Options for a Paltry Load Panel

[Aikouka]

I'm strongly considering installing a 27kW electric tankless water heater to replace my existing 40 gallon electric water heater. Now, I know that gas tankless water heaters are arguably better in their throughput (about 5gpm vs. 9-10gpm), but given that I'm considering selling my place, I need to replace the water heater anyway, and the cost for an electric tankless and electric tank are not much different, I'd like to give this a shot. (I've also spoken with an old coworker that uses a 27kW electric tankless water heater, and he has no flow issues with it.)

Now, that's not really what I'm curious about, but rather I added it to provide motive. So, my issue is that I don't really have circuit space for two or three two-pole breakers right now, which is what I would need to support a larger electric tankless water heater.. My current load panel may be a 200A panel, but it's rather small in two ways... (1) it's only a 20/40 panel, and (2) it's 12" wide. From what I've read, 12"-wide panels aren't used anymore due to the lack of space between the bars, which explains why I can't find a 12"-wide panel that has more capacity. To help alleviate this, I've considered two different solutions...

1. Replace the load panel.
This is probably a task that I wouldn't tackle myself... especially since I lack a safety shut-off at the meter. I've inquired with one of those... "boutique electricians"... you know, about the equivalent of Roto Rooter. Anyway, they quoted me $5,276 to upgrade my service, which would include other upgrades to meet code. Given that I'm looking to move, it seems like a rather poor investment.

2. Add a sub panel.
This is a task that shouldn't be an issue for me to perform myself. I ran some calculations with moving my dryer (5400W), pool pump (7.5A @ 230V), and HVAC (34.7A min, 50A max), and I ended up around 90A with an additional 25% buffer. I think the only thing that makes me think twice about this idea is that it might look weird to have a sub panel placed right by your main load panel.

I've also considered whether to mount it flush right below the main load panel (it would be about 3 feet off the ground) or surface mount it to the left of the main load panel. The flush mount might look a little odd given the low height, but NEC doesn't have strict minimum heights. (You could likely argue that there is a minimum limit given this is the utility room with the washer, and water ingress would be a concern if it was closer to the floor level.) The surface mount might look nicer, but would likely require more work to run the wires.

Ultimately, it seems like #2 is the best choice, but I wouldn't mind hearing some thoughts on the matter. To note, I did consider just replacing the water heater with a normal tank unit, but I'd really like the space back in my utility room, which is already so tightly packed due to my washer and dryer being larger than what the room was ever designed for. (The house was built in the 70's.) If I could at least shift the dryer to where the current water heater is located, it would look and function so much better.

 

[Greenman]

Why do you need two more breakers? Wouldn't you just use the same two slots the existing water heater uses? Obviously you'll have to upgrade the wiring to the new water heater, but it still only uses 2 slots in the panel.

 

[Aikouka]

Why do you need two more breakers? Wouldn't you just use the same two slots the existing water heater uses? Obviously you'll have to upgrade the wiring to the new water heater, but it still only uses 2 slots in the panel.

A 27kW unit requires 3x 40A two-pole breakers. The problem goes back to my panel's small size in that it only has 20 spaces. Given it allows for 40 circuits, there are a heavy amount of tandem breakers in use. Most of those were already in place, and I "made it worse" when upgrading the kitchen. That's part of the reason why I'd love to just upgrade the panel and make everything cleaner. Anyway, the point is that due to the existing water heater being on a 30A tandem breaker with the dryer, I cannot simply use that space. If I shift around breakers and maybe combine two more single breakers into a tandem breaker, I can possibly free up four more spaces, but I'd be limited to a 24kW unit at that point (2x 50A).

Kind of like I alluded to, none of the solutions are great due to either high cost (new panel) or just feeling like a dirty patch (sub panel).

 

[Greenman]

A 27kW unit requires 3x 40A two-pole breakers. The problem goes back to my panel's small size in that it only has 20 spaces. Given it allows for 40 circuits, there are a heavy amount of tandem breakers in use. Most of those were already in place, and I "made it worse" when upgrading the kitchen. That's part of the reason why I'd love to just upgrade the panel and make everything cleaner. Anyway, the point is that due to the existing water heater being on a 30A tandem breaker with the dryer, I cannot simply use that space. If I shift around breakers and maybe combine two more single breakers into a tandem breaker, I can possibly free up four more spaces, but I'd be limited to a 24kW unit at that point (2x 50A).

Kind of like I alluded to, none of the solutions are great due to either high cost (new panel) or just feeling like a dirty patch (sub panel).

