Dometic Power Consumption

[GallenH]

I've been toying for some time with replacing my Dometic 2310 3-way fridge with something.......it's begining to not respond to the thermostat control and doesn't seem to make a difference if it's on max or min temp. So the logical 3-way replacement seems to be the 2354 which is the same size.

BUT, from what I can understand from on-line comments, it takes 1.3A constantly just to run the circuit board. If that's the case, it seems like a small jump to a compressor fridge of similar size which appears to be using 2.2A when running.........and it wouldn't run all the time.

Does anyone know if my stats on the 2354 are accurate?

If so, I'd have to increase my battery capacity either way.

Thanks in advance
Glenn

[hbn7hj]

My memory says that it takes over 1 amp (1.2 amps) to run the circuit board and the propane solenoid when the flame is on. The circuit board alone is about half that.

A compressor fridge takes 40-60 amp-hours per day to run, I think. Maybe you should try for 100-200 watts of solar. 100 watts of solar worked for me with a 2354 even before the addition of a 100AH lithium battery. Were I to add a compressor fridge I would add a second lithium battery. Just an opinion. I can do more accurate current readings when the Roadtrek gets back on the road in November.

[GallenH]

Thanks, Harry for your responses on both issues! Hope all is well. White Mountains had snow last week. Pads at Winn were completely covered with
snow so you couldn't tell if you were on or off. They said they got 4".

[RT-NY]

Originally Posted by hbn7hj

it takes over 1 amp (1.2 amps) to run the circuit board and the propane solenoid when the flame is on

It is possible to reduce the solenoid draw by putting in a converter to lower the voltage once the solenoid is engaged. It's a bit of effort to install, but it works OK. See: https://sprinter-source.com/forums/i...threads/68288/

Mine seems to draw about 1/2 amp at the lower voltage, but I do not have a good monitor installed so that is approximate. With the house battery I have now, 12 amps hours a day for the propane fridge is manageable but 40-60 for a compressor would not be. On the other hand, LifePO4 prices have come down a lot!

[GallenH]

So is the larger draw when the LP solenoid is engaged? Having an old 2310 which doesn't have any circuit board, I believe that the thermostat controlled whether or not you were in "heat" mode when the temp in the fridge had to be raised, or in a (basically) "pilot light" mode when the temp in the fridge met the thermostat control setting. Is that what is happening in the circuit board? That the higher amp usage occurs when the fridge is in heat mode to engage the solenoid and it drops in maintine mode. IOW the higher amps are necessary to keep the LP valve at "high" level? And IOW the higher amp draw is due to keeping the solenoid engaged?

[SteveJ]

Originally Posted by hbn7hj

My memory says that it takes over 1 amp (1.2 amps) to run the circuit board and the propane solenoid when the flame is on. The circuit board alone is about half that.

I'm thinking that would be a bit strong on the current. I'm seeing about 9-10 watts with solenoid engaged on our 2862 Dometic. IIRC, the Dometic(RM2553?) in our RT was the same. About half without the solenoid. These numbers came from our shunt based monitor.

[booster]

The no circuit board versions would likely be using a push button to turn on the valve pilot flow path and strike an arc to light the pilot.


The then lit pilot would heat a mechanical proof switch that would start the main burner. I am not familiar with valves, but it might be a milivolt opening or pure mechanical, I think, so would use essentially no power.


Even 10 watts is quite a bit of power for a gas frig in the big picture, I think. We are talking about 20ah per day if the frig on full burner all the time like many seem to be. Add another 10ah per day for detectors, battery monitors, etc that run 24/7 and you use nearly half of the usable power of a 100ah battery every day (assuming 80ah usable).


Compressor frig power use seems to be kind of variable, and most people don't have the ability to do 24 hour use data collection in a variety of situations so they don't really know for sure how much they are putting into the frig.


Our 3.1CF Isotherm on the bench in 70* ambient and 38* inside temp will use a bit over 20ah per day for instance, and will come very close to that in good conditions while camping. We have seen it in the 40ah range when temps are very hot in the 100*+ range, though. So, for us a gas frig would use 1/2 to 1/4 as much as the compressor frig assuming the gas valve was on all the time.


