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  #1  
Old 11-27-2007, 09:50 AM
mrblaine mrblaine is offline
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Hydronic Tent Trailer Heating

I came across an article on the web about a guy who heated his 24 foot travel trailer with a home brew hydronic heating system.

For those who don't think they are familiar with the concept, I'd venture that no one isn't, you just have never heard it called by it's proper name.

Essentially you circulate heated water through a water to air heat exchanger and blow air through it to extract the heat and circulate it into a living space. (think heater in your vehicle)

The touted benefits are it's much safer with no fumes at all. The heat is of a different nature being more radiant and smoother if you will, without the harshness of a forced air furnace with it's higher on and off temperature differences.

I built a working prototype with parts in my garage in a few hours and so far I am highly impressed. So much so that I may consider one for the camper.

The basic design is a Setrab oil cooler as the heat exchanger, a pair of computer fans on a dimmer switch, our shower water heater, a propane tank and a small circulation pump.

The water heater is used to heat the water and then it's circulated through the heat exchanger. The pair of 4" muffin fans then blow air through the core of the exchanger and warm air is dispensed out the other side.

The goal is to solve a few minor problems and drive the efficiency of the system way up and not have any portion of it be louder than the burner on the water heater.

I found some near silent computer fans with a 6db sound level that accept variable input DC voltage. It remains to be seen if the variable input voltage will also vary the blade speed which we need. Being DC though, they should be controllable with a DC motor speed controller.

I also found a miniscule pump for circulation that is brushless and it will need to be tested for it's sound level and efficiency, although at 2.5" square and 95 gallons an hour, I don't think anything more efficient is available for the price.

I am testing with a small single fixture RV pump slightly smaller than the orange juice glass at the cheap restaurants and it's a whiny little beast, so that will have to change.

The goal is to have the majority of the system be able to be run during the daylight hours on a portion of the output from a decently sized solar panel for the electrical side and then not have it cycle the water heater enough that propane use becomes exorbitant.

I'll get some pictures of the process as it gets more refined.
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  #2  
Old 11-27-2007, 10:53 AM
ABQ TJ ABQ TJ is offline
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sounds like a neat idea!
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  #3  
Old 11-27-2007, 09:45 PM
NAILER341 NAILER341 is offline
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that is a great idea.. i look forward to seeing the results.
my "buddy" heater is loud, puts out too much light and is less than safe.
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Old 11-28-2007, 08:36 AM
mrblaine mrblaine is offline
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I need a better thermometer, but some more proof of concept testing last night showed that varying the fan speed does affect the temp output.

Not by much though. Bear in mind that I'm testing in an open garage and my return air is not being reheated. I'm drawing in fresh non heated return air on the backside of the computer fans.

I was able to get our digital camp thermometer up to 118?F and when I reduced the fan to an inaudible level, the temp dropped to 114?F.

The next step in testing will be with some off the shelf computer cooling components.

We found a small brushless pump that works on 12v DC and some silent or near silent computer fans that run at 6 db at near full speed.

Along with the fan, we found purpose built radiators that accept the 120mm cooling fans.

I'm pretty happy with all the results so far.

BTW- does any one know how to convert a Cubic meter per hour fan rating to CFM?
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Old 11-28-2007, 08:46 AM
Kiwi Kiwi is offline
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Quote:
Originally Posted by mrblaine View Post
I
BTW- does any one know how to convert a Cubic meter per hour fan rating to CFM?
1 cubic meter/hour = 0.5885777549 cubic foot/minute
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Old 11-28-2007, 09:08 AM
mrblaine mrblaine is offline
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Originally Posted by Kiwi View Post
1 cubic meter/hour = 0.5885777549 cubic foot/minute
Did I do this correctly? We are looking at the 1200 series fans and they show 81 CMH which I translate to 47 CFM.

If so, that should be more than ample for air circulation if I use a pair of them on a DC motor control.
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Old 11-28-2007, 09:12 AM
Kiwi Kiwi is offline
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Originally Posted by mrblaine View Post
Did I do this correctly? We are looking at the 1200 series fans and they show 81 CMH which I translate to 47 CFM.

If so, that should be more than ample for air circulation if I use a pair of them on a DC motor control.
That's correct, 47.7 cfm
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Old 11-28-2007, 09:42 AM
steelman steelman is offline
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Nice work Blaine!
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  #9  
Old 11-28-2007, 11:31 AM
Lawrence Lawrence is offline
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Quote:
Originally Posted by mrblaine View Post
Did I do this correctly? We are looking at the 1200 series fans and they show 81 CMH which I translate to 47 CFM.

If so, that should be more than ample for air circulation if I use a pair of them on a DC motor control.
I thought we were going with the quieter one which is the 800 rpm? If so, the airflow is 59 m3/h translating in 34.7 CFM. Let me know which one to order.

For our test radiator, I am thinking of ordering the Thermaltake AquaBay M2 http://www.coolerguys.com/840556020844.html It comes out to be cheaper than the Swiftech since it is comes in a case providing mounting point. It also comes with a 1,300 rpm/16 db fan providing 54.4 CFM. The only downside is that it weighs 925g or about 2 lbs.

Edit: Nevermind, the swiftech radiator it is and the 1,200 rpm fan since we can slow it down.
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Old 12-07-2007, 04:29 PM
Lawrence Lawrence is offline
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Last weekend I went over to Blaine’s to test the computer water pump and the purpose built computer radiator. The water pump was a bust as it never ran, no idea why. As for the radiator, it was extremely inefficient compared to Blaine’s Setrab.

The outside temperature was 62 F, and running the 2 fans (on med-low speed) hooked up to the Setrab, the blown air temperature quickly rose to 114 F and held steady. Then, we hooked up the computer radiator with its attached fan, and it could not hold the temp. As a matter of fact, you could see the temperature dropping quite rapidly, and we stopped the test when it was in the mid 80’s F, still declining. Conclusion: the Setrab rules.

Overall, I was really impressed by this system, it puts out a nice soft heat. Think of your home central heat, with a “softer” air to it. It also doesn’t cycle the water heater that much, thus in theory, not consuming much more propane than required to heat the water. There are no fumes to worry about and you can touch every part with your hand without running the risk of getting burnt. This is a nice system so far.
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  #11  
Old 01-07-2008, 04:31 PM
Lawrence Lawrence is offline
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So this weekend, we did a little more testing.

We hooked up the Noctua computer fans (rated at 81CMH or 47.7 CFM) and they sucked, both literally and figuratively. They were whisper quiet but didn't work well at pushing air through the cooler. Regardless of what we did, air was being sucked out instead of being pushed through.

But, not all was lost as the best results of the day were regarding the cooler. One of those tests involved using Blaine’s Setrab cooler and another (B&M type, the one with the fan mounted to it) commonly used for transmission cooling. Bottom line is that we knew the Setrab was good, but we didn’t know it absolutely ruled. It dissipated heat like crazy. Although it was warm to the touch, you could handle the Setrab without any problems. With the other cooler, after running hot water through it for about 2 minutes, you could not leave your hand on it, it was burning hot.

So far we will be sticking with Setrab for the cooler. The next step is to find some high CFM fans that are both relatively quiet and don't draw too much amp, and I am ordering a variable speed water pump to test.
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