"Shallow rock" affects vertical loop's capacity to heat?

Okay, that was the piece I was not considering. What about the TMW120 with a coil in the hi velocity system for some forced air heat to back up the radiators?

 

Tamar you have indicated that not only do you not insist that the radiant provide all the heat (meaning high velocity can do the lions share or at least a good deal of it) and I believe that you have an area that depends on HV. Then you don't need to use high temp as high temp. use it as medium or low temp, with WTA as second stage. In this way you have gas boiler as auxiliary and never need geo to go to 130.

 

Joe, this is all true.

I do not know what the CM district manager means when he says there might be a better unit for our application. I assume he doesn't mean I should purchase a different unit. If a 5 or 7 ton hydronic medium temp unit is what he's referring to, then Doc pointed out that the split probably won't be able to run at the same time (based on the size of our current ground loop). That's why I thought maybe a hydronic coil in the SpacePak might be in order.

It's now ringing in the back of my head that someone told me continuing to utilize the split (maybe at least for AC?) was much more efficient than a hydronic coil for the high velocity unit.

I have made peace with the fact that we will have to add toe kick or radiator heat to our new kitchen. That should have been in the initial design.

 

Tamar:

You own what you need to heat your home.

You need different piping.

Mark

 

Mark,

I do not dispute that. We made it through the polar vortex, with one night dropping to -24.

The CM district manager has said in passing that there might be a better unit for my application. How "better" is defined is still TBD...more efficient, easier to design a control strategy for, a more appropriate size given the load, other?

Because I'm not as smart about this as everyone here, I feel I need to pre-consider the options he might mention so that I can ask the right questions and take full advantage of having his (and possibly the local distributor's) undivided, face-to-face attention for a few hours. I do not believe this is a sales call.

 

TMW120 is a 10 ton W-W heatpump, asking for 30 gpm flow, something your current loopfield design does not support. You can probably get by with 25 GPM, but not with an undersized loop. CM has nothing in the arsenal, which would top the 3 ton and then the 5 ton split as second stage. The only "better way" in my opinion is the 7 ton high temp from Waterfurnace, which obviously would be at a different price point.

 

Thanks Doc. Maybe he has rethought things since mentioning that a few weeks ago, and maybe it won't even come up.

Sorry to be such a nitwit sometimes! John Manning is doing a webcast on hydronic systems on Friday sponsored by MNGHPA, I'm going to try to attend to get smarter.

 

You will enjoy John. Just remember Doc's idea of your radiators being the buffering tank.

Mark

 

John Manning is the best one I know when it comes to geo. I know he told me about the "Minnesota talk" he was going to give. .

 

I've invited everyone involved in messing up my project.

The webinar is described as: A Candid Discussion on the Importance of Technical Competence
With the following topics:

• A simple detail can reveal a lot !
• Conventional Pipe Sizing can destroy a geothermal system !
• Are you screwing up Hydronic System Designs?

 

ROFL!
Good on you for inviting all parties to participate and hopefully get som much needed education on the finer points.
Eric

 

John Manning did bash a designed pond loop field I built once. Which does very well in a pond in upper New York. Live and learn.

Mark

 

Much of the presentation was way over my head (not feet of head, my actual head). Which, to be fair, it should be.

 

If John Manning ever tells me that there is something wrong with one of my ponds loops, he would have my full attention. What was his reasoning?

 

Doc:

He thought that using pex which is CTS and not use HDPE SRD 11 which is IPS would cause the system not to work. All of my designs using pex work fine.

Mark

 

So just to clarify, you put in 3/4 pex in a pond loop?

I can see John raising a flag (knowing him), since pex at the same nominal size has an inside diameter which is 80% of SDR11 HDPE. That means the CV of pex is 50% less, meaning the pressure drop is 200% of HDPE pipe, requiring higher pumping power.
Plus for durability, isn't that the reason why we use HDPE?

Maybe you could fill us in how you designed it.

 

There is a sign of life, and movement in generally the right direction. The installing contractor has now come back with a control plan that for sequencing the units that has both units running together under the following conditions:
1. once the split by itself is not able to maintain temperature the W2W will engage
2.the EWT remains above 35 degrees
They seem to feel that once the EWT drops below 35 degrees, the W2W must be shut off and gas backup must be engaged, in order to "save the loop" so it lasts the whole heating season. They also admonish us that if we don't use cooling enough the loopfield won't regenerate for the next winter.

I am still not jazzed by much of the proposal and by what details are missing, but at least they are making an effort to move in a direction where we can have a meaningful conversation about what WILL fix the issues.

 

What is the reasoning for the 35F threshold? Loops usually drop down to 30F and then stabilize. It is nonsense to shut off geo at 35F. While larger commercial loopfields can be influenced by disbalanced loads (usually not enough heat extracted in the winter, so they slowly increase in temperature over the years), this is not the case with smaller residential loops.
Climatemaster set the desired minimum entering water temperature in the geodesign software to 30F, waterfurnace to 28F.

Both publish performance data down to 20F entering water temperature, and specify the operating range between 20F and 120F. So why do they need to "save" the loop at 35F?

Here is an example of a drilled loopfield with heating only, no A/C at all. Plus hot water all year around.
It recovers every summer to about 45F, and then drops again to 30Fat the peak of the heating season, just as designed.

They continue to show a lack of knowledge how geo works and how it should applied…..

http://welserver.com/WEL0383/

 

"Due to the need to retain the continued operation of the high velocity HVAC system, the water to water heat pump would be disabled once the incoming geothermal well field temperature reaches 35º F (adj.) or less. The remaining geothermal well field capacity would be dedicated to retaining the heating operation of the high velocity HVAC system."

They also conceptually don't understand the ability of radiators to provide heat at relatively low water temps. Here's their prososal for buffer tank temps:

Buffer tank supply temperature setpoint reset schedule shall be as follows:

OAT SETPOINT (Adj.)
50º F 100º F (adj.)
20º F 130º F (adj.)
0º F 150º F (adj.)
-20º F 170º F (adj.)

Now, I know for a fact that with an outdoor temp of -24 and a windchill of even lower, the top temp of 156 that we got out of our Phoenix last month kept us warm. I don't see why we'd need to raise the setpoint so agressively, and why it'd ever need to get above 160 F. Anything over 130 switches the W2W off and moves to third stage gas boiler.

 

Oh, and they want to remove the desuperheater, they feel the heat is best dumped back into the ground in the summer. I know what most of you will think of that idea....