Hot Water Radiant Heat - My Installation

[malconium]

I did actually do some approximate heat loss calculations a long time back to get a feel for what might be needed. One of the concerns that surfaced at that time was that I might not have enough floor area to heat the space in worst case conditions. That is why I have had the back up idea of using a fan assisted heating coil if needed.

Using an IR gun is a good idea. I do have a small one that I used a while back to do some tests on the effectiveness of reflective foil insulation. I didn't think of using it for testing the surface temps or heat loss. I will definitely dig it out and start using it. Also I did buy the dual heat probe assembly recommended earlier in this thread so I will be able to monitor the water temperature in the PEX at two points.

I did not mean to imply that I actually removed the strainer altogether. I just found that it was clogged up with some debris which I removed. That would be interesting if I could fall back to a smaller pump and I will be looking to see what the new flow actually is. I still have the two pressure gauges in place so that I can monitor what the new flow resistance actually ends up being. I can then see if the number is low enough to fall back to a different pump.

I did buy a toggle switch that I intend to use to allow me to turn on/off the fan in the fan assisted heating coil. The water would still flow through the coil but I could at least turn off the fan if I want to for noise reasons or for power consumption issues.

Now I just need to be able to focus enough time to get back out to my Airstream and finish the installation.

More later...

Malcolm

[Jammer]

Originally Posted by animatt

I did not see it mentioned anywhere. For anyone in the future the aluminium plates for the pex radiant install would have helped out a bit in this situation.

It pulls much more heat from the pex. Which would have heated space quicker, and left the water going to how water heater much cooler.

With out the plates the flooring directly over the tube heats up. This then slow the movement of heat for tube to the floor. Air does heat up much slowee and does transfer heat but not nearly as much as heat transfer plates.

With 6" spacing the aluminum plates will probably not make a significant difference (maybe 2-3%). The maximum floor temperature is usually the limiting factor in a radiant floor system. An IR thermometer will show if the radiant system is heating the floor to the design point and any unevenness. Most flooring materials are conductive enough that you can't get much of a temperature difference over a 3" span.

There is no magic to radiant heat. You can't "pull more heat out of the PEX" if the floor is already evenly at 80 degrees, unless you want the floor hotter than that.

[Jammer]

Originally Posted by malconium

or.

Relative to tank type water heaters it was my thought that typical RV units simply do not have enough BTU capacity to heat water enough. Perhaps I am wrong about that. If I recall most of the units that I looked at were rated somewhere in the range of 30k BTU's which did not seem like enough.

Malcolm

Hydronic system design is all about balance.

Malcolm's system, based on radiant surface area, can't dissipate more than around 8,000 BTU/h. The fan coil should have its own BTU rating though these are usually based on 180 degree water and would have to be derated for the water temperature actually in use. I have a table somewhere but for 130 degrees it's roughly half.

Any of the standard tank-type RV water heaters could deliver 8,000 BTU per hour.