Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

3 Indoor Sand Volleyball Courts - Radiant In-Sand Heating (Electric!)

Options
bman86
bman86 Member Posts: 14
Ive got 3 indoor beach sand volleyball courts in Connecticut. I'm looking to get a little heat into the sand to supplement the overhead propane radiant tube heaters. And I'd like to source some advice on the system

The 3 courts are 26ft x 52ft and side by side. I'm not too concerned with even distribution of heat around the area of each court. Just some decent heat for the toes about 8ft in from the sides where most of the time on court is spent.

The sand is about 11in deep, and sitting on 4in thick of rigid foam which is sitting on the dirt. So I have 4in of good insulation between the sand and the ground. I even have 2in going around the edges of the 112ft x 75ft building to keep heat from creeping out the sides! The building is just a fabric tension structure with literally zero insulation (think very large thick-fabric tent.

I can put the heating system - 3 zone panel, electric tankless heater, valves, etc - near the 26ft edge of the middle court. This puts the whole system right in the middle, as balanced as it can be. From this central location I'd like to (and this is where I need help) run a single loop out to each court. The loops would be ~180ft for the outer courts and ~120ft for the inside court. Each loop is just over-out-over-back-over ... no zig zagging or tight spacing.

If I just did the 1 loop out to each court, the out and back lines going the length of the courts would be 10ft apart if they are 8ft from each side line (seems crazy, but stick with me here). If I use 3/4in pex I could get some good flow through a relatively short loop, allowing me to transfer a good amount of heat to the sand.

So ... open fire ... let me know your thoughts and ideas here. If you've got some know how, let me know.

Right now I'm looking at buying, as examples ...

https://www.homedepot.com/p/Rheem-Performance-36-kw-Self-Modulating-7-03-GPM-Tankless-Electric-Water-Heater-RETEX-36/300800822#overlay

https://www.homedepot.com/p/Apollo-3-4-in-x-500-ft-Oxygen-Barrier-Radiant-Heating-PEX-Pipe-APPOB50034/302354347

https://www.homedepot.com/p/FloorHeat-3-Zone-Preassembled-Radiant-Heat-Distribution-Control-Panel-System-DP003/205675944?MERCH=REC-_-searchViewed-_-NA-_-205675944-_-N&

Thanks for the help

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,436
    Options
    If you really want electric heat, may I suggest looking at a purpose built electric boiler, rather than a water heater? Slant/Fin, for one, makes a good range with at least one model more or less in the size you mention. Couple with a thermostat in the sand somewhere typical it would be, in my opinion, a better choice than attempting to use a water heater which isn't meant to be used that way.

    Even if you are just going to keep the sand warm, in Connecticut... it's going to cost you.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    bman86
  • kcopp
    kcopp Member Posts: 4,443
    Options
    Sand is a terrible conductor of heat... and 11" of it would take forever to heat it up...if ever. I think it will cost a fortune to run.
    DerheatmeisterZmanSTEVEusaPAcross_skier
  • hot_rod
    hot_rod Member Posts: 22,256
    Options
    Just say no to heating sand :). Ever notice when you dig your toes into hot beach sand. A few inches down, it's not so hot.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    STEVEusaPA
  • Derheatmeister
    Derheatmeister Member Posts: 1,549
    Options
    As others have said:
    1. Due to the fact the sand has silica and tons of entrapped air is a terrible conductor of heat. In fact it acts as a thermal insulator..
    2. Using Electricity to heat a tent is going to cost a small fortune (Approx 3 to 4 times more than nat. gas)
    3. If you install the Resistance wires or tubing approx 12" below the surface it will have a serious lag. Probably days
  • bman86
    bman86 Member Posts: 14
    Options

    If you really want electric heat, may I suggest looking at a purpose built electric boiler, rather than a water heater? Slant/Fin, for one, makes a good range with at least one model more or less in the size you mention. Couple with a thermostat in the sand somewhere typical it would be, in my opinion, a better choice than attempting to use a water heater which isn't meant to be used that way.

