Yes, Rheems HPWH's will override your settings.

JakeCK

It's been discussed before if, at least rheems anyways, will override the settings if set to HP only.

Some didn't believe me when I said it can and will do that. Well tonight I can conclusively say that it will. I watched it. Multiple loads of laundry, and loads in the dish washer, a few showers, plus the very cold late January fresh water coming in caused it to run both the elements and the compressor while set to heat pump only. 


It is interesting that I could see what it was doing when probed by the home automation but the actual econet app didn't show that the elements were running too. I figured it out when I looked at the current power consumption and noticed I was using almost 7500 watts. 

EBEBRATT-Ed

Just shows Rheem is smarter than we are

psb75

The folks at Rheem know that people don't like to run out of hot water--and that the energy bill comes AFTER the hot water gets used.

kcopp

If you are that concerned about it, unwire the elements

EBEBRATT-Ed

@kcopp

It could be so smart if you unwire the elements it will go into a fault LOL

ChrisJ

So,
Why even put the option there?

Jamie Hall

At least you are controlling it after a fashion, and not the power company or the public utilities commission...

JakeCK

ChrisJ said:

So, Why even put the option there?

The option does change the behavior. If you use high demand, or "energy saver"/eco mode it will use the elements much more readily. It is obvious what high demand is. It will work to recover as fast as possible. Eco mode is a bit of a misnomer. From what I have read(but this isn't from official documents so it could be BS) that Rheem discovered during testing that most families want their cake and to eat it too. They would set it to save them the maximum energy without understanding that the recovery is slower and then complain or set it to high demand all the time which eliminates much of the savings. "Eco" mode is supposed to work with the psychology. It'll use the heat pump most of the time but will switch on the elements much quicker so people don't whine.

Heat pump only mode will only run the heat pump except for very rare situations. Maybe to stop from slugging the compressor? In my case this is the first time I have ever seen the behavior, or perhaps actually caught it. I only noticed it because I just happened to see the power usage of the house and noticed in the home automation the hp saying it is using both. Most families do not have that level of visibility of the functioning of their home. And infact using just Rheems econet app you can't even see that. It still said it was using the heat pump. And the enlighten app for my solar panels doesn't show the current power usage, just the energy used. I use Home Assistant to probe both of these devices to see a bit more of what's going on under the hood.

I can understand why these companies hide most of this information, many people can't even grasp the difference between a kWh and kW. 

JakeCK

Jamie Hall said:

At least you are controlling it after a fashion, and not the power company or the public utilities commission...

This water heater does have the module installed for remote control by the utility. I just do not have it connected and I don't even think First Energy even does that yet.

JakeCK

EBEBRATT-Ed said:

@kcopp It could be so smart if you unwire the elements it will go into a fault LOL

It will indeed give an error from what I have read. Idk if it will prevent it from running however.

JakeCK

psb75 said:

The folks at Rheem know that people don't like to run out of hot water--and that the energy bill comes AFTER the hot water gets used.

Mostly right. Most people just expect hot water when they turn the knob. They care not about the details of how it happens.

Running the elements for a few minutes doesn't really use that much energy over all, wouldn't even be noticed on the bill.

JakeCK

I wish there were a few Rheem representatives or engineers on this site. Or are there?

ethicalpaul

Remember the poster some months ago who kept complaining that his Rheem was ignoring his "heat pump only" setting? After LOTS of questioning we discovered he was power cycling it like every day for some reason and it was discovered that if it was power cycled with low temp water in it that it always turned on the elements.

Jake's situation is similar to this (without the powering off) and yes it looks like when the water's really cold it turns on the elements regardless.

I agree too with Jake that the "Energy Saver" mode is kind of strange and driven by psychology and normal hot water expectations.

It's very weird that if you have it set to "heat pump only" which is the absolute cheapest way to run it, that in the interface it will try to get you to switch over to "energy saver" which it (incorrectly) says is the most efficient setting.

