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[FJmonkey]

Looks similar to a chiller I use for home brew.

[Pat Conlon]

You’re trying to shed heat off the compressor, but not subject the compressor’s water jacket to your hard well water....so I’m looking at a heat exchanger....Correct?

[giantkiller]

Looks similar to a chiller I use for home brew.

Good eye Mark.

I was going to try to make the coils myself. But then I found pre-made coils for home brewing. For $10 more than buying a roll of copper. 2 coils one for the geo unit.  Circulated with the pump  built into the unit. And one for the domestic hot water. Circulated with the pump on the wall. That is tied into the pump on the unit. (So it only comes on when the unit runs) that goes to a 40 gallon electric hot water heater. With both the elements turned way down. And then I just have to replace the one $80 coil on the domestic side. Igloo cooler. Filled with water to exchange the heat. I put a spigot on the bottom of the cooler to hook a hose too. So I can drain the water.

Correct Pat

[Sparky84]

I know your question was directed to Dan. My 2 cents would be, thermocouples do go bad and having to replace one that is embedded in concrete would be a bigger headache then replacing an air sensor.

Usually if you are installing a thermocouple in the slab, it installed via a conduit all the way back to controller on wall in that room, that way if it becomes faulty, you can pull it out and push another in. That’s here in Australia on heated floors I’ve done.

[Pat Conlon]

I know your question was directed to Dan. My 2 cents would be, thermocouples do go bad and having to replace one that is embedded in concrete would be a bigger headache then replacing an air sensor.

Usually if you are installing a thermocouple in the slab, it installed via a conduit all the way back to controller on wall in that room, that way if it becomes faulty, you can pull it out and push another in. That’s here in Australia on heated floors I’ve done.

I thought about this Alan....If I put conduit in the slab (pvc sch40) and the thermocouple in the conduit, connect the conduit with a sweep up to a wall box....sure, a bad thermocouple will be retrievable, but how accurate will the thermocouple read the slab temp inside the pvc conduit?
Thin wall EMT is a no no encased in concrete....intermediate or rigid metallic conduit I guess would be ok for heat transfer....better than sch 40 plastic.
I think I will roll the dice and just directly embed the thermocouples in the concrete. I’ll put in two, in case one goes bad.....I found the dual sensor thermostats Dan mentioned, so even if both embedded thermocouples go bad, the zone thermostat can always read the air temp.

[Sparky84]

I know your question was directed to Dan. My 2 cents would be, thermocouples do go bad and having to replace one that is embedded in concrete would be a bigger headache then replacing an air sensor.

Usually if you are installing a thermocouple in the slab, it installed via a conduit all the way back to controller on wall in that room, that way if it becomes faulty, you can pull it out and push another in. That’s here in Australia on heated floors I’ve done.

I thought about this Sparky.....If I put conduit in the slab (pvc sch40) and the thermocouple in the conduit, connect the conduit with a long sweep up to a wall box....sure, the thermocouple will be retrievable, but how accurate will the thermocouple read the slab temp inside the pvc conduit?
Thin wall EMT is a no no encased in concrete....intermediate or rigid metallic conduit I guess would be ok for heat transfer....better than sch 40 plastic.
I think I will roll the dice and just directly embed the thermocouples in the concrete. I’ll put in two, in case one goes bad.....I found the dual sensor thermostats Dan mentioned, so even if both embedded thermocouples go bad, the zone thermostat can always read the air temp.

I’ve always installed conduit bent with large sweep as one, no separate manufactured bend and no corrugated conduit either.
Then the floor heat installer installs thermocouple afterwards.
As you said Pat, a second sensor installed would be good , just in case!
As for accurate temp in slab, you’ll get to know what you want after using it, like most things.

Enjoy

[giantkiller]

Pat the  piece of pex on the left side  sticking out. Is the channel for the sensor to  slide into. It is embedded into the concrete. So it  goes to about the center of the slabs. The  pex will be  fine and If you are  worried about accuracy. You could fill the pex with a fluid. Oil of some kind so it  won't evaporate but I don't think it would be  necessary. The end of the pex that is in the slab is plugged of course. I put tape over the ends. So stuff won't get into the pipes. The  manifolds actually had a Schrader valve and a  pressure guage. So it  could be monitored while the concrete was poured. I forgot.  Mine maintained 75 psi. For over a  year before I got around to hooking them up

[Pat Conlon]

Thanks guys...

[giantkiller]

I have a cold climate ERV. Energy (or Entalpy) Recovery Ventilation system. Out going stale air  passes by the incoming fresh air through basically a honeycomb. So they never actually touch. But they exchange the heat in the winter. Or cold in the summer. Since I have an ERV it also transfers some of the humidity.
I figured it probably raised the temperature enough so that the incoming air at least wasn't super cold.

The  other morning it was -16f when I got up.  So I thought it would be a good time to  check the difference between the outgoing air and the incoming air. I took my laser thermometer and measured the outgoing air at the vent in the bathroom. 70f. And at the incoming fresh air in the bedroom. 68f. Wow just a 2 degree loss. From -16 to 68. Simply amazing. Doesn't seem possible to me.

[Motofun]

What drives heat exchange is delta T.  After that surface area, velocity (ie time in contact with surface area), resistance (ie copper better than Aluminum better than steel). 

[giantkiller]

What drives heat exchange is delta T.  After that surface area, velocity (ie time in contact with surface area), resistance (ie copper better than Aluminum better than steel). 

Yes the honeycomb is a massive amount of surface. I'm sure. But it still doesn't seem possible. You would think it would meet in the middle. Halfway between the -16f and the 70f. Somehow almost all of the heat is coming back in with the fresh air.

[Pat Conlon]

Hey Dan, maybe the difference could be that your laser IR thermometer is reading the surface temp of the register vents, which could be different than the air stream? Is the steel vent register influenced by the 70* ambient indoor air temp?
IOW, the temp of the fresh air stream affects the skin temp of the register, for sure, but perhaps the ambient indoor air temp also plays a part in the temp of the register?

I’ve read that 75% efficiency is the norm when the erv units are new. Efficiency drops off after the heat exchanger gets some hours on it....so keep your filters clean.

I’m debating an erv for my house. I’m not sure I want another mechanical system to fuss over...
Being a desert rat, I’m a fan of evaporative coolers, a low cost alternative to a/c (in low humidity) plus a great source of fresh air when SWMBO burns the tortillas.

[Troyskie]

plus a great source of fresh air when SWMBO burns the tortillas.

And that's how the fight started......

[giantkiller]

Pat. The registers are plastic. I made sure the thermometer was reading inside of the ducts. I only have it pulling 50cfm. Since my living space is just under 1000 sq ft. They run anywhere from 55% efficiency all the way to 93%. Mine only uses 17 watts at 50cfm.

It comes with a merv 8 filter. Can get a merv 13 filter.  It automatically adjusts itself if anything restricts the airflow.

[Pat Conlon]

Very cool, I’m looking at the Panasonic cold climate erv units adjustable 50 to 100 cfm.
I’m happy to hear you like it.

Fresh air in the house is good.