It would nice if they still made a manual lighting, no power use, gas fridge for those that don't have much battery capacity and aren't able to increase the capacity and charging.

[RT-NY]

Originally Posted by booster

The no circuit board versions would likely be using a push button to turn on the valve pilot flow path and strike an arc to light the pilot.

This is the what I have on my fridge, so I suppose that all of the draw is from the solenoid. The point of the modification I linked to above is that it takes more power to engage the solenoid to start the flow of gas than it takes to keep it engaged. So, you install a converter and a switch -- you apply 12 volts when you turn the gas on, then lower it to about 6 volts.

I misstated the amperage numbers on my fridge above: it is about .6-.7 amps to run the solenoid at 12 volts. I can reduce it to about .2 amps so perhaps 5ah per 24 hours.

[booster]

Originally Posted by RT-NY

This is the what I have on my fridge, so I suppose that all of the draw is from the solenoid. The point of the modification I linked to above is that it takes more power to engage the solenoid to start the flow of gas than it takes to keep it engaged. So, you install a converter and a switch -- you apply 12 volts when you turn the gas on, then lower it to about 6 volts.

I misstated the amperage numbers on my fridge above: it is about .6-.7 amps to run the solenoid at 12 volts. I can reduce it to about .2 amps so perhaps 5ah per 24 hours.

Using reduced voltage hold on solenoids is quite common, but I don't know if I would do it on a propane valve. The last thing you want is it to get into a partially open position and I think the variables of gas pressure and voltage would be something to consider

[avanti]

When designing our current van, I researched the availability of bi-stable gas valve solenoids, which would only consume power during an on/off or off/on transition. I concluded that it was possible (though not easy) to source such a thing. I ultimately concluded that the approach was somewhat less safe than a conventional valve, since in a crash the latter has a decent chance of shutting off due to power interruption. How much difference it would make in practice is hard to say.

[RT-NY]

Originally Posted by avanti

bi-stable gas valve solenoids, which would only consume power during an on/off or off/on transition . . . I ultimately concluded that the approach was somewhat less safe than a conventional valve, since in a crash the latter has a decent chance of shutting off due to power interruption.

I agree that is safer to have the non-powered state of the propane solenoid to shut off the gas.

I do not think that there are any safety issues using the standard solenoid at a lower voltage in order to reduce power consumption because the worst case is that it shuts off unexpectedly not that it stays open when you do not want it to.

[RT-NY]

Originally Posted by booster

The last thing you want is it to get into a partially open position

I have experimented with slowly adjusting the voltage and from what I see it clicks open at the threshold voltage or just stays shut. Is it possible to hold a solenoid in a partially open position based on power level? I would imagine that the tension in the spring would prevent that.

[avanti]

BTW: my ultimate solution was to have a very convenient inside switch to turn the gas on or off as needed (in series with an outside switch for filling). This works great for us since our only gas consumers are the genset and the cooktop, and we never use the genset. Obviously this doesn't help if you have an absorption fridge.

[booster]

Originally Posted by RT-NY

I have experimented with slowly adjusting the voltage and from what I see it clicks open at the threshold voltage or just stays shut. Is it possible to hold a solenoid in a partially open position based on power level? I would imagine that the tension in the spring would prevent that.

I have no idea how the solenoids in the gas valves is designed and built, but I can almost guaranty that the trigger voltage limit will change with wear, temperature, and maybe even barometric pressure if it atmosphere references.


Again, personally, I would not mess with a gas valve safety system like that. If I wanted zero electricity use, I would look for how they did the older frigs and get the manual lighting and power free on/off valve if that is what they used before doing the valve modification.


I don't know if the person in the link that sells kits is an individual or business, but even if it isn't the kit's fault and there is a fire he may well have to defend and prove that it wasn't the kit. If he doesn't have product liability insurance it could easily bankrupt him. The frig manufacturer would likely be mostly off the hook as they could show alternation of the frig if they could put almost any question toward the modifications. Of course in the real world the lawyers will go after everyone so all could have to pay.

