Power Boost not working? Multiplus 2x120

Q&A and troubleshooting
, ,
1

Hi Folks!

New user here so think simple :slight_smile:

I just installed my Multi II 2x120 in my RV and enabled Power Boost. I set the voltage to 120V

The RV is connected to a 30A pedestal and I set the input power to both 30A and also tried 24A

I have a kill-o-watt plugged into one of the outlets that the MPII feeds and I’m seeing line voltages of around 110V at the receptacle.

I thought it would ‘condition’ the outlets to the 120V setting by using battery power, ie, Power Boost.

Am I missing something in my config or my understanding of how Power Boost works?

Many thanks in advance, this is an important feature for me.

Btw, I just checked and when I kill the power to the MPII and when it’s inverting, the measured power at the outlet goes up to ~118v which seems right.

Interesting…if I dial the AC Input down to 15A, while on shore power, then it will selectively go into Power Assist while the load exceeds that level, but…the line voltage does not go up to 120v it will still remain at around 110V. I also found I had to restart the inverter for those changes to take effect.

It seems like I’ve configured it properly, the phone indicates it’s going into Power Assist, but the line voltage does not reach the 120V target.

2

Boost can’t change the grid’s voltage or frequency without powering your whole town. It only provide additional current to supplement the grid that it’s synchronized with. UPS mode will disconnect from the grid and makes it’s own voltage and frequency.

3

Hi Paul!

That makes sense. Unfortunately, that’s the primary reason I bought it, I thought it would increase the voltage to the connected outlets by supplementing with battery when the park voltage was too low.

The underlying issue is that one device in my unit, the washer and dryer, injects water into the tub during the dry cycle whenever the voltage drops too low.

4

It will go into UPS mode if the voltage gets too low, but 110V is pretty much in spec for a grid.
If you have occasional brownouts, the UPS function will take over and keep things running until the grid recovers.

Your laundry has issues with 110V?

5

Yes!

This has been ongoing for some time but the bottom line is when the line voltage drops too low, usually around 110 or 108, in that neighborhood, the dry cycle fails and it injects water into the tub soaking the clothes it’s supposed to be drying - at the very end of the cycle.

I guess my question is, is it failing because of line voltage or current? That is beyond my understanding. I’m trying a load now with the unit plugged into one of the inverter outlets and my other heaters on. This should be a recipe for a dryer failure. Line voltage is at 109 and when it hits the dry cycle it will be interesting to see what the voltage drops to as the dryer heaters come on…

Edit: I just asked AI “when voltage is low are amps also low”

and it said this, “Not necessarily; it depends on the type of load in the circuit. For simple resistive loads, like a heater, lower voltage means lower amperage “

The dryer in the unit will be a giant resistive heater. You mentioned that the Victron unit cannot boost voltage (for now obvious reasons, you’d backfeed the park, but is the dryer actually starving for volts or amps? My guess would be amps, which you mentioned is what the inverter boosts?

I’m trying a load, we shall see :slight_smile:

6

Good test. Check the MP grid settings using VE configure. You can set the low connect/disconnect values and the UPS function. It’s the UPS function you’ll want if voltage is the cause. It would be interesting to find out if the voltage dip is at the pedestal or somewhere within the coach.

That seems pretty sensitive for a device like that. I wonder if it’s a transient drop caused by a high resistance, and not a steady state drop that a meter can see.

7

Historically, that low voltage will also be seen at the pedestal. I’ve been through the AC in this unit and replaced breakers and…to the point where I know it’s the supply voltage from the pedestal running low. I have a meter on the same circuit so I can watch the voltage when it fails.

But…you raised a good point (I think) above (and I edited the post above) and it seems that you’re saying that the unit will boost the amps and not the voltage. It may be that my test with the meter is showing me low voltage, but my guess is that, because the dryer has a giant resistive heater, that the low voltage might be a symptom of the underlying condition, low amperage.

It’s all just a guess because I’m not an electrician, but it seems to me that amperage is what would drive a large resistive heater. So if the unit does boost the amps, then perhaps that will fix it. Either way, with both electric heaters on, and the dehumidifier, the dry cycle should kaff.

I’ve seen this happen in new parks with new 50amp power. In every instance, the symptom is low voltage as shown by the meter. In one park, with really nice power, it only happens at the peak of August when everyone (120 units) have both AC units running to keep cool. So the issue is intermittent but the symptom I see is always the same, low voltage on the meter.

