Dometic AES Ventilation flue temperature and some other Qs (1 Viewer)

[sallylillian]

Some of you have comprehensive temperature management so I am hoping for some insight. I have one of my Oregon sensors positioned inside the box section at the back of the fridge, close to the top vent. On gas with an outside temperature of circa 20c the inside flue/box temperature is 35c, on electric its 22c. I would like to understand how gas can be a more efficient energy in these fridges if the air temp surrounding the tubes is lower with electric. In both cases the exhaust fans (rainbow dual unit) are on the low setting.
We constantly fight with this fridge, and my wife is getting tired of its need for babying, and me warmish wine after we have been to the supermarket and topped up with fresh fruit, juices milk etc which shoots the temperature of the fridge up to 15c for hours before finally coming back down.
We have water regularly in the bottom tray although my wife insists that items are not touching the fins?
Is the thermostat on the fins and if so would moving it up make the fridge work harder?

 

[Lenny HB]

I think the different temperature with different fuels is down to the heater rating i.e. the gas burner produces watts of heat than the electric elements.
The thermostat for the fridge is inside the fridge behind a plastic cover bottom right hand corner of the fins, the Rainbow one will be built into the fan housing.
On gas it is worth playing with the burner alignment although not adjustable it's only held in by metal tags, when I had the burner out to do a repair on the previous van after putting it back together it ran much better, also on the same fridge I'd previously had the burner changed.
The rainbow unit doesn't have any temperature adjustment I think it would help if you controlled the fans via a temperature controller then you would be able to adjust it for optimum performance.

Have you thought about fitting an internal fan like Robert did, he found it gave a bit improvement in performance.

I think the spec for the fridge is in to achieve an internal temp of 7c with an ambient of 30c which we all know is not cold enough for beer.

We are finally getting away in the new van on Tuesday, I'll monitor my fridge and see how it performs my initial tests showed it to be a different beast to the last one, it appears to work. Both the same model RMDT 8505 but looking at the back I think it looks different to the last one.

 

[Alistair33]

.

We are finally getting away in the new van on Tuesday,

Have a great time.... all those new things to check

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[Robert Clark]

As an aside the Dometic 40L coolbox I have in the garage was SO effective yesterday it froze the contents and a tin of coke exploded !

 

[sallylillian]

I think the different temperature with different fuels is down to the heater rating i.e. the gas burner produces watts of heat than the electric elements.
The thermostat for the fridge is inside the fridge behind a plastic cover bottom right hand corner of the fins, the Rainbow one will be built into the fan housing.
On gas it is worth playing with the burner alignment although not adjustable it's only held in by metal tags, when I had the burner out to do a repair on the previous van after putting it back together it ran much better, also on the same fridge I'd previously had the burner changed.
The rainbow unit doesn't have any temperature adjustment I think it would help if you controlled the fans via a temperature controller then you would be able to adjust it for optimum performance.

Have you thought about fitting an internal fan like Robert did, he found it gave a bit improvement in performance.

I think the spec for the fridge is in to achieve an internal temp of 7c with an ambient of 30c which we all know is not cold enough for beer.

We are finally getting away in the new van on Tuesday, I'll monitor my fridge and see how it performs my initial tests showed it to be a different beast to the last one, it appears to work. Both the same model RMDT 8505 but looking at the back I think it looks different to the last one.

Thanks Lenny. I have been looking at the spec and I believe I have found the issue. I have an AES option on the Solar regulator, the theory being that it would switch to DC with excess solar, which we have discussed in another thread. Now I have become aware and the manual confirms this that the fridge will switch to Solar as primary if it is available. ie will put the fridge into DC mode. And there's the rub! The unit is rated at 170 watts with DC but 250 watts on AC! So that's why I am noticing this problem which I did not have last year. I am going to force it to mains for 24 hours and see what happens! @funflair you may want to pick up on this.

 

[Lenny HB]

Thanks Lenny. I have been looking at the spec and I believe I have found the issue. I have an AES option on the Solar regulator, the theory being that it would switch to DC with excess solar, which we have discussed in another thread. Now I have become aware and the manual confirms this that the fridge will switch to Solar as primary if it is available. ie will put the fridge into DC mode. And there's the rub! The unit is rated at 170 watts with DC but 250 watts on AC! So that's why I am noticing this problem which I did not have last year. I am going to force it to mains for 24 hours and see what happens! @funflair you may want to pick up on this.

50% more power on mains that's a big difference. Typical Dometic design probably hasn't changed it since adding the solar function. Previously the fridge would have only been on 12v when traveling and plenty of cool air flowing over the van.
When using on solar you are probably going to be in a hot country, a bit hard for Dometic designers to think that far ahead.