    Thanks for that. I think you're right in that I really have an electric boiler application, and not a water heater or pool heater application

    And you're right that the Slant / Fin product offers a series of sizes. Here is an example of one available from Supply House

    https://www.supplyhouse.com/Slant-Fin-EH40-135-S2-EH40-135-S2-137000-BTU-Output-40KW-Single-Phase-Eight-Element-Electric-Boiler

    And yep, electric is going to cost me. But propane for the overhead radiant heaters is already costing me BIG TIME. Part of the business model for a few months out of the year. So it really wont hurt if my electric bill quadruples if it means my customers are happier, and I might save a little on the propane I'm using already to heat the sand.

    NOTEthat I'm really only looking to this system to raise the temperature of the sand by like 10F, maybe 20F on an extremely cold day or two. And even then, not completely or consistently. The sand gets moved around A LOT when players are running around, so that's my heat distribution concept. Even if I can use the system to keep the sand from getting cold overnight after it is already warmed up naturally or via my overhead heaters, then that's a win.

    Lots to think about. Thanks for your insight
  • bman86
    bman86 Member Posts: 14
    Options
    kcopp said:

    ... if ever.

    Indeed, that's the science part that I havent modeled or understood yet. Even if I do throw 30kw of energy down a 1in tube over 200ft, will that energy 10 or 11in down in the sand ever equate to making a toes-in-the-sand comfort difference a few inches down from the surface. Exactly what I need to prototype or model somehow. Or, get the "dont even bother" advice here on this forum - fully acceptable answer!

  • bman86
    bman86 Member Posts: 14
    Options


    1. Due to the fact the sand has silica and tons of entrapped air is a terrible conductor of heat. In fact it acts as a thermal insulator..

    Right, so it seems that if I can get the mass of sand heated to some baseline temperature (a big if), then the insulating ability of the sand would allow it to retain that heat for quite some time.


    2. Using Electricity to heat a tent is going to cost a small fortune (Approx 3 to 4 times more than nat. gas)

    I'm not trying to heat the air in the tent with this system, though I inevitably would a little bit. I'm just looking to heat the 11in deep volume / mass of sand such that it provides some level of comfort up in the top few inches to players' feet. Regardless, I agree that my electric bill will be seriously increased, which is tolerable.


    3. If you install the Resistance wires or tubing approx 12" below the surface it will have a serious lag. Probably days

    Right, exactly. If a cold spell comes through I can manually bypass the thermostat to tell the system to start heating ahead of the expected energy loss from the cold air. It will take days to heat up, but it will also take days to cool down which is the real meat on the bone here.
  • hot_rod
    hot_rod Member Posts: 22,256
    Options
    Bob Ramlow up in Wisconsin has been build sand bed radiant solar systems for years. Basically dump solar thermal into a large sand bed under the slab. It re-radiates to the space throughout the winter.
    So while being a poor conductor it can store and transfer heat energy.
    A 2' sandbed under 2000 sq ft would be around 400,000lbs of mass!

    Getting the warm sand to where it can be felt may be the issue.
    Make it wet or damp sand and conductivity goes way up :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Zman
  • delcrossv
    delcrossv Member Posts: 748
    edited January 2022
    Options
    I don't think just running a tube will do it. The heating is too localized (into an insulator). Now if the PEX was attached to some aluminum plates under the sand, then maybe you'd get some results as even though the thermal conductivity of the sand is low, you're applying heat to a much larger area than your tube.
    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • bman86
    bman86 Member Posts: 14
    Options
    hot_rod said:

    Bob Ramlow up in Wisconsin has been build sand bed radiant solar systems for years. Basically dump solar thermal into a large sand bed under the slab. It re-radiates to the space throughout the winter.

    I sent a message to him (hopefully) through the web site he is associated with. Fingers crossed that he will get back to me. I have VERY good southern exposure and plenty of area to put solar panels!! Thank you for that suggestion and referral.

  • bman86
    bman86 Member Posts: 14
    Options
    delcrossv said:

    Now if the PEX was attached to some aluminum plates under the sand, then maybe you'd get some results as even though the thermal conductivity of the sand is low, you're applying heat to a much larger area than your tube.

