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Old 01-13-2010, 12:32 PM   #81
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Originally Posted by Jammer View Post
Malconium,

There are lots of alternatives in fan-forced units if that's what you want.

Rear Air Conditioners RV Van SUV Specialty Vehicles

The amp draw and quiet operation benefits are lost however so scorched air starts to look good again.

If you anticipate having shore power available then there are many choices for boilers. The yacht guys all use electric for hot water. They're small and cheap, install as many as you need and have electricity for.

Marine Water Heaters on Sale

You asked about expansion tanks. Hydronic systems have more water in them than a water heater alone and so the amount of expansion is proportionally greater. Expansion tanks are cheap and easy to install. You want one.
Is it your thought that radiators that do not have fans in them would be a better way to go? I was looking at the fan base units as extra heat capacity when it was cold. I do not mind going with some back up radiators but I need to find (or build?) some economical and lightweight units of some sort. The fan driven heaters at about $170 each are pretty reasonable for the extra capacity when it is needed.

I see that the electric marine water heaters for the most part are only 1500 watt appliances. I believe that translates to just over 5,000 BTU. That being the case it would take several units and probably more shore power than my 30 amp system would handle to do the heating. I was interested to see though that a large number of these units had built in heat exchangers through which hot water could be pumped when available. This might be an interesting type of unit to go with if I had a tankless LP water heater. I could have both a heat exchanger and a holding tank without the need for an extra pump or a siphon action. The electric element could be backup for the potable hot water heating only. I could run coolant in the rest of the heating system too if I wanted too. More food for thought...

Malcolm
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Old 01-13-2010, 01:30 PM   #82
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A new-in-box heater core for a 5 or 7 year old car can be had for $25 shipped off ebay - add a one or two low RPM Panaflow 12VDC Fans (also off eBay) and borrow the neighbors rural route mailbox or kids' Transformers metal lunch box and you have a $40 heat exchanger...

Only hitch to using automotive is they are designed for 200F water and may not be too efficient at 140F - but its better than being bled $170 for something you could do yourself...



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Old 01-13-2010, 07:45 PM   #83
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How about copper radiators?

I remember that some years back you could buy copper solar collector panels that were made out of copper sheets that were stamped with a pattern of channels and then were soldered and/or crimped together. I have done some surfing but I can not find any source for this type of copper panel. Has anyone seen this type of panel anywhere?

I thought this might be an interesting way to get some extra radiant heat surface above the floor depending on size and price of course. They should be relatively thin so they would not intrude into the living space too much. I might even be able to flex them a bit to get them to conform to the curve of the outer wall or ceiling depending on where I wanted to put one.

Malcolm
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Old 01-15-2010, 02:57 PM   #84
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I have been looking at various combinations using some of the componets that various ones have mentioned. First of all it seems like I need a water heater of some sort that puts out more heat than does a typical 10 gallon tank type water heater. I thought for a bit that using a marine electric water heater with a heat exchange coil built into it would be a good way to isolate potable water from heating fluid. I say fluid because the heating part of the system could be some form of coolant if it was isolated from the drinking water. I thought about using just one heating pump with two solenoid valves that would select what part of the system got water flow when the pump and tankless water heater were running. One valve would let the heating fluid flow through the heating loops and the other would let the heating fluid flow through the heat exchanger in the electric water heater. I thought that I could tap into the heat sensor of the electric water heater for a signal to tell the system when to pump water to that part of the system. In investigating the various configurations I found out some interesting things.

From what I can tell solenoid valves that can handle hot water run close to $200 each. See the following:

Asco-Valve | 2 Way Valve | 8221 Series Slow Closing Solenoid Valves

Adding two such valves is way more expensive than just adding a second hot water pump to pump fluid to the hot water tank.

While the marine electric hot water heaters do not cost much more than a flat plate heat exchanger would there still is the space and weight issue of having a tank full of hot water - as well as the expense. Also it seems to me that having to maintain a tank full of hot water somehow defeats the intent of having a tank-less on-demand water heater to begin with.

I don't really like the idea of having fans involved in my heating system both for noise and electrical consumption reasons. I would rather supplement the heating loops in the floor with radiant panels mounted somewhere on the walls or ceiling. I am leaning in the direction of figuring out how to make something that fits the need my self rather than buying something. I might use some sort of radiant heating fins attached to PEX tubing for this. Perhaps this type of fin could be made to look attractive enough in an exposed location.

Ultra-Fin Radiant Floor Heating System

Maybe there is some type of radiator that I can scavenge from some other type of system. I also happen to have some flexible copper tubing left over from an old project that I might be able to use. Any thoughts on how to build an inexpensive radiant surface for mounting on the the wall or ceiling would be appreciated.

I seem to be gravitating back toward my original idea of having an open loop system where the domestic hot water is taped off of the same plumbing that is used for heating. The system is very simple and the number of components is reduced. If I use an outdoor tank-less water heater that has freeze protection and consider letting my heating system run at least some while on the road when it is cold I should be able to avoid needing coolant in my system. The unanswered questions at this point are:

1.) Which tankless LP water heater to use? This issue also involves figuring out a way to get around the potential problem of having the water heater shut down if the input water temperature is too high. The front runner right now is the following unit:

Eccotemp L10 high capacity battery and propane powered tankless water heater

I have been told though that it might shut off if the input water temp reaches about 105 degrees.

