High Temperature Alarm/Overload Power Cut Out

[dsparshott]

Hello,
I am running a MultiPlus-II 48/5000/70-48 and have the AC Out 2 wired to a 3kw immersion heater in my thermal store.

With moderate high temps (in the UK, above 24degC) the multiplus will momentarily shut off. The subsequent alarms will be High Temp and/or Overload. This will occur fairly randomly but correlation to having the washing machine on/kettle on.

The system is houses outdoors, under the cover of a metal shed, open fronted with two solar powered fans removing heat. The shed doesn’t get too hot tbh, certainly not higher than the outside temp and it is vented.

On Victron Connect I have the following settings in this order.

1. AC2 off when high temperature alarm is on for 2 seconds.
2. AC2 on when battery above 90%
3. AC2 off when battery below 80%

Q’s.

• Any idea why my no.1 parameter doesn’t seem to be working?
• Is there a better solution to prevent the system shutting off?
• Is there a UPS that I could fit between the multiplus and the house fuse box to prevent the power being cut?

Many thanks.
David

[nickdb (Nick)]

The inverter is rated to 4000W at 25C.
If you have a 3000W load on and add a higher load like a washer or kettle, the former possible having a startup surge as well, it would no doubt trigger an overload and restart.

[anon39974850]

Hi @dsparshott ,

a.) Am I right in assuming you are NOT connected to the grid?
b.) What cable sizing do you have from your battery bank to your inverter?
c.) Please supply a photo of your MPII installation and 300mm around it including the inverter battery isolator and post here
d.) Can you screen shot your MP VE.Configure settings and post here.

What is the make and model, and also the power consumption of:
1.) Your Washing Machine.
2.) Your kettle

Most standard domestic kettles are 2-3Kw @ 230vac.
Most standard washing machines 2-3Kw @ 230vac (during the initial heating cycle on anything other than a cold wash, which will settle back to 200-500w for the actual wash cycle).

6Kw combined with undersized battery cables = Low voltage disconnect.
6Kw combined with undersized / low-end inverter isolator = Low voltage disconnect.

[anon39974850]

The OP’s model has a peak power output of 9000W, so surge power should not be an issue at all on the AC output, unless it’s prolonged > 10s.

[nickdb (Nick)]

Go try get 9000W out, let me know how it goes.
Regardless, too few would have sized their battery to be able to buffer that kind of peak. Overloads aren’t only triggered by the inverter.

[anon39974850]

We did a test with friends decommissioned MP 48/5000 on a 30Kw LIFEPO4 bank, when they replaced with a 48/15000. Why, because he loves seeing things go bang! It didn’t…
Held the load for 20 seconds (although it was 8500w (7Kw car charger and an 1.5Kw immersion heater)) then had a temperature disconnect and the 95mm cables were pretty warm!

So in the real world the published spec is achievable, go-on try it!

[nickdb (Nick)]

@anon39974850

So in the real world the published spec is achievable, go-on try it!

You’re braver than I am.
Like all things, terms and conditions apply.
The OP hasn’t shared what his battery is, and some appliances, motors, compressors etc will surge orders of magnitude above their rated power which will overshoot anything the system is rated for.

[anon39974850]

HE is braver… I’d expect lots of magic smoke.
NEVER try this at home, and I wouldn’t recommend anyone doing that in a production environment and relying on the peak output for anything other than an absolute emergency situation for only seconds.
This sums him up completely, HE NEVER reads the manual, he says that’s what I’m for. I tell him what the manual and theory says, then he disregards that and see’s if it goes bang.

You make a very good point though, too many people think cable is cable, isolators are isolators, crimps are crimps, and the cheap options are just as good as the more expensive ones. This just is demonstrably untrue. Always buy the best you can is what I advise people.

The WHOLE system is only as GOOD as the WORST part.

That inverter is now used to supply a trickle input to the 15000 MP during depths of winter sun (using the current limiter), and it works like a charm (that MP 48/5000 still lives!) to ensure all loads are met at all times and prevent batteries going into an unwanted low SoC state.

[dsparshott]

Hi all, thanks for the input.

a. Yes, off-grid
b. Cables are 50mm from 3 x Pylon 3.5kw US3000, through a Lynx distributor, into the MP via a 160A breaker.
c. d. Photos and screenshots attached. The VE configure screenshot show the assistant that is top of the list of three (the other two are for turning the AC2 on and of when battery is charged). Note that the alarm on display with be either High Temp or Overload.

Kettle is 2200w, washing machine 2100w. These are never simultaneously in use when the immersion is also on.

