Fridge power requirements

[Jamie Gates]

Hi All

I recently bought a 2016 T6 that has been converted by Teahpoo. Will get some pics up shortly.
The power management unit is a PMS3H and i have a RM123 fridge.
I can operate this on gas but as yet have been unsuccessful running it on 240volts or 12v DC. My assumption is that this is a pretty standard setup so i am hoping that the hive mind could tell me which which positions i need the switches on the PMS3H to operate when on EHU and when driving.
Thanks all

 

[Spaghetti]

Hi, I have a PMS3 and the converter said to leave it on ‘van’ when driving, which in mine is the leisure battery. I initially switched mine to the ‘off’ position when driving, which is what the printed instructions suggested. That means that you couldn’t use the USBs or lights in the back when driving.

The EHU should mean that the charger can be switched on. If the charger is on, and the neon is lit, it will charge whichever battery is active. If the ‘van’ battery is switched on, it’ll charge the leisure battery. If ‘car’ is selected, it will charge the starter battery (both assume yours is wired the same as mine). In the centre position, it will charge neither, but run the 12v side straight from the EHU.

I had a split charge relay initially, which means that the electrics and leisure battery see the voltage peaks and troughs of the smart alternator (not good). Since fitting the CTEK 250SA I leave it on ‘van’ when driving so the kids can use the lights and stuff in the back, as the charger smooths out the voltage nicely.

I also printed out new labels for the PMS3 and labelled them ‘starter’ and ‘leisure’.

I can send over a PDF of the instructions for the PMS3 if you need them?

 

[Spaghetti]

Actually, you can find the instructions here:

https://www.olearymotorhomes.co.uk/ekmps/shops/olearys/resources/Other/pms3-instructions.pdf

 

[Jamie Gates]

Hi, I have a PMS3 and the converter said to leave it on ‘van’ when driving, which in mine is the leisure battery. I initially switched mine to the ‘off’ position when driving, which is what the printed instructions suggested. That means that you couldn’t use the USBs or lights in the back when driving.

The EHU should mean that the charger can be switched on. If the charger is on, and the neon is lit, it will charge whichever battery is active. If the ‘van’ battery is switched on, it’ll charge that. If ‘car’ is selected, it will charge the starter battery. In the centre position, it will charge neither, but run the 12v side straight from the EHU.

I had a split charge relay initially, which means that the electrics and leisure battery see the voltage peaks and troughs of the smart alternator (not good). Since fitting the CTEK 250SA I leave it on ‘van’ when driving so the kids can use the lights and stuff in the back, as the charger smooths out the voltage nicely.

I also printed out new labels for the PMS3 and labelled them ‘starter’ and ‘leisure’.

I can send over a PDF of the instructions for the PMS3 if you need them?

Thanks for the reply

I'm fairly comfortable with the pms3H tbh. I got to grips with that by trial an error.
Van is leisure battery
Car is main battery
off is off
Charging both the car and van batteries happens when driving.
Charging the van battery with EHU. Turn on charger supply and select van.
It's the fridge that has stumped me. Just can't seem to find the correct switches to operate on 240v and 12v. Instruction say i should isolate 12v and gas to run on 240v, so i'm assuming i turn off the gas supply (including gas temperature knob) and leave the charger supply turned off? Then turn the internal temperature control knob to any setting.
For 12v use, should i switch anything on the PMS3H when driving?
Thanks

 

[Spaghetti]

Not sure how yours is wired, but my PMS3 allows the fridge output on 12v to be active regardless of the position of the 12v switch. It just isolates the other circuits in the ‘off’ position.

My fridge is 12v only (Webasto) so can’t help you on the gas or 240v I’m afraid. The fridge will effectively run from 240v on EHU as the PMS3 steps it down the charge the battery as it’s used to power the fridge.

 

[Jamie Gates]

Not sure how yours is wired, but my PMS3 allows the fridge output on 12v to be active regardless of the position of the 12v switch. It just isolates the other circuits in the ‘off’ position.

My fridge is 12v only (Webasto) so can’t help you on the gas or 240v I’m afraid. The fridge will effectively run from 240v on EHU as the PMS3 steps it down the charge the battery as it’s used to power the fridge.

Ok thanks anyway. Have emailed Teahpoo for some help. Fingers crossed

 

[Spaghetti]

Good luck!

 

[DPDP]

Does anybody have knowledge of how long a Dometic Crx50 fridge will run on my 12v liesure battery. I'm not a technical person so just hours,days would be very helpful. Thanks in advance Dave.

