# Wood boiler piping



## b33p3r (Aug 29, 2010)

Could anyone clear up some confusion on my part. The diagram below is the suggested scheme for me to use on my Econoburn boiler. This scheme was based on me saying I wanted the simplest setup I could get for this year. No water storage etc etc. I failed to mention that my DHW is supplied by the oil boiler. When there is no call for heat, will the supply from wood boiler "backflow" through oil boiler and return to woodboiler? If so, this will keep my DHW satisfied. If not, I need to come up with another scheme. Any help is appreciated. I'll be tying the boiler in within the next 2 weeks so all help is appreciated.


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## stee6043 (Aug 29, 2010)

Do your heat zones have zone valves on them?  I assume that's what the "21-22-23" are?  Are there any check valves on your oil boiler?  If you don't have any check valves on your oil boiler and your heat loads have zone valves that close when there is no call for heat I suspect you will be sending hot water through your oil boiler when there is no call for heat.  If "21-22-23" are circ's and not zone valves you may not get the desired flow, however. 

Any reason they have you setting up two air separators?  It seems like you could avoid this by plumbing your connection upstream of the existing separator.  Just a thought.


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## b33p3r (Aug 29, 2010)

Sorry, the picture isn't real clear. It is Z1..2...3. Zones. They are circulators on each zone. Not valves. The air seperator may be necessary because my wood boiler sits higher than my oil boiler. If the added air seperator is not necessary that would be great. One added expense avoided.
   There is not a check valve visible in my piping for the oil boiler. I'll have to check to see if there is an internal check valve in the oil boiler.


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## in hot water (Aug 30, 2010)

If the oil boiler has a tankless coil to supply DHW, then you will need to pipe them so the wood boiler keeps the oil boiler hot, even when there is no heating call.  But you do not want the oil boiler keeping the wood boiler warm when it is not fired, as it becomes an oil fired cooling tower. 

 Becareful with a piping arrangement that could lead to increased oil consumption, when you are running on oil.  The tankless coil complicates a "simple" piping arrangement.

hr


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## b33p3r (Aug 30, 2010)

Any suggestions how this should be set up?


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## Nofossil (Aug 30, 2010)

If you are set up with circulators for each zone rather than zone valves, I don't know of any simple/easy/cheap way to do what you want.

You could do the following:

1) Plumb the wood and oil boilers in series (outlet of wood to inlet of oil)
2) Add a circulator with check valve between the zone return and the inlet of each boiler
3) Set up controls to run the wood boiler circ ONLY when the wood boiler is hot and the oil circ ONLY when there's heat demand and the wood boiler is cold.

Or you could use some other approach to DHW - electric with sidearm or indirect, for instance. I use an indirect tank, and there's lots of discussion about sidearms on the forum.


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## b33p3r (Aug 30, 2010)

Thanks for the suggestions. But there doesn't seem to be any simple way around my setup. Givin my situation, how would you modify your setup to make it work.


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## in hot water (Aug 30, 2010)

I think a primary secondary works well.  It allows one or both boilers to input.  Allows the wood to circulate through the oil by opening the zone valve "Z"
all pumps are pumping away from the PONPC.  No pumps are in series.

The control will take some "imagineering", nofo is great at unique control logics.

Ideally the oil fires when the loop, or wood boiler drops to a certain temperature.  The wood boiler should flow through the oil boiler, but the burner needs to be locked out until needed, like when the wood burns out.

I don't see a way around of flow through the oil boiler, even when un-fired due to that pesky tankless coil.  So some heat energy will be lost up the flue and as standby loss from the boiler block.

The oil boiler can just circulate through itself for summertime DHW with this primary secondary piping.

On a DHW call the both boiler pumps run, and the zone valve opens.  for instant DHW that oil boiler will need to be maintained 24/7, not a great method.

Lose the tankless coil and improve the entire system efficiency 

hr

I may have missed some appropriate components, iso flanges, relief valves, etc


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## kabbott (Aug 30, 2010)

nofossil said:
			
		

> Or you could use some other approach to DHW - electric with sidearm or indirect, for instance. I use an indirect tank, and there's lots of discussion about sidearms on the forum.