Thanks

[anon39974850]

HI,

So,… In relation to:

b.)

The installation manual (48/5000) states:

Model	Battery Capacity	DC Fuse	Cable Cross Section 0-5m	Cable Cross Section 5-10m
48/5000/70	200 - 800Ah	200A	70 mm2	120 mm2

You have installed with 50mm cable (30% under the required cable sizing for this product), this straight away creates a circuit bottle neck between the batteries and the inverter (and your potential 5.2Kw load (immersion (3Kw) and kettle(2.5Kw) - 104% of the service output)). This will increase heat generation in all components in this section of the circuit due to resistance.

ALSO what cable sizes are connected to the Pylon US3000’s. It looks worryingly like 25mm positive and the same for a single negative? These are supplied cables for Pylon US3000.

HOWEVER the manual states recommended discharge current is 37A and it looks like the installation is 3 x US3000’s daisy chained (3 x 37A = 111A), with a single 25mm to the ‘Lynx Power In’? IMHO the final connection to the LPI from the last US3000 should be with 70mm cable too (as for the inverter).

Due to the cable undersizing I would not be surprised to see the inverter enter a low voltage or overload alarm and disconnect.

c.) Am I right in observing that the temperature sensor from the MP is connected directly to the busbars of the ‘Lynx Power In’ ?

Is this is the same busbar that carries all system loads and is bottlenecked by the 50mm cables, and will get rapidly warm under load?

The temperature sensor is primarily for temperature charging compensation, and is meant for direct connection to the battery terminal (also prevents low temperature charging of the battery when correctly configured in VE.Configure).

For your assistant we need to see the settings you have input. In VE.Configure → Assistants, select the assistant that you have programmed with the high temperature rule, and then click on the ‘Summary’ button. Screenshot the displayed settings.

My first thing would be to install as per the Victron installation manual for this product, 70mm cables from battery to inverter. Move the temp sensor to the output terminal of the US3000 which connects to the LPI. This should be less than £50 to rectify (cable, crimps, heatshrink) yourself.

If I had spec’d your install I’d have recommend the 48/10000 (due to the potential 7.3Kw load). I’d have installed a 48/8000 with a sigh, and totally advised against the 48/5000 for your use case.

So I would consider an upgrade to the 48/10000, and off-set the cost against selling the 48/5000, before it gets damaged.

A standard domestic kettle will draw it’s load, for half a kettle full (1.5L) for about 4-5 minutes.

We don’t know what volume of water the immersion is heating but 3Kw will be going for 45-150 minutes based on a standard 120L immersion tank (starting water temp, ambient temp, in service draw et. al.) On a 48/5000 that is quite some inverter heat generation over that time with that cabling, then add in the kettle and / or washing machine.

These people offer a great calculator: Water Heating Calculator. - Immersion Heaters UK

As you have a thermal store the target temp will need to be greater than 65C as this is the required temp to kill legionella bacteria, I used 74C in the calculation (my own 55L calorifier gets heated to 85C).

[dsparshott]

Thanks for the thorough reply.

Firstly, the cable to the MP, my mistake, is actually 70mm as specced by Bimble Solar from where the system was purchased. The cables on the batteries are supplied with it and you are correct in that they are 25mm in size. Now these have a unique connector on them so I’m not sure whether a 70mm cable can be swapped in to connect into the Lynx. I will look into this though.

Moving the temp sensor I will also need to try and figure out as this too will need to attach to the Pylon’s particular cable connector.

The immersion is heating around 280l in a thermal store, the calculator states around 2.3 hours for this, but with hot water being used during the day I’d say the immersion is actually on for much longer than this. No doubt as you say this is adding substantial heat to the system.

Screenshot attached of the summary. This should be my first priority to sort before swapping out cables and hardware. Hopefully there is a more reliable way to disconnect the AC2 when required.

[anon39974850]

OK, don’t sweat the temp sensor, this is all dealt with by the US3000 BMS, but the point was you were measuring the temperature of the Busbar, not the batteries. Just fix it against the battery box case as fallback low temp protection for your US3000’s. Refer to MP configuration in this regard in the various manuals.

The connectors look like SurLok (pronounced ‘SureLock’) connectors, they are not inexpensive at 70mm but they are out there, as are 50mm ones. Better than 25mm.

The Assistant shown is for an overload event, but your original post stated:

@dsparshott

• AC2 off when high temperature alarm is on for 2 seconds.
• AC2 on when battery above 90%
• AC2 off when battery below 80%

If the rule is for an overload event, what makes you think it isn’t functioning?
Is it the fact the MP shuts down and then re-energises?