    Now that's an interesting idea. I wonder if some corrugated galvanized steel roofing panels would help. They are $30 each for a 2ft x 12ft section. Maybe cut them down to 1ft wide, or leave them 2ft. Interesting though, thank you!!
  • GroundUp
    GroundUp Member Posts: 1,926
    Options
    delcrossv said:

    I don't think just running a tube will do it. The heating is too localized (into an insulator). Now if the PEX was attached to some aluminum plates under the sand, then maybe you'd get some results as even though the thermal conductivity of the sand is low, you're applying heat to a much larger area than your tube.

    Until one of the players steps into a deep spot and lacerates their foot on a plate... Great idea, but the liability is not so great.
  • delcrossv
    delcrossv Member Posts: 748
    Options
    GroundUp said:

    delcrossv said:

    I don't think just running a tube will do it. The heating is too localized (into an insulator). Now if the PEX was attached to some aluminum plates under the sand, then maybe you'd get some results as even though the thermal conductivity of the sand is low, you're applying heat to a much larger area than your tube.

    Until one of the players steps into a deep spot and lacerates their foot on a plate... Great idea, but the liability is not so great.
    Only if the plates present an edge, but i get 'ya.
    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • MikefromMn
    MikefromMn Member Posts: 9
    edited January 2022
    Options
    A local bar & grill that offers sand volleyball leagues in the summer, tried to go year round with a large inflated dome (doubled as a golf dome). It advertised "heated" sand. I played there the first couple seasons and the sand was always freezing cold (this was in northern Mn). I believe they gave up on trying to heat the sand by the second year & frankly you couldn't tell the difference. Their other trouble was poor lighting, they had some indirect lighting bounced of the dome and it just didn't provide enough light. They gave up on the volleyball shortly after & stuck with the golf.
  • gsk3
    gsk3 Member Posts: 21
    Options
    Builditsolar.com has a bunch of info on solar thermal, including sand bed and cheap vacuum solar panels. I think in general the sand never gets hot hot hot but if you dump heat into it for months it’ll get to warm throughout.
  • GroundUp
    GroundUp Member Posts: 1,926
    Options
    Back in high school when I was tending block for a mason, the trick to keep things from freezing was to dump a truckload of sand over an old culvert at a slight angle and light a wood fire inside the culvert. The sand got so hot it would snap crackle and pop. We also parked our water barrel in the sand pile and it would make steam some days. So all you have to do is line your volleyball court with 24" culverts and light a bunch of fires inside, easy peasy!
  • Matt_67
    Matt_67 Member Posts: 288
    Options
    We have done some work on a concrete company’s sand heating system. They blow superheated steam through pipes with holes in the bottom. It works well but the sand does get damp. I wonder if some type of similar hot air system would work.
  • bman86
    bman86 Member Posts: 14
    Options
    gsk3 said:

    Builditsolar.com has a bunch of info on solar thermal, including sand bed and cheap vacuum solar panels. I think in general the sand never gets hot hot hot but if you dump heat into it for months it’ll get to warm throughout.

    Wow, I hadnt ever heard of the vacuum solar panels before. Just coming out of a giant rabbit hole there. But learned a lot. And yeah, a system like the one produced in Canada by Hydro Solar could in fact get me there.

    Youre right, in that I dont need (or want) the sand to be hot hot hot. I just want it to have some base level amount of heat in it such that it doesnt go down to ambient overnight when we shut the overhead radiant heaters off.

    Great stuff. Thank you so much for that idea!!!
  • bman86
    bman86 Member Posts: 14
    Options
    GroundUp said:

    So all you have to do is line your volleyball court with 24" culverts and light a bunch of fires inside, easy peasy!

    Hahahah ... well, I do have paid staff and 10 acres of woodland on my property. So it's not out of the question :). Thanks for the response
  • bman86
    bman86 Member Posts: 14
    Options
    Matt_67 said:

    We have done some work on a concrete company’s sand heating system. They blow superheated steam through pipes with holes in the bottom. It works well but the sand does get damp. I wonder if some type of similar hot air system would work.