You stumped me. I've never seen a residential device that required 3 breakers. Since it must be a three phase panel you're most likely not in the US, so anything I know about codes and practices won't apply.

 

[Micrornd]

You stumped me. I've never seen a residential device that required 3 breakers. Since it must be a three phase panel you're most likely not in the US, so anything I know about codes and practices won't apply.

That's actually really common on higher flow (single phase) tankless electric water heaters. They have separate heating elements that kick in based on flow. Greatly helps to reduce electric consumption.
My 24kw unit uses 2x 60a double pole breakers.

 

[Greenman]

That's actually really common on higher flow (single phase) tankless electric water heaters. They have separate heating elements that kick in based on flow. Greatly helps to reduce electric consumption.
My 24kw unit uses 2x 60a double pole breakers.

I had no idea. Thanks for the info.
I've actually never seen an electric water beyond the point of use type. They're all natural gas around here. Though they are going to be used exclusively in Berkeley as they banned the use of natural gas in all new construction starting this year.

 

[Micrornd]

2. Add a sub panel.
This is a task that shouldn't be an issue for me to perform myself.

From what you've posted this would seem to be your best option.
But I would urge you to look into several brands of tankless electric as they do have different sizes available.
For what you are proposing, you may also want to step down 1 notch in sizing.
In the brand I chose, a 29kw unit requires 3x 50a double pole breakers, while the 24kw unit I installed only needed 2x 60a breakers.
So for the 29kw 6 runs of #8 plus a ground, while the 24kw only needs 4 runs of #6 plus ground, so money saved.
The difference in max flow rates was only .75gpm and while the 29kw turned on at .87gpm, the 24 kw turns on at .58gpm.
Maybe consider more options ?

 

[Micrornd]

Though they are going to be used exclusively in Berkeley as they banned the use of natural gas in all new construction starting this year.

Really? Why? Will LP be banned also?

I'd love to have NG available here, just based on cost.
We only have LP available and that (cost) was the deciding factor on going electric tankless.
But I'm stuck with LG on my genset, where NG would be much cheaper to run, when needed.

 

[Aikouka]

You stumped me. I've never seen a residential device that required 3 breakers. Since it must be a three phase panel you're most likely not in the US, so anything I know about codes and practices won't apply.

Ahh, apologies for not being clearer on that. As @Micrornd said, electric tankless water heaters typically work with heating chambers, and they'll usually have at least two. (The heating capability and amount usually dictates the maximum flow.) Each of the heating chambers will have its own breaker, which you can usually determine by the wattage / 240 / chambers. So, for example, I also looked at a Stiebel 24kW unit (24000 / 240 / 2 = 50), and that requires two 50A breakers. Of course, another 24kW unit requires from Rheem takes three breakers instead.

From what you've posted this would seem to be your best option.
But I would urge you to look into several brands of tankless electric as they do have different sizes available.
For what you are proposing, you may also want to step down 1 notch in sizing.
In the brand I chose, a 29kw unit requires 3x 50a double pole breakers, while the 24kw unit I installed only needed 2x 60a breakers.
So for the 29kw 6 runs of #8 plus a ground, while the 24kw only needs 4 runs of #6 plus ground, so money saved.
The difference in max flow rates was only .75gpm and while the 29kw turned on at .87gpm, the 24 kw turns on at .58gpm.
Maybe consider more options ?

I think I've been so focused on how to make the transition to tankless possible that I haven't focused too much on the specific unit. My current panel is literally full on breakers, but not all of them are in use. (When redoing the kitchen, some of the old breakers were left in there.) Looking at my spreadsheet, I might be able to do it... but I'm not sure if one idea is technically oversizing a breaker.

It looks like I have two open/unused spaces (not in line), and two tandem breakers that are only using a single latch. If I combined the two tandems and moved everything down, I could get three open spaces. I currently have two normal breakers (15A and 20A) that could be combined into a single tandem breaker, which would require some rewiring due to the one breaker being 15A. (It should be upgraded anyway due to it being used for outlets.) That would leave me with four open spaces.

Now, the one thing that I'm not sure about... my water heater is on a 30A two-pole tandem breaker with my dryer right now. If I swapped to the tankless, the one tandem part of the tandem breaker would be open. Currently, my pool pump is using its own 20A two-pole breaker. Would it be a problem to put the pump on a 30A breaker instead of a 20A? I'd imagine it's fine since it only operates at 7.5A anyway, which means 20A is already quite large. If I could move that to the water heater's spot, that would free up another two spots. (It's also possible to run my pool pump on a single pole breaker too.)