JakeCK

ethicalpaul said:

Remember the poster some months ago who kept complaining that his Rheem was ignoring his "heat pump only" setting? After LOTS of questioning we discovered he was power cycling it like every day for some reason and it was discovered that if it was power cycled with low temp water in it that it always turned on the elements. Jake's situation is similar to this (without the powering off) and yes it looks like when the water's really cold it turns on the elements regardless. I agree too with Jake that the "Energy Saver" mode is kind of strange and driven by psychology and normal hot water expectations. It's very weird that if you have it set to "heat pump only" which is the absolute cheapest way to run it, that in the interface it will try to get you to switch over to "energy saver" which it (incorrectly) says is the most efficient setting.

It is the most efficient setting when you take into account typical stupid human behavior. :P

mattmia2

This sounds like a cpcs level complaint. It could be dangerous if you were running it on temporary or emergency power and you turned the elements off to keep withing your available power and it turned them on anyhow especially if it didnt tell you it turned them on. Also various types of fraud.

Larry Weingarten

Hi, I’m off grid, so must be careful with loads. I installed one of these and the elements would come on in HP only mode and fry fuses. I replaced the 4500 watt elements with 1000 watt ones. Now it alarmed continuously. Eventually I had to give up and put a propane heater in. Gave the HP to a friend. Not much of a success story. 😒

Yours, Larry

Illinoisfarmer

Not to pile on here, but I have one of these too, and the installation manual pretty clearly states that a 30 amp breaker and #10 wire should be used - which I did. If the control logic is intermittently surging 7500 watts - which almost has to be more than just one element and the HP compressor - I'd think we're into a NEC issue. I don't have the ability to look as closely at the operation as @JakeCK, but we've never run out of hot water in the 14 months it's been here, and it's most definitely set to Heat Pump only mode. I've been impressed it's kept up - but maybe it's not being honest.

Is it possible that some unemployed Volkswagen Emissions Engineers went to work for Rheem? (Sorry)

psb75

It's not just Rheem. I think Brad White and State (A.O. Smith) operate similarly.

mattmia2

I'm sure thy buy the control form the same manufacturer.

psb75

I betting that all of those compressors and circuit-boards are Asian.

EdTheHeaterMan

I take cold showers, do laundry in cold water, and only use hot water to cook with on my franklin wood stove. I can't understand what all the Hubbub is all about!

Quote from someone in the 1880s

ChrisJ

@JakeCK Can that heater actually get to 140F with just the heat pump running?

JakeCK

ChrisJ said:

@JakeCK Can that heater actually get to 140F with just the heat pump running?

Yes it can.

JakeCK

Illinoisfarmer said:

Not to pile on here, but I have one of these too, and the installation manual pretty clearly states that a 30 amp breaker and #10 wire should be used - which I did. If the control logic is intermittently surging 7500 watts - which almost has to be more than just one element and the HP compressor - I'd think we're into a NEC issue. I don't have the ability to look as closely at the operation as @JakeCK, but we've never run out of hot water in the 14 months it's been here, and it's most definitely set to Heat Pump only mode. I've been impressed it's kept up - but maybe it's not being honest. Is it possible that some unemployed Volkswagen Emissions Engineers went to work for Rheem? (Sorry)

The water heater it's self wasn't drawing a full 7500 watts. That was the load of the entire house. If you look at the graph you'll see that the baseline for the time of day is closer to 1000 watts or so. The large spikes to 7500 was when the elements kicked on. In other words it was drawing closer to 6500 watts. At 240 that is only 27amps. Is a water heater considered a continuous load?

JakeCK

Larry Weingarten said:

Hi, I’m off grid, so must be careful with loads. I installed one of these and the elements would come on in HP only mode and fry fuses. I replaced the 4500 watt elements with 1000 watt ones. Now it alarmed continuously. Eventually I had to give up and put a propane heater in. Gave the HP to a friend. Not much of a success story. 😒 Yours, Larry

That sucks. They do have 120v plug in models coming out. Those don't draw nearly as much. 

JakeCK

mattmia2 said:

This sounds like a cpcs level complaint. It could be dangerous if you were running it on temporary or emergency power and you turned the elements off to keep withing your available power and it turned them on anyhow especially if it didnt tell you it turned them on. Also various types of fraud.

