First Snowmelt Project: Near Boiler Schematic

Ross_24

Excuse the rough drawing, but I thought I'd check in with the powers before going further and making things pretty. This is my first snow melt project and any advice would be greatly appreciated! I'm sure there are things I'm missing.

The heat loss, manifolds and loop layout has already been figured but I can attach those documents if needed. The project is in Massachusetts.

What changes would you suggest? Any tips?

Rich_49

Would be interested in seeing those design docs . Drawing looks good . What is the control , Aerial or ground sensor or will this ramp up at temp ?

Ross_24

Rich said:

Would be interested in seeing those design docs . Drawing looks good . What is the control , Aerial or ground sensor or will this ramp up at temp ?

I've attached all the documents I have except for the material list because it contains pricing. I can always email that to you if interested.

The design includes Uponor's pavement snow and ice sensors (part # A3040090) and a single zone snowmelt control for each zone (part # A3040654).

The loops are all in 5/8" HePex.

What do you think? Any suggestions or ideas?

The driveway has a steep slope towards the street. I'm assuming I will need to install a trench drain at each driveway entrance?

What type of provisions are needed for the underground pex runs to each manifold? Just pre-insulated hepex?

Zman

Ross,
You have a nice design going here.
I have a couple thoughts....

On the near boiler piping, the LLH is not really doing anything. The heat exchanger has a known, constant resistance and required flow rate. It is your hydraulic separator. If you add the pool, the same thing will be true.

With a firetube boiler, you could actually get rid of the heat exchanger as well. You would have to reconfigure things a bit to make sure you maintain the minimum flow.

On the tubing layout, getting the tubing in the center of the slab rather than at the bottom make a big difference. The only reliable way I have found to do that is to uses rebar on chairs. Otherwise the knucklehead concrete guys will push the mesh to the bottom and nothing is gained.

I like the detail for the stairs with the tubing on the nose. Again, good luck with the concrete guys. If it where mine, I would put about twice that much heat in the stairs. Make sure to get the treads on the nose, then get more in anyway you can. There is so much surface area on stairs you can't throw too much heat at it. At least (2) 250' loops.

Carl

Rich_49

Everything Carl said above is on point .

As far as the design . I have no problem with the 0* design temp although it does not snow much below 10* but there is that pesky ICE . The surface temp of 38* at 0* is what gets me . A degradation of surface temp down to 35* is acceptable as the outdoor temp declines . 38* is nice when it's 15* out but using that much boiler to maintain it at 38* whilst 0* is not necessary . You'd be amazed at how much energy that 3* takes to achieve .
Just a thought .

hot_rod

I like the HX if for the fact you don't want to glycol the entire system. Remember glycol will change pump requirements, and lower heat exchange, especially with high % mixes..

Agree with Carl, consider three runs across each stair tread. That nose is the critical detail, two exposed edges there. It takes a lot of patience to get, and keep a tube back 1" from the nose edge of a step. Ice on the nose, while the rest of the tread is melted negates the point.

A few contractors have found a method with PAP to run tube up and down the stairs instead of across. That allows a 6" OC or even tighter spacing.

Ring up John at Advanced Radiant Design, upstate NY. He is the "king of clever snowmelt installation", and one of the nicest guys you will meet. His website has many examples, of his award winning designs.

radiant-design.com

Photo credit: Advanced Radiant Design Inc

Ross_24

Zman said:

With a firetube boiler, you could actually get rid of the heat exchanger as well. You would have to reconfigure things a bit to make sure you maintain the minimum flow.

Thanks so much for the help!

So, if I went with an HTP Elite FT 399,000 BTU boiler, you're saying that since it's a firetube boiler I can eliminate the the FPHX and simplify the set up? I could also eliminate the primary secondary piping with that boiler as well.. hmm.

That would be great because space is very tight in the mechanical room and the less piping the better. Perhaps I'll try a new sketch if you think this will work.

RobG

I don't believe you will need a trench drain at the bottom of the driveway. The systems that I deal with melt and evaporate the snow. Granted I am in a different climate but I have never had ice dams. If it is 0 degrees outside any water that went in the trench drain will just freeze there and block it up.

