Has anyone built a snow melt system?

LouNY wrote: ↑

Mon. Jun. 05, 2023 9:33 pm

Heating a sidewalk is a nice project. One thing to consider is you will need at least a tempering valve as your water temp should usually stay under 110F. My preference would be to use something like a boiler mate hot water heater to run the outside heat that would make it easy to maintain a good temperature and allow easy adjustment of the out going temperature and provide a surge buffer and storage capacity. This would also allow for separation of an anti freeze outside loop and your boilers fill.

I was wondering how to do exactly what you described. I'm just learning the way of the boiler and any and all suggestions help. I did read 130* was the ideal temp. Why does it matter? I mean I get you essentially want to warm it above freezing, but why any specific temp? Heat loss through the loop?

If you use too hot of a water the thermal shock and expansion rates of the pex and the concrete will be different so they will be trying to grow at different rates. The lower temperature of the hot water the more gradual your concrete will warm up.
I don't know how your boiler is set up and I know that others have mention the domestic heating coils for your boiler. My main boiler has a supply and a return header with the circulators on the return header. Each "zone" or loop has it's own circulator and the thermostats control the circulators, the boiler runs to maintain it's temperature. My two separate house zones and my domestic hot water each have a circulator with one zone actually having two circulators.

LouNY wrote: ↑

Wed. Jun. 07, 2023 8:11 am

If you use too hot of a water the thermal shock and expansion rates of the pex and the concrete will be different so they will be trying to grow at different rates. The lower temperature of the hot water the more gradual your concrete will warm up.
I don't know how your boiler is set up and I know that others have mention the domestic heating coils for your boiler. My main boiler has a supply and a return header with the circulators on the return header. Each "zone" or loop has it's own circulator and the thermostats control the circulators, the boiler runs to maintain it's temperature. My two separate house zones and my domestic hot water each have a circulator with one zone actually having two circulators.

I won't do concrete. Probably pavers. So how do you knock the temp down to say 130* when you are running boiler at 160?

Or separate the system by interfacing a boiler hot water maker set @130.

This ink has some information on indirect water heaters;
[hurl]https://www.energy.gov/energysaver/tankless-coil- ... er-heaters[/url]

I like the BoilerMate products,
https://www.amtrol.com/product/boilermate-indirec ... r-heaters/

This type of setup would require a circulator from your boiler to circulate boiler hot water to it, to heat the boiler mate fluid (anti-freeze) and a circulator and expansion tank for your snow melt loop.
To me this would be a good setup as the boilermate would act as a heat reserve when not actively circulating heat and when heat is called for it will act as buffer for your boiler allowing it more time to ramp up and produce the needed heat. Also it will allow you to use most any kind of circulating fluid you desire in the outside loop without hardly any chance of cross contamination.

Rob R. wrote: ↑

Wed. Jun. 07, 2023 1:28 pm

Mixing valve.

I know what the mixing valve is, but being a boiler newb I had no idea how it would work. I found a diagram and I now get it. It never dawned on me that you could use the cooler water at the end of a.loop in that way. Seems to be a cheaper solution.

LouNY wrote: ↑

Wed. Jun. 07, 2023 1:46 pm

Or separate the system by interfacing a boiler hot water maker set @130.

This ink has some information on indirect water heaters;
[hurl]https://www.energy.gov/energysaver/tankless-coil- ... er-heaters[/url]

I like the BoilerMate products,
https://www.amtrol.com/product/boilermate-indirec ... r-heaters/

This type of setup would require a circulator from your boiler to circulate boiler hot water to it, to heat the boiler mate fluid (anti-freeze) and a circulator and expansion tank for your snow melt loop.
To me this would be a good setup as the boilermate would act as a heat reserve when not actively circulating heat and when heat is called for it will act as buffer for your boiler allowing it more time to ramp up and produce the needed heat. Also it will allow you to use most any kind of circulating fluid you desire in the outside loop without hardly any chance of cross contamination.

I'm not against this setup, but it seems like a large.expense for the application. Of course I.guess it depends on what type of winter I get. One like any of the last 3 or a more normal winter.

I've done Two systems, one is a 4 foot wide, 100 foot sidewalk. We used an indirect water tank to heat boiler anti-freeze to 130 degrees. In dollars, Anti freeze is not less efficient than water, but it is less efficient in moving the heat. If you know you are using anti freeze with baseboard heat, add 20% to the length of the baseboard. A leak is not a health concern as the domestic water pressure is so much greater than the boiler pressure. If I remember correctly, 1/2" pex is good for 200 feet. The side walk was 6" thick, insulated underneath and halfway up the sides with 2" blue foam, tubing in the middle tied to rebar, not chicken wire. The first tube 3 inches from the edge, all others 6" apart. It was one pour of concrete with expansion scores every 10 or 12 feet. At those spots, the pex should have had 6" of foam insulation to allow a bit of movement.... but we didn't know that at the time. It's going on 20 years ago & still working. One thing discovered with use.... it's uses a LOT of heat to melt all the snow. For the most part, the sidewalk get's snow-blowed. The heat is for melting off ice and keeping it dry. We had a thermostat on it, but it died after 10 years & was never replace. Now "Mom" flips a switch in the cellar way as needed.
The other system is smaller and using a plate heat exchanger . It works, but it's slower than the tank system. I don't know why!

Thanks Freddy! Real life experience is the best example.

waytomany?s wrote: ↑

Fri. Jun. 09, 2023 1:16 pm

Thanks Freddy! Real life experience is the best example.

It takes about 334000 joules per kilogram for ice to turn into liquid water. 1000 joules is about 1 BTU.

So you have snow/ice at 0 C ... add heat ... becomes liquid still at 0 C

Liquid water then raises temp 1 C for about 4200 joules (about 4 BTUs) of energy per kilo of water.

And how efficient are melt systems to get the heat needed to the place needed (snow/ice material) ? Likely very poor with a pex system. One can calc. efficiency if they run their system and note: mass of snow melted and lbs of coal expended.

Rob R. wrote: ↑

Fri. Jun. 09, 2023 2:42 pm

I agree. Typically a buffer tank is used to keep a low mass boiler from short cycling with a small load. In this case we have a high mass boiler with a large load. If it were me I would use a plate heat exchanger to isolate the glycol from the rest of the system.

Larger diameter tubing allows for longer runs. Check out the literature from Watts Radiant and others, they have some great information about snow melt systems using their products.

Real men die shoveling their drives and sidewalks.

davidmcbeth3 wrote: ↑

Fri. Jun. 09, 2023 3:32 pm

Real men die shoveling their drives and sidewalks.

I'm not Chuck Norris.

davidmcbeth3 wrote: ↑

Fri. Jun. 09, 2023 2:37 pm

It takes about 334000 joules per kilogram for ice to turn into liquid water. 1000 joules is about 1 BTU.

So you have snow/ice at 0 C ... add heat ... becomes liquid still at 0 C

Liquid water then raises temp 1 C for about 4200 joules (about 4 BTUs) of energy per kilo of water.

And how efficient are melt systems to get the heat needed to the place needed (snow/ice material) ? Likely very poor with a pex system. One can calc. efficiency if they run their system and note: mass of snow melted and lbs of coal expended.

Sooo, yeah. Numbers.

waytomany?s wrote: ↑

Sat. Jun. 10, 2023 9:09 am

Sooo, yeah. Numbers.

Real men don't care about numbers.
Waytomany discussing the issue with me