Westyss
I hope I’m not about to give you more information than you want. I am camped out in the Sonoran Desert in Arizona, but it has been raining steadily for over 24 hours; the ground I wanted to be riding/exploring is saturated and is now impassible mud; and I have 4 bars of 4G cellular data availability so I can take the time to respond.
I have tinkered with my system quite a bit over time and frankly it now seems to perform brilliantly. The heat is reliable, even, non-desiccating, and handled -11°F for a week.
I’ll start with a picture of the control panel:
View attachment 141912
I can trigger the Esbar D-5 in two ways:
a) with a simple-to-program Honeywell thermostat, <$25.00 from Home Depot; [this is out of the picture, mounted in a more representative location for sampling general temperature]
b) with the Esbar 7-Day timer in the upper left corner of the picture; I use this for interval running of the D-5, like running for 30 min to heat hot water in warm weather.
A 3-position toggle switch determines which device triggers the D-5. This switch is at the lower right corner of the 7-day timer.
Each of the (3) three-position switches to the right of the above controls a fan on one of each of the three radiators. The "AUTO" position routes through the thermisters; "MANUAL" by-passes them and turns the fans ON. [The radiator-fan marked “REAR” sends heat via ducting to the bed area, the bathroom and the rear storage locker accessed from outside. This provides sufficient heat to prevent freezing of gray and potable water in very cold weather. The other two radiator-fan units vent directly into the house from behind standard rectangular grills.
Above each of the toggle switches is an indicator light, giving visual indication respectively whether the D-5 or any of the (3) fans is “ON”.
Between the two analog meters is a two-position switch that controls whether the fans operate at high or a low speed The latter is governed by a parallel-wired path thru a set of high-amp-rated resistors. I plotted resistance values against amp draw and perceived air flow in real time until I found what seemed to be an optimal resistor value. My recollection is that I found a value that reduced the already-low-noise level to almost inaudible, seemed subjectively to give enough air flow (which it does!) and reduced the amperage draw to about 1/3 that of high-speed.
The fans I settled on using are Mechatronics 1751 units. I selected these as the best combination I could find of low amp draw, high airflow and low noise [esp at low speed which is all I ever use.]
I used standard Heater Craft radiators, cutting new openings for the fans since they were much larger diameter than the stock [very noisy and high drawing] fans.
As to the thermistors: Each radiator housing has one mounted on the outside of its metal case, wired in series with the power supply to the fan motor. These were supplied by Darren Fink in the original package. I recall wanting to get a couple of extras, but… While they have a number on them, there is no name or trademark. Google search turned up nothing, and Darren told me he could not remember any details about them. The heated air coming out of the radiators runs ± 160°F when the hydronic is burning; the fans come on at about 90°F and seem to go off about the same. As you can understand, this keeps the fans from running until the radiators are hot enough to do some good, and shuts them off after they have cooled down — all to prevent unnecessary electrical consumption.
If you are willing to pony up for the 7-day timer, not only is it good for timed runs but it will read fault codes from the D-5. This is VERY USEFUL. However, you need to be sure that the “ignition” wire is hot. The manual with the timer explains this and gives clear details about which post to connect. I simply added a 2-position switch in line to a hot source. In my setup, the timer simply connects to the ignition-ON wire to the D-5, as does the thermostat, regulated by the 3-position switch described above. So I had to wire the ignition circuit in separately. Simple to do, and very well worth it.
I hope this helps. If you want any further info, just lob a question at me.
Best, John