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edwards

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Posts: 6
Reply with quote  #1 

I am planning on building a hot water system to heat our water and provide some space heating. I have several questions, but will deal with them one at a time.

We have wood floors in our house. Including the subfloor, it is just over 2 inches thick. Is it worth putting in radiant heating under all that floor? The basement is also heated, if that makes a difference in the answer.

Thanks,

Ed

kenneth w

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Posts: 3
Reply with quote  #2 
I am not a expert But I would from my own staple up under floor radiant that the answer is. yes
Your radiant heat will have a slower response time. But the therm mass will help in cloudy weather. 
If your heating  the basement. The heat that doesn't go through the floor will help heat the basement.
Kenneth W
MN
netttech

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Posts: 720
Reply with quote  #3 
Assuming your basement ceiling isn't insulated, you may want to try a hot air panel & blow the heat into the basement. Once the basement is heated the natural flow upwards would heat the floor above.

A hot air panel is very cheap, easy to construct compared to installing pex onto the floor. It may be worth while to try that option 1st.  I have pex under the floor (crawl space) & when my hot water panel is running I can easily detect when I step on a section with pex. My floors is about 1 1/2" thick.

My parabolic panel isn't producing very hot water (115 degrees). To answer the question, yes I believe it will work with 2" floors. Especially if your panel produces hotter water than mine currently is.

Jeff
Central IL.
edwards

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Posts: 6
Reply with quote  #4 
Thanks for your two responses so far. Currently my main heat source is a wood stove in the basement. It's surprising how much hotter the basement can be than the main floor. One problem, which I plan to rectify before going solar, is lack of insulation in the walls.

I want to use water so I can heat our DHW with solar as well.

I am an acupuncturist that works from home, so the main room I need to heat is the treatment room, and it needs to be pretty cozy. Right now, I use one of those oil filled electric heaters. Also there is a one foot square vent, directly above the wood stove, into the treatment room. On 40+ degree days, like to day, I turn the heater off mid morning, but when it is in the 30s or colder, The heater is going all day long.
netttech

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Posts: 720
Reply with quote  #5 
You probably know this, BUT insulate. It's a big return on your money if there isn't any insualtion right now. Spend your money on insulation, windows first before buying/installing pex.

Retaining whatever the heat you generate from any source is an important part of the goal. Adding a second vent would help.

FYI, solar DMH requires special attenation if you use a pubic water source. You may need to check local regulations prior to starting your project.

Jeff
Central IL
solardan1959

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Posts: 1,845
Reply with quote  #6 
Radiant floor heating questions,
   One of the early things I read that really got me thinking about water was something Scott Davis has on his website.  He states that if you don't want to build a tank just build a collector and hook it up to a pex tubing radiant loop directly.  It seems like the more I read the more I stray from this most basic heating concept.  My questions are:
1. Is anything else needed for safety etc, other than a panel, a run of pex with flashing, a pump, a snap switch? 
2. Could it overheat and how can that be prevented.
3. How much collector for each 10 feet fun of flashed pex? (any other guideline will work)
4. Using the tank drawing attached, what's the best way to keep from overheating, or would it with say 60 square feet of collector.
Dan

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netttech

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Posts: 720
Reply with quote  #7 
This is my 3rd year for a solar hot water panel. Until this year I didn't have a storage tank & pumped the heated water direct thru the pex tubing. Matter as fact, I just completed the plumbing into the storage tank tonight.

The hottest temp I've ever had (seen) in my panel was 190+ degrees last year. It happened on a weekend & I was outside spreading salt to clear ice from the driveway. I have themometers mounted on the input/output piping & noticed the temps was way higher than normal & climbing.

My pump had burned out & the water wasn't circulating. I had enough large pieces of carboard to quickly cover the panel. I have no idea how hot the water was inside the panel but it smelled very hot. The output thermometer was registering 192 after I got the panel covered.

I don't know if anyone has dual pumps or a backup but I think that would be the best option to ensure it doesn't over-heat.

Even though my parabolic panel isn't working as well as I think it should be....I do know it heats to 160 degrees if I manually turn off the pump in about 15 minutes.

As for the size, bigger is always better.

Jeff
Central IL
solardan1959

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Reply with quote  #8 

Jeff,
   I wonder why people don't make high temp alarms?  I bought some water detector alarms at I think northern tool. Something like this replacing the water sensor with a snap switch, or a snap switch with a red bulb, etc to alert you when something goes wrong.  Still I guess you have to be home.  Maybe a second snap switch at a higher temp setting hooked to that second pump. That way when it starts to get hotter the second pump speeds up flow or takes over for the failed pump.  This should be a whole new topic as I could go on and on.

How big were your loops as compared to your panel and what kind of temps do you get through the pex heat loops? 
Dan

netttech

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Posts: 720
Reply with quote  #9 
I've never measured the returning water temps after it's pumped thru the pex.

I currently have about 450' of pex loops under my floor. My parabolc panel is 10'L x 5' T & only producing about 8 degree increase. That's pretty poor performance & haven't figured out why it's that bad. I'm compring to 2 previous panels that performed a lot better.

I pre-heat the water going into the solar panel. When heated water enters my crawl space I have a dedicated direct line that returns back to my circulating tank. That quickly raises the temp in the tank, that increase the water temp entering the solar panel.

That being said, this panel is only producing 100-115 degrees maximum temp. Pretty poor performance.

I'm planning to change from parabolic to Flat Panel configuratiopn this spring.

I'm betting someone DOES make a high temperature alarm system that likely notifies you in somehow.

It's likely being used in outside of Solar panel though. Standard furnaces DO have a sensor (hi-limit switch) that will shut-off the gas valve in the event the fan doesn't turn on. Basically it is a snap-switch that is used as you described.

The only fail-safe method is to have a 2nd pump wired to activate if temps raise too much (primaru pump failure).

I haven't seen any postings about pump failures causing a lot of problems though.

Jeff
solardan1959

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Posts: 1,845
Reply with quote  #10 
Jeff,
  One 10X5 panel was all you used to feed 450 feet of pex?  I am thinking about running 120 feet of pex through my Long horizontal screen collector this summer and directly feeding it to something to either preheat water via a direct storage tank, I would only use 1/2 the year, or directly to pex on floors and walls.  I was only figuring about 150 feet of this at the most.  I am also interested in running it to baseboard water heaters or radiators.  I may add 3 or three 4X8 water/air heaters on my garage to help heat it and some more pex under the tile in my entryway and additional house heating.  This recent cold though has really shown the benefits of a storage tank for night time heating also.
Dan
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