Washington Hp Home DIY Geothermal

Looks good. Again, I would encourage you to bypass the buffer tank to increase your system performance by 10%.

 

Chris, I think we touched on this before.
In the heat pump world, every degree you have to make the water hotter will cost you efficiency, which is not really the case with boilers, since there is a minimum temperature to a flame. Closely space Ts as discussed in the context of coming off a manifold, going to a zone, and coming back to the same manifold, have 2 conceptual disadvantages for geothermal heat pump applications:

1) You need a pump for each circuit.
2) You mix the return water with the supply water for the next zone coming off the manifold.

While you can get very efficient small pumps for each circuit, so #1 might not have an impact on system efficiency, reducing the supply water temperature with every closed spaced T (through mixing the colder return water back into the manifold) will reduce the heating capacity of the zones the further they are down on the manifold, which will require you to feed with hotter water, which will reduce your efficiency. Not the case with boilers.

This can be simply avoided by simply piping the zones in parallel so each zones gets the same temperature.
While closely space Ts might simplify designs, they negatively impact the efficiency of geo system.

 

If I do this should the 1.5" pipe in my drawing going to/from the zones be 1.5" all the way to the heat pump? Or does it not need to be that 'generously sized'?

 

Doc,

I look at it like there are things 90F geo can't do effectively. So rather than the entire system being bumped up to 110F to support a desire for a warm bathroom floor (or fan coil), hydraulic separation of different load temps is smart design. Lots of layouts but I know we both know.

Generally I'm using T's on multi boiler systems not really on primary/secondary plumbing. Though a delta T (vs delta P) pump solves that 20F drop pretty easily.

 

HP's piping is a ladder not primary secondary. See the picture to the left? That is a ladder, with the small pumps BTW.

 

Yep, nothing wrong with "the ladder" if that is what it is.
For my taste you are wasting energy with the amount of pumps, but again, this is my taste.

 

Chris,
I agree, sometime you have to play with the cards you got, especially in retrofits. But I really cannot see the benefit of a closely spaced T for a heat pump system. An example would help.

Also, lets say you have a scenario with 3 zones, but with different temp requirements (110F for 1 zone, and 90F for the other 2 zones), I would be curious how you heat the 110F zone without bringing the system temp up to 110F, and how do you keep feeding the 90F zones at the same time? 3 way valves to direct the water? With different setpoints and priorities?

 

I thought about using 1 1/4 pvc or cpvc on my 3 ton. Did the math and 1" copper was good enough. (Trying to remember but I belive 1" copper flowed about the same as 1 1/4" pvc in terms of psi loss @9GPM)

Now your system may very as my buffer tank is right next to the HP (short pipe run). So the more feet of pipe you use the bigger the pipe needs to be.

To figure this pipe size puzzle out I first picked a ECM pump, Taco bumblebee (little noisy for my taste so if I did it again I would try another brand pump, but it works great and runs efficient).
Then using the pumps chart @ 9gpm I found the max feet of head., Or psi.
Next added up all my planed feet of pipe the fittings and the HP exchanger. On my system I fell I bit short of 9GPM but if I remember correctly it's about 8.5 GPM and that was close enough for me.

Also the cost of copper fittings and pipe in my area went up drastically in price between 1" and 1 1/4".

 

1.25" is pretty much a save bet, depending on your pipe length, total pressure drop (wether there is antifreeze in the system, what kind of antifreeze, how many elbows etc, what kind of heat exchanger), what kind of pump....it gets complex. But with 9 gpm it is usually a safe bet without knowing the details.
1" could also work well, but then you should do the exact math.

 

I am planning to go with 1.25" copper.

CPVC would be five times cheaper and easier to install. And it is not very likely POE oil would ever actually contact it.

But I feel that I should follow the manufacturers specification so I am covered in the event of a failure.

In addition to the 1" connections on the heat pump I also have a motorized three way valve and a hose kit that are 1".

The hose kit I got with the non-pressurized flow center from Geo-Systems USA, but I am not sure if it's necessary to use hoses or not? Is there any reason not to just plumb everything with copper?

Pump flanges and ball valves for the Wilo circulator are 1.5". Where is the best place to reduce it down to 1.25"? Right away or after the 12D length of straight pipe?

 

No, we pipe it also all the way to the heat pump in PE, the load side we use copper due to higher temps. I don't like the hoses due to their small internal diameter, adding a lot of pressure drop to the system.
Also, 1.5" pump flanges seem excessive for the Wilo. What type and model of pump do you use?

 

If there is no need for a flexible connection at the heat pump or flow center then I will just pipe it all with 1.25" copper.
I don't like the hose either but I had been led to believe it was required to have flex.
Now that I see the heat pump there is some flex in the connections to the unit.

I have this pump for the radiant load-
http://www.supplyhouse.com/Wilo-414...-w-Rotating-Flange-Built-In-Check-Valve-115-V

and this flange set-
http://www.supplyhouse.com/Wilo-2706084-1-1-2-Sweat-Ball-Valve-Kit

Next size smaller flange was 1". Or I could use this type instead-
http://www.supplyhouse.com/Wilo-2706064-1-1-4-Cast-Iron-Flange-Set-for-Star-ECO

 

well, the wilo eco is an excellent pump, extremely efficient, but it can only make 9 ft/hd at 9 gpm. It is pretty tiny, not sure why you have 1.5" flanges. What pump do you use between the buffer tank and the heat pump?

If you use copper piping, the only concern is to ensure that the HP vibration is not transferred to the house. We use rubber isolated hangers.

 

The Wilo is the only pump I have bought so far. I still need pumps for heat pump to buffer tank and for the fan coil on the cooling load side.

I originally bought the 1.5" flanges thinking I needed "generously sized short fat header pipes". Should I exchange them and keep everything 1.25"?

I have been considering the vibration issue, I was going to try not mounting anything to the walls at all.

But that is impossible almost everything will be attached to a wall one way or another.

Do the rubber isolated pipe hangers do a good job of blocking the vibration?

 

You bought the pump without knowing how much it should pump and at what pressure?

With 9 gpm, there is not that much difference between 1.25" and 1.5".
Yes, the rubber isolated pipe hangers do a good job.
But I'd be worried more about your system design than your pipe hangers.

 

Not exactly. I bought it last winter when I was temporarily heating the slab with a water heater to keep the place above freezing.

I still need to calculate before I buy the other pumps but I had hoped the wilo would handle the radiant zones since I already had it.

 

water heater might have higher temps requiring lower GPM.......Plus you might want to have temps higher than "above freezing" when you live in it.
The pump between the heat pump and the buffer tank is easy, since the line is straight forward, your radiant is maybe a bit more challenging.

Again, geo needs more flow to compensate for the lower temperature it needs to operate efficiently.

 

The water heater setup was a pretty shady hack job but it worked in a pinch. My power bill for those months says it was not very efficient to say the least but I expected that.

Now that I have the pipe size variable figured out my next homework assignment is calculating head loss and sizing the pumps. I might need to find another home for the Wilo pump if it turns out to be too small.

 

Well it's looking like the Wilo pump is too small for the radiant heat zones.

It would be just right for heat pump to buffer tank, except the delta P variable speed is not necessary. Would it be a dumb idea to use it here anyways?

I'm now leaning towards the Gundfos Alpha for the radiant zones. Delta T instead of Delta P but a much more powerful pump.

 

Sure, you can use the wilo between HP and Buffer tank, where the pressure drop is much lower.