circulator selection

I'm designing my loop feild for a dual w2w heat pumps.

Planning on (6) 500' loops of 3/4"
1 1/4" or 1 1/2" main lines to the home. 75' (one way)

Accessible vault for the manifold.

Looking to push 18gpm with both units running and 9 gpm with one unit.

By my calcs im at 40-45 ft head at 18gpm.

What pump(s) should I use?

So far the only one I see that will work is a wilo stratos-Z 1.5/3 40 (this is a delta p pump correct?)

I also see that dual grundfos 26-99 would do what i need but cant do the 9 gpm that will be needed most of the time with only a single unit running. (would pump more then needed and waste KWH)


Also I could use the same footage of 3/4" but have more loops to lower the ft head if needed.

Any advise or education would be welcomed! Thanks

 

Steph is in the hospital tonight did not get to your project.

 

Anyone have ideas?

 

Don't use 3/4".

 

Ok that makes sense.

I believe in this application I need a delta P pump, Is the Wilo stratos z series Delta P ?

Here is what Wilo says about them;

"Optional interface modules available including: LONworks, BACnet, 0-10 Vdc, Ext Off, Ext Min and SBM Run Signal"

 

Yes the stratos is a pressure differential pump.

But when you start laying out plumbing, I would suggest just two fixed speed pumps. Maybe a two circuit non-pressurized unit. You only have two flow requirements. A pressure differential pump may be overkill.

You also need to know your solution viscosity at its thickest-what design EWT?

 

With Geodesigner I used 26degF minimum.

And looking at it again I had 1" hdpe sdr 11


Also it looked to me like if I used dual grundfos 26-99 for both, that with one pump and one unit running it would flow much more then the 9 gpm I need.
I will look at my math again now that we are talking 1"

Thank you for the help!

 

Also I have been looking at the Bosch W2W units. They claim to be 2 stage units.

So possibly 4 different gpm requirements, but I would be fine with minor pump electricity waste if I pump the full 9 gpm in stage 1 and 2

 

You will start seeing the difficulty in staging one pump to deal with multiple flows coming from circuits opening (easy) and compressor staging (harder).

So I'll point you to a 2-circuit non-pressurized flowcentre as being a simpler solution.

 

Well said.

 

While a flow schedule you are describing is fun to talk about in a residential application, I would add that sometimes the simpler solution is the most elegant in its execution. I second the notion that a fixed flow non pressure system would give you years of faithful service. Sometimes we get focussed on the wrong thing. Good design and install first, wasting some watts second.
Eric

 

I'm not sure what min temps people are designing with these days... but I know I used a min temp of 30 when I did mine.

As the guys here said, look at the non pressured systems.

I'm not sure how much value add a 2 stage vs 1 stage W2W system has. I know this topic has been discussed here before.

 

I asked Siegenthaler about the benefits of multi speed w-w units. He said the expected "to match loads".

It still doesn't add up for me when you have tank sizing and temperature differentials that can do the equivalent.

Maybe if you had really far ranging load demands.

 

Minimum EWT of 30F is fine to start with. It then becomes "economic arts".

You then see how this is an iterative process sometimes? Now adjust your EWT. See the pressure drops change? Loopfield change? Circ pump sizing changes? Different heat pump now?

Back and forth until you get a feel for it.

Then someone mentions some sort of rule of thumb and we lose our $$#!

 

Rule of thumb! There I said it.
Eric

 

Haha thanks guys. I agree with a correctly sized buffer tank that multi stage is not really needed.

However due to my cooling load being much much lower I opted to do 2 w2w 3ton units. I believe it will run more efficiently over all with this somewhat different way that I'm planning on heating and cooling.

I'm no stranger to closed loop and can refill/service if needed, so in this case would open loop still be better?
For open loop do you size pump the same as closed loop?

 

I'm guessing you meant to ask about pressurized vs. non pressurized?

 

Yes

 

Yes, no effect on circulator sizing.

 

Thanks!