I don't feel like this is them being dishonest. Them just trying to keep customers happy who may not really understand what these are and how they work. 

And in my case it maybe the system protecting it's self. If it is to prevent damage I'm 100% ok with it running the elements and using a few extra kilowatts. We're seriously talking pennies here.

JakeCK

Found this error in the memory. So it did have some issues. We never felt it during the showers but our clothes may have gotten a cold wash instead of a hot one. 

ChrisJ

JakeCK said:

Illinoisfarmer said:

Not to pile on here, but I have one of these too, and the installation manual pretty clearly states that a 30 amp breaker and #10 wire should be used - which I did. If the control logic is intermittently surging 7500 watts - which almost has to be more than just one element and the HP compressor - I'd think we're into a NEC issue. I don't have the ability to look as closely at the operation as @JakeCK, but we've never run out of hot water in the 14 months it's been here, and it's most definitely set to Heat Pump only mode. I've been impressed it's kept up - but maybe it's not being honest.

Is it possible that some unemployed Volkswagen Emissions Engineers went to work for Rheem? (Sorry)

The water heater it's self wasn't drawing a full 7500 watts. That was the load of the entire house. If you look at the graph you'll see that the baseline for the time of day is closer to 1000 watts or so. The large spikes to 7500 was when the elements kicked on. In other words it was drawing closer to 6500 watts. At 240 that is only 27amps. Is a water heater considered a continuous load?

As far as I know,
On electric water heaters they do consider them continuous loads and NEC wants you to derate to 80%. So 24 amps for a 30A circuit. My understanding is this is to prevent nuisance trips.


However, I suspect the rules are likely different for what you have being the manufacturer specifically asked for #10 wire and a 30A breaker. I have a feeling they didn't just throw darts at a chart to come up with that.

Larry Weingarten

Hi, Just to clarify, the unit I got stated on the tag that the maximum fuse size for it was 15 amps. Seemed to me that it drew a lot more than that. The 4500 watt elements clearly draw more than 15 amps. Maybe sales and engineering folks at Rheem don’t talk to each other much 🤭

Yours, Larry

PC7060

Probably not @Larry Weingarten.  Physics just gets in the way of a good sales pitch!

JakeCK

Larry Weingarten said:

Hi, Just to clarify, the unit I got stated on the tag that the maximum fuse size for it was 15 amps. Seemed to me that it drew a lot more than that. The 4500 watt elements clearly draw more than 15 amps. Maybe sales and engineering folks at Rheem don’t talk to each other much 🤭 Yours, Larry

That just doesn't make sense. Obviously an oversight by who ever is writing up the literature. :S

hot_rod

Rheem has a line up of 120V hpwh, some require a dedicated 20A circuit

They have a “shared circuit” model the runs on a slow blow 15A 120v plug. I doubt it has much of a backup element. If any?

bburd

On electric water heaters with two elements, they are nearly always interlocked for non-simultaneous operation, so if you have two 4500 W elements, the maximum load is 4500 because they cannot run together.

On a heavy draw the top element will come on until the upper part of the tank is heated, then power will switch to the bottom element to heat the rest of the tank. A HPWH adds a heat pump to this  setup.

ChrisJ

Larry Weingarten said:

Hi, Just to clarify, the unit I got stated on the tag that the maximum fuse size for it was 15 amps. Seemed to me that it drew a lot more than that. The 4500 watt elements clearly draw more than 15 amps. Maybe sales and engineering folks at Rheem don’t talk to each other much 🤭 Yours, Larry

If the maximum fuse size is 15A and you followed the instructions how could it possibly draw more than that?

  

Larry Weingarten

Hi, The math I did says that a 4500 watt element at 240 volts is 18 3/4 amps. Maybe my math is no good?

Yours, Larry

mattmia2

ChrisJ said:

On electric water heaters they do consider them continuous loads and NEC wants you to derate to 80%. So 24 amps for a 30A circuit. My understanding is this is to prevent nuisance trips.

you have to derate even if it isn't a continuous load but less. the rule is to protect the wiring and especially terminals and other devices from the heat. it is more complicated than that because the ampacity of #10 copper is 30a by decree in another rule, the engineering calculates a higher ampacity depending on the temp rating of the system.

ChrisJ

Larry Weingarten said:

Hi, The math I did says that a 4500 watt element at 240 volts is 18 3/4 amps. Maybe my math is no good? Yours, Larry

I think your math is good but the unit cannot pull more power than the protection device will allow.

If it used 15a breakers I don't see how it could've been more than 3600w and even that's wrong.

EBEBRATT-Ed

@Larry Weingarten your math is fine. @JakeCK water heaters are continuous loads. And you are correct 24 amps is max on a 30 a circuit if it is a continuous load. Breakers can only take an 80% load over an extended time.

Because a heat pump water heater contains electric elements and a motor (compressor) it is considered a combination load. If both (elements and compressor) can operate at the same time the incoming power feed has to be figured two ways

#1 (compressor amps x 1.25) because of the starting load + amps of the heating elements that can operate at the same time. The "1.25" is not continuous load.

#2compressor amps + heater amps (assuming they run at the same time) cannot exceed 80% of the circuit rating.


Whichever #1 or #2 comes out with the higher rating would be the circuit size to use.


As you can see the size of the compressor and the size of the heating elements can vary.

Example: 15 amp compressor and (2) 1500 watt elements

#1 15 x 1.25=18.75 + 1500x2=3000/240v=12.5 amps=31.25 amps

#2 15 + 12.5=27.5 x 1.25 (for continuous load)=34.375 amps minimum circuit rating 80% of minimum breaker & wire is 34.375x.8=27.5 amp load on circuit.

So in this case #2 would be used


It gets funky because on a straight motor circuit (without other loads) you take the motor amps x 1.25 for
the starting surge and when that is added you don't have to add anything else for continuous load. But that is only for straight motor circuits with no other loads. And on a motor circuit like a condensing unit you could have a 40 amp breaker on #10 wire.........that's because motors have thermal protection to protect the motor which will not allow the motor to overload the circuit and the 40A breaker to hod the starting current

In any case a packaged piece of equipment is wired based on the equipment name plate which gives you MCA=minimum circuit amps which is your wire size and MOCP=max overcurrent protection which are your breakers or fuses.

It was not always this way back in the 60s you would have to do the calculations. This led to untold problems and changed things to the unit nameplate which standardized things.

If the name plate is undersizing the wire or breaker that is a problem that UL should take care of (if they are not being paid off LOL)

ratio

ISTR that HACR-rated breakers can be sized to run at 100% without issue?

00crashtest

JakeCK said:

It is interesting that I could see what it was doing when probed by the home automation but the actual econet app didn't show that the elements were running too. I figured it out when I looked at the current power consumption and noticed I was using almost 7500 watts. 

What is the name and publisher of the home automation app that you're running? I couldn't find one with that level of detail on the Google Play store. I want to DIY replace a gas heater with a heat pump water heater and replace the ICE vehicle with a used plug-in EV (including adding the 120/240 V high-powered feeder circuit with a subpanel and heavy-duty receptacles for the garage) to save money and came across this. I live in California well below the snow line so resistive heating should never ever be needed.

00crashtest

I'm new to this forum, so I don't know the past history of JakeCK's posts, if s/he has already mentioned the name, publisher, and version of the app in those posts. In fact, because it never snows below the snow line, the heat pump alone should be plenty enough even during the very coldest day per decade, meaning that it will never even come close to needing the resistive heating elements. As a result, after I buy a Rheem HPWH or AO Smith HPWH (because it is most energy efficient), I want to prevent the resistive elements from turning on as much as possible, thereby saving energy and consequently saving money and the environment. Obbiously, because of saving money, I never use Apple products and only use smartphones running on open-source Android. So, may anyone please tell me what that app is. Also, is it possible to turn on the "Heat Pump" mode from Rheem's EcoNet app or any other app published by Rheem?