Yeah, this refer showed below was used only on electric. It is an extreme case (the worst I've seen anyhow), but it shows the potential hazard one could encounter. When I arrived at this job site, the sheet metal around the boiler was glowing red hot!
Like Chris said, the recall includes a thermal cut-off (see the last picture). This would have prevented the overheating and potential fire hazard as seen it the 1st 3 pictures.
Note: Thermal cut-off photo courtesy of bigdodgeram. Tim
Like Chris said, the recall includes a thermal cut-off (see the last picture). This would have prevented the overheating and potential fire hazard as seen it the 1st 3 pictures.
Note: Thermal cut-off photo courtesy of bigdodgeram. Tim
Okay, this thread is hopelessly long, so I figured few would read it all. Kudos to you for your patience;). As for which element to run, I think moving the hot spot away from the place where the boiler cracks, and then evenly distributing the heat to the rest of the pocket would be more important than total watts. I also believe this was Dometic's reasoning in redesigning these elements. If you look at the picture above, you can see the heated portion of the element does not extend all the way to the bottom like it did before.
As for why they didn't replace the elements as part of the recall.......who knows? Perhaps Dometic is more concerned about liability and maybe isn't too terribly concerned about the longevity of the existing refers (just a guess) -OR- Perhaps they figured the stress patterns were already set, and changing the elements now wouldn't matter (just more speculation). Regardless of their reasoning on the older units, I'd be willing to bet they're concerned about the longevity of the new refers they're manufacturing now.
For those of us with the older refers (with original elements), it may be too late to reverse the existing stress patterns, but I'd still feel much better knowing I had the latest element (I'd consider the $40 cheap insurance). BTW, I stock about 10 or more of these elements and try to sell one to almost every customer I run into with a recall refer. Needless to say, I sell a lot of them. Tim
I did read this post before making the decision to install the transformer. My line voltage was 120 volts before installing the transformer which (Volts X Amps = Watts) would give me 348 Watts. Now that the voltage applied to the heater is 113volts I have 327 watts. Since the performance of the refrigerator hasn't changed I feel it was worth ten dollars to lower the heat applied to the poorly manufactured cooling unit.
Do you recommend the replacement of the heating element because of the hot spots you found on the older element? Thanks again for the info.
Mark W.
Do you recommend the replacement of the heating element because of the hot spots you found on the older element? Thanks again for the info.
Mark W.
timsrv wrote:
Keep in mind calculating heating element watts in the manner you did (using resistance only) is not the most accurate method (your estimated watts will always be on the high side). It's totally understandable as I initially made this same mistake myself before giving it some more thought. Anyhow, here is a better and more thorough explanation I posted earlier in this thread. Read on. Timtimsrv wrote:
Okay, Okay, I'm making some major headway here and had to share it with you all. Please understand It's been a while since my college electrical / electronics training, so this took some thought to get back into the swing of things. I started remembering there are more ways to check watts:h. Although testing resistance is the easiest way, it's not the most accurate way.......especially on something that gets hot. Once you energize an element, the heat changes resistance, therefore changing the calculated watts. Checking in this manner is only going to be approximate and always on the high side (more heat = more resistance).
As I just said, there is more than one way to calculate the watts of a load (3 to be exact). Method 1.= Volts squared divided by Resistance = Watts. Method 2.= Amps squared X Resistance = Watts. Method 3. (and the most accurate in this case) Volts X Amps = Watts
Due to the fluctuation in resistance caused by heat, the best way to determine Watts in an element is to eliminate resistance from the equation.
Okay, now for the good stuff. I energized an element and measured Amps by routing current through my Fluke. When cold the current was slightly higher so I waited for element to heat and stabilize. Once there I measured 2.63 Amps. Using method 3 to calculate (Volts X Amps) this works out to 315 Watts:W.
On a side note, remember the old style element I tested? Remember the hot spot at the bottom (right adjacent to the cracked weld)? Well, looks like they did something about that too. Check out the nice even heat of this new element!
Okay, so I'll have to take back some of my bad thoughts of Dometic (but not all;)). This makes me feel a whole lot better and should go a long way to solving the problem with these refers. I still think they should be replacing elements as part of the recall, but that's another subject. Would also be nice if they put a little more effort into explaining things, but I think we do a pretty good job figuring them out here. Just takes a bit longer to get to the bottom of things. Tim
Keep in mind calculating heating element watts in the manner you did (using resistance only) is not the most accurate method (your estimated watts will always be on the high side). It's totally understandable as I initially made this same mistake myself before giving it some more thought. Anyhow, here is a better and more thorough explanation I posted earlier in this thread. Read on. Tim
timsrv wrote:
Okay, Okay, I'm making some major headway here and had to share it with you all. Please understand It's been a while since my college electrical / electronics training, so this took some thought to get back into the swing of things. I started remembering there are more ways to check watts:h. Although testing resistance is the easiest way, it's not the most accurate way.......especially on something that gets hot. Once you energize an element, the heat changes resistance, therefore changing the calculated watts. Checking in this manner is only going to be approximate and always on the high side (more heat = more resistance).