 

[Dellmassive]

Hi Dave, got a pic of your leisure battery so we know the spec?

 

[Fish]

Solar?.

 

[Dellmassive]

Fridge Spec...



ELECTRICAL
Input voltage (DC) 12/24 V
Rated input current (DC) 5 A

PERFORMANCE
Refrigerant, type R134a
- Contains fluorinated greenhouse gases
GWP 1430
Refrigerant amount 38 g
CO2 equivalent 0,054 t
Energy consumption (DC@5/25°C) 0.26784 kWh/24h
Energy consumption (DC@5/32°C)0.556992 kWh/24h
Climate class (EN62552) T



So a 75ah leisure battery would last 15hrs if running continuously..... 50% duty cycle 30hrs.

I haven't got one, just running some numbers.

 

[Davenjo]

We have a similar fridge and with our 75ah leisure battery we used to struggle to get 2 days running in summer when the compressor is running for longer, especially if I’ve got my drinking head on and continually opening the door. Added a 100w solar panel and can now run 24/7.

 

[Peatey]

Its sounds daft but it will depend on how many times you open the door and what setting it is on
Go solar!

 

[Hah!]

I have 2x 85ah batteries and on test will run for 5 to 6 days but batteries definately need charging afterwards. This is with minimal other battery use and a little fridge use.

Also ran and used regularly for 3 - 4 days on a single 110ah battery with a 3 to 6 mile trip either end of the day and an 80 mile trip either end of the week and off at weekends without having to do any other battery charging. Did this for the best part of a year without issue. There was some other battery use in this time but not hugely siginificant as I was primarily just using the fridge as a fridge and making tea ...

Under test (as above) would get 3 to 4 days before battery got low which is in line with the extended use from the 2x 85ah combination.

Hope that lot makes some sense...

 

[DPDP]

Thanks everyone for the advice.

 

[Ann3x]

Wired my fridge in yesterday then had some thoughts (/worries) about whether I've used the correct gauge wire for it, given the fact it's wired from a fuse box in the side panel.

My cable run is as follows, all wires are auto grade multi-stranded 10AWG in conduit:



From this site I can see that for a 15A load on 12v I should be able to have a 20 foot (~6m) cable run safely.

What's confusing me is whether I should count the run from the fuse box to fridge (a 5m loop) as separate to the run from battery to fuse box (a 3m single wire).

If I count them as 2 loops, im at 9m which is over the safe limit for the 10AWG cable. If they're 2 separate loops due to the 2 fuses however, I should be ok.....

Informed opinions?

 

[Dellmassive]

you follow the total route for the current from source via load back to source . . . . . . so for the diagram above its 9mtrs. (amusing you are using the same gauge cable for the entire route?)

looks like you have a 30A supply fuse at the battery to the rear fuse panel, a 15A fuse for the fridge feed . . . . . but have you also fused the 0v fridge ground? (you dont need to)

whats the spec on the fridge?

you could however upgrade the main 30amp feed cable from the battery to the rear fuse box for a nice thick beefy cable. . . . . . . and then down-rate the cable size from the rear 15A fuse-box feed.

6/8awg is good for 40A over 6-9mtrs (main 30A max run from front battery to rear fusebox)

12awg is good for 15A over 6-9mtrs (15A max from rear fuse box to fridge runs)

re:

https://www.t6forum.com/attachments/cable-jpg.38818/


nice diagram BTW.

******************

Installing 12v Socket /s - How Its Done -

*******************

 

[Ann3x]

you follow the total route for the current from source via load back to source . . . . . . so for the diagram above its 9mtrs.

looks like you have a 30A supply fuse at the battery to the rear fuse panel, a 15A fuse for the fridge feed . . . . . but have you also fused the 0v fridge ground? (you dont need to)

The ground is just run back to the fuse box (shared bus bar).

So by that reckoning, 10AWG is not enough.....? :'(, that or I have to use a 10A fuse and hope that fridge draw is within that.

 

[Pete C]

I over specified the cable to the fridge as I had heard that the surge current could be quite high. This resulted in a larger voltage drop than expected at fridge start-up, which meant it could fail to start.

Will try and find out what gauge I used.

Pete

 

[Dellmassive]

The ground is just run back to the fuse box (shared bus bar).

So by that reckoning, 10AWG is not enough.....? :'(, that or I have to use a 10A fuse and hope that fridge draw is within that.

what does the fridge draw? . . . . any idea?

if not - make/model and weel find out for you.