Another option could be that I could hamper my EV's recharge rate by taking away its solo 50A two-pole breaker and putting it on the 30A breaker with the dryer. I'd go from 40A charge to 24A, but it would free up space for me. The only downside is that I've considered putting in a 100A sub panel in the garage, and I was going to use the EV's 50A spot for that (and move the EV charger's breaker to the garage sub panel).

Out of curiosity, which model did you go with?

 

[NutBucket]

In terms of the thread, without reading through it thoroughly, given OP is planning on selling I'd go the cheapest/easiest path. Seems like that may the "cripple EV charging" option? Yeah, I wouldn't spend the money/time to do any major electrical. Plus, if you do something new the potential buyer/inspector would be prudent to ask for permits, etc. F that noise.

Really? Why? Will LP be banned also?

I'd love to have NG available here, just based on cost.
We only have LP available and that (cost) was the deciding factor on going electric tankless.
But I'm stuck with LG on my genset, where NG would be much cheaper to run, when needed.

I've never seen anyone with an LP tank in a dense residential neighborhood. Anyway, this only applies to new residential. There's not much new construction going on there...unless this includes major renovation too.

 

[Micrornd]

So, for example, I also looked at a Stiebel 24kW unit (24000 / 240 / 2 = 50), and that requires two 50A breakers.
*****************************************
It looks like I have two open/unused spaces (not in line), and two tandem breakers that are only using a single latch. If I combined the two tandems and moved everything down, I could get three open spaces. I currently have two normal breakers (15A and 20A) that could be combined into a single tandem breaker, which would require some rewiring due to the one breaker being 15A. (It should be upgraded anyway due to it being used for outlets.) That would leave me with four open spaces.

Now, the one thing that I'm not sure about... my water heater is on a 30A two-pole tandem breaker with my dryer right now. If I swapped to the tankless, the one tandem part of the tandem breaker would be open. Currently, my pool pump is using its own 20A two-pole breaker. Would it be a problem to put the pump on a 30A breaker instead of a 20A? I'd imagine it's fine since it only operates at 7.5A anyway, which means 20A is already quite large. If I could move that to the water heater's spot, that would free up another two spots. (It's also possible to run my pool pump on a single pole breaker too.)

Another option could be that I could hamper my EV's recharge rate by taking away its solo 50A two-pole breaker and putting it on the 30A breaker with the dryer. I'd go from 40A charge to 24A, but it would free up space for me. The only downside is that I've considered putting in a 100A sub panel in the garage, and I was going to use the EV's 50A spot for that (and move the EV charger's breaker to the garage sub panel).

Out of curiosity, which model did you go with?

Some of ^this^ scares me !
While NEC does have allowances for 2 circuits to be on the same breaker, they are very restrictive and also they are not allowed by most AHJs.
You really should have an electrician doing this work, especially if you intend to ever sell this house as you will be held liable if anything goes wrong with this rewiring.

I went with an Aquapower DHE-24 unit. Same OEM as Stiebel, Tempra and Eltron, made on the same assembly line in the same building.
When I purchased my unit the manufacturer's recommendations was 2x 60a double pole breakers, based on 2x 50a 240vac heating elements.
I see that now they recommend 2x 50a double pole breakers for the same 2x 50a 240vac elements.
Even being a non-continuous load, I'm skeptical as to that meeting the needs of the unit, although as far as I can tell, it does meet NEC.

 

[Micrornd]

I've never seen anyone with an LP tank in a dense residential neighborhood. Anyway, this only applies to new residential. There's not much new construction going on there...unless this includes major renovation too.

You shouldn't see the tank, as most building codes and NFPA have restrictions on where it can be placed.
Also most building codes have some "nuisance" provisions they use to require it not being easily seen in residential areas (plantings, backyard, screening fence, etc.).

Do you know why NG was outlawed on new construction?
The code requirements are safer and more stringent than have ever been, so it doesn't make sense on the surface.
(Unless politics are involved)

 

[NutBucket]

Hydrocarbons. Like I said, environmental nuts. Plus that whole explosion in San Bruno back in 2010.

But really, I'm not even aware of a propane delivery service that would service metropolitan areas of CA. NG infrastructure is everywhere so why would anyone go through the inconvenience of propane tank + delivery?

 

[Greenman]

You shouldn't see the tank, as most building codes and NFPA have restrictions on where it can be placed.
Also most building codes have some "nuisance" provisions they use to require it not being easily seen in residential areas (plantings, backyard, screening fence, etc.).