As I just said, there is more than one way to calculate the watts of a load (3 to be exact). Method 1.= Volts squared divided by Resistance = Watts. Method 2.= Amps squared X Resistance = Watts. Method 3. (and the most accurate in this case) Volts X Amps = Watts
Due to the fluctuation in resistance caused by heat, the best way to determine Watts in an element is to eliminate resistance from the equation.
Okay, now for the good stuff. I energized an element and measured Amps by routing current through my Fluke. When cold the current was slightly higher so I waited for element to heat and stabilize. Once there I measured 2.63 Amps. Using method 3 to calculate (Volts X Amps) this works out to 315 Watts:W.
On a side note, remember the old style element I tested? Remember the hot spot at the bottom (right adjacent to the cracked weld)? Well, looks like they did something about that too. Check out the nice even heat of this new element!
Okay, so I'll have to take back some of my bad thoughts of Dometic (but not all;)). This makes me feel a whole lot better and should go a long way to solving the problem with these refers. I still think they should be replacing elements as part of the recall, but that's another subject. Would also be nice if they put a little more effort into explaining things, but I think we do a pretty good job figuring them out here. Just takes a bit longer to get to the bottom of things. Tim
After reading all of the post on the "Dometic Recall" I decided to try installing a transformer (per the post below) to lower the voltage going to the heating element. I wanted to replace the element but the local RV dealer only stocked the new part# from Dometic and I didn't trust it considering the stock element was stamped 325watts and had 38.9 ohms resistance. I called RV Mobile this morning and ordered a new element and asked the salesman to check the resistance before completing the order. I got a call 30 minutes later from RV Mobile to let me know that they had just received a new shipment of elements and the wire color had been changed and the resistance on all were 39-41 ohms so I cancelled the order. I feel that the metal used in the cooling system is at fault but I also think that the heating element that is over powered only aggravates the defect in the welds. I installed the transformer (got it @ radio shack) today and it worked great. I also switched the position of the heating element to the 12 volt side of the tube. My element has 38.9 ohms resistance and the refrigerator runs on LP or 115-120 volts & 2.9 amps. After installing the transformer the voltage applied to the heating element was 113 volts almost a 7 volt drop! Volts squared divided by resistance = watts so I was running @370:E watts and after the transformer install I am @ 328 watts. The transformer cost $10.00 and was easy to install. The new elements can run you 30.00-70.00 dollars + shipping. The refrigerator still cools great. Thanks to all of the people that took time post on this very important issue. ๐
Mark W.
Mark W.
WilleyB wrote:
Hi trouble1263, and thank you for your kind thought.
For those members who would like to do the transformer fix :W I'll try to clean up my drawing and terminology. As LScamper has suggested an autotransformer is an expensive item indeed. What is proposed here is a method to compensate for, by lowering the wattage of an underrated 120 volt element. Namely those heating elements with a resistance below 40 ohms.
What is proposed is a Radio Shack #: 273-1511 or Circuit City #: 2731511 Transformer
Transformer: primary is 120 VAC, HD type. Volts: 12.6V CT. 3.0A. in either case the price is about $10. The 120 volt PRIMARY winding has two black wires that are smaller in diameter than the three wires of the 12.6 volt SECONDARY winding. The CT in the "12,6 CT" stands for "Center Tap" meaning that the 12.6 volt winding is equally divided. There are two yellow wires which are the 12.6 volt leads with a black lead from the Center Tap and from the black lead to either yellow lead we would measure 6.3 volts while in operation.
Click-->
The connections:
Connect one wire of the fridge 120v element to a transformer Primary wire as shown (like Red wire shown) and to one side of the 120 volt line (AC black wire). The other element wire will be connect to the other transformer Primary wire. Then connect the white 120v AC supply (from the control board where the element is connected to now) wire to the black Center Tap wire of the Secondary winding. Then connect one of the 12.6 volt secondary wires (yellow A or B) to the point marked "C" as shown on the diagram. These connections make the transformer operate like a step down transformer in that now there are many more windings across the 120 volts, by using only the primary leads as an output the voltage will be reduced to about 113.7 volts. (120 - 6.3= 113.7) If you have less you can connect point "C" to the opposite side of the secondary.
Unused leads should be taped (insulated as voltage will be present) In operation the Transformer will be warm to the touch, but it should not real hot. I anyone wishes to do this instead of replacing the heating element and wishes to ask questions " go for it " if can help I'll be glad to.Willis
My thanks to LScamper for pointing out my omission that the 120V for the circuit comes from the circuit board and not directly from the line voltage ๐ฎ
