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[RSI]

Around 110 feet and prob six feet at highest point a 18x16 heat exhcanger and a 10 plate for hw
and a 80k tube exchanger for hot tub with  8 90's

That 10 plate is gonna hurt ya.  There pretty restrictive.

Yeah, no way an Alpha will work with a 10 plate. A 10 plate is equivalent to adding 270' of 1" pex. At 6 GPM it is about 11' of head pressure loss.
A 20 plate is equivalent to somewhere around 120' of 1" pex and a 30 plate is equivalent to about 45' of 1"
Each elbow is equivalent to about 10' of pex.
So, going with these numbers, you have 110' (assuming round trip) + 270' + 80' (elbows)= 460' and once you add up the rest of the system it is probably close to 500' total. With these numbers I calculate that an Alpha pump will a about 4-1/4 GPM.

If you get an alpha, I would upgrade to a 30 plate or put the 10 plate on a secondary loop and another pump just for it.
Going with a 30 plate would get you 6 GPM with an Alpha. Putting the 10 plate on a secondary loop with another pump would get you a little more than that.

[RSI]

A PL 36 pump should move between 7 and 8 GPM  through your current system and draw around 150-160 watts or so.
An Armstrong E9 would do slightly more (almost the same) and possibly use less. They advertise it as typically drawing 115 watts but I never tested one so now sure.

You Broeder is probably doing about 7 gpm. The PL36 would probably gain you around 1/2 gpm or so.

If anyone wants to check my math, send me a PM and I will send all the info I am using to calculate.

[Scott7m]

Rule of thumb, what should you be pumping per minute through a system to get the best efficiency?

I don't think it is necessarily efficiency, it's carrying enough btu to do the job at hand and still have return temps that aren't hazardous to the boiler.  In many instances we see folks who can heat the building with low gpm numbers, but it varies per install.  You may be able to get by with 6gpm where someone else might need 10gpm

[victor6deep]

Armstrong e9 draws 2.0 amps. I am assuming that is a single speed motor which my broeder draws 2.0 amps on high.

[RSI]

Armstrong e9 draws 2.0 amps. I am assuming that is a single speed motor which my broeder draws 2.0 amps on high.

You can't just go by amps on a motor. The power factor makes a huge difference on actual watts used.
The more a pump is restricted, the less power it uses. This is because it is under less load.
A PL36 is 2.1 amps but on my system it uses 170 watts and will drop as low as 130 with no flow. If you just went by the amp rating on the plate it would be 252 watts.

[victor6deep]

Why do people not run strickly 240v pumps?

[RSI]

For what reason would you want to? They are a tiny more efficient but not enough to be worth running the outlet for it.
I used to run one because you can get them cheaper sometimes.

[victor6deep]

I'd say cutting the load in half is definently worth it. Less heat from the motor also.

[RSI]

Rule of thumb, what should you be pumping per minute through a system to get the best efficiency?

To get the best efficiency of what? Most heat transfer or least power usage?
Running at the lowest flow rate possible while still supplying enough heat will be the most efficient.

If you are talking about efficiency as in getting the most heat possible from your heat exchangers then the most possible flow would be what you are looking for.

If you want to really cut down on power usage, you could put a small pump to run 24/7 and a large pump controlled by a strap on aquastat that comes on as soon as you start using heat.

If you need more flow in the boiler to keep it mixed better you could put another small pump there between the extra ports. It could probably just run when the boiler is running. Without having to pump through the whole system, a small pump would circulate more water in the boiler than a large single pump.

[RSI]

I'd say cutting the load in half is definently worth it. Less heat from the motor also.

It will cut the amps in half but the watt usage will be exactly the same. The motor will put out the same amount of heat too.
The difference in efficiency is probably not easy to measure it is so small.

[victor6deep]

I am now confused. Ohms law doesn't allow that calculation. A watt is a watt is a watt but if a 2 amp load at 120volt is equivalent to 1 amp load at 240v. There is still a good savings there, plus 240v motors tend to last longer compared to 120v. When we are talking a continuous load that is a pretty respectable savings imo.

[RSI]

If you have two pumps that are the same model and only difference is 120v or 240v, if the 120v pump draws 2 amps, the 240v pump will draw 1 amp. 120 x 2= 240 and 240 x 1 = 240 No power saving what so ever.
The only reason the amp rating really would make a difference is on larger motors where you can use smaller wiring for the same size motor.

[RSI]

Going to return temperature drop is the best way to size the pump. If you are getting too much temperature drop then the pump is too small or there is too much restriction. If it is going back almost as hot when under load as it is arriving at the house then you are just wasting power.
Raising the water temperature will make your heat exchangers put out more heat and give you bigger temperature difference between supply and return.

[Drivebymashing]

Well my current setup is working great plenty of heat / hot water.Its only three months going .I am looking for a better pump and keep my broeder for backup.Changing to a 30 plate maybe a couple years down the line.Ill check out those pumps you suggested  .Thanks!!

[Drivebymashing]

Yes i have 1 inch pex  the tube shell exchanger hardly has any flow loss its a 55k not a 80k like i thought.Its a straight through design.