@dsparshott

the multiplus will momentarily shut off

Could this be due to a MP overload event?

Maybe the temperature alarm (sensor connected to the overloaded and hot busbar, and not the system battery), is a red herring?

You could simply place an ammeter on the MP battery cable and measure the current to determine any overload. Just recreate an over temp / overload event.

@dsparshott

This will occur fairly randomly but correlation to having the washing machine on/kettle on.

If the ammeter reads higher (you’ll need one with a max reading memory) at any point than the MP operational spec (5000/48 = 104A) then:

1.) Physically reduce the ability to overload the system.
2.) Install as per installation requirements.

or

3.) Upgrade system specification (higher spec MP, cables et.al.) to accommodate maximum potential system load.

[dsparshott]

Thanks for all of this and noted re. the cable connectors, I had looked into this overnight and found some 50mm ones for sale on ebay.

With the alarm - it will show as either a High Temp or Overload on the GX, both will trigger the system to shut-off and reboot. I have had used both as the trigger on the Assistant for the AC2 to stop, i.e ‘2 seconds high temp alarm’ and ‘2 seconds overload alarm’ but neither has ever prevented the system from tripping.

Attached is a scrrenshot of the alarm log, as you can see alarms are mixed between temp and overload, the Assistant settings are never activated to prevent the MP tripping. So I’d be interetsed to learn a better way to set-up an Assistant in order to reliably prevent this.

Thanks again.

[anon39974850]

Hi,

Is there any reason you have an LED switch condition and not an AC load trigger?

Try AC Load for the switch condition > 3500W > 3s
Recreate overload event by loading with immersion, then any other load > 1Kw < 2Kw

[dsparshott]

Thanks, I will do this and report back.

Settings were as they were as I assumed the LED alarm would be a good gauge to activate the assistant, clearly not!

[dsparshott]

So it doesn’t appear that the Assistant is working at all. I uploaded last night with the relay for AC2 to be off when the AC load is above 3200w. Well, today with the washing machine on and the immersion it’s been able to put out 4600w without issue - therefore the assistant clearly isn’t doing it’s job as it should have shut off the AC2 at that level.

However, the MP just tripped when the kettle was turned on (in order to double check the assistant). The load jumped to 5800w and GX showed an overload alarm.

After resetting the washing machine and immersion both continued working. This lasted about 10 minutes when the MP tripped again, this time showing a High Temp alarm. Just checked and the temperature is is showing 26degC on the MP.

I think this may need to be a call to Bimble Solar or Victron directly unless there is something obvious I’m missing.

[anon39974850]

Sorry for the question but just re-read everything carefully.

1.) What is connected to AC1 output?
2.) Can you post a pic of your AC input / AC output connections on the MP?
3.) Can you confirm again you are completely off-grid.
4.) Can I see a total of 5, 3 core PVC sheathed cables leaving your MP, from the previously posted shots?

[dsparshott]

1. AC1 is connected to the house main fuse box.
2. Yes
3. AC1, AC2, AC In (as separate + and - through the breaker), Earth. The other cable you can see is a AC supply to a shed, this cable comes back from the main house fuse box (you can see the breaker in the bottom right of the previous photo). It’s only running a small fridge.
   
   

[anon39974850]

Just so I am clear;
1.) What is connected to AC-IN (Generator?)
2.) What is connected via AC OUT-1 (If its the house, what exactly?)
3.) What is connected via AC OUT-2 (The Immersion, Kettle, WMac?)
4.) How are the appliances connected to AC OUT-2 being earthed?

I’ll probably have some more Q’s based on the responses.

Also thinking out loud, the MP2 AC OUT-2 by design should shut down when no AC IN supply is detected and the MP is inverting from battery power. AC OUT-1 is a No break output.

It would also be nice to see some effective strain relief on AC OUT-1&2

[dsparshott]

1. The AC in is from a genset, currently disconnected for the summer.
2. The house distribution board, so doing lights and household appliances (fridge, freezer, computer etc.) This is rarely using above 500w at any one time except when the washing machine or kettle are on.
3. AC out 2 is directly connected to the immersion heater only. AC 2 is only activated when the battery SOC is above 90% and turns off at 80%, or when the water in the thermal store is up to 70degC or thereabouts.
4. The immersion heater is earthed to the main earthing block (just out of the photo) where the cables pass through a fused breaker.

Apologies but not sure what is meant by effective strain relief. Thanks