Ross_24

RobG said:

I don't believe you will need a trench drain at the bottom of the driveway. The systems that I deal with melt and evaporate the snow. Granted I am in a different climate but I have never had ice dams. If it is 0 degrees outside any water that went in the trench drain will just freeze there and block it up.

That's what I was hoping to hear. Skipping the trench drains eliminates a lot of work due to how the site is set up. I was planning on running some tubing around the trench drain to help it on its way down to the drainage pit. The method doesn't quite feel right to me. Perhaps I can skip this altogether. Thanks!

Rich_49

Ross , how many circs are you planning on ?

Zman

Definitely check with he manufacture on the minimum flow rates and running 50% glycol. I know Triangle Tube is OK with it.

I doubt that your manifold 1 would have enough flow to satisfy a boiler that large when it is the only one zone calling. A differential bypass valve located between the supply and return manifolds would give you the flow you need.

If you had an indoor radiant heat system attached, I would keep the heat exchanger. With just a future pool attached, I would look into piping it direct.

As HR mentioned you need to factor the glycol into your circ and exchanger calcs.

Carl

Tinman

Great planning and preparation, Ross. That's so rare and a pleasure to see. Also some great tips from the guys. I agree with Rich that its rare to get heavy snow in really cold weather BUT...

I'd also stick with the 0* design as Rich said also. On Feb. 2, 2015 we got 19" of snow in the Chicago area in a very short time. The low that day was 9*. I had just finished a snow melt job a few weeks before and the driveway was clear and dry.

Based on personal experience, I'd advise everyone to stay away from aerial sensors unless there aren't any other options. Feedback from the slab is priceless.

hot_rod

Is it possible that a snowmelt zone and pool heat would ever call on at the same time, maybe that is too far down the road to determine? If so, or you start zoning with circs, I would still consider a hydrosep of some sort.

I was thinking more about the heat transfer hit you will take with glycol in the boiler. A HX wold allow the boiler and pool HX to run without the penalty of the glycol for pumping power and thermal performance.

Maybe a combo HX, separator, like a buffer tank for handling the zoned snowmelt potential, isolation between the fluids, and hydroseparation.

Maybe I'm overthinking the options. The old RayPak Thawmasters or whatever they were called, were a copper tube boiler, single pump and bypass valve No return protection, mixing device, anything. Flip the switch for melting.

Ross_24

I've made an updated schematic eliminating the LLH.

I'll be on the phone today with some of the guys from Emerson Swan in MA. I'm hoping they can advise me on running the HTP Elite FT with glycol and eliminating the FPHX.

This schematic includes the FPHX simply because I feel a little more at ease seeing it on there and getting that glycol separation!

I don't have much experience with these heat exchangers or using glycol. Do I size P2 through P6 using head loss and flow rates like normal? I think the flate plate and glycol is making me second guess myself.

On the pool side of things, I plan on using HTP's SuperStor Pool Heater (SSU-20PH).

Space is still VERY tight in the mech. room and it will take some careful planning to get it to fit.

hot_rod

Better see what type of flow that boiler requires, looks like that'll HX may have a tight cupornickle HX coil. I wonder that you can shove enough gpm through it to satisfy the boiler minimum.

I like the first drawing that provided hydraulic separation and isolates the glycol.

Ross_24

hot rod said:

Better see what type of flow that boiler requires, looks like that'll HX may have a tight cupornickle HX coil. I wonder that you can shove enough gpm through it to satisfy the boiler minimum.

I like the first drawing that provided hydraulic separation and isolates the glycol.

I agree. I feel better isolating the glycol.

You're right. I will need to add a LLH to this set up. Thanks.

Ross_24

The minimum flow rate for the Elite FT 399 model is 25 GPM.

Ross_24

Here's some revisions thanks to hotrods advice.

Tinman

What software are you using for the piping schematics?

Ross_24

Stephen Minnich said:

What software are you using for the piping schematics?

Siegenthaler's HydroniCAD
http://www.hydronicpros.com/

Extremely easy to use.

Tinman

Thanks. I've been thinking about getting that for a long time now. That just made the decision easier.

hot_rod

Ross said:

Here's some revisions thanks to hotrods advice.

I like! Expansion and fill on "A" side is just right, everything should work fine.

Zman

Be sure to put check valves on P1-P6...