Tankless water heater

[mbrooke]

Are you saying ignore the NRC load calcs and go by gut feeling. I wonder how well that will go over with the Building dept or Insurance when things start to melt.

IMO, I doubt anything will melt. OCPDs are meant to prevent that.

 

[hillbilly1]

IMO, I doubt anything will melt. OCPDs are meant to prevent that.

Yeah, it will keep his maintenance man busy resetting mains during the winter! LOL!

 

[Sierrasparky]

IMO, I doubt anything will melt. OCPDs are meant to prevent that.

I guess you don't do much service on apartments and condos with 100amp service and a fully loaded panel. I replace melted Mains, service and much more over the years. The only thing that saves is when folks have removed load from the original build such as a heater or two and switched to pellet stove or propane. Main breaker is not meant to survive a long and continuous load near the max breaker setting.
IMHO and experience

 

[mbrooke]

I guess you don't do much service on apartments and condos with 100amp service and a fully loaded panel. I replace melted Mains, service and much more over the years. The only thing that saves is when folks have removed load from the original build such as a heater or two and switched to pellet stove or propane. Main breaker is not meant to survive a long and continuous load near the max breaker setting.
IMHO and experience

How do we know this isn't just poor installation practice and age? I'd hope equipment can actually survive being loaded to 80% of its rating indefinitely.

 

[mbrooke]

Yeah, it will keep his maintenance man busy resetting mains during the winter! LOL!

Typically services are loaded to 1/3 to 1/2 the NEC load calcs.

Not sure how much is here relative to the main however.

 

[Sierrasparky]

Typically services are loaded to 1/3 to 1/2 the NEC load calcs.

Not sure how much is here relative to the main however.

Says who, When you have a all electric house with many large loads it probably is not a issue. You have here a 17kw water heater, Electric dryer, electric heat pump. Highly probable that those things are running at the same time. As you indicated the Main at the building may see some diversity. However the loads we are speaking of are hard on equipment. That is why they are looked at as continuous loads. I doubt the service is rated to accept the additional load as buildings are built at the lowest code compliant price.

 

[robertd]

What did the tankless heater replace? Did each unit just have a normal electric tank water heater?

 

[GoldDigger]

What did the tankless heater replace? Did each unit just have a normal electric tank water heater?

There is a good chance that the hotel used one or more large common heaters for groups of rooms. Not so desirable for apartments where utilities need to be separated.
There may or may not even be space for individual tanked units.

 

[Sierrasparky]

What did the tankless heater replace? Did each unit just have a normal electric tank water heater?

There is a good chance that the hotel used one or more large common heaters for groups of rooms. Not so desirable for apartments where utilities need to be separated.
There may or may not even be space for individual tanked units.

Yes , Yes , The OP states these are all electric apartments.

 

[mbrooke]

Says who, When you have a all electric house with many large loads it probably is not a issue. You have here a 17kw water heater, Electric dryer, electric heat pump. Highly probable that those things are running at the same time. As you indicated the Main at the building may see some diversity. However the loads we are speaking of are hard on equipment. That is why they are looked at as continuous loads. I doubt the service is rated to accept the additional load as buildings are built at the lowest code compliant price.

Code still lets you size service conductors at less than 100% in dwellings.

Dryer will draw closer to 20 amps, and cycle on and off after about 15 minutes of run time.

How many kw is the heat pump? I'm assuming emergency heat.

 

[petersonra]

Are you saying ignore the NRC load calcs and go by gut feeling. I wonder how well that will go over with the Building dept or Insurance when things start to melt.

as long as the proper OCPD are in place the worst that would happen is some nuisance tripping.

 

[petersonra]

Says who, When you have a all electric house with many large loads it probably is not a issue. You have here a 17kw water heater, Electric dryer, electric heat pump. Highly probable that those things are running at the same time. As you indicated the Main at the building may see some diversity. However the loads we are speaking of are hard on equipment. That is why they are looked at as continuous loads. I doubt the service is rated to accept the additional load as buildings are built at the lowest code compliant price.

Continuous loads are not any harder on the electrical system than non-continuous loads.

 

[mikeames]

How about the utility? EVEN IF somehow you can get the premise wiring to accommodate these 17kw heaters, can the utility transformer handle them? Imagine at certain times of the day when multiple occupants are taking showers, or washing clothes. The utility transformer might have a say in this. I am not a fan of large electric tankless simply because too many people don't understand the infrastructure needed.

 

[petersonra]

Oh, just change out the entire service and meter pack, replace every panel and feeder. Nothing major, LOL! (Two story, 40 units)

Might be more cost effective to leave the existing feeders alone and just add another feeder for the new loads. It is going to be expensive no matter what though.

 

[petersonra]

How about the utility? EVEN IF somehow you can get the premise wiring to accommodate these 17kw heaters, can the utility transformer handle them? Imagine at certain times of the day when multiple occupants are taking showers, or washing clothes. The utility transformer might have a say in this. I am not a fan of large electric tankless simply because too many people don't understand the infrastructure needed.

It would not surprise me at all if the utility left the existing transformer and service conductors under their control in place.

 

[Sierrasparky]

Continuous loads are not any harder on the electrical system than non-continuous loads.

Yes and no, Frame size of a 15, 20 , 30 , 40, 50 amp breakers I have seen way too much failures on water heaters, electric heaters, and others that are operating long and continuous loads. There is heat build up and that creates a compounding failure. However my 40+ years of experience means nothing.

 

[mbrooke]

Yes and no, Frame size of a 15, 20 , 30 , 40, 50 amp breakers I have seen way too much failures on water heaters, electric heaters, and others that are operating long and continuous loads. There is heat build up and that creates a compounding failure. However my 40+ years of experience means nothing.

Experience can be just as important as book knowledge. Out in the field one can start to see patterns which are unshakable. I believe you. Bolt on breakers exist for a reason. However, at the same time, electrical equipment should survive continuous loads at least to some degree.

 

[kwired]

as long as the proper OCPD are in place the worst that would happen is some nuisance tripping.

And if you don't tell them now that this is pretty likely to happen, guess who they expect to fix the tripping issues when they become a PITA?

 

[kwired]

Yes and no, Frame size of a 15, 20 , 30 , 40, 50 amp breakers I have seen way too much failures on water heaters, electric heaters, and others that are operating long and continuous loads. There is heat build up and that creates a compounding failure. However my 40+ years of experience means nothing.

You seeing these failures in the first five to ten years after initial installation very often? Many such failures I encounter are equipment at least 20+ years old, with occasional earlier failure that can possibly be attributed to installer failures, bad environmental issues, etc.

 

[hillbilly1]

Went out there today, yep, it was a 17 kw. Turned on all of the faucets and the shower. Second stage on water heater never turned on. Turned off the second stage breaker, tried it again, water still plenty hot. Noticed all new faucets, they had put in low flow fixtures. I’m just going to leave them on the one 40 amp circuit. Problem solved.