Dometic fridge issue

[Alan de Enfield]

25 minutes ago, matthewbalzan said:

No not on same wire. Each has a dedicated wire from fusebox. I don't keep it on for security purposes especially due to high temperature...i have seen so many accidents caused by fire locally and almost every time due to electrical faults when boats are unattended 

 

I think you have identified the problem.

 

4mm2 cable is suitable (according to the manual) for a 12v fridge approximately 0.5 metres (certainly under 1 metre) from the batteries.

 

What is the actual distance of your installation - NOT the straight line, but following curves, corners, height changes etc. THE ACTUAL wire length.

 

 

 

Edited July 29, 2023 by Alan de Enfield

[matthewbalzan]

Actual wire length would not surpass 1.2m

[Alan de Enfield]

4 hours ago, matthewbalzan said:

Forgot to mention that battery is 260ah agm and have a 200w solar panel with mppt. The wiring from the fusebox to the fridge (about 1 metre away) is 4mm as recommended by maker

 

Check you manual - I think you will find that 4mm is not suitable.

 

2 minutes ago, matthewbalzan said:

Actual wire length would not surpass 1.2m

 

I think you are undersize at 4mm.

Edited July 29, 2023 by Alan de Enfield

[matthewbalzan]

Thanks for info...will definitely check

[Tony Brooks]

11 hours ago, matthewbalzan said:

Thanks for info. Definitely helps to understand better from what you are saying. During the day I have no problem with the load as my solar panel can give up to 11amp which compensates for any equipment I have on at anchor. My worry is during the night as I will have the fridge drawing approx 6a, two 12v fans drawing 1.5a each and some occasional lights...which put me near 10a. My battery is 260ah so should resist a full night with this load until the solar kicks in again. Will test the battery leaving it on for 24 hrs with fridge on and see what happens

 

Trying to clarify the potential problem because I think the above is a bit muddled. I am not so sure the cable is too small because the Danfos recommendation of cable size is one sq mm CCSA for each metre of cable run from battery to fridge and use the same for the return. We need to see the text that goes with Alan's chart. If I am correct, then 4 sq mm CCSA meets the spec. but have a good read of the manual again. It never hurts to over spec the cable. However, I note that you keep talking about the fuse box, not the battery, so if it is a volt drop problem it could be betaeen battery and fuse box.

 

Back to the point. If it is a volt drop issue then when any charging source, be solar, engine, or charger, starts charging it raises the voltage on the system so any volt drop does not doip the voltage below 12V

[Alan de Enfield]

52 minutes ago, Tony Brooks said:

We need to see the text that goes with Alan's chart.

 

The only 'verbage' that goes with the graph is .................................

 

 

 

[matthewbalzan]

All my equipment is connected to a fusebox at the back of the helm, nothing connected directly with battery. I had a voltage drop problem but resolved it and also installed a new battery 5 days ago, also I have a smartshunt installed so I can check better against any voltage drop. What I am not understanding is hiw the fridge increases the load over time...the first hour or so it remains approx 4.5amp then increases. Correct me if I am wrong but if there was a voltage drop problem wouldn't this be visible immediately once I switch on fridge?

[matthewbalzan]

Perhaps this will help aswell .. just checked right now,m with clamp meter the current flowing into the fusebox through 16mm2 cable is 4.6amp, current flowing into fridge through the 4mm2 cable is 6.7 amp

[Tony Brooks]

19 minutes ago, matthewbalzan said:

All my equipment is connected to a fusebox at the back of the helm, nothing connected directly with battery. I had a voltage drop problem but resolved it and also installed a new battery 5 days ago, also I have a smartshunt installed so I can check better against any voltage drop. What I am not understanding is hiw the fridge increases the load over time...the first hour or so it remains approx 4.5amp then increases. Correct me if I am wrong but if there was a voltage drop problem wouldn't this be visible immediately once I switch on fridge?

 

Normally yes, the recommended cable size is to accommodate the start-up load that is only present for fractions of a second, so unless you have a high speed oscilloscope you will never read the surge current or the voltage. Especially with typical sampling multi-meters.

 

What others have said about the motor starting against a very low gas pressure that increases as the fridge runs makes sense to me, especially as the Danfoss units have an over pressure lock out to prevent it trying to start under pressure. I would also comment that at least some go the gas heats up during operation so will expand and increase the internal pressure that way.

 

Last question - I think that you are wrong, unless you have some very sophisticated measuring equipment that stores or remembers the maximum value found.

[matthewbalzan]

Thanks. To correct my last statement I connected the clampmeter wrong at the fusebox...checked again the values are the same around 6.9 amps both to fuses and to fridge

[Alan de Enfield]

17 minutes ago, matthewbalzan said:

Perhaps this will help aswell .. just checked right now,m with clamp meter the current flowing into the fusebox through 16mm2 cable is 4.6amp, current flowing into fridge through the 4mm2 cable is 6.7 amp

 

Being a 'bear with little brain' that sentence makes no sense to me.

 

So, a wire connected from the battery to the fuse box (supply) has 4,6 amps flowing thro' it.

A cable is now connected to the end of the 16mm2 cable (via the fuse box) and then to the fridge and this cable has 6.7 amps flowing tho' it.

 

 

Are you absolutely sure the fridge is wired in with 4mm2 cable and not 4mm OD cable ?

 

Disconnect the cable and strip back a short length.

A typical 4mm2 flexible cable/wire would be 56 strands with each strand being 0.3mm diameter.

 

BS6862 (automotive cable which is commonly used for boats) 4.5mm2 cable is 65 strands each strand being 0.3mm diameter.

 

 

[Tony Brooks]

The BD35 manual has this text associated with the cable size table

* "Length" means the distance between battery and electronic unit.
 

Shoreline confirm it is just the outbound length by words to the effect that the conductor cross-sectional area must be 1 sq mm for each metre between battery and fridge. So that is 0.5 sq mm for every meter of total run (out and back).

bd-compressors2.pdf

[MtB]

5 minutes ago, Alan de Enfield said:

Being a 'bear with little brain' that sentence makes no sense to me.

 

So, a wire connected from the battery to the fuse box (supply) has 4,6 amps flowing thro' it.

A cable is now connected to the end of the 16mm2 cable (via the fuse box) and then to the fridge and this cable has 6.7 amps flowing tho' it.

 

I bet it is daylight and the solar is contributing the 'missing' current.

 

 

[Tony Brooks]

3 minutes ago, Alan de Enfield said:

 

Being a 'bear with little brain' that sentence makes no sense to me.

 

So, a wire connected from the battery to the fuse box (supply) has 4,6 amps flowing thro' it.

A cable is now connected to the end of the 16mm2 cable (via the fuse box) and then to the fridge and this cable has 6.7 amps flowing tho' it.

 

Snip

 

An excellent spot Alan, I missed it. This suggests that his solar is connected to the fuse box rather than the battery. It also may suggest that his meter and/or the way he uses it is not very accurate. In this instance I would not use a clamp meter, but use an ordinary multimeter using the 10 or 20 amp range, but the OP needs to really  know how to do that unless he wants to risk damaging his meter.

Way back at the start, you asked if the fridge needs maintenance, and the answer is yes. If it has an external evaporator radiator, it needs keeping fluff free. You also need to ensure there is an adequate gap all around the fridge, boat builders are very bad at that so the aperture the fridge sits in get hot and reduces the radiator's efficiency. It also seems important to ensure any freezer compartment door works properly and stays shut.

 

If your solar is connected to the fuse box then how do you ensure the batteries are charged when you are away from the boat with the master switches off? Charging and a few other items are allowed to bpyass the master switch.

 

 

[matthewbalzan]

Sorry, solar are connected to battery. All equipment is connected to fusebox 

 

Problem increased, after 3 hrs use the fridge surpassed 8.5amps and could feel the wire quite hot! Definitely not leaving it on overnight

 

 

[Tracy D'arth]

3 hours ago, matthewbalzan said:

Perhaps this will help aswell .. just checked right now,m with clamp meter the current flowing into the fusebox through 16mm2 cable is 4.6amp, current flowing into fridge through the 4mm2 cable is 6.7 amp

That is impossible. If you can do this you are a multibillionaire.  Either the meter is duff or you are not using it properly.

[Tony Brooks]

6 minutes ago, Tracy D'arth said:

That is impossible. If you can do this you are a multibillionaire.  Either the meter is duff or you are not using it properly.

Or something is feeding into the fuse box, as Mike and I said, solar is what I suspect.

[magnetman]

3 hours ago, matthewbalzan said:

Thanks. To correct my last statement I connected the clampmeter wrong at the fusebox...checked again the values are the same around 6.9 amps both to fuses and to fridge

 

 

Or this ^^^

[Alan de Enfield]

3 hours ago, matthewbalzan said:

Thanks. To correct my last statement I connected the clampmeter wrong at the fusebox...checked again the values are the same around 6.9 amps both to fuses and to fridge

 

It is very frustrating to try and help you if we cannot even get the correct voltage readings - its like going to the Doctrs and saying can you give me something for my sore throat, he looks and says "I cannot see anything wrong with it" and you say, "sorry I meant my ears".

[MtB]

18 minutes ago, Alan de Enfield said:

 

It is very frustrating to try and help you if we cannot even get the correct voltage readings - its like going to the Doctrs and saying can you give me something for my sore throat, he looks and says "I cannot see anything wrong with it" and you say, "sorry I meant my ears".

 

Yeah, like the joke about the geezer who arrives at the doctor with jelly and cream in one ear, and sponge in the other. 

 

Doctor says to him ... "I can see you're not eating properly.

 

 

(Bet you were expecting a different joke!! ) 

[1st ade]

All - as a relatively new member, "matthewbalzan" is subject to moderation (the site has had a spate of one time new members posting spam)

 

Please cut a little slack if the poster appears to be slow to respond - they have to wait for a Mod to approve each post (for now) - we're trying, honest!

[MtB]

2 minutes ago, 1st ade said:

All - as a relatively new member, "matthewbalzan" is subject to moderation (the site has had a spate of one time new members posting spam)

 

Please cut a little slack if the poster appears to be slow to respond - they have to wait for a Mod to approve each post (for now) - we're trying, honest!

 

Can you not turn that restriction off now, givn he has amply demonstrated he isn't here to spam the site?

 

 

[1st ade]

21 minutes ago, MtB said:

 

Can you not turn that restriction off now, givn he has amply demonstrated he isn't here to spam the site?

 

 

I'm sure it's possible but (as a relative Newbie Mod) I don't know how - a question for the boss methinks... (I'll ask)

[MtB]

12 minutes ago, 1st ade said:

I'm sure it's possible but (as a relative Newbie Mod) I don't know how - a question for the boss methinks... (I'll ask)

 

Boss won't know either, I bet!!

 

[Alan de Enfield]

1 hour ago, 1st ade said:

All - as a relatively new member, "matthewbalzan" is subject to moderation (the site has had a spate of one time new members posting spam)

 

Please cut a little slack if the poster appears to be slow to respond - they have to wait for a Mod to approve each post (for now) - we're trying, honest!

 

 

NO problem - except - that when his posts are finally listed it makes the thread very distorted as we 'appear' to have been asking certain questions which he has already answered, as his 'delayed' post goes into the thread at the time he posted it, not the time the mods released it.