Pump location?

[Josh Carmack]

So,,, Earth Outdoor came through. They sent the pump and FPHE to me which arrived today. I'm about to install the new equipment, but I had an idea. SO, if I install the pump at the lower point on the furnace it should help with air locking in the pump, but I'm a little concerned about stratification, and loss in efficiency from that. Anyone already have a wood boiler that draws from the bottom of them water tank? As currently setup, the boiler draws water from the top right of the boiler, and returns it to the bottom left. I am considering drawing from the bottom left, and returning to the top right. The furnace is well over sized for my current needs, and will be that way until I enclose and insulate the barn, so currently I do not need to draw every single BTU the furnace can produce from it.

 

[warno]

I would draw from the top port of the boiler and return in the bottom opposite side if it was me. That's how mine is running and it seems to be working great.

If your boiler is in fact well oversized you are going to go through some growing pains like I'm doing right now. The boiler will idle alot and smoke a bunch without a proper load on it. You will probably be running what ever you are heating much warmer then you expect to try to make the boiler do work.

 

[Josh Carmack]

What brand/model do you run?

 

[warno]

I was running a Bell and Gossett NRF-36 but it turns out that was way too much pump for my system. So I have ordered a grundfoss 15-58 to replace it. The new pump isn't here yet, but the bell and gossett was running like a champ.

 

[maple1]

What does the furnace manufacturer recommend? I would go with that. I think typical is draw from the top, but I also think there are a few out there that want you to draw from the bottom, for whatever reason.

And it doesn't matter if you put the pump at the top or bottom for that, it's which way you point the pump. If you are saying the pump was at the top before (and pumping out), and you want to put it at the bottom, you should be able to do that and turn the pump around to pump into the boiler. Your post was a bit confusing in a couple spots. I would maybe say at the bottom is better as it will see more water pressure, but it kind of depends on the rest of your system. You don't want the inflow to the pump to see any restrictions.

 

[leon]

So,,, Earth Outdoor came through. They sent the pump and FPHE to me which arrived today. I'm about to install the new equipment, but I had an idea. SO, if I install the pump at the lower point on the furnace it should help with air locking in the pump, but I'm a little concerned about stratification, and loss in efficiency from that. Anyone already have a wood boiler that draws from the bottom of them water tank? As currently setup, the boiler draws water from the top right of the boiler, and returns it to the bottom left. I am considering drawing from the bottom left, and returning to the top right. The furnace is well over sized for my current needs, and will be that way until I enclose and insulate the barn, so currently I do not need to draw every single BTU the furnace can produce from it.

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Do not change a thing!

What you have is a "circulator" not a pump
it is designed to work with low pressure of 12-18 PSI
strictly depending on the number of stories your home
is and what ever else you are heating.

Please, Please, Please, order a copy of Dan Holohans
paperback book "Pumping away" from Amazon.

It shows the layperson and plumber how and why the
pumping away method works and works well.

If you visit the "heating help" forum it offers the
layman and the plumber alike a wealth of information about
heating systems and methods.

Its easier to pull water through a hot water boiler to the top
and then circulate it as the circulator is not working as hard to
move the water to the heating load of your home and barn/garage etc.

Pleasee go to the heating help forum for more help as they will explain how the
pumping away method works and works well.

www.heatinghelp.com

It costs nothing to join the heating help forum

Your "circulator" was working just fine the way it was.

Your "circulator" will not air lock as long as the air bubbles
and water are pushed away from the boilers water jacket
as was the case when they installed the circulator at the top
of the boiler.

("Pumps" work better with flooded suction because they
have to deliver very high pressures).

"Circulators" work only to move water at low pressure and only
need 12 to 18 psi depending on how many stories your house has.

Let me tell you a little secret and dont tell anyone else;
When fossil fuel boiler manufacturers build their boilers
they also have to crate them.

They put their circulators close to the boiler at the bottom
to reduce the cost of crating their boilers.

By "pumping away" from the boiler you are making it much easier
to remove air bubbles and not creating greater issues with thermal shock.

You should leave the new circulator as the unit was installed on your boiler
because its easier to bleed the system of air bubbles as the pump is pulling the
water through the boiler and out the top.

Before you activate the new circulator with the system "COLD" pour an ounce of
Dawn Dish Soap in the boiler water and it will break up the air bubbles in the water
and force the microbubbles back through the system to your air vents and your
circulator will no cavitate and make more air bubbles AND you should not have to
chase airbubbles and bleed them out.

This is also explained in the heating help forum as well.

Do not change anything, install the circulator on top of the boiler as it was done
and you will have zero issues. Just be sure to pour an ounce of Dawn Dish Soap
to eliminate the airbubbles. This also raises the PH of your boiler water which will
aid in creating a near neutral PH in the boiler water.

Lleave everything as it is and add a squirt of Dawn Dish Soap and then run the circulator
with out firing the boiler to get rid of the trapped air in the system.

 

[Pat32rf]

My boiler (Portage & Main) draws from the BOTTOM of the boiler. The circ pump runs constantly and is in this line so there is no stradification but if there is a boildown or other problem it seems to me that the pump would always have some water ..

 

[warno]

It's your P&M a gasifier? I have read that it's recommended the P&M gasifiers pull their water from the bottom since on those units it's the hottest location. Maybe I'm wrong though.

 

[Bob Rohr]

Pretty sure that is an unpressurized furnace. Mount then pump as low as possible as the water level above it is the only static pressure on the circ pump.

Keeping it low with what little pressure is available will help keep it from cavitating. Cavitation is the formation of vapor pockets in a fluid, the higher the temperature the closer you are to cavitation as the suction of the circulator is a low pressure zone. Lowing pressure below atmospheric also lowers the boiling point. It's possible to flash to steam below 212F if you have negative pressure, just as water boils at lower temperatures at higher altitudes..

Pumping into the furnace also puts then pump in the cooler fluid. Although they are rated for 225F, they live longer in cooler fluids as the fluid cools the motor. If it is a wet rotor type circ pump?.

Taco does have a special circ pump for OWF use, it is coated to prevent corrosion and the motor is not in the fluid, a two piece pump.

Pumping away in this case doesn't apply as you have no expansion tank, just an open tank.

It sounds like they include a FPHX to isolate then-pressurized OWF from the heating system, excellent idea.

http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10.pdf

 

[Josh Carmack]

Bob, some of your comments touch on my reasoning about location. Earth's design puts the pump drawing about 6" +/- below the fill level. I was running at 190F with a 5F differential, and a typical over run of 3F. I was thinking that the pump could very well be causing the water to flash to steam in the suction port due to the slight pressure drop caused by it's own operation. I have since dropped my operating temp to 180. I had raised it to 190 to improve the efficiency of my DIY hydronic clothes dryer. I'm tempted to place the pump at the end of my loop. so the flow points and directions would remain the same but my pump would be pulling water through the entire loop instead of pushing it through the loop. I know it may be inefficient in doing so, and am therefore very hesitant to attempt this. It is also important to note I have had two boil over events since installation. The first, was a major event where I left the door open and got distracted and was alerted later to the violent boil lover by one of my panicked children. That event was very soon after initial installation. I will never step more than 5 feet away without closing the door again. The second boil over was just a few weeks ago, I awoke to a moderate amount of steam coming from the vent. It was early morning, and some time during the night the damper stuck open. It allowed enough draft to cause a very slow and gentle boil over that perhaps boiled off 5 gallons.

 

[Whitepine2]

I put my pump in the basement after working on one outside for years in cold windy dark weather. Don't know if it right,wrong or whatever but now if it needs work I'm in a warm basement with light and can change out a pump in about five min. in comfort.