If it's a money issue then I understand that, otherwise just go to an indirect or electric with sidearm. I use a sidearm because I already had the electric tank. 
If I were starting from scratch I would just bite the bullet and go with a stainless indirect tank, That's what I will end up with before it's done anyway. :shut:


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## b33p3r (Aug 31, 2010)

Thanks again all. The general concensus seems to be lose the tankless coil. I'm waiting on a price to spray my pex in ditch, should have the price tomorrow, if that pans out well I don't think the indirect tank will be an issue? Any idea what size I would need and approx. cost?



 Also you got me thinking with the zone Valve(s). Check out the diagram below and let me know what you think.
    C1 is on if water is >150. ZV3 is open whenever C1 is on. ZV2 is always opposite ZV3.
    If C1,C2 or C3 is on, ZV1 is closed, otherwise it is open.
So if wood boiler is off, Oil boiler will operate as it does now. Only flows when a zone is calling for heat but fires whenever temperature calls for it.
 If wood boiler is >150, C1 is on and flows through oil boiler out to heat zones, or through ZV1 if nothing is calling for heat, and returns through ZV3(ZV2 will be closed) to wood boiler.
    Of course I'll have to keep the oil boiler from firing as long as C1 is circulating since the boiler will want to maintain 180 deg. 
Thoughts? Am I missing something logically? I know there are valves and such required but left out for simplicity reasons.


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## Nofossil (Aug 31, 2010)

Zone valve can't be used in series with a boiler because they have REALLY small orifices. They are designed to provide a lot of flow restriction. There are full port valves out there, but they're a lot more expensive than zone valves.


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## stee6043 (Aug 31, 2010)

nofossil said:
			
		

> Zone valve can't be used in series with a boiler because they have REALLY small orifices. They are designed to provide a lot of flow restriction. There are full port valves out there, but they're a lot more expensive than zone valves.



+1.  Add to this the fact that a failed (closed) zone valve on your mail boiler line will be bad news with a roaring fire in your wood boiler.  They do make normally open zone valves but I'd still be very hesitant to place it on your boiler in/out lines.

You should keep in mind during your design phase that the boiler should be able to dump a fair amount of heat "naturally" in a power failure situation.  Some have normally opened "dump zones" while others among us use our elevated storage as dump zones...


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## in hot water (Aug 31, 2010)

Any valve or device used in a fluid stream will have a Cv rating.  The Cv is the number of gallons that can flow through a valve, let's say, with a 1 psi pressure drop.  This is an accepted industry standard.  Typical off the shelf, hydronic zone valves 2 or 3 way will have a 7- 8 Cv.  This means you could flow 8 gpm through the valve.

Now it is possible to flow more gpm through that valve, but the pressure drop will be higher.

I've enclosed a cv sheet that you can play with.  Lets look at a 7.5 cv valve flowing 12 gpm to see what pressure drop it presents. 

I have used 3 way zone valves on the return tapping to boilers in a number of installations.  The concept was to toggle from the heating load to the indirect DHW tank to give full power, and flow, to quickly recover the DHW load.  They work fine in that application.

Also enclosed is a sheet from Bellimo.  They build many different valves and actuators.  We commonly use the 300 series spring return 3 way valves on large solar arrays. Note the Cv on these valves is much higher.   We currently have a 24 gpm solar system with the B325 valve as a divertor to various loads.  Yes they are a bit more $$ than off the shelf hydronic zone valves.

I'm not sure how to attach this Excel file, if anyone wants this calculator drop me a line.

hr


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## b33p3r (Aug 31, 2010)

Thanks for all the feedback. I'm really struggling to make this work without adding anything extra this year. Budget is being pushed to the limit. If I have to add a water heater to help things out I will.    
 I have no problem with any electrical scheme someone designs. I work with electrical controls for a living. Plumbing I know nothing about. So if anyone can show me a plumbing design that will work and talk me through the logic flow That would be GREAT! 
If everyone still feels I'd be better off adding a water heater, then that's the way I will go. Again with some help with piping diagram. Stainless steel indirect storage is out unless I can get a hell of a deal on a tank.
    Just got a price back to spray foam my lines in a ditch................$900.00.  6" of 2lb closed cell for 65'. No savings there.
    Please keep giving me your feedback and advice. I plan on having things set up in 2 weeks. I'm getting anxious for the first fire.


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## ewdudley (Aug 31, 2010)

b33p3r said:
			
		

> ...
> If I have to add a water heater to help things out I will.
> ...
> If everyone still feels I'd be better off adding a water heater, then that's the way I will go. Again with some help with piping diagram. Stainless steel indirect storage is out unless I can get a hell of a deal on a tank.



For DHW I'm the same situation, two boilers, low budget, and don't want flow though the idle boiler at all times.  I can't say how well it will work but what I'm building is an upside-down inside-out indirect DHW heater using the tankless coil from the existing fossil fuel boiler.

My tankless coil is a real nice finned copper '10 gpm' type so, what I've done is to cut a hole in the top of a small propane tank, then welded a flange to accept the tankless coil.  The tank will have it's own circ controlled by a scrap aqua-stat in a well in the top of the tank.  I've seen comparable coils for $200 or so from Patriot surplus recently. To do it right I'm planning on another $100 or so for a tempering valve to limit DHW temperature because I doubt the output temperature could be controlled well enough with the aquastat.

YMMV   --ewd


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## in hot water (Aug 31, 2010)

Glass lined steel indirects are often less$$.  They perform as well, maybe better.  Watch for scratch and dents.

I like the Bock or Caleffi brand.  They have 1-1/2" coils and can easily handle 200,000 btu input with a small circ.  Heat Transfer Products offer steel tanks, Bradford White, Lochinvar, and others.

Yes a tankless coil is another great option.  HTP, Amtrol and a few others build these.  Here is an example from an older Trianco tank.  DHW is in the coil, boiler water around it in a 20 gallon tank.  Intended to produce as needed, endless DHW.  With enough HP and appropriate DW flow rate.  It basically the same concept as a coil in the boiler.

Any insulated tank can be used with an external HX.  Electric water heaters are inexpensive and easy to find.  Ask the box stores about scratch and dents.

I still prefer the dump load that a tank style DHW offers, and it can be tied to solar easily at a later date.  A dual coil tank would be a score if you can find a bargin.  Solar in the bottom, oil and or wood in the top.

hr


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## Nofossil (Aug 31, 2010)

A used electric can be set up with a sidearm for not too much - probably the lowest cost option, and might be cheaper to operate than the oil boiler for DHW during the summer.


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## sgrenier35 (Aug 31, 2010)

Just a question, exactly how much heat is going to be lost "up the chimney" by the original design which is by far the simplest and cheapest way for this system, with the existing tankless coil.  This poor guy just wants to get his wood boiler hooked up, and now you all are telling him he needs to re-plumb his whole system and add an indirect water heater.  So what are we talking for "stand-by loss" ?  .1 cord of wood, .5 cord 10 cord???


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## b33p3r (Aug 31, 2010)

I guess maybe I should go back to my original post at the top of this thread. Will the design shown there also keep my DHW hot. I was told in another post that I would need to add controls to keep my oil boiler off while my wood boiler is running because the oil boiler will want to maintain 180 deg while the wood boiler will circulate at anything over 150 deg. 
    Will it keep supplying my DHW or will I need to keep the oil boiler fired up at the same time?  Do I need to match temps between the 2 boilers?
    I like everyone else on here will be looking to tweak and improve the system over the next few years, especially after reading all the great ideas on here. But yes, if I can just hook up, burn and and save money on my fuel bill this year that would be great!


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## in hot water (Sep 1, 2010)

The wood consumption would probably be minimum.  It's hard to guestimate, depends on the temperatures, draft up the flue, etc.

The bigger issue is the amount of oil fired energy that goes up the wood flue.  The only way to get performance from that tankless is to maintain the oil boiler at 180F or more.  You need to drive the wood boiler fairly hard to stay at that temperature.  So I suspect the oil will fire more than you think.

 As I see it the flow is always through the wood boiler, even when the oil kicks in.

I suspect the days of 4 bucks a gallon for fuel oil may return, not a drop should be wasted heating the great outdoors.

It ALWAYS comes down to how much $$ to spend to gain how much control-ability.  Simple piping for up front savings sure, but wasting oil, or even wood to a point, seems silly when a few hundred bucks more could pipe the system in a way to provide all the options and highest efficiency.

If your DHW needs are small, I agree an electric tank may be a good method.  How much DSHW do you use, what are your electric rates.  There are a bunch of online calculators for oil, gas, electric to show that cost difference.  your local utility may have one at their site.

Simpler yet would be a wood stove in the living room.

We all present options and reasons, I think that is why you came here.  It's always better to work out the options on paper or via the WWW.  I suspect you want to eliminate or severely cut down visits from the oil delivery. 

hr


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## b33p3r (Sep 3, 2010)

One more try. Wouldn't the following diagram be an example of a P/S system. The wood boiler would flow from supply of WB to return of OB through the 1-1/2' black pipe of the Ob out the supply of the OB and back to the return of the WB. Wouldn't that be the primary loop? No flow to  secondary unless a zone pump turned on.


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## ewdudley (Sep 3, 2010)

b33p3r said:
			
		

> One more try. Wouldn't the following diagram be an example of a P/S system. The wood boiler would flow from supply of WB to return of OB through the 1-1/2' black pipe of the Ob out the supply of the OB and back to the return of the WB. Wouldn't that be the primary loop? No flow to  secondary unless a zone pump turned on.



Maybe need to take the return line into the wood boiler and bring in counterclockwise around to the bottom of the diagram and have it pull from the the return manifold of the zones.  Supply from wood boiler stays where it is and injects heated water into the load loop at a point just after where the new wood boiler return line pulls from.

The way it is now you can't get return water back to the wood boiler until after it has been mixed with hot water from the boiler, seems to me.

[Except then there would be no flow through the oil boiler when no zone calling for heat.  You could add a small circulator that would need to loop water through the oil boiler whenever the wood boiler circ is running and no zone is calling.]

Cheers   --ewd


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## willworkforwood (Sep 4, 2010)

My system is piped very similar to your most recent diagram, Beeper.  The only differences are the supply from the OB going back to the WB happens before the expansion tank, and the loop from the OB to the zones is done with a single circ on the return side, along with zone valves.  Also, I have a Superstor for DHW instead of a coil.  The hydronics gurus hopefully can give you good feedback on your current design.  Also, just checking to make sure you're aware of the need for a near loop for boiler return protection - is it just not in the diagram to simplify things?  And, you'll also want to include overheat/power out specs in a final design.  
I've got my OB turned down to 140/160.  I don't have a control to keep the OB off while the WB is on, but the low OB setting effectively keeps it always shut down.  The sound of the OB coming on hurts my ears, so I'm militant about keeping the WB fired.  However, my WB is in the basement, which makes monitoring very easy.  This type of procedural control might be more difficult with your boiler outside at some distance from the house.  It might be something you could consider short-term, and then retrofit a control in later.  I fully agree that you want to have a solid design that you are comfortable with before you start anything.  Redos usually translate into $ down the drain.  There are a bunch of threads on underground piping - try to read as much as you can before dropping anything into the trench.  Good luck!


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## b33p3r (Sep 4, 2010)

Yes I left alot of necessary valves and such out for simplicity reasons. I'm still fighting to get a design that will work with my tankless DHW in the oil burner. I must keep that heated on way or the other. 
      I could move the return to wood boiler to return side of zones but that will only give me a return path when a zone is pumping. I could add another circulator and loop such that if all heat zones are off, the extra circulator would run to complete the loop.
      Willworkforwood.....You tap your return before the air eliminator/tank? Do you have these components hooked to your wood boiler also? Any air problems? Also my wood boiler will be 75 feet from the oil boiler and about 6-7 feet higher. Do you think I would need to duplicate the mechanicasl package on the wood boiler?  Any special reason why you tapped yours prior to the pressure tank?
     I plan on adding an indirect water heater next year. Budget is shot for this year.
     I also like the idea of knocking down the oil boiler temps to 140/160. I know the oil boiler is supposed to be less effecient at these temps but I think the fact that I'm usind wood to heat 90% of the time would definately out weigh these efficiency losses. I'll also be mostly radiant floor this year so 150 would suit me fine. If the radiant holds its own on cold days, I will probably keep the baseboard zone off.
     What size piping did you use from your Econo to boiler? And do you happen to have a model # for the return temp valve? 
     I'm thrilled to hear someone has their boiler piped this way and it works. Could be my saving grace for burning wood this season.


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## in hot water (Sep 4, 2010)

willworkforwood said:
			
		

> My system is piped very similar to your most recent diagram, Beeper.  The only differences are the supply from the OB going back to the WB happens before the expansion tank, and the loop from the OB to the zones is done with a single circ on the return side, along with zone valves.  Also, I have a Superstor for DHW instead of a coil.  The hydronics gurus hopefully can give you good feedback on your current design.  Also, just checking to make sure you're aware of the need for a near loop for boiler return protection - is it just not in the diagram to simplify things?  And, you'll also want to include overheat/power out specs in a final design.
> I've got my OB turned down to 140/160.  I don't have a control to keep the OB off while the WB is on, but the low OB setting effectively keeps it always shut down.  The sound of the OB coming on hurts my ears, so I'm militant about keeping the WB fired.  However, my WB is in the basement, which makes monitoring very easy.  This type of procedural control might be more difficult with your boiler outside at some distance from the house.  It might be something you could consider short-term, and then retrofit a control in later.  I fully agree that you want to have a solid design that you are comfortable with before you start anything.  Redos usually translate into $ down the drain.  There are a bunch of threads on underground piping - try to read as much as you can before dropping anything into the trench.  Good luck!



Will the 140- 160F setting keep the coil hot enough to produce sufficient DHW?  I suppose with an indirect tank, in your case it would just extend the recovery time?  I doubt that 140- 160F would provide enough DHW with a tankless coil in the OB, when running on oil only.  It's something you could try before you make any changes.  Lower the OB to that range for  day or so and see how the HW performs.  

Remember not to run the oil too cool or you will soot up and maybe start to condense.

 hr


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## sgrenier35 (Sep 4, 2010)

To keep the oil burner from firing, just use an aqua-stat to break the TT terminals on the oil burner.  these are probalby jumpered on you boiler now.  Just use an open on rise  aquastat, set it to what ever temp your wood boiler circ will turn on at and it will turn off you oil burner accordingly.  Or if you use a relay like a TACO SR501 to control the circ from your wood boiler there is an extra set on NO/COM/NC contacts in the relay that will do the same.


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## b33p3r (Sep 5, 2010)

I appreciate all the feedback.  The electrical controls for the oil boiler are not an issue for me. The logic of when and why to make it happen is a challenge for me since heating is a science in itself.  If I have to use some controls to make the oil boiler take over if there is a call for DHW, then that's what I'll do. I have a heat manager installed already monitoring DHW so I'll tweak it if need be. But not piping the wood boiler in would definatley be my biggest loss. That's the conclusiom I have come to thanks to this forum.
    This year whatever it takes to save a buck. Next year more to save more bucks. Payoff is the key. Not afraid of work. Afraid of working for the arabs.
    Please keep the ideas and watchouts coming. I want to be economical, not stupid.


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## willworkforwood (Sep 5, 2010)

in hot water said:
			
		

> Will the 140- 160F setting keep the coil hot enough to produce sufficient DHW?  I suppose with an indirect tank, in your case it would just extend the recovery time?  I doubt that 140- 160F would provide enough DHW with a tankless coil in the OB, when running on oil only.  It's something you could try before you make any changes.  Lower the OB to that range for  day or so and see how the HW performs.
> Remember not to run the oil too cool or you will soot up and maybe start to condense.
> hr


For the complete story, I should have added that the lower settings are only used for the heating season. The OB almost never needs to run because the WB is keeping it hot enough.  I don't used the WB for DHW alone, so the OB setting goes up once the heating season is over.
Beeper, My return before the expansion tank was done just because the piping in my system was easier - it probably can go either way (the hydronics pros can weigh in on that one).  There is no return mixing valve needed with an EB - the dual pump design takes care of that completely.


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## b33p3r (Sep 6, 2010)

WWFW,   Your right I forgot about the pump setup. More savings. Just power outage and over temp dump zones. Thanks again.
      Turning the oil boiler temps down as a test is a great Idea. I will do that this week.


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