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[sallylillian]

Lenny, how does the water drain from the fins, I have a tray but cannot find an exit hole. I had assumed it drained through the clear plastic tube into the white box on the picture

 

[funflair]

Our fridge is an older 7 series so I guess the control parameters are different it also does not have the dedicated S+ function so I am using a modification on the D+, I am surprised at the priority on yours Michael @sallylillian as ours conforms to these parameter that I have copied from the AES11 instructions from a 5 series brochure.

2.1 Priorities

The refrigerators selects the type of energy according to the following priorities: 1) 230V: if the voltage > 200 V
2) 12V: if the motor is running (D+ signal from the generator) and voltage > 11V 3) Gas: if 230V is not present or < 200V, or 12V voltage < 11 V

2.2. Switchover Times / Time Delays

The following diagram displays the switchover times between the individual energy sources:
sorry but these didn't copy and paste over but the only significant time delay is the 15 minutes from 12v to gas which of course our set up is subject to every time it comes off the solar switched D+ and onto gas, but saying that I have no complaints about the overall performance and on 12v we have seen the freezer go down to -16 while driving.

Martin

 

[funflair]

Lenny, how does the water drain from the fins, I have a tray but cannot find an exit hole. I had assumed it drained through the clear plastic tube into the white box on the picture View attachment 161473

Hi Michael

There should be a sloping sort of tun dish affair underneath the fins inside the fridge and then it should drain down that pipe and into the plastic tub that sits on the heat exchanger pipe, which should then evaporate the water.

Martin

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[Parapilot]

Lenny, how does the water drain from the fins, I have a tray but cannot find an exit hole. I had assumed it drained through the clear plastic tube into the white box on the picture View attachment 161473

It does exactly as you assume, evaporating from the tray due to the heat in the black pipe.
You can also drain it directly to the outside if you extend the tube and insert it into the little clip in the outer cover retainer (plastic part with a letter T in foreground).

 

[sallylillian]

Hi Michael

There should be a sloping sort of tun dish affair underneath the fins inside the fridge and then it should drain down that pipe and into the plastic tub that sits on the heat exchanger pipe, which should then evaporate the water.

Martin

It does exactly as you assume, evaporating from the tray due to the heat in the black pipe.
You can also drain it directly to the outside if you extend the tube and insert it into the little clip in the outer cover retainer (plastic part with a letter T in foreground).

Thanks both, the pipe is dry. I have the tun tray as you call it Martin but cannot find an exit in it. When I blow up the pipe from the outside it is blocked, is the exit from the internal tray at the bottom of the V?

 

[Robert Clark]

Thanks both, the pipe is dry. I have the tun tray as you call it Martin but cannot find an exit in it. When I blow up the pipe from the outside it is blocked, is the exit from the internal tray at the bottom of the V?

Yes it is at the bottom of the V tray inside the fridge
Maybe needs a pipe cleaner down it if blocked

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[funflair]

Thanks both, the pipe is dry. I have the tun tray as you call it Martin but cannot find an exit in it. When I blow up the pipe from the outside it is blocked, is the exit from the internal tray at the bottom of the V?

Yes Michael blowing up that pipe should be blowing into the water collecting "tundish" thing inside the fridge.

Martin

 

[funflair]

Hi Michael

I assume yours is 8 series and as you say the priorities are, if you wanted to change the priority to favour 240v followed by solar you would have to take the Votronic AES out to the D+ instead of the S+ (I just have a diode on the end of the alternator wire to make the D+ work on the solar AES)

Martin

Automatic operation

n Change over to "Automatic" with button (5) Automatical energy selection (if available)

17

Sequence of priority:

1.) Solar (12V DC)
2.) 230V AC
3.) 12V DC
4.) Liquid gas

n Set temperature step by pressing button (6)

 

[sallylillian]

Right found the exit hole at left end but tray is not attached to back wall so water runs out to inside fridge. So need to glue it with something. Can anyone advise how it's fixed on when done properly?

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[funflair]

Right found the exit hole at left end but tray is not attached to back wall so water runs out to inside fridge. So need to glue it with something. Can anyone advise how it's fixed on when done properly?

I thought it was all moulded into the back wall as one but van is back in the shed so can not check.

