Water pipe heat tape

Page 1 of 3  
We're re-building our hoop green house and using wood this time. We have a aquaponics system where we raise fish, pump the fish water into grow beds so the plants and plant media can filter the water, pump that water into a sump and then that water goes to a large rock and sand filter before it's pumped back into the fish tanks.
We're looking for a way to keep the water in the tanks warm in the winter without it costing us an arm and a leg to heat the green house itself. We're going to have about 800 to 1000 gallons of water in the green house tanks, plus have passive solar heat from the ground that'll have a thick layer of gravel in addition to having windows at the proper angle to capture the winter sunlight and heat. We'll also have vents and windows we can open at the peak of the green house to vent moisture and too much hot air when needed on warmer days.
The problem is that if we heat the greenhouse along with using water tank heaters the temps can drop dramatically in the greenhouse and plants and fish don't do well if the temps are too drastic at night, so I was thinking of using heat cables/tapes around the pvc pipes that connect all the water flowing from tanks to plants to sump to filter vs. using in tank water heaters.
We're also hoping for a solution that'll cost less to power and at the same time keep the temps more stable in the green house. All the walls and roofs are being insulated, too.
Does anyone know if heating tapes would work for this or not?
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Friday, October 9, 2015 at 12:26:10 PM UTC-4, Muggles wrote:

From the description, very unclear what the objectives and requirements really are.
"We're looking for a way to keep the water in the tanks warm in the

The problem is that if we heat the greenhouse along with using water tank heaters the temps can drop dramatically in the greenhouse and plants and fish don't do well if the temps are too drastic at night, so I was thinking of using heat cables/tapes around the pvc pipes that connect all the water flowing from tanks to plants to sump to filter vs. using in tank water heaters.
If you're heating the GH, how will the temps drop dramatically? Fish? Where are the fish, in the GH? In the tanks? In the tanks that are in the GH?
Heat tape isn't going to do much at all to raise the temp of water running through it. It's designed to keep the temp of water in the pipes above freezing when the water isn't moving. You'd have to have a very long pipe and/or very little water flow for heat tape to make a significant temp rise in the water. But you also say that you need to keep the water in the tanks warm? Without knowing how much water is required, what kind of temp rise, etc, not much to go on.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 11:35 AM, trader_4 wrote:

During the day the sun can raise the temps in a green house quite a lot, but at night all the heat is lost from the air and it pulls the heat from the water too. It was a big issue with our hoop house. We heated it with tank heaters plus propane heaters.

I think the low temp the fish can tolerate is in the middle 60's, but that's pushing it. The plants can tolerate some change at night in the temps, but if the temps go too low they start to lose leaves and production is set back.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Friday, October 9, 2015 at 12:43:43 PM UTC-4, Muggles wrote:

Wow, that sure added a lot of clarity. I have a car, it won't go. What's wrong with it?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 9:26 AM, Muggles wrote:

It's pretty simple thermodynamics. In summary, "there ain't no free lunch" A lot depends on the geometry of your system and how the heat gets in and out. You insulate the system. You replace the energy that's lost. Costs the same, given the same energy source, no matter how you do it.
The water tank has very much more volume than the pipe. You have to either raise the pipe temperature considerably, or move a lot of water thru it.
PVC pipe is a lousy conductor. Use metal pipe if you insist on heat tape. Use multiple temperature sensors so a single point failure won't kill your fish. There are several types of heat tape. The self regulating ones won't help you. You need unregulated tape that can withstand the temperatures you need and some kind of controller.
I bought one of these and built it into a wall electrical box. I plan to use it this winter to control heat tape on the outside water spigot. http://www.buyincoins.com/item/45040.html
What if you put a small domestic water heater in the water loop? Put light bulbs in series with the heating element. The water heater heats the water. Lights heat the air in a manner that's easy to distribute to get heat right where you need it. Size the lights so that the ratio of heat in water/air is right for your application. Put the temperature controller on that.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 10:25 AM, mike wrote:

This one is better packaged for your application. http://www.buyincoins.com/item/15054.html

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Friday, October 9, 2015 at 1:26:17 PM UTC-4, mike wrote:

And there goes any remaining hope of sanity..... Did someone put something in the water today?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 12:25 PM, mike wrote:

We've been experimenting with various options. One thing we've done is turn off the water circulation during the colder evening hours and the sheer volume/mass of the water loses very little warmth at night. That might be another option. We already have timers on the pumps.

I wasn't even sure if heat tape would be an option to try. It's not looking like it would work based on what people are saying so far.

hmm hadn't thought of a small water heater. Interesting.
We are building a rocket stove and have already buried pipe in the ground for that. It seems many people incorporate those in their green house designs.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 9:26 AM, Muggles wrote:

What is the year-round soil temperature in your area? E.g., often there is very little seasonal fluctuation in that temperature once you are below frost line.
You may find it more economical to "sink" the tanks to that level to take advantage of the thermal mass of the soil to maintain a nominal temperature. Likewise for the plumbing.