Do you know why NG was outlawed on new construction?
The code requirements are safer and more stringent than have ever been, so it doesn't make sense on the surface.
(Unless politics are involved)

In Berkeley, NG was banned in new construction to reduce CO2. I'll be curious to see how that works out in an area with a power grid that is turned off when it's windy. With gas you have hot water and can cook, with electric only those folks will have drive to another county to eat. The smell of unexpected consequences is in the air.

 

[Micrornd]

Hydrocarbons. Like I said, environmental nuts. Plus that whole explosion in San Bruno back in 2010.

But really, I'm not even aware of a propane delivery service that would service metropolitan areas of CA. NG infrastructure is everywhere so why would anyone go through the inconvenience of propane tank + delivery?

I got to thinking about it after I posted.
You said "Berkeley", and also said "California", so either was really all the explanation needed

I was thinking smaller cities for LP delivery, as here in FL, NG is not that widespread. In my town they have it in the core of the city, since about the 19teens, but that covers less than 1/2 mile square. Beyond that, if you happen to be along the route of the NG mains, you can usually be connected, everywhere else is LP, if you want gas.
At least here LP is available by the tank-full or by gas metered usage.

I don't understand what you mean by "inconvenience of propane tank + delivery".
They fill the tank when needed and send you the bill if you (for by the tank-full usage) or read the meter and fill the tank and send the bill once a month (for metered usage)
Did you have a different concept of how it worked?

 

[Micrornd]

In Berkeley, NG was banned in new construction to reduce CO2. I'll be curious to see how that works out in an area with a power grid that is turned off when it's windy. With gas you have hot water and can cook, with electric only those folks will have drive to another county to eat. The smell of unexpected consequences is in the air.

We have forest fires here started by lightning that burn thousands of acres, but I have yet to see or hear of any powerlines causing fires.
We have laws that require power companies to keep the area around power lines trimmed clear AND they are enforced.
From what we see/hear on the news, enforcement of that kind was lacking in Cali until the fires were started by power lines and faulty transformers.
Now it's a "bandwagon" thing going on out there.
Sound right?

 

[Aikouka]

While NEC does have allowances for 2 circuits to be on the same breaker, they are very restrictive and also they are not allowed by most AHJs.

While I do my best to pedantically read the NEC prior to changes, of course it's possible to miss something. However, I've never seen any restrictions on tandem breakers so long as they meet the specifications of the panel itself. My panel is a 20/40 meaning it's designed for each space to accommodate a tandem breaker. I would prefer to not do this because of how crowded it makes things... especially given my box is only 12" wide. Anyway, my last tandem breakers (the ones used for the kitchen) were actually wired up by an electrician, and they had no remarks about using them. If I had to guess, the biggest worry that most inspectors would have are temperatures in a crowded panel, and my temperatures are fine. Although, I can say that if I were to do this "circuit shuffle" that I've described earlier, I'd also take the time to reorganize the wire runs.

Honestly, one of the larger reasons why I want to sell this house are that I feel like I have to constantly make concessions to make an older house work better for modern technologies (e.g. Ethernet), and when your house was built in the 70's... a lot of things today are considered modern compared to said house. Also, some of the wiring is just... awkward. You'd likely wince if you saw my panel layout spreadsheet as there's just so little room isolation. (I had to make it a spreadsheet due to not being able to fit all the writing on the actual panel's listing.) At one point, one circuit controlled the lighting in the family room, kitchen, and dining room as well as one outlet in the dining room and three out of four outlets in the living room. I've corrected a lot of this for areas that I can get to as now the family room, kitchen, dining room, and living room are all isolated on their own circuits (the kitchen has six circuits), and the lighting is on its own circuit. That same multi-room circuit also had its neutral bridged to the family room's circuit, which was a... shocking revelation! (I fixed that problem too... turned out to be excessive electrical tape residue on the neutral wire in the dining room chandelier.)

I went with an Aquapower DHE-24 unit. Same OEM as Stiebel, Tempra and Eltron, made on the same assembly line in the same building.
When I purchased my unit the manufacturer's recommendations was 2x 60a double pole breakers, based on 2x 50a 240vac heating elements.
I see that now they recommend 2x 50a double pole breakers for the same 2x 50a 240vac elements.
Even being a non-continuous load, I'm skeptical as to that meeting the needs of the unit, although as far as I can tell, it does meet NEC.

That does seem odd that they wouldn't factor in the 20% allowance that's considered for your usual home circuit. Have you been pretty happy with the unit so far? I guess I'd be mostly worried about multiple things running at once. For example, shower + dish washer or shower + washer, and I'm mostly focused on the