In the current (pardon the pun) park, I’m stuck on new 30A service. The dry cycle kaffed but I was able to get it to complete by shutting off everything else so that the line voltage was back at 120v.

It could be transient in that the dehumidifier kicks on, or the heaters, or I use the microwave, but the symptom is the same, low voltage. Or is it low amperage….if the Victron unit boosts that then it may fix it. I’ll go outside and see if it’s in boost mode when the dry cycle starts and I’ll also plug the phone in to see what the total draw is.

Btw, it’s a new computer controlled washer/dryer with at least 3 computers, all of which I have needlessly replaced in my quest to fix this issue!

8

I think I’m SOL on this one. The clothes look pretty wet and the voltage dropped to 106v at one point. It’s drawing 8.6A on the dry cycle or about 960 watts. The power assist is on. Not sure what to think, but glad I cancelled the Cerbo that I ordered up this morning.

According to AI, “A 120V supply is considered too low when it consistently drops below 114V (a 5% drop) or 108V (a 10% drop), though the latter is often considered the point of unacceptable performance. Voltages below 114V can damage equipment or cause overheating, while voltages below 108V can lead to more severe issues and indicate a significant problem with the electrical system.“

9

Yes, it can only boost current. There is really no such thing as low amperage or current in this situation.

The grid provides a voltage, a device will draw the required amperage/current to operate. There is always resistance in series along the way, as the device draws current, some of the grid voltage is consumed (voltage drop) in that resistance, the remainder of the voltage appears at your device. IF that resistance is higher than normal, as a device draws current, the voltage drop will increase, lowering the remainder to the device. For a given resistance, as current increases, the voltage drop increases, the voltage remainder to the device decreases. That resistance can come from wires that are smaller and/or longer than they should be, or a loose connection, bad contact, etc. Some devices will draw increased current as the voltage decreases, causing the voltage to further decrease.

IF this problem happens consistently, it could be within your coach. You can test this by turning everything off inside, and measuring the voltage at pedestal. (carefully expose a bit of the prongs of the shore cord). Turn on large repeatable loads, then repeat that measurement. The difference is the drop external to your coach. Now do the same test steps right at the plug for your load. The difference is the drop inside your coach,

IF that internal drop is large, you could have a transfer switch contact going bad, or a loose connection in there, bad shore cord, bad shore plug (hot?), loose screw in the breaker panel, bad breaker, or those pesky press together RV plugs is bad right at the laundry.

The external and internal drops are additive, so it could be when the park is low because of everyone’s heavy draw, your own internal drop during a heavy draw makes the difference.

10

Low voltage (and sometimes high voltage) is not uncommon in campsites. Depends on how many users there are. A Hughes Autoformer will boost voltage. There may be others but this is the only commercially available device I know of that does this.

11

OK, first, thanks very much for the help! I really thought that the Victron would just bump all the line voltages to a perfect 120v and boost as necessary, that’s on me.

I wanted to buy a Hughes Autoformer because I always felt that would fix everything. But…they aren’t made anymore and the used ones are basically $1000 still so, based on my previous (incorrect assumption) I figured I’d buck up another $600 and replace the inverter thinking it would do the same and I’d get pure sine wave and all the latest and greatest features.

With respect to testing the unit for the issue, I eliminated it some time ago. Going from memory, I upgraded the washer breaker to 20 amps and also replaced the receptacle with a 20amp unit. I then measured the voltage going into the transfer switch and after to check for drop. There was none. At one point I did clean the contactors in the transfer switch. I also polished the prongs with brasso on the cables. I have tightened all the connections in both the transfer switch and at the breaker panel inside. This was long ago and there were loose ones from the factory and from time to time I check them again.

I also replaced about $500 worth of parts in the washer thinking I had it beat. It was all unnecessary.

The conclusion I came down to was that the unit is tight and that the problem was park power. It is intermittent but it presents this way, the voltage will always be low. Turning everything off inside will help the chances of success. It happens more in the heat of the summer when park power draw is high OR when in a park with goofy power.

The park I’m in right now is brand new. Very few people - it’s almost deserted. With no loads the line voltage is 120V. Start turning on things like electric heater (1500 watts) and the line voltage starts to drop. The more you turn on, the more it drops. If I’m using the dryer at anything around 115v it could act up. Anything like 110v and it’s almost a certainty. The damn thing injects water during the dry cycle

My thinking was erroneous. It was autoformer or victron inverter. I thought the inverter did the same, and if anything, did way more.