What's the relative cost of water in your area? E.g., here, prior to predicted low temperatures. we water the citrus trees heavily. This helps hydrate the tress but also helps the soil under the trees hold heat and radiate it upward as the air temperatures fall. (but, we are typically looking for very small gains -- just to keep the trees from damage as they approach their limit of ~28F)

You can also explore a "poor man's" ground-sourced heat pump system. I.e., you aren't concerned with bringing that heat into a living space. So, a below grade pipe (even channels of cinderblocks?) with air blown through could bring the temperature in the greenhouse up a bit (from what would otherwise be ambient). A water-based approach would be more efficient but also more costly.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 12:50 PM, Don Y wrote:

We can't really sink these tanks into the ground because they are pretty big and they need to be mobile (in case we need to disassemble the green house at some point). We are building a rocket stove, though, and it has venting buried for that.

We don't really see much in the way of a water cost increase because the tanks are filled and the water is re-circulated continuously. Every couple of weeks we will add water to the main tank, but it's really not much to maintain water levels. The grow beds are directly above the water tanks right now, but we may move them and alter the current design of the water flow once the new green house is ready to move everything into it (maybe in another couple of weeks).

Right now we're planning for several passive heat sources: the water itself will hold heat, the floor is gravel, and a rocket stove. For additional heat we use portable propane heaters.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 1:40 PM, Muggles wrote:

Can you berm earth around them (or water tanks, etc.)? Anything to add to the thermal mass that *insulates* them from the surrounding air temperatures?

My point was whether you could afford to "throw away" water by hydrating the soil in the area to add to the effective thermal mass *in* the greenhouse. Water is easy to "move"; blocks of stone, not so easy!

Propane heaters cost a bit to operate. So, you'd like NOT to have to rely on those -- if you can "store" (or, "prevent from leaking away") heat that is already available.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 4:08 PM, Don Y wrote:

We have gravel on top and around it.
[...]

Well, the site the green house is on if the former hole that we had our above ground pool sitting in. It was dished out for the pool and we never filled it back in, so we're gradually filling it with gravel and when it rains the water goes the lowest point in the yard which is that spot. There's about 8 inches of sand where the hole is at and it drains fairly well, plus there's a drainage pipe that goes out to the street from that point, too. Between the gravel and sand under it the mass should hold some heat.

--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 4:08 PM, Don Y wrote:

[...]

We'd like to not rely on the propane heaters, so we're trying to add other options. Right now we're adding as many passive heat ideas into the build and hopefully can incorporate some solar panels soon, too.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/10/2015 12:06 AM, Muggles wrote:

In PRNY, propane is generally cheaper than electric.
Solar heat collection and heat saving options might work best for you.
- . Christopher A. Young learn more about Jesus . www.lds.org . .
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Friday, October 9, 2015 at 12:26:10 PM UTC-4, Muggles wrote:

You might want to consider the cost of heat tape vs. Roof De-Icing Cables, and which is easier to install. You may need to put the thing on a thermos tat to cycle the heat on as needed. If you try heat cable, be mindful of i nsulating over it, as the heat buildup could possibly cause a fire.
Also, consider insulating any part of the system that can accept it (like m aybe the sand filter) with a few removeable polyiso boards all around.
Beyond that, I'm sure you're familiar with thermal mass. So paint anything big and heavy with some black paint and let it sit inside the greenhouse.. . maybe paint some pavers black and scatter them around too as stepping sto nes.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 12:54 PM, snipped-for-privacy@yahoo.com wrote:

Roof de-icing cables? hmmm I've never worked with those or heard of them before. How efficient are they? I'm looking for any idea that might work.
Eventually, we're installing some solar panels to run anything we might need in the green house, but right now it's all on the grid to the more efficient the heat source the better.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Friday, October 9, 2015 at 4:44:24 PM UTC-4, Muggles wrote:

es, and which is easier to install. You may need to put the thing on a the rmostat to cycle the heat on as needed. If you try heat cable, be mindful of insulating over it, as the heat buildup could possibly cause a fire.

ke maybe the sand filter) with a few removeable polyiso boards all around.

hing big and heavy with some black paint and let it sit inside the greenhou se... maybe paint some pavers black and scatter them around too as stepping stones.

.

They are 100% efficient.

Converting solar to electric and then back to heat would be nuts.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 4:48 PM, trader_4 wrote:

The solar power would be used to run pumps.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/9/2015 9:08 PM, Muggles wrote:

Would be interesting to see the thermodynamic math and financials including payback period for the solar part. What percentage of the system energy would be derived from solar electric?
I'm sure there are many success stories, but every time I've looked at the math, I couldn't see any way to make solar conversion costs "pencil out"...unless you get someone else, MY taxes for instance, to subsidize your system thru tax credits and rebates and raising MY electricity rates to pay for your use of the grid as storage.
Environmental impact not withstanding, It's very hard to make solar/electric pay off if you have access to the grid. Direct heat capture/storage is another matter because the initial cost can be much less.
I never quite understood the objective. Are you selling the fish? Growing your own food?
There are some interesting solar heat exchangers for heating water. It will be too hot for the fish, so you have to have a separate holding tank. But, if you're adding a lot more water, it might be more sensible to use it to farm more fish.
I've had some interesting discussions with local solar enthusiasts. One question I ask is, "if you added up all the time and effort working on solar and used it to take a job at minimum wage, and used that to pay for energy, would you be ahead?" They don't wanna talk about that.
The devil is in the details. Make sure you do all the math before launching a solar project.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not interesting. Horrifying. Or is that what you meant.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.