Poor Service From the Utility Company - What Does the Utility Owe the Costumer - On Demand Water Heater

Doinedaname

Member
Location
Washington PA
Occupation
EE PE self employed
A construction buddy against my advice installed an electric on demand water heater in his father's house. It used 2x 60 amp feeds and was installed into a 200 amp panel. The water heater after briefly putting out hot water starts putting out warm water at best. What I found out was the voltage at the water heater was dipping and the unit would only heat the water as much as the line could supply. In this case it would pull the 240v supply down to 220v and try to keep it there. I went back to the main panel and got on the utility side of the main breaker and got the same voltage reading. 240v with no water heater load and 220v when running. I then inspected the outside and looked at the meter and the mast and seen the insulation on the utility line from the transformer was a little cracked. I thought the connection may be corroded because of water getting in so I re-crimped both phases and neutral. Same results and even when measured at the top of the mast it was 240v no load and 220v when running. There were no other major electrical appliances running at the time. I did put an amp clamp on but don't rember the exact reading but they were well below 200.

The service is 175', actual measurement, of #2 AL cable to the transformer. The transformer is shared with another house and a garage. I don't know what load the house has but the garage is the owners and it had no to very little load at the time we were doing this troubleshooting.

The owner got with the utility company and this is what they came up with. The first trip a lineman looked at it and said nothing was wrong. After explaining the situation more someone went out and said that for $5200 they will move the transformer closer to the house.

The owner then went out and returned the instant hot water heater in put a new conventional one in. Problem solved for him.

My question is what does the utility owe the costumer? The house was built with a 200 amp service but it seems they cant even get close to providing that. The utility seems to be in the position to just say too bad so sad. If it matters this is in Pennsylvania and West Penn Power/First Energy. If the customer pushed it who should he talk to?
 

drcampbell

Senior Member
Location
The Motor City, Michigan USA
Occupation
Engineer
This is, I fear, completely "normal".

The 175-foot service will have a resistance of about 0.9Ω.
If the thankless water heater draws 96 amps, (80% of 120amps (?)) there will be about a 9-volt drop in the service cable alone. Plus another volt or three inside the house.

If it's a fairly-standard 15 kVA transformer with 3% impedance, that'll be responsible for another 10-volt drop.

Moving the transformer closer to the house -- without installing a larger one -- wouldn't have much effect.

It would be interesting to know the actual current, duty cycle and voltage drop, but I see that it has already been replaced.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
It depends on the tolerances allowed by public utility commission rules for your state.
While most utilities are allowed to supply 5% less than the nominal voltage this is not a universal value.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
If
This is, I fear, completely "normal".

The 175-foot service will have a resistance of about 0.9Ω.
If the thankless water heater draws 96 amps, (80% of 120amps (?)) there will be about a 9-volt drop in the service cable alone. Plus another volt or three inside the house.

If it's a fairly-standard 15 kVA transformer with 3% impedance, that'll be responsible for another 10-volt drop.

Moving the transformer closer to the house -- without installing a larger one -- wouldn't have much effect.

It would be interesting to know the actual current, duty cycle and voltage drop, but I see that it has already been replaced.
If it’s older, it may even be only a 10!
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
Car chargers and electric tankless water heaters are going to cause utilities grief in the future because they use such small wires to feed houses. My "200A service" is on a 25 KVA transformer (along with another house), and it has a 100' overhead drop and 150' of underground (250' total). Both of those sets of wires were specified by the power company and are #2 Al (overhead) and 1/0 Al (underground). This was intended for a house that had gas heating and other gas appliances. It works fine for that. But when you start adding loads to near 100A, the voltage drops (the AC kicking on with its LRA of 105A makes a very noticeable lighting flicker). That doesn't happen often, but I don't have an EV or an electric tankless water heater.

The poco can upgrade the wire size from the street, but mine charges for that. I did it at my last house and I think it was about an extra $700. I also paid to have the transformer size increased at that house (it had a 400A service) which was about $1500 I think, to go from 25 KVA to 50 KVA

So the OP house perhaps could have fixed it with a wire upgrade and maybe a transformer upgrade depending on what size he had. Moving the service closer is certainly better, but that usually costs more and I don't think that is even an option for me.
 

David Castor

Senior Member
Location
Washington, USA
Occupation
Electrical Engineer
This sounds pretty normal. Utility voltage can be +/- 5% of nominal 240 V . It might have been possible to change the transformer tap provided that didn't make the voltage too high at no load. Or install a larger transformer.
 

kwired

Electron manager
Location
NE Nebraska
Something tells me the voltage drop will likely be annoying with it's impact on lighting and a few other items, the reduced wattage of the water heating is probably not so significant that if you got rid of that VD it still may not quite heat the water to the right temp at whatever the flow rate was. If this were a 11-12 kW heater (based on what you have for breakers) and you are dropping voltage by about 20, you probably only getting about 10-11 kW instead of 11-12. Combination of incoming water temp and flow rate is critical here when sizing a unit and you maybe were marginal from the start before even considering electrical input ability.
 
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