I still don’t know what power assist even does. I can see it operate, it’s operating when the dryer is running, it just doesn’t seem to do anything. I’m wondering if the answer lies with Paul’s post above regarding UPS functionality. When inverting the unit puts out ~118v at the outlet.

This causes me to wonder, can I set the unit so that it goes to UPS mode at something like 115v? In other words, disconnect from shore power and go UPS? It may be that there is another way to skin the cat but I’m not sure. I thought power assist would fix this but I certainly understand that if it’s connected to shore power and shore power was 110V and it boosted to 120V it would try and raise the power in the park.

There is good news, the microwave seems to be much faster!

12

The Autoformer and Multiplus do different things. The Autoformer boost voltage, the Multi power assist boost current. Just a quick aside on 50 amp vs 30 amp at the campsite. 50 amp is 240 volts at 50 amps. That’s 2X 50 amps at 120 volts. So actually it’s 100 amps at 120 volts. 30 amps is 120 volts, so less than 1/3 the current of 50 amp shore power. So on 50 amp you will likely never use the power assist feature but on 30 amps, it’s quite likely. If you use a watt-amp-volt calculator, you will find 30 amps@120 volts is about 3600 watts. Reduce the voltage and you have even less. A rooftop AC unit draws about 1200 watts, a coffee maker, toaster, etc may draw about the same. In addition a motor (or AC compressor) starting will draw quite a bit of current when it starts. Soft starts on the AC units will help here. OK, so if you exceed 30 amps with the Multi, the inverter will assist with whatever amps it can. We have a Quattro in our motorhome, slightly different to your setup but essentially the same. We occasionally camp at 30 amp sites and pretty much live as normal, running 2X AC units and various electric devices at the same time with no issues. We don’t have a washer so I can’t comment on how that would work. The inverter switches to assist seamlessly depending on load. Now the Autoformer is very different. It boost voltage, but cannot boost current, in fact it takes a bit of current to increase voltage. So if you exceed 30 amps it will not help. In my opinion, if you had to choose between an Autoformer or power assist inverter, the Multi is much more beneficial than the Autoformer in day to day usage. I just bought a very nice used 30 amp Autoformer for US $40, so you just have to keep looking, they are out there. I have only used it once, so can’t really report on how well it helps. Couple things I might suggest, is the washer on a dedicated circuit? Do you know what size wire is going from the panel to the washer? You could be getting a power drop there, I might be tempted to run a 12 gauge cable from a dedicated 20 amp breaker to the washer if possible. Finally, yes you could run the washer on just the inverter by disconnecting shore power but my guess is you will need a good size battery to run it.

13

Hi Bobbie - thank you for the great reply!

I’ve replaced my hot water tank (2000w) with an on demand that uses only 12v and propane. I also replaced the Norcold 1200 fridge that used 500w 24x7 for a residential that uses less in a year than the Norcold used in a month :slight_smile: I also installed one of the new 18K Chill Cubes with the variable speed compressor - and numerous other things to make the unit less 50A dependent and much more 30A friendly. It’s not just power savings, although there’s been a ton of that, it’s really about opening up options with sites and when this new park, with only 30A came up, at a really good off-season rate, it was just too good to pass up, hence the Multiplus II purchase.

I thought I had it all beat until I replaced the Splendid condenser washer/dryer with the new GE unit.

It’s a great unit, WAY better than the Splendide, but it’s dependent on very specific power, it seems. To that end, it is on it’s own dedicated circuit with 12/2 Romex (20A cable) I replaced the 15A breaker with a new 20A and also the wall receptacle with a new 20A.

So that circuit, end to end, is good. Whoever designed the washer/dryer unit is the actual culprit and there are many reports out there about the same issue. So far it seems I’m the only person that’s tracked it back to the power that’s being fed to it. Experience seems to show that at or around 115v it gets iffy.

If I have two heaters on and the dehumidifier the line voltage can easily get down to 110 and the new low so far is 109. For that you need the microwave etc. Either way, my current workaround is to shut everything off and then do laundry :slight_smile: To make is simple, with 95% of items off at night the line voltage is 120V and with everything on it can go down to 109 and then the dryer kaffs every time.

On the autoformer pricing, I was always looking for 50A units as I’m plugged into both and have seen issues with both. I just looked at e-bay and even 30A units are roughly $500 CAD when you include shipping. I’ll keep my eyes open though.