snow melt

Steve_210

We installed a Buderus 162/ 80 with 40% radiant (Warmboard) 60% oversized cast iron radiators with a 70 gallon indirect. Boiler should be in condensing mode most of the time, we submitted a bid for a small snow melt, approx 20 x 10FT. The following is a commect from the architect which makes no sense to me, but I would like some help refuting the advise he got. Or am I mistaken;

Re: snow melt, we are going w/ an electric matte as we were being advised against hydronic due to maintenance over time.



 

Brad White

Hydronic vs. Electric

Operating cost differences aside, electric mats can and do burn out and not in a way you can repair such as a leak with hydronic.



The only maintenance I can think of is testing your glycol and adding inhibitor so it does not become acidic. Properly designed, controlled and isolated with a brazed plate heat exchanger, you can keep the water temperatures lower than your boiler enough so that the tendency to break down the glycol from over-heating is greatly reduced.



I would go with hydronic. Also, of the snow melt area is in the sun, it can be leveraged as a form of solar collector, good to keep the glycol moving and not stagnating where it gets bored and goes to mischief.

lchmb

just guessing

But want to bet whoever told them it requires more only sells electric matte's? Just had a customer replace all of his electric matte's on a beautiful house. They were 6 year's old. They failed but were told it was an unusual instance (yea ok) but they did not want to rework the boiler so they stayed as is...

Steve_210

Thanks brad

Anybody have any data on operating costs

Brad White

Depends

are recommended when opening your electric bill



Seriously, depending on your local utility costs, electricity tends to be 1.5 to 3.0 times the cost of fossil fuel.



First off, in my first response (and not knowing where the installation is), I had meant to comment on your BTU density and the ability of the system to support that with other things going on. The BTU density could be 100 to 300 per SF also depending on the confidence level of how reliably clear they want the panel to be.



In your case, say your 200 SF panel requires 200 BTUH per SF or 40 MBH total.  Electrically that is 11.72 call it 12 kW to operate.



With gas at 90% efficiency, that 40 MBH output will require 0.444 therms per hour.



If your costs locally reflect ours, (18 cents per kWH and $1.85 per therm gas), your hourly costs would be $2.16 electric and $0.82 for gas, a factor of 2.62 for electric over gas.



If each snow cycle, say an hour before and for 12 hours total, your "cost per storm" would be nearly $26 for electricity and $9.84, call it $10 for gas.



How many storms in your area? If say ten per year, the math is easier. In the scheme of things, it seems about in line with hiring a local kid who does excellent work including good edges.

yellabelly

Hydronic vs Electric

"Operating cost differences aside, electric mats can and do burn out and not in a way you can repair such as a leak with hydronic. "



Repairing electric systems really depends on if it is High Voltage or Low Voltage. Low voltage snow melt systems are VERY easy to repair and find. Using a radio signal(tracer) you can locate the break, usually in a control joint or crack in the concrete, although joint breaks are prevented anyway using Joint Jumper technology ALWAYS. When the break is found the heating element is spliced together using a standard butt splice with solder and heat shrink. These connections are as strong if not stronger than the original heating element. Low Voltage systems do not burn out as there is no stress on the heating element like there is with a high voltage cable. Warranty differences reflect this and so does price.



Hydronic systems idle, because they are inefficient to shut down completely which tends to waste energy. Electric systems turn on when it snow and shut off completely when they are not needed. The cost of electricity may fluctuate and be higher than gas in some areas, but when you consider operating time, response time and efficiency, electric systems don't look so bad and the ELECTRIC BEING EXPENSIVE stereotypes go right out the door.

Mark Eatherton

Really???

An electronic electric leak detector eh.. Got manufacturers names and model numbers? I've been looking for a reasonable cost unit for 35 years, to no avail.



What centers does one have to install low watt/low volt density heating wire when the demand is 150 btu/sq ft/hour?



Curious minds and all....



ME

yellabelly

For Sure

Pasar Amprobe Tracer - AT-2000



ALWAYS USE JUMPERS and you WILL NEVER NEED ONE; unless it is to fix jobs that somebody didn't use control joint jumpers. Its amazing how many don't use them, even though ASHRAE calls for them every time.



150btu is quite high for ASHRAE standards in most areas, when using the Ar .5 ratio. If you wanted that much heat however, you would install the cables on 3.5" centers. If you are talking Boston, NY or in New England, 4" centers work great at 32 watts/sqft or about 115 btu/sqft due to the fact that the heating elements are closer together as well as closer to the surface as you get a faster reaction time and more even heat distribution. In other areas such as the Rocky Mountains, 23 watts on 6" centers works very well too and falls in line with ASHRAE standards. Some high voltage cables can produce 30-40 watts a foot (MI Cables) but spacing those more than 8" apart leaves striping and you have to install them deeper than 2" for even heat distribution.



good luck

Mark Eatherton

Thanks!

I will check the product out.



The 150/btu/sq ft is for Colorado Mountain ski areas... Second or third homes dontcha know...



Strange year here in Colorado. Most mountain snow packs are 101 to 172 percent of normal. But here in Denver, we are on the verge of declaring a drought. One of the driest winters on record. Now, the Spring is running extremely dry, and fire danger is up significantly across the front range.



