Voltage Question

[Jopopsy]

So - is this normal?

I’ve never run a camper at my house with a EMS before. This afternoon I cut the power cord to 3’ long running from my C and put a male end on it. I then put my Progressive EMS in the power cord compartment, plugged into the coach. I then connected a heavy duty 20amp power cord from the EMS to the 15 amp circuit on the side of my house.

My voltage meter in the coach reads around 114v-116v. When I turned on the shop-vac to clean up inside the coach, it tripped my EMS. Turns out I drop to 102 - 103 volts when I run the small 3 gallon shop-vac. I then decided to try a space heater, and on low it dropped me to 109 but on high it would trip the EMS again.

So - I took the volt meter into the garage and ran the shop-vac off a house outlet - the house outlet dropped to 105 volts. So I get a slightly bigger voltage drop in the coach (not surprising) but not much.

Is this normal behavior? Now I’m wishing I didn’t put the EMS in that compartment - I was blissfully unaware before I had that bright idea.

I was considering not packing my autoformer this year, but now I’m strongly reconsidering.

???

[SloPoke]

Start checking the other outlets in the house... None of your house outlets should drop to that low of a voltage reading while under load.

Isolate this outlet from the rest of your house / other outlets on that same circuit.

[JaycoMLOK]

My guess would be you have something else in the house running that on that circuit. Then by using the shop vac it's causing the voltage low.

[Jopopsy]

So the vac is rated 120v, 11.8 amps.

When I put the vac on other outlets inside the house (other circuits) I go from 116 to 107. When I put it on the outlet that the camper is plugged into, it goes from 116 to 103-104. There are other things on that outlet as I discovered the first time I tripped it.

So I’m guessing maybe this is normal given it pulls almost a full 15 amps? When it turns on I can watch the garage light dim when I turned it on directly off the camper’s outlet (camper unplugged).

[SloPoke]

or an open neutral... turn on lots of lights in the house... do you have some going brighter / dimmer than others when other lights and appliances are being turned on ?

[Jopopsy]

No, the power in my house never fluctuates. Lights are always constant.

[RPR]

Shop vac motor may be going bad and motor is drawing a lot of current. Turn house microwave on and check volt at any outlet.

[Vicr]

No, things are not normal. #1 what is the voltage at your house main breaker, A phase to neutral and B phase to neutral? #2 What is your service amperage? #3 What electric heat loads do you have in your house?

[JimD]

I worked in the field for 45 years installing equipment that would plug into a customer's standard power outlet. Anytime we experienced a power line that would drop down to 107 volts it would cause the electronics in our units to have problems, sometimes causing them to basically reboot. If I saw a power line drop below 108-109 we would telling the customer to have their line repaired. I think it was referred to as a "soft" line.

Voltage should not be dropping that low in your house. I would try various outlets with the same load and see if they all react the same way. If so I would suspect the voltage coning in may have a problem. Also try monitoring one outlet while you connect the load to another and see if the voltage drops.

My inlaws once had a problem at their house where 1/2 the input was causing problems. Since the 240 coming in is split into 2 120 volt legs sometimes you can have a problem with only half.

One last thought. I once installed a machine that every time it would initiate main power it would reboot because the power line would drop real low. I looked at the customer's circuit breaker panel and saw the breaker would spark when our machine would fire up. I swapped their breaker with an unused one and the problem was solved.

I don't recommend you play around in your 120 volt system unless you are comfortable around voltages that can kill you. You may have to contact an electrician.

[RetiredOne]

Originally Posted by Jopopsy

So I’m guessing maybe this is normal given it pulls almost a full 15 amps? When it turns on I can watch the garage light dim when I turned it on directly off the camper’s outlet (camper unplugged).

Where is that outlet in relation to your main circuit breaker panel? Any chance you're getting a voltage drop between the panel and that outlet? How far is the run, how long is the cable? Any chance it's a 14 gauge wire (15 amp circuit) feeding that outlet, instead of a 12 gauge?

[us71na]

I just checked my shop vac which draws 9.5 amps at 120 volts. The outlet voltage drops 2.5 volts when the vacuum is running at full power. This outlet is on a 20 amp circuit breaker and wired with 12 gauge wire.

What you don't provide is enough information realistically solve your problem. You need to tell us:

1. What is the rating on the circuit breaker feeding the outlet in the house?

2. How far is that outlet from the main panel?

3. What size wire feeds that outlet? What is the rating of the electrical outlet? If it was the $1.95 variety from the local big box store buy a better outlet.

4. How long is the "20 Amp" wire you ran to the outlet in the house from the trailer? What are the ratings of that wire stamped on the insulation?