    Yeah, damp sand woudnt be ideal at the top layer, but at the bottom layer I could care less. Having some moisture in the top layer does reduce the dust and allows the sand to sort of clump, which is great to play on. But inside the building I would get all sorts of condensation that I would then have to deal with (mold, water drips, etc)

    Your idea is sort of similar to the vacuum tube solar setups that gsk3 mentioned above. They basically create steam in a closed copper tube that you would then run water over in a manifold to transfer the heat convectively.

    Very cool, thanks for pitching in here!
  • bman86
    bman86 Member Posts: 14
    Options
    gsk3 said:

    Builditsolar.com has a bunch of info on solar thermal, including sand bed and cheap vacuum solar panels. I think in general the sand never gets hot hot hot but if you dump heat into it for months it’ll get to warm throughout.

    I've got a call in to Duda Bio in Decatur AL. Hoping to talk to one of their technical advisers regarding their solar water heater systems tomorrow!

    https://www.dudadiesel.com/solar.php

    Thanks again for the recommendation
  • bman86
    bman86 Member Posts: 14
    Options
    gsk3 said:

    ... cheap vacuum solar panels ...

    I spoke to a woman named Jill at Duda - super helpful and knowledgable! I am getting Qty 2 of their 30-tube systems, with all plumbing and glycol and etc, on order now. VERY reasonably priced if if works out. Envisioning having a little bit of heat in the sand (anything > 0 is a win here) with no electric bill (well, the pumps I guess) or propane bill ... seems too good to be true. So I'm cautiously optimistic.

    https://www.dudadiesel.com/choose_item.php?id=DS-SC5814-30T

    I will report back as I get this going.

    Note: I've had some little Govee thermometer / hygrometer units (qty 3) going for a few weeks now logging sand temperature, ambient indoor temperature and humidity. 2 units are in the sand at the bottom of 2 of the 6 net posts, and 1 is at the top of one of the posts (8ft ish tall). So none are located exactly where the radiant pipes would be routed, but nearby. I will download the data out of them and start parsing it in Excel. I will be curious to see how the delta between ambient air temperature and sand temperature tracks with and without the overhead heaters on.
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    Options
    The Duda site doesn't include a pump module/HX with their parts. 2 panels won't get you very far in the Northeast for output. It barely works for DHW in the winter and a boiler backup is required. There is solar software to calculate output required depending upon location.
    Derheatmeister
  • bman86
    bman86 Member Posts: 14
    Options
    The Duda site doesn't include a pump module/HX with their parts. 2 panels won't get you very far in the Northeast for output. It barely works for DHW in the winter and a boiler backup is required. There is solar software to calculate output required depending upon location.
    They include pumps and fittings as parts in their kits. Control is either via a timer or photovoltaic cell. Or something a bit 'smarter'.

    A lot to learn I agree. My need is FAR different from a typical household need. Im looking to improve the feel on the feet when people come in the door in the evenings. And looking for o reduce how early I turn on my overhead radiant heaters in order to warm the sand up ($$$$)
  • hot_rod
    hot_rod Member Posts: 22,256
    Options
    It's just going to take a lot of energy to warm that sand bed, you have ambient temperature and a poor thermal conductor, the sand, working against you.

    Here is an example of a 30 tube evac tube array performance. I didn't see that brand on the OG-100 rating chart, this is a similar size.

    So 1 array of 30 tubes on a really high radiation day, category C, would get you about 44,000 BTU, that is per day, not per hour. A solar day is around 6 hours.

    You would probably need at least 10 of those 30 tube arrays to really contribute much. See an example of a typical radiant heat array.

    As @Paul Pollets mentioned, one 30 tube array would heat a 50 gallon water heater, over 6 hours.