Martin

 

[sallylillian]

Hi Michael

I assume yours is 8 series and as you say the priorities are, if you wanted to change the priority to favour 240v followed by solar you would have to take the Votronic AES out to the D+ instead of the S+ (I just have a diode on the end of the alternator wire to make the D+ work on the solar AES)

Martin

Automatic operation

n Change over to "Automatic" with button (5) Automatical energy selection (if available)

17

Sequence of priority:

1.) Solar (12V DC)
2.) 230V AC
3.) 12V DC
4.) Liquid gas

n Set temperature step by pressing button (6)

I think I will disconnect the Votronic AES wire and get some advice on the diode from you Martin when I get home.

 

[sallylillian]

OK brush down pipe from inside and can now blow up pipe. Thanks @Robert Clark. So now to fix it with some sealant I'll have a rummage.

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[sallylillian]

As an ancillary question, after 2 days my fridge has settled down. Having cleared the pipe I do not have any residual water in the fridge itself now, as far as I can see and I propose further investigation to identify how the drain hole from the internal tray works, I am wondering if there is a spigot which sits loose into another spigot in the back wall moulding of the fridge, and that spigot is connected to the drain pipe. A blockage in that would stop the water draining and backup and out to the fridge I have also disconnected the solar AES connection. So in a previous post I have highlighted the issue of the lower DC wattage. What I would like to ask now is the failure of the drainage a reason for higher fridge temperatures, or is the drain merely a convenience?

 

[Robert Clark]

Hi Michael
The drain on the fridge is there simply to allow any condensation forming on the internal cooling fins to escape.

 

[sallylillian]

Robert would the excess water and therefore humidity within the fridge would not reduce its performance?

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[Robert Clark]

Robert would the excess water and therefore humidity within the fridge would not reduce its performance?

I don't believe so
It's more about drainage of condensation which is created when you open the door and warm air enters the fridge and hits the cooling fins.
Like you, we've noticed a massive difference in performance between the three power sources. I'll certainly be thinking twice before connecting the S+ on my new van. If I do it will only be for situations where LPG is in short supply such as in Morocco.
Fitting an internal fan at the top of the fridge certainly helped improve performance, by circulating air over the cooling fins.

 

[Robert Clark]

I wonder if there was a way to use the S+ to trigger a relay to connect 240v from your inverter to power the fridge when there was excess solar?

 

[sallylillian]

Thank you for that opinion Robert. I have been thinking this morning that I should look to insert a simple switch in the AES signal wire from the regulator so I can use where appropriate, but I want to see if I can achieve a better cooling result first and will look at the addition of an internal fan.
Another point which I sort of raised earlier was the thermostat on the cooling fins. Going back in my mind to my fantastic but much berated Norcold in my RV, there was advice that by raising or lowing the thermostat on the fins altered the temperature at the different settings, and it too had a simple number dial which bore no relationship to a specific internal temperature. I will have to try and search out that information.

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[Robert Clark]

If you decide to fit the internal fan you may find this useful

http://www.motorhomefun.co.uk/forum/threads/fridge-internal-fan.134648/

 

[sallylillian]

I wonder if there was a way to use the S+ to trigger a relay to connect 240v from your inverter to power the fridge when there was excess solar?

Now that's an interesting idea, however it is not normal to wire the fridge through the inverter, its normally a direct to EHU in. But with this new Dometic Solar priority they have got something wrong.

 

[Robert Clark]

Now that's an interesting idea, however it is not normal to wire the fridge through the inverter, its normally a direct to EHU in. But with this new Dometic Solar priority they have got something wrong.

I'm guessing that the relay would disconnect the fridge from the EHU circuit and connect it to the inverter outlet circuit.

@Lenny HB - could this work ?

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[sallylillian]

Robert, here is one of the articles I remember reading back in the day! There is a comprehensive report which the position of the thermistor is discussed in detail, the likes of which I have not seen with Dometic. Also your fan concept is shown.
http://www.irv2.com/forums/f54/norcold-thermistor-on-wrong-fin-85973-2.html

 

[funflair]

Now that's an interesting idea, however it is not normal to wire the fridge through the inverter, its normally a direct to EHU in. But with this new Dometic Solar priority they have got something wrong.

So solar S+ takes no1 priority according to Dometic info, so when you are driving and there is an excess of solar does the fridge run of 12v via solar?

If the answer to the above is Yes then that prompts the next question which is what happens in a filling station when it decides its time to switch over to gas without the 15 minute delay that is built into the 3 energy choice AES.

The plot thickens.

Martin

 

[sallylillian]

So solar S+ takes no1 priority according to Dometic info, so when you are driving and there is an excess of solar does the fridge run of 12v via solar?

If the answer to the above is Yes then that prompts the next question which is what happens in a filling station when it decides its time to switch over to gas without the 15 minute delay that is built into the 3 energy choice AES.

The plot thickens.

Martin

Certainly, it's like the smart alternator issue!

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