Heating using the hot water tank.

[WoodSmith]

I just found this thread and am fascinated by it. I see links to the pump and fans, where did you get the clean radiator? It seems like this would be the hardest part to source.

[Socal Tom]

I just found this thread and am fascinated by it. I see links to the pump and fans, where did you get the clean radiator? It seems like this would be the hardest part to source.

A heater core from any number of vehicles would work good for this. Here is one for an early bronco that would probably work well
http://www.napaonline.com/Catalog/Catal ... 0278419494

It $29 at napa.
Tom

[lrrowe]

I just found this thread and am fascinated by it. I see links to the pump and fans, where did you get the clean radiator? It seems like this would be the hardest part to source.

The transmission ones I found were found on eBay.
Example = http://www.ebay.com/bhp/aluminum-transmission-cooler

[MtnDon]

My device is a transmission oil cooler. Never used as a tranny cooler, I previously used it on a different heating project a few years ago. It was pressure washed and rinsed before being introduced into the potable water system.

[MtnDon]

Interesting to note the degree equivalents for the L-M-H settings Bob


An additional discovery tonight. The thermostat gas control in the water heater is not a precision control device. That is, the water temperature drifts somewhat. For example, the water temperature can vary from a low of around 108 F just before the thermostat calls for more heat, to about 127 just after the thermostat cuts of the gas to the burner.



With the trailer interior at about 65 F I have measured the temperatures just before and after the radiator. This is using an IR thermometer with the sensor face held close to the pipe.* With the inlet temperature reading 126 (125.9) the return line was reading 125 ( 120.8 ). The center of the finned face was reading 100.9.

More as it develops.


* The sensor is recessed about 1/3 of an inch inside the snout of the IR thermometer. I held the case face against the PEX.

[Socal Tom]

Interesting to note the degree equivalents for the L-M-H settings Bob


With the trailer interior at about 65 F I have measured the temperatures just before and after the radiator. This is using an IR thermometer with the sensor face held close to the pipe.* With the inlet temperature reading 126 (125.9) the return line was reading 125 (120.. The center of the finned face was reading 100.9.

More as it develops.


* The sensor is recessed about 1/3 of an inch inside the snout of the IR thermometer. I held the case face against the PEX.

Is the outlet 125 or 121?
If it's 121 and the pump is moving the 3 gallons/minute then it shou.d be 7200 BTU/hr. If it's 125, then it's 1440 btu. I'm guessing the 1440.
Tom

[bdosborn]

How does it compare to a heater outlet on your car? Is it the same volume of air when your car heater is on high, med, or low? Does the air coming off feel hot or just lukewarm?

Bruce

[MtnDon]

By inlet, I mean the inlet to the radiator. By outlet I mean the exit from the radiator; returning to the water heater. Sorry, I realize the way I worded it could lead to some confusion between the radiator and the water heater. So the pipe going into the radiator was 125 and the pipe on the outlet side of the radiator was 121.

[MtnDon]

Bruce, I would characterize the fan speed as a low setting compared to our car or truck.
Temperature of the air blown by the fans would be characterized as medium warm.
Considering the car & truck both have a 195 F thermostat I don't think there is much chance this experimental heater will ever blow hot.
But it is much warmer in the trailer than outside; exterior is running 44 right now and the inside is at 70 and warming. Water heater on high.



I just came back in with another set of measurements.

Water heater set on high.
Just after the water heater thermostat control shut off the burner the Pex pipe going into the radiator read 136.5
The pipe exiting the radiator read 132.0.
The center face of the radiator core read 114.5.

15-20 minutes later the temperature going into the radiator was 128.1 and the temperature exiting was 123.5, with the radiator face at 105.2


Maybe tomorrow I'll run the two 90 CFM fans. (Present set are twin 45 CFM.)

[Socal Tom]

I just came back in with another set of measurements.

Water heater set on high.
Just after the water heater thermostat control shut off the burner the Pex pipe going into the radiator read 136.5
The pipe exiting the radiator read 132.0.
The center face of the radiator core read 114.5.

15-20 minutes later the temperature going into the radiator was 128.1 and the temperature exiting was 123.5, with the radiator face at 105.2
)

If the water in the water heater is cooling from 132 to 128 over 15 to 20 minutes, then the 48 lbs of water are losing 4 degrees for a total of 192 BTU every 15 or 20 minutes, which is 600 to 800 BTU/hr.( assuming no extra heat is being added)
Tom

[lrrowe]

And wouldn't the numbers be better if you insulated the pex pipes and had a shrould around the raditor and fans?

Also would not the temp of the air before the fan affect the outcome? Recycling the heated cabin air through the system should help.

[Socal Tom]

And wouldn't the numbers be better if you insulated the pex pipes and had a shrould around the raditor and fans?

Also would not the temp of the air before the fan affect the outcome? Recycling the heated cabin air through the system should help.

The overall temps will come up as the air is reheated, but as it warms in the trailer, the rate of heating ( BTUs/HR) will drop. for example, heating from 30 to 40 degrees with 100 degree water will go pretty fast, but heating 90 degree air to 100 will take longer with 100 degree water.

A shroud would direct the air over the radiator better, which might improve the BTU/hr.
Tom

[MtnDon]

The numbers might be better with insulated pipes, but by how much? Any heat loss from the pipes goes into the heated space anyhow. A fan shroud could help, especially if the fan could be spaced back a few inches from the fins. (I think). But in my situation that runs counter to my space allotment.

To get more heat out of the heated water, the best method would likely be to increase the size of the radiator, increase the finned area. As well shroud the fan more or less like an automobile uses a shroud with the fan and radiator. This test was done with the radiator I had on hand. There is one similar to it that is a few inches longer, same height/width. If I was buying new I might pick that. If space was not tight I'd probably choose even bigger. Maybe. As it is, with the twin 45 CFM fans the outside / inside temperature differential, with water heater on high, is about 36 F with pump and fan running continuously. That would let us camp easily in places where the outside night time temperatures could drop to freezing and slightly below. At least that is my thinking.

We'll see if increased fan speed has much effect. I could add a second, series plumbed radiator in the space I have. That would mean more fans unless I figure out where and how to make small shrouds work. Or move the whole radiator to some other place. I don't see a lot of options for placement though, while keeping the plumbing runs simple.

[lrrowe]

MtnDon's encouraging results so far and the fact that I probably do not the trailer warmer then 70 anyway during the day and in the 50/60's at night, this really does look like the way I want to go for primary heat and a Mister Buddy or a Nu-Way for back up for serious camping.

I am sitting in the recovery room with my wife right now as she winds down from cardio catherization process. She does not have an artery blockage as was thought, but rather a valve malfunction that will be dealt with later. And I had my last back steroid injection, so this means I can back to back to trailer work. And I believe I will get many of these parts on order.

[Socal Tom]

If I were starting from scratch, I would use an automotive heater core rather than a transmission cooler. The transmission cooler is really designed to cool a petroleum product from 300F down to 200F or so, in a 60 MPH wind, so its going to struggle taking the heat out of a 120 degree water with a small fan. A heater core is intended to work with something closer to water, at temps around 150 to 200 degrees, and to work with a much slower fan speed. My guess is that moving to something like the one I posted would pull a lot more heat out of the water on a single pass, and transfer much more energy to the cabin.
Tom