[RT-NY]

Originally Posted by booster

I don't know if the person in the link that sells kits is an individual or business

I don't know anything about the kits. I am just talking about putting a buck converter and switch from Amazon, inline to the solenoid, which is the topic of the discussions that I have seen on this matter on a few different forums over the last several years.

[avanti]

Originally Posted by RT-NY

I don't know anything about the kits. I am just talking about putting a buck converter and switch from Amazon, inline to the solenoid, which is the topic of the discussions that I have seen on this matter on a few different forums over the last several years.

If I cared about this issue, I would build a setup that applied full power to close the solenoid and then backed off to an adjustable lower voltage, which could be tuned for reliability. By all accounts, the "hold" voltage is much lower than the "close" voltage. There are various ways to accomplish this--not rocket science. Such a setup wouldn't frighten me in any way.

[KanzKran]

Originally Posted by booster

Compressor frig power use seems to be kind of variable, and most people don't have the ability to do 24 hour use data collection in a variety of situations so they don't really know for sure how much they are putting into the frig.

My 7 cf Norcold AC/DC fridge with separate freezer and fridge sections (2-door) draws about 6A when it's running, which is about 40% of the time in fairly hot weather once temperature is established and stable. That's just under 60Ah per day, though it's mitigated by the solar panels on the roof. On sunny days, they keep up and then some (300W). Being that it's AC/DC, I don't need the inverter to be active for it to run, which helps as the inverter is less than 100% efficient (of course).

It will switch to DC when AC power is cut, and will default to AC when it's present.

That doesn't directly answer the OP's question, but it is real world data should the OP consider moving to a compressor fridge.

[SteveJ]

Originally Posted by booster

The no circuit board versions would likely be using a push button to turn on the valve pilot flow path and strike an arc to light the pilot.


The then lit pilot would heat a mechanical proof switch that would start the main burner. I am not familiar with valves, but it might be a milivolt opening or pure mechanical, I think, so would use essentially no power.


Even 10 watts is quite a bit of power for a gas frig in the big picture, I think. We are talking about 20ah per day if the frig on full burner all the time like many seem to be. Add another 10ah per day for detectors, battery monitors, etc that run 24/7 and you use nearly half of the usable power of a 100ah battery every day (assuming 80ah usable).


Compressor frig power use seems to be kind of variable, and most people don't have the ability to do 24 hour use data collection in a variety of situations so they don't really know for sure how much they are putting into the frig.


Our 3.1CF Isotherm on the bench in 70* ambient and 38* inside temp will use a bit over 20ah per day for instance, and will come very close to that in good conditions while camping. We have seen it in the 40ah range when temps are very hot in the 100*+ range, though. So, for us a gas frig would use 1/2 to 1/4 as much as the compressor frig assuming the gas valve was on all the time.


It would nice if they still made a manual lighting, no power use, gas fridge for those that don't have much battery capacity and aren't able to increase the capacity and charging.

I was not thrilled having to replace our old non circuit board Dometic with the new and "improved" circuit board version for exactly that reason. In practice, unless something weird happened the fridge did not run steady on for 24 hours, even in the heat. Our daily AH consumption generally ran in the 20 to 25 range, exclusive of furnace/Fantastic Fan usage. !50 watt portable solar system fully charged the group 29 battery on most days, per the battery monitor. I did install one of these for temperature regulation as the preset thermostat on the Dometic kept freezing the fridge box. It was wired to cut all power to the fridge, which did not have the 12v heating element. BTW, it would appear the the actual draw is closer to 8 watts with gas valve engaged upon further evaluation.

https://amazon.com/gp/product/B019I3...?ie=UTF8&psc=1

Had I known that a year later that my Onan was going to be removed I would have gone the marine fridge route, what with the room for more batteries.

FWIW, discussions such as these are a major part of why I still hang around here since selling the RT last fall.

Have fun, y'all.

[peteco]

Originally Posted by SteveJ

I was not thrilled having to replace our old non circuit board Dometic with the new and "improved" circuit board version for exactly that reason. In practice, unless something weird happened the fridge did not run steady on for 24 hours, even in the heat. Our daily AH consumption generally ran in the 20 to 25 range, exclusive of furnace/Fantastic Fan usage. !50 watt portable solar system fully charged the group 29 battery on most days, per the battery monitor. I did install one of these for temperature regulation as the preset thermostat on the Dometic kept freezing the fridge box. It was wired to cut all power to the fridge, which did not have the 12v heating element. BTW, it would appear the the actual draw is closer to 8 watts with gas valve engaged upon further evaluation.

https://amazon.com/gp/product/B019I3...?ie=UTF8&psc=1

Had I known that a year later that my Onan was going to be removed I would have gone the marine fridge route, what with the room for more batteries.

FWIW, discussions such as these are a major part of why I still hang around here since selling the RT last fall.

Have fun, y'all.

Steve J,
Does this come with the temperature sensor?

[booster]

Originally Posted by SteveJ

I was not thrilled having to replace our old non circuit board Dometic with the new and "improved" circuit board version for exactly that reason. In practice, unless something weird happened the fridge did not run steady on for 24 hours, even in the heat. Our daily AH consumption generally ran in the 20 to 25 range, exclusive of furnace/Fantastic Fan usage. !50 watt portable solar system fully charged the group 29 battery on most days, per the battery monitor. I did install one of these for temperature regulation as the preset thermostat on the Dometic kept freezing the fridge box. It was wired to cut all power to the fridge, which did not have the 12v heating element. BTW, it would appear the the actual draw is closer to 8 watts with gas valve engaged upon further evaluation.

https://amazon.com/gp/product/B019I3...?ie=UTF8&psc=1

Had I known that a year later that my Onan was going to be removed I would have gone the marine fridge route, what with the room for more batteries.

FWIW, discussions such as these are a major part of why I still hang around here since selling the RT last fall.

Have fun, y'all.

The Inkbird is one of the controllers that I have heard of being used to put electronic control on the compressor frigs, also. Most have had good luck with them in those applications.


I have a very similar 12v unit on the control system I built for our HRV ventilator in our house to replace the garbage touch screen version the manufacturer provided that failed every few weeks. I am using on a defrost circuit in the HRV. I do wonder a bit about the <3 watt power use spec, though, (ours is 2W) as they have a fairly large LED three number display on 24/7 with no way to time it out. I have not measured our use on the HRV because it runs on the HRV power supply so is essentially on house power. But even 3 watts is about 6ah per day. The other essentials running like detectors and monitors I put at 10ah earlier in a post may or may not be high depending on what you have, so still 15ah or so before you actually use any for other things.



The one we have works well once we got by the poorly done instructions, hopefully the Inkbird is better that way. A big deal is that they have settable hysteresis that has a wide range of settings which seems to be critical in using these in frigs because you have to allow for delay in cooling response and overshoot issues. The electronic control that I got with the Isotherm compressor frig this year does not have hysteresis setting capability, but it should have from what our test use of the frig this year has shown.


Does your 20-25ah per day use include the solar running and supplying some power? Solar can really mess up trying to find out how much power you really use because the solar controller output totalizers are often not very accurate and don't take into account charge efficiency, and the normal battery monitor subtracts off what goes back into the battery or is used in the van from you daily AH gain. The power that goes back in or is used in the van is lost from the monitor, also.



We can get a better, but not great, power use for the frig by doing a shorter run of time overnight when nothing from the solar is confusing things, but it is still off from what I get from putting a Wattsup totalizer in the frig only.


There is one thing about the power use in the gas frigs these days that is good compared to a compressor frig, and it is that a gas frig usage doesn't vary nearly as much with run time and temperatures when compared to a compressor frig, so the gas frig is easier to estimate total use for figuring out power needs.