Can A Heat Pump Cause Overvoltage?

[OldNavyGuy]

Does anyone have any idea of what could cause the following:

The hardwired surge protector in the coach kicked off the 120v three times this evening, apparently due to an overvoltage. The front heat pump was running, and the outside temp was approaching - but still above - 40 deg F, the cutover point where the heat pump compressor kicks off. The propane furnace kicks in a little later when the inside temp continues to fall.

I have a voltage monitor plugged in that shows real-time what exactly the 120v is on that particular circuit. Having a 50 amp coach, there are at least two such main circuits I presume.

All 120v appliances that could be shut off were turned off before the time delay on the surge protector restored the power. When I turned the heat pump back on after the power was restored, the voltage on the monitor immediately increased one volt, and then slowly climbed to 128v before the surge protector kicked off the power again.

This cycle repeated one more time before I shut off the heat pump for the night. In previous situations with temperatures like this, the handoff from the heat pump to the propane furnace was seamless, and there were no issues from the surge protector.

The coach converter monitor didn't show excessive draw from the shore power post, so it didn't look like anything was shorted. No circuit breakers popped during all this, including the one on the campground post.

Turning off the heat pump lowered the indicated voltage every time, and I am at a loss for what could cause such a problem. I understand the theory but lack the practical experience of a seasoned electrician to understand this.

Any helpful thoughts would be greatly appreciated.
Thanks!

[Old-Biscuit]

Surge protector has no clue what is happening 'downstream' (load side)
It only senses/monitors what is going on 'upstream' (Line side)

High voltage is a condition from CG Electrical Grid as a result of LACK of demand by RVs in CG.....cold evening, few using AC Power etc.
Just as a low voltage condition is a result of over demand (hot afternoon and ALL A/C Units running on all RVs in a full cg)

Heat pump would NOT generate higher voltage.
Issue is with CG AC power system OR with their Utility Company.

[OldNavyGuy]

Originally Posted by Old-Biscuit

Surge protector has no clue what is happening 'downstream' (load side)
It only senses/monitors what is going on 'upstream' (Line side)

High voltage is a condition from CG Electrical Grid as a result of LACK of demand by RVs in CG.....cold evening, few using AC Power etc.
Just as a low voltage condition is a result of over demand (hot afternoon and ALL A/C Units running on all RVs in a full cg)

Heat pump would NOT generate higher voltage.
Issue is with CG AC power system OR with their Utility Company.

Old Biscuit, thanks! That's what I thought at first too, but the voltage went up when I turned on the heat pump and right back down when I turned it off again. I did that about four times to test that it was me and not outside variations.
Any chance that there could be some slight path created between the two legs of the 120v in the coach when the heat pump is turned on? Doesn't make sense to me, but I don't know how else to explain this.

[YC1]

Interesting question and I think you may be on to it. If possible, try another 50 amp post.

Never say never when it comes to electronics or electrical. It would be interesting to see what happens if you use an adapter and plug into 30 amp.

I found voltage between the drain of the bath tub and the water faucet that feeds the tub in a new apartment. It was only there when the oven or dryer were running. Could have been a real disaster. The building ground was immediately repaired.

[mrmattmoyer]

Usually sporadic voltage as you are describing is due to a loss if neutral (white wire). This will fry your electronics. Unplug immediately.
Often this condition is not recognized until you apply a load such as your heat pump to the circuit.

In case you are wondering, yes I am a Master Electrician.

[Kiawah]

I would suspect a bad neutral. The power post has 2 power legs, which are out of sync in their wave pattern. Call one leg A, call the other leg B. When you measure the voltage from A to neutral, it should be 120v. When you measure from B to neutral, it should be 120v. When you measure from A to B, it should be 240 volts.

Since there are devices on both leg A and leg B, lets assume your battery charger (converter) is on leg A and draws 10 amps, and your A/C is on leg B and draws 15 amps. What should happen is that 15 amps will be on the shorepower current on leg B, 10 of that current will then go thru the converter back to the shore transformer, and the remaining 5 amps will go down the neutral.

If the neutral has a bad/loose/missing connection, the current can't go the way it's supposed to, the two devices have different resistances and power consumption, and the apparent voltage of the legs will change because the neutral is floating away from 0.

So instead of each leg showing 120 v as measured to neutral, one could be 140v and the other leg would be 100 v.

So anytime you see an apparent high voltage on a leg, if you look at the other leg you'll undoubtedly see a low voltage there, and you need to check all the neutrals and grounds along the path. If your EMS detected the problem and shut down, then have the CG check their power post and/or transformer connection if need be. I have seen underground cables go bad as well.

Your symptom of the voltage changing when you turn off your heatpump is not because the heatpump is putting voltage on the line, it's because when the heatpump tries to draw current from the leg it is on, the current can't leave and go to neutral, it has to try and find a path out thru the other leg. Since the devices and resistance are unbalanced, the neutral floats off 0.