2.) Where to find a suitable mixing valve to temper the heat of the output for the domestic hot water part. That is an item that I have not yet found and priced.

3.) Identify an appropriate type of thermostat and pump controller for running the system. I might need to have some sort of temperature sensors on the radiant surfaces - at least the floor. That is unless the wall mounted radiant surfaces can run at the same temp as the floor. What I am concerned about is keeping the floor from getting too hot.

4.) Determining what type of pressure and temperature gauges to use in the system. I would love to find some sort of monitoring panel to which I could attach electronic sensors such that I could centralize control and monitoring of the system. I need to find something that is cost effective though.

5.) Find a specific expansion tank to put in the system.

Any further input would be appreciated. Once I get all the details sorted out I want to start another thread to detail the progress of the installation and testing.

By the way the hot water pump that I ordered just arrived today and it is a nice little unit. One very interesting feature is that it can run on voltages from 8 to 24 I think. Also it has a flow rate adjuster. The brush less motor has an estimated lifespan in excess of 50,000 hours at 12 volts. The company that I bought it from was very helpful on the phone and shipping was very quick too. Take a look:

East Coast Solar :: Laing D5 VARIO Bronze PV-Direct Circulating Pump $169.90

Malcolm
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Old 01-15-2010, 03:17 PM   #85
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I hope you are thinking in terms of dollar value and complexity when you consider how to build this system, Malcolm. If having a hot water radiant system in your Airstream is more important than the cost and complexity then I think you should proceed immediately! But I tend toward the K.I.S.S. principal, and this is NOT a simple, effective way to achieve the heating of a trailer. I have been intrigued by this idea for some time also, but the complexity as described here makes me want to run from this idea.
This is just my opinion Malcolm, and should be taken as such. The research and information presented here has been very worthwhile to me. Thanks for starting this thread.
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Old 01-15-2010, 03:24 PM   #86
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Rich,

I think that the biggest part of the complexity is sorting out the design and performance issues such that I can avoid a complicated and expensive solution. I agree that the information posted here has been very valuable to me as well. It has been a bit disappointing to discover that some aspects of what I want to do are not entirely practical. It has also been a source of some frustration to be tempted to select solutions that are more expensive and more complicated than what I was hoping for.

Thanks,

Malcolm
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Old 01-15-2010, 11:48 PM   #87
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Malcolm, check out www.pexsupply.com They have mixing valves down around $30. They also have selonoid valves, thermostats, heat exchangers and just about everything else you are looking for.
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Old 01-20-2010, 06:19 PM   #88
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Control and monitor from my laptop?

I would love to be able to monitor and control my heating system from an older laptop that I have laying around. It would be great to do some performance logging of some sort to see how the system performs.

To do that I need to find a source of temperature and possibly pressure sensors as well as as a pump control relay that I can hook up to my laptop through a serial, parallel or USB connection. I have an electronics background and am computer literate but I have no idea what is available in the way of sensing or control stuff these days. Can anyone point me in the right direction?

Thanks,

Malcolm
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Old 01-20-2010, 06:45 PM   #89
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One way to have the water heater work, when the trailer is in motion, is install a gasket around the two sides and the top of the water heater door.

I did that many years ago, and even the pilot would not blow out, during travel. I went accross the USA without that happening.

Strange thing though, the pilot light would still blow out, from a wind, when the trailer was parked, not often, but once in a while.

I used the same gasket as used on the screen door.

Andy
Andy,
The reason was "tunneling effects"...the wind swept over the surface..and around this point...never really got invasive enough to blow out your pilot light.
While stopped and,in use,,,the wind was free to come in at any direction.
As I see it..no big deal. perfect world.
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Old 01-20-2010, 11:08 PM   #90
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Cheap entry level USB Data Acquisition System.

The $ky is the limit once you get into HVAC and refrigeration monitors...
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Old 01-21-2010, 01:24 PM   #91
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Cheap entry level USB Data Acquisition System.

The $ky is the limit once you get into HVAC and refrigeration monitors...
This looks like a good start at he interface to my computer. These folks do not seem to have the necessary sensors for temperature or pressure though.

Thanks for the lead,

Malcolm
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Old 01-21-2010, 05:12 PM   #92
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There are cheaper ways

PC USB Thermometer thermostat measure log temperature For Sale

Keep looking around. Lots of cheap data collection stuff out there these days.

Most of them are based on the microchip PIC controller which costs about $1 each, less than that with the quantity discount. It is possible to build high quality instruments this way that while not precise by scientific standards will get you within a degree or two which for most purposes is sufficient.
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Old 05-05-2010, 11:15 AM   #93
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Malconium,

Any updates on your system? I'm interested in doing something similar. Biggest problem for me is I haven't found "my" Airstream yet. I'm looking hard, though.

I would think that the system you are thinking on has an advantage that I don't think anyone has mentioned yet: you will not be constantly exchanging the air in the trailer like you do with forced air. Your pressure inside the trailer will be more neutral. Maybe I'm way off base, but it is something to think about when estimating BTU requirements As compared to forced air.

Best of luck,

Stephen
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