carver p4 furnace for isolde - part 5

This is a continuation to a previous post carver p4 furnace for isolde- part 4.

Why so many damn parts, one may ask. The reason is simple. This is a blog, and not a review of a product publish on a for profit online media. Most of my posts are driven by the photos and video that I capture during daily life. They are not planned, but rather result from chance encounters or spur of the moment.

I want to share the finesse operation cycles of the Carver P4 furnace because to cite how quiet it is and how much or little current consumption cannot convey how it was designed to work in the most efficient and unobtrusive ways. It is worth noting that recording video with a common consumer electronics the sound level of the audio cannot be trusted to gauge the true level in situation. These devices, such as the iPhone used here implemented automatic and dynamic recording volume control. The algorithm continues strive to capture the faintest bits of sound even when it is dead silent.

00:00 - 00:17
Comfort air circulation fan runs at a murmur still transporting warm air from the residual heat of the cast alloy heat exchanger from the previous burner cycle. The murmur circulation of the air is the mean for the furnace micro-controller to sample the cabin air temperature.

00:18 - 00:32
One of the two micro-controllers decides a "call for heat" cycle is required to maintain target cabin temperature; pre-purge ensures; the current jumps from 180mA to 320mA because the combustion blower starts but is modulated to very low speed.

00:32 - 02:50
Gas valves (there are two out of three used in this mode) for the high BTU setting open and immediately followed by the spark ignition; you can hear the faint pop as the flame ignited; the current ramps from 320mA to 380mA due to the increase load of the gas solenoids. The burner blower also speeds up and the current steadily increases quite quickly, to around 750mA. Note that during this time the comfort air blower is still running at a murmur, as there is no need to waste energy running it any faster, because the heat exchanger has not built up in temperature quite yet.

02:50 - 03:26
By about 02:45 the current creeps up to 770mA as the comfort air blower speed is modulated up ever so little to transfer more heat energy from the heat exchanger into the cabin. At 03:25  one of the two micro-controller turns off the burner, and the current drops rapidly to 190mA.
03:26 - 04:11
There is a lot going on here. It just coincidental in this situation that when the burner is switched off, the comfort air blower is being modulated up to manage the heat energy that is stored in the heat exchanger by transferring the heat faster into the cabin, but not all at once in a short time. Because the spread of the actual cabin temperature and the target cabin temperature is small (not super cold outside the Vanagon) the blower fan runs at the murmur, and consumes 190mA.

Note: if you are unable to read the texts on the meter, please set the Youtube playback option to 720pHD



As you can see in this complete combustion cycle (with the furnace set to high, 2200W), the maximum current consumption is only 750mA, and only when the burner is running at a steady state. There can be time that the entire furnace consumes close to 1.75A, if my memory serves, when the outdoor ambiance is extremely cold, and the burner on cycle duration is very long. During this situation, the comfort air blower also runs at higher speed to transfer much more heat energy (per unit time) from the heat exchanger into the cabin air.