Speaking of grout... We hit bedrock within 8' of the surface here in Southern NH.  Is that a better or worse conductive situation for DX vs. different soil types?

Yes , it is good .....

Ledge is very good .... I am waiting to have my wells drilled for a DX system.....

I should hit ledge within 10 feet . I am in Western ,NH ......


Dave

depends on the type of rock vs the type of soil , some are better some a little some a lot , and some are worse
it realy is splittling hairs , except for the drill guy

Bedrock almost has a higher thermal conductivity than regolith (i.e. unconsolidated deposits). The only exception is saturated sands/gravels that are highly transmissive to groundwater and then it is due to the moving water transferring the heat.

As far as I know, it's all granite. Some places we couldn't get more than 4' down when digging the basement.

this chart tells the story

Something else to consider is that DX is not sized based on the subsurface strata, but rather the mean earth temperature. This is due to the face that DX relies on a much higher temperature gradient associated with the latent or phase-change heat exchange method it utilizes.

Thanks Dewayne, that chart makes bedrock look fine.

The phase change idea does sound better than moving all that water around for a small delta, I like it!

What do the "cond" and "diff" numbers mean, and what are their signicance?

Bruce

Conductivity and Diffusivity.

Ability of ground to provide / absorb / dissipate heat. Factors in chart are entered into loop design software and impact loop length needed per system ton. The factors for the various soil types listed will result in greatly different loop designs. It is critical to system performance and cost of operation that this be gotten right.