    Those sand bed radiant systems in Wisconsin pound solar energy into the bed all summer, like a large battery, to coast through some of the winter.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • bman86
    bman86 Member Posts: 14
    Options
    hot_rod said:
    It's just going to take a lot of energy to warm that sand bed, you have ambient temperature and a poor thermal conductor, the sand, working against you. Here is an example of a 30 tube evac tube array performance. I didn't see that brand on the OG-100 rating chart, this is a similar size. So 1 array of 30 tubes on a really high radiation day, category C, would get you about 44,000 BTU, that is per day, not per hour. A solar day is around 6 hours. You would probably need at least 10 of those 30 tube arrays to really contribute much. See an example of a typical radiant heat array. As @Paul Pollets mentioned, one 30 tube array would heat a 50 gallon water heater, over 6 hours. Those sand bed radiant systems in Wisconsin pound solar energy into the bed all summer, like a large battery, to coast through some of the winter.
    Yep, your math looks about right but I would need to go through it in a bit more detail. Again, my application is a bit unique and the bar is VERY low. For the initial cost and a bit of sweat equity, it's totally worth a try. I will post some of the sand and ambient air temperature swing data when I can
  • gsk3
    gsk3 Member Posts: 21
    Options
    Glad you found it useful! I’m obsessed with solar thermal, but also have very few unshaded spots at my house and recognize they’re not as good for high temp/radiator systems like my house, so will probably never pull the trigger. Lots of cool ideas on that site (especially for building thermal tanks).
    bman86
  • hot_rod
    hot_rod Member Posts: 22,256
    Options
    But you already have radiant heat! It’s a top down system with those overhead radiant tubes😉
    Radiant heat is the same concept as the sun, it warns whatever is in its line of sight

    The sun is 93 million miles away and it warms the sand on a beach.

    You could put numbers to all this knowing how many pounds of sand you want to increase the temperature in. The unknown is how warm you want the sand? With the load number, you could convert that to operating cost.

    Cranking  the overhead to raise the ambient would lower the load on the sand bed radiant. I would think a 65 ambient would provide reasonably warm upper sand layer?

    Skin temperature runs in the 90’s, if you want the sand warm to the touch or bare feet

    IF you could get the sand that warm, you could do without the overhead heaters.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • bman86
    bman86 Member Posts: 14
    Options
    hot_rod said:
    But you already have radiant heat! It’s a top down system with those overhead radiant tubes😉
    Radiant heat is the same concept as the sun, it warns whatever is in its line of sight

    The sun is 93 million miles away and it warms the sand on a beach.

    You could put numbers to all this knowing how many pounds of sand you want to increase the temperature in. The unknown is how warm you want the sand? With the load number, you could convert that to operating cost.

    Cranking  the overhead to raise the ambient would lower the load on the sand bed radiant. I would think a 65 ambient would provide reasonably warm upper sand layer?

    Skin temperature runs in the 90’s, if you want the sand warm to the touch or bare feet

    IF you could get the sand that warm, you could do without the overhead heaters.
    You get it!!! Thank you!!!

    The top down radiant is effective but not efficient. Our building is essentially uninsulated (inexpensive initial build, but high cold-monthly costs), so that's the main reason.  The less we have to run the overhead radiant, the better.

    That's why even if we can get some modicum of heat load into the sand during the day, then we won't have to turn the overhead heaters on hours early - HUGE savings. And when we do turn the overhead radiant heaters on, presumably the sun will be down or less effective and we will actually turn the solar collector pumps off so that we don't suck heat out (we mainly are open 500pm to 1100pm). But the heat load that's in the sand should stick around for a while.  Then the next day the cycle would start again.

    If the thermal load in the sand is substantial enough, and maybe we could insulate better, then yes we might be able to significantly reduce or maybe even eliminate the overhead radiants (wishful thinking).

    So yeah, that's what we are doing
  • hot_rod
    hot_rod Member Posts: 22,256
    Options
    Yeah, there is no free lunch when warming any building, much less a tent
    I doubt you could get enough heat output from the sand, even a concrete radiant for that load 

    Was there ever a heat load calculation done for the building

    I worked on some of the Bird brand fabric tennis court tents. The blower that kept them inflated also heated the space  Forced air by far will be the quickest way to heat a large space like that

    And yes it did deflate a few times and poke holes from the net posts 😗 It was at a ski resort and big snowfalls overwhelmed it also.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream