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[victor6deep]

Is it possible to use less wood with a pump on high versus being on med or low? Where do most on this site keep your pumps set at? Figured I would toss this question out and see where everyone stands on these speed settings for efficiency etc. Thanks

[Scott7m]

This has been discussed at length in the temp vent topic, there are no set answers


Read this, it should help

http://outdoorwoodfurnaceinfo.com/forum/index.php?topic=3485.0



There is no standard answer, every system is different

[Trint]

Vary mine based on the temperature outside and thus how much heat I need in the house.  It will only change you electric bill and the amount of heat availble.  Shouldn't change wood consumption unless you have bad lines.

[victor6deep]

This is a very common question I get. Well all this information I provide is based on experience not books. Most pump charts that provide "Head and GPM" are based on pressurized systems which we are NOT using so the charts are worthless to assist us for proper sizing. I have talked to many pump experts who tell me "that it will never work" well I then tell them I have hundreds in the field working great. The bottom line is these pumps are designed to be in a closed pressurized loop, and experts only know that information.

Most outdoor wood furnaces are not pressurized and work with a closed loop. So this is experience comes in handy. What is important for our application is GPM (Gallons per minute) I have found shooting for 10 GPM is ideal. Most of use do not have the testing tools to determine GPM, so the simple way is to time how long it takes to fill a 5 gallon bucket and do the math. Don't worry if you’re not 10 GPM, 6 GPM or more usually does the trick for heating most homes. Here are the basics: less the 25 feet one way you can use a Taco 007 BF5-j or Armstrong 30 3 speed on high. 75 feet or less one way Taco 009 BF5-J or Armstrong Astro 50 3 speed on high. Over those distances I recommend using Taco 0011 BF4-J, Taco 0013 BF3-J or Taco's Newest pump made for this industry Taco 2400-20 WB (wood boiler) or Armstrong pumps: Armstrong E7, Armstrong E8, and Armstrong E9. Both pump companies excellent and offer 1 year warranty. Don't buy cheap pumps because they will fail much sooner then these units. It is a hard environment that these pumps work in so you need good quality pump here. Basically if they are not working you have no heat. You might want to consider an extra pump on the shelf. Even the good pumps fail. Another note is the Taco pumps use a BF_-J are pumps bronze cartridge pumps and this helps with pump life. This does not mean you can use it in potable water applications.Another common question I get is which pump is better. Well they are both excellent well made pumps. The fail rate on both pumps is less the 1% and I have had a lot experience with both pumps. If I had to choose I would give the smallest edge to the Armstrong E series pumps. Hope this helps all you guys out there. Jeff Luff

[Scott7m]

Yea if your at 10gpm you can't ask for much more, but that still don't mean you can run 2-3 coils or more things off of that one loop.

If you have 1 20 plate and a hx, 6gpm "should" be sufficient


His pump sizing would only be if he knew what size pex he was using each time, 3/4" pex vs 1" pex or pex al pex would be a huge huge difference

[willieG]

most pump cahrts (i believe) can be used to figure yoru pump size to get teh gpm you require

most charts let you figure 'head pressure" by the size of pipe...lenght of run..fittings in the system.. to get your head pressure (this is for closed loop system) now to use this  for open loop you now must add the "real head" (static head) for any elevation change. in a closed loop system you do not need to add acutual "head" created becasue  both the rise and fall of the loop are under pressure and equal each other, in an open loop you must push the liquid you are pumping "up hill" so you have to add the  elevation change in "feet of head"

[RSI]

If the water returns lower than the top of the level in the boiler it shouldn't make that much difference about the height of the loop.

As far as pressurized vs open systems, the pump won't know the difference most of the time. For instance on my system I have a pressure gauge in the basement and have almost 20 psi from gravity. If I were to seal it and put an expansion tank on it and run at 20 psi nothing would change. It would be almost 0 psi at the highest point (at the boiler).

Just having it sealed would make no difference to the pump other than maybe having less air in the water.

[Scott7m]

If the water returns lower than the top of the level in the boiler it shouldn't make that much difference about the height of the loop.

As far as pressurized vs open systems, the pump won't know the difference most of the time. For instance on my system I have a pressure gauge in the basement and have almost 20 psi from gravity. If I were to seal it and put an expansion tank on it and run at 20 psi nothing would change. It would be almost 0 psi at the highest point (at the boiler).

Just having it sealed would make no difference to the pump other than maybe having less air in the water.

You answered the very thing I was gonna ask you about lol

I wasnt real sure but this cleared it up.

[willieG]

put a pressure gauge on both sides of your pump in the basment with a valve beteween them..close the valve and read the pressure on each side, if you are normally pushing water to a second floor (or higher than your OWB) with the valve closed the pressure on the return side of your pump will be more than the pressure on the feed side. ( it wont matter where your pump is, if you have water above the OWB you will have more pressure on the valve at what ever side is higher)

so in you have 20 pounds pressure on the feed side of your pump and if the piping is higher than the boiler on the return side, the pressure will be  higher (how much higher will depen on how much higher the piping is)

so lets say the difference is 2 pounds that means that when you open the valve all things will return to even pressure (and this may fool you) but when you turn the pump on it must now push harder to overcome that 2 pounds psi difference (thus, adding head pressure)

now if you closed the system and put in 12 psi (like a normal house hold boiler) the highth differnce is gone...there is 12 pounds psi everywhere in the sytem, so no vertical pressure is created in an elevation change so as far as the pump is concerned, no additional head

thats the way i read it anyway?

[RSI]

It is not possible to have 12 psi everywhere in a system. With a pressurized system it will be exactly the same as it is now (keeping the current pressure). The most it could do it raise the pressure some at the bottom so there would be a little at the top.
If I were to seal the system and run the pressure at the top of the system up to 12 psi then it would be running at over 30 at the lowest point.

Even in a closed system the pressure will drop behind a pump and increase in front. How much depends on the piping and pump size.

[willieG]

OK

[woodywoodchucker]

seems like some over thinking is going on here. I have a 3 speed pump and have it on the slow setting.My question is not about gpm but heat transfer.If you slow the water down, wouldnt the heat transfer be greater and speeding the pump up would less?
 I could be missing something here but thats my thought.

[RSI]

Faster water flow will equal more heat transfer.
The only time you would want to run it slower to get better heat transfer it if was a one pass system and you were dumping the water. (something that never happens on a boiler system)

To find out the best setting for the pump, just turn on the everything (blower, water faucet, etc and see how much temperature drop you are getting. If it isn't that much on low then it is fine. If it it really dropping the temperature turn it to a higher speed.

[victor6deep]

I did the turn everything on test and I conclude to keeping my pump on high.

[woodywoodchucker]

Ok thanks. Ill give it a try.I do remember on a tube type heat exchanger use for removing heat from oil, we would restrict the outlet of the cooling water to allow it to absorb heat.And now thinking back that water ran into the drain.