Now, the mountains (13' of snow in places) is starting to melt, and the concern is flooding, avalanches and mud slides...



http://www.9news.com/rss/story.aspx?storyid=197275



Global Warming? Where?



ME

yellabelly

Question

Mark,



How come you use 150btu so much in Colorado? In Park City, Deer Valley, Breckenridge, etc 22-27 watts or 75-100 btu works absolutely perfect for electric systems in those areas. Just curious, have you tried lower btu as a comparison to save any energy with the hydronic systems?



I read an article today toward the bottom of the linked page titled "Aspen sorts out the nuances of energy"



http://www.mtexpress.com/index2.php?ID=2005136523



Pretty crazy the snow this season, In Utah we are double our normal snow pack(hasnt even melted yet) and 200% above our normal rain for the spring and its still coming. Even in Salt Lake City. They say that if you have had flooding the past 40 years, start sand bagging.

nicholas bonham-carter

melting time

how long will it take to melt 4 inches of snow off your driveway when the air temperature is 20 degrees

if you have a system with light heat output such as electric, then would it take a lot longer than say the 150 btu hydronic snow-melt

what are these idle costs. a little constant circulation? surely the system will not be using much energy until it snows.--nbc

Mark Eatherton

The numbers....

came from WIrsbo's Snowmelt Design Manual, and was based on the amount of anticipated snowfall per hour, snow temperature, 20 MPH wind, and 0 degrees F ambient conditions.



Granted, the chance of all those conditions occurring for any significant length of time are slim, but if you can't cover it, snow will accumulate. And that is not what my clientele pays for. They pay for completely dry surface under those conditions.



With todays modcon boilers, if the demand is not there, the energy is not delivered. If the demand is there, then it is delivered.



One thing I can do with my hydronic snowmelt that can't be done with an electric snowmelt is solar collection during the summer for whatever use I need. DHW, spa, pool heating...



Aspen.... It makes Boulder Colorado look good... I had a customer once who NEEDED snowmelt, to maintain access to his property. They have some extremely rediculous requirements for what is referred to as REMP fees. (Renewable Energy Mitigation Program). He finally gave up because he didn't have enough space for the solar array that they wanted to see. We offered up to use woody bio-mass thinking that it would be considered latent solar energy, and they shot that down as well.



I refuse to do any work in Aspen Colorado. I have people on the inside of the city limits that I can call upon if need be.





ME

yellabelly

Melting

When it snows the temperature rises, usually around 38 degrees allowing the perfect conditions for snow. This is not saying that it cannot snow at 20 degrees but it is unlikely you will have any accumulation because the wind will be blowing so hard, speaking from my experiences in Wyoming, where those conditions do occur. The bottom line is that you would need a blast furnace out there to melt snow at temperatures below 20 anyway and electric, hydronic etc will have an extremely hard time doing it no matter how many btu/watts you deliver.

It is important to get the melting started when the snow starts with a good activation device, as it is the eyes and ears of the system. You don't want a snow melt system to have to play catchup.



According to ASHRAE standards, which has snow melt data by region including snow fall hours, temps, moisture content, wind with acceptable snow fall ratios being 1, .5 and 0.



1 = the system will melt snow rapidly enough that no snow accumulation occurs

.5 = a thin layer of snow may be present on all or part of the slab

0 = The surface will be covered with snow of sufficient thickness to prevent evaporation losses, but will melt the snow underneath at the same rate that the snow is falling



Now designing for ration 1, is a waste of energy because many areas require 200-350 btu to melt at that ratio 100% of the time(BLAST FURNACE). Designing for 95%-98% of storms at the .5 ratio is where most snow melt systems are designed, hydronic or electric. 150 btu may be required in Colorado where Mark installs them because as he said thats what his customers want even though there are different acceptable snow melt ratios in ASHRAE. 150 btu also may be required because it is a hydronic system due to the fact that the pex is spaced 8"-12" apart and deep in the slab. You have to heat that slab slower to get even heat distribution.



Hydronic systems cannot heat up too fast or they will cause striping in the slab. If you have striping it will melt the snow directly above the tube and then you will lose the insulation value of the snow causing too much heat loss and it prevents the slab from heating up as fast. You have to heat the slab evenly and that is easier to do when the heating elements are closer together. This is also why many hydronic systems idle. Idling is running the system at a small capacity priming the system for a faster reaction to the snow. Electric systems are either on or off and do not require idling, however, one manufacturer (I will not name for advertising purposes) just came out with an idling system that will maintain slab temp before the snow starts and then when activated by a sensor, runs as normal. Heat goes to cold so with electric systems there is a faster reaction time because they are closer to the surface with less space between runs.



Electric systems can deliver the same heat output that any hydronic system can (70 to over 300 btu sqft). The question is, how do we make an UN-GREEN technology that is for safety and convenience, the most environmentally responsible that we can? We try to not over design and have them activate quickly and effectively as well as turn off when they are no longer needed.



To comment on the idling, I always turn a light off when I leave a room, shouldn't everyone? Idling should be minimized as much as possible. There are two homes in Park City (neighbors) one has an electric system in their driveway, the other has a hydronic system in their driveway (that idles). Similar driveways, similar melting, however, the one with electric pays about $300 a year in snow melt, the hydronic system costs $2000 a year to run all because, either it is over designed or it IDLES too much! Someone needs to service that hydronic system for SURE!



thanks for reading my novel.