FOH / 100') = 22.4 FOH

Similarly:

560' * (6FOH / 100') = 33.6 FOH
900' * (4FOH / 100') = 36 FOH
900' * (6FOH / 100') = 54 FOH

Add 50% of these values to themselves (the 1.5 figure in the calculations above) and you're in the same ballpark

As a side note, another reason I like your system description is that I don't plan to run glycol and the bypass allows for continual flow which would minimize any risk of lines freezing as long as there is no power outage. My planned LP backup generator for house 1 could provide that assurance because I'm running a 200 amp service from house 1 to the GB. The electrician can put all Garn and house 1 circulators, zone valves, etc. on that generator. House 2 already has a gasoline backup generator to do the same there.

Can you please provide some diagrams illustrating how a 3/4" system could be configured to do this?

 

[Antman]

I was talking more of the issue of just getting that much flow through that much 3/4" pipe over that much distance with a reasonably sized pump. All in all, this is a rather challenging project, but should be do-able with a proper amount of pre-thinking.

Had one more thought on the run-time monitoring related talk above. You might also get a verification or rough 'second opinion' on the heat load if you have a decent history of past fuel useage over the course of a winter. Or winters. Not sure how old they are & how long you've been there though.

We've been here 4 years so I have a handle on propane usage. For house 1, the furnaces are 2005 goodman and we burn ~2000 gallons of LP per season (the 3 furnaces, 3 DHW, and stovetop, and very rarely the LP fireplace - no chimney). We have an LP pool heater but elected not to repair it as it wasn't working when we moved in. The hot tub and all other appliances are currently electric. House 2 burns 400 gallons of LP per season (single LP furnace), all other appliance are electric. I'll have to get in the attic and check how old that furnace is, but eventually it will only be for backup heat (no plan for WTAHX as it will have radiant floor)

 

[maple1]

We've been here 4 years so I have a handle on propane usage. For house 1, the furnaces are 2005 goodman and we burn ~2000 gallons of LP per season (the 3 furnaces, 3 DHW, and stovetop, and very rarely the LP fireplace - no chimney). We have an LP pool heater but elected not to repair it as it wasn't working when we moved in. The hot tub and all other appliances are currently electric. House 2 burns 400 gallons of LP per season (single LP furnace), all other appliance are electric. I'll have to get in the attic and check how old that furnace is, but eventually it will only be for backup heat (no plan for WTAHX as it will have radiant floor)

I just did some quick Googling, and made a couple of assumptions.

Found a figure of 91,333 btu/gal for LP.

Taking the 2000 gallon LP figure for house 1, and guessing that was for 6 months, I came up with around 42,000 btu/hr. of average fuel use. Throwing another assumption in of 80% efficiency, means the 42,000 btu/hr of fuel used is about 35,000 btu/hr delivered to the house.

You would no doubt need more than an average, during the coldest months. I'm not sure how much more though, or if there is a rough quick factor some use for an off the cuff calc. Heat loss calc should turn it up though. But I wasn't expecting to see the average be 25% of the heat loss calc - but maybe it would be? I haven't done this much.

Playing with numbers is fun, sometimes. Sometimes it leads to head scratching & hair loss. Would like to see more input on things & more number playing from others. Also some run-time measuring during the coldest months should bring a clearer picture.

(I might have also done something wrong....)