[OldNavyGuy]

Originally Posted by mrmattmoyer

Usually sporadic voltage as you are describing is due to a loss if neutral (white wire). This will fry your electronics. Unplug immediately.
Often this condition is not recognized until you apply a load such as your heat pump to the circuit.

In case you are wondering, yes I am a Master Electrician.

Originally Posted by Kiawah

I would suspect a bad neutral. The power post has 2 power legs, which are out of sync in their wave pattern. Call one leg A, call the other leg B. When you measure the voltage from A to neutral, it should be 120v. When you measure from B to neutral, it should be 120v. When you measure from A to B, it should be 240 volts.

Since there are devices on both leg A and leg B, lets assume your battery charger (converter) is on leg A and draws 10 amps, and your A/C is on leg B and draws 15 amps. What should happen is that 15 amps will be on the shorepower current on leg B, 10 of that current will then go thru the converter back to the shore transformer, and the remaining 5 amps will go down the neutral.

If the neutral has a bad/loose/missing connection, the current can't go the way it's supposed to, the two devices have different resistances and power consumption, and the apparent voltage of the legs will change because the neutral is floating away from 0.

So instead of each leg showing 120 v as measured to neutral, one could be 140v and the other leg would be 100 v.

So anytime you see an apparent high voltage on a leg, if you look at the other leg you'll undoubtedly see a low voltage there, and you need to check all the neutrals and grounds along the path. If your EMS detected the problem and shut down, then have the CG check their power post and/or transformer connection if need be. I have seen underground cables go bad as well.

Your symptom of the voltage changing when you turn off your heatpump is not because the heatpump is putting voltage on the line, it's because when the heatpump tries to draw current from the leg it is on, the current can't leave and go to neutral, it has to try and find a path out thru the other leg. Since the devices and resistance are unbalanced, the neutral floats off 0.

mrmattmoyer, kiawah,
Thank you! We will be unplugging and moving ASAP.

The campground does have some strange wiring, but the surge protector lights have indicated things were OK at the post. We have been at this campground almost a month and at this site for a week. Last night was the first time we had an issue, but also the first time it has gotten that cold.

I will unplug in a couple of minutes, and will be moving sites in a few hours. If problems persist, we will change campgrounds.

I will also discuss this with the owner, who is a terrific guy, so I am sure he will get this fixed as soon as he can.

You guys are awesome, and I really appreciate the good advice. I'll let you know how all this turns out.

[billdreamlv]

Originally Posted by Kiawah

I would suspect a bad neutral. The power post has 2 power legs, which are out of sync in their wave pattern. Call one leg A, call the other leg B. When you measure the voltage from A to neutral, it should be 120v. When you measure from B to neutral, it should be 120v. When you measure from A to B, it should be 240 volts.

Since there are devices on both leg A and leg B, lets assume your battery charger (converter) is on leg A and draws 10 amps, and your A/C is on leg B and draws 15 amps. What should happen is that 15 amps will be on the shorepower current on leg B, 10 of that current will then go thru the converter back to the shore transformer, and the remaining 5 amps will go down the neutral.

If the neutral has a bad/loose/missing connection, the current can't go the way it's supposed to, the two devices have different resistances and power consumption, and the apparent voltage of the legs will change because the neutral is floating away from 0.

So instead of each leg showing 120 v as measured to neutral, one could be 140v and the other leg would be 100 v.

So anytime you see an apparent high voltage on a leg, if you look at the other leg you'll undoubtedly see a low voltage there, and you need to check all the neutrals and grounds along the path. If your EMS detected the problem and shut down, then have the CG check their power post and/or transformer connection if need be. I have seen underground cables go bad as well.

Your symptom of the voltage changing when you turn off your heatpump is not because the heatpump is putting voltage on the line, it's because when the heatpump tries to draw current from the leg it is on, the current can't leave and go to neutral, it has to try and find a path out thru the other leg. Since the devices and resistance are unbalanced, the neutral floats off 0.

Dave,

That was an outstanding explanation. Good on ya, mate. One thing to mention is that the neutral line on the coach needs to be checked as well. If he changes locations and has the same outcome, it might be the coach neutral that is the problem. In other words the neutral on the coach could be floating and not just the neutral on the post. I think you alluded to it but I don't think OldNavyguy was aware of this additional possible problem.

Bill

[Hgrace56]

You could also see a spike when a high load by your rig like the heat pump or even someone else on the CG grid shuts down.
I would suspect ling ccontinuous heat loads like Electric dryers or heaters

Also Master Electrician and 35 year contractor

[wa8yxm]

Can a heat pump cause overvoltage.. Well, normally I'd say NO but.. ther eis a way. There is a way. This gets a bit technical but if you understand electricity it really makes sense.

Some folks will tell you that 50 amp Service is 240 volts (they are partially right)
Others will yell "NO NO It's 120 volts twice" (likewise they are partially right)

It is 120/240/120 volts, or in terms your family cook might understand.. 240 volts divided

(Think of a line in a recipe 2 cups sugar Divided Yup, just like that)

now if you divide that cups at 1/1 you get 120/120
But if you divide it at say 3/4 cup, and 1 1/4 cup you get 80/160 Still totals 240 but clearly one leg is low and one is high.

This is what happened in my house when I had a weak or open neutral.

And it's your problem as well

All devices UP LINE of the EMS are suspect. Including the wires buried under the RV park.

Have you ever heard the phrase "Think outside the box"

Well in this case there are at least 4 boxes
1: The heat pump.. Think outside this one
2: The master power distribution panel in your RV (Not this one either)
3: The Park Outlet box atop the pedestal (Suspect You should think "inside" this box)
4: The park's main distro panel (Likewsie this is one that may need thinking within)

Thinking means haveing it tested by the park electrician.

Also suspect are your plugs and cables up to the EMS.

TO TEST

If the outlet box is the common 50/30/15-20 park outlet box
Plug a volt meter into the 20 amp and watch what it does (I suggest an analog) when the heat pump fires up and shuts down... Any change more than a volt or two indicates park side problems.

[OldNavyGuy]

Thanks to all of you! Again!

I moved to next campsite and the same problem existed on 50 amps. Engage the heat pump, and the voltage rose two volts on the monitor.

I then connected with the 30 amp adapter. Using only one leg of the power seems to work OK. Voltage drops appropriately when the heat pump is turned on from 118 to 116.

Everything seems OK, and I do have a multimeter onboard, but it is digital. No 20 amp outlets on the posts either - just 50 & 30.

Think this is safe using one leg, or is the risk unacceptable from a possible bad neutral even on 30 amps?

And.....how do I test my coach to ensure the neutral is good on her?

Thanks in advance!

[Kiawah]

how do I test my coach to ensure the neutral is good on her?

The first thing I would do, is to make sure all of your connections are tight.
- Unplug shorepower, and make sure generator isn't configured to start. Turn your inverter off, so it isn't making 120v power. Before you put a screwdriver on connections, make sure they have no power by checking with your voltmeter. Measure connection to green/bare wire ground.
- Look at the plug, make sure it doesn't look like any of the spades have melted plastic around them, or are pitted.
- Take the cover off the EMS, make sure the shorepower connections in the EMS are tight. 4 wires, make sure they are all tight (red/black/white/green). Make sure the output wires of the EMS are tight.
- Take the cover off the transfer switch. Make sure the wires from the EMS coming into the transfer switch are tight. Also make sure the wires coming in from the generator, and the output wires connections are all tight.
- Inside in the circuit breaker panel, make sure the main wires coming into the breaker box are tight. Tighten the wires on all of the breakers, tighten the white wires which are back on a common buss bar, and the green/bare wire grounds which are back on a common buss bar are tight as well.

If you turn the power back on now, you can tell if the problem is on your side by measuring the voltages at different places, and see how they compare.

You have the EMS box open, you can carefully measure the voltages on the two legs as the shorepower wires come INTO the EMS box with your heat pump running. Except for the possibility of your shorepower or electric reel (if you have one), this should be the post voltages. You are measuring red to white (one leg), and black to white (second leg).

Now go inside to your circuit breaker box, and do a similar measurement on your main breaker. red to white, and black to white.

If your voltages at the breaker box are comparatively the same as the input to EMS, then the problem is most likely outboard of your EMS unit to the campground connection (still could be your shorepower cord). If the voltages are comparatively different, then you have a problem, and be doing additional measurements should be able to figure out where it is.

[billdreamlv]

And always use safety procedures. Always consider all wires hot until verified otherwise. There is a tester at home depot that can give you an audible sound when there is 120v present. And always use one hand to work with wires that you don't know are hot. Using two hands can allow the voltage to go right through your chest. You are going to have 120v on wires when the inverter is on and batteries connected. Stay safe my friend.

[OldNavyGuy]

Update:
Very much appreciate all the responses. I have learned much.

The campground owners had an electrician out here as soon as they were made aware of the problem. His first solution, and he will be doing more,was to ground every post in the campground to keep the neutral from floating. It seems to have worked, because we've had no more problems, and the heat pump functions perfectly. I will be testing the various wiring aspects of the coach shortly, but given what has happened, i believe the problem was external.

Again, my surge protector has saved the coach from major damage - or worse - for the third time in 18 months. Don't leave home without one!

The voltage monitor does rise by a volt or two when the heat pump is turned on, but stays stable and does not continue to rise as before.

We're out of here in the morning in any event, but again, thanks for all the info and excellent advice.

Warm regards and safe travels!