Pumps and efficiencies

[magnumhntr]

Just curious as to what difference pump speed/volume has on an OWB fire times/wood usage? My woodmaster 4400 came with a taco011. The heat loss through 105' (65' of underground and 40' boxed in and insulated along the garage wall) to my sidearm is 5 degrees. The temp setting I have are 155-175, and it fires about every 2 hours. I load the stove about half full twice a day with seasoned softwood that was given too me about 4 years ago. I do use less wood when burning my good seasoned wood, but I need to use up the "junk" first as I have about 5 more cords of it. Anyway, my question is would a smaller pump like a taco007 be more efficient as it would move the water slower, in theory putting less cold water back into the 112 gallons around the firebox, and needing less cycles to keep the water temp up. I know the OWB are not efficient in design, but am looking for ways to maybe maximize any efficiencies that can be gained.

Hope this made sense.

Thanks!

Chris

 

[BrownianHeatingTech]

What you really need to look at is the temperature difference between the supply and return.

Joe

 

[in hot water]

The size of the pump has to do with the amount of energy you are trying to move. Generally the faster the flow the more BTU's you move. The delta t as Joe mentioned is the way to measure how much you are moving.

The pump needs to be sized to move the max. amount of energy you need at the loads, against the pressure drop (resistance) the piping, boiler, and loads present to it.

Does the pump run non stop? If so, consider running the pump only when there is a call for heat in the building. This would reduce energy loss to the ground and also the amount of energy (wood burned) to keep those underground lines warm.

hr

 

[magnumhntr]

What you really need to look at is the temperature difference between the supply and return.

Joe

Is there a way to measure the difference without tearing apart the return lines and putting in a gauge? Like a surface mounted thermometer? And say I am above or below the 20 degrees? What would deviating from the desired 20 degrees tell me?

Thanks!

Chris

 

[magnumhntr]

The size of the pump has to do with the amount of energy you are trying to move. Generally the faster the flow the more BTU's you move. The delta t as Joe mentioned is the way to measure how much you are moving.

The pump needs to be sized to move the max. amount of energy you need at the loads, against the pressure drop (resistance) the piping, boiler, and loads present to it.

Does the pump run non stop? If so, consider running the pump only when there is a call for heat in the building. This would reduce energy loss to the ground and also the amount of energy (wood burned) to keep those underground lines warm.

hr

The pump does run non-stop, and woodmaster recommends to have it running continuously.

Chris

 

[BrownianHeatingTech]

Is there a way to measure the difference without tearing apart the return lines and putting in a gauge? Like a surface mounted thermometer? And say I am above or below the 20 degrees? What would deviating from the desired 20 degrees tell me?

A surface-mounted thermometer would work fine.

Alternately, you can use an infrared thermometer. You need to paint or apply tape to the copper, though, as it's a good mirror for infrared.

The pump does run non-stop, and woodmaster recommends to have it running continuously.

You could save some energy by slowing the pump down when not transferring heat, even if you can't stop it completely. A variable-speed pump would work for that, or even a second (small) pump. I'm presuming that the idea of constant flow is to reduce the risk of freezing, so it would not require much flow to do that.

Joe

 

[Sawyer]

You could save some energy by slowing the pump down when not transferring heat, even if you can't stop it completely. A variable-speed pump would work for that, or even a second (small) pump. I'm presuming that the idea of constant flow is to reduce the risk of freezing, so it would not require much flow to do that.

Joe

Joe, of the two which do you prefer? Is there another method you would suggest for freeze protection that seems better? Obviously 20' down and insulated would be ideal. I am 5-7 feet but would not want to find this is not enough to protect the pipe.

 

[brad068]

Another thing that I think people are missing is that when you use a bigger pump (0011) is that the power consumption is greater on the motor plac but when installed and under load the pump actually works easier. Check it with a amp draw. Same thing with a fan when you restrict the discharge the fan can speed up meaning it is using less power.

 

[Redox]

Another thing that I think people are missing is that when you use a bigger pump (0011) is that the power consumption is greater on the motor plac but when installed and under load the pump actually works easier. Check it with a amp draw. Same thing with a fan when you restrict the discharge the fan can speed up meaning it is using less power.

True, but a bigger pump slowed down is even more efficient.

Chris

 

[pybyr]

Another thing that I think people are missing is that when you use a bigger pump (0011) is that the power consumption is greater on the motor plac but when installed and under load the pump actually works easier. Check it with a amp draw. Same thing with a fan when you restrict the discharge the fan can speed up meaning it is using less power.

True, but a bigger pump slowed down is even more efficient.

Chris

aren't the two of you saying different variations of the same thing ? i.e. a moderately oversized pump with an easy task will pull less electricity than an undersized pump trying to bust a gut-- and, if you need to throttle down the flow, then a moderately oversized pump throttled back by electronic management will be most efficient of all?

 

[brad068]

I'm just saying that what the motor plac reads is the max as to what that pump will do. When the pump is put up against head pressure say half of its rating, it will actually use less power. A oo11 rated at 1.7Amp with no head. This is when it will draw its most power. Now put it up against 20' head and the amps will drop, say 1-1.2 amps. I know its doesn't seem right but thats the way it works.

I work in the ww field and have come across this a few times. When I work on big submersibles and pull them out of their seats and run them they will ramp up on the amps because they can move the most amount of water when just hanging in open water (no head). When they get placed back into the seat they will drop off on amps when they have to work against the restriction of gravity and friction.

But remember, only restrict pumps on the discharge side not the suction side or you'll be buying a new pump shortly.

 

[in hot water]

Regardless, the wire to water of any wet rotor, even at it's sweet spot on the curve is mid 20% efficient. Eff= .00302 X density of fluid (60.7 for water) X flow X head divided by watts

So an 80 watt circ moving 10 gpm against 10 feet of head would calc out to be about 23% efficient.

So select the circ that will do the job operating on the knee or mid point of the curve.

The ECM circs hitting the market will be about 40% or more efficient.

A variable speed circ adjusting to delta T would be ideal. Most boiler manufacturers will publish flow rates required at acceptable delta t's.

When you look at a heating system you have several efficiencies at work. Combustion efficiency of the appliance, distribution efficiency, and not to forget building efficiency.

hr

 

[BrownianHeatingTech]

Joe, of the two which do you prefer? Is there another method you would suggest for freeze protection that seems better? Obviously 20' down and insulated would be ideal. I am 5-7 feet but would not want to find this is not enough to protect the pipe.

Check what your frost line is. If you're below that, you're safe, and going deeper would just cost more money.

The issues with OWB's (assuming proper burial), is where the pipe comes up to the boiler, and is above the frost line.

Variable-speed pumps are preferrable from an efficiency and control standpoint, but between a ECM circulator and a control for it, you'll probably be spending between $500 and $1000, at a guess (all depends upon what size you need).

So, using a second pump, or hacking a three-speed pump and adding relays to control its speed, will tend to be a much-cheaper method of achieving similar flow results. The power consumption of a true ECM circulator will be lower, as was mentioned in the post above this one.

Joe

 

[Sawyer]

Joe, I am under a driveway for part of my run but the pipe is well foamed with close cell, then as suggested, 2’ foamboard was placed above the foamed pipe. I guess without coring the driveway I have no way of knowing how deep the frost goes.

I will take particular care insulating the chase that contains the pipes into the building.

I tend to think a second pump or a relay/timer may be the best for my pocket book and still achieving peace of mind. I also have the option of installing a heating element to maintain a minimum temp which with a small circulator should protect the system when I am on my annual 12 day vacation. It is obvious that planning the electrical connections is going to take equal or more effort as the piping.

 

[brad068]

Regardless, the wire to water of any wet rotor, even at it's sweet spot on the curve is mid 20% efficient. Eff= .00302 X density of fluid (60.7 for water) X flow X head divided by watts

So an 80 watt circ moving 10 gpm against 10 feet of head would calc out to be about 23% efficient.

So select the circ that will do the job operating on the knee or mid point of the curve.

The ECM circs hitting the market will be about 40% or more efficient.

A variable speed circ adjusting to delta T would be ideal. Most boiler manufacturers will publish flow rates required at acceptable delta t's.

When you look at a heating system you have several efficiencies at work. Combustion efficiency of the appliance, distribution efficiency, and not to forget building efficiency.

Absolutely, Thats why when exact metering of fluids is essential piston or diaphragm pumps are used with check and possibly pinch valves. The exact volume can be move and controlled best with these regardless of head pressure.

Rotors "slap" fluid around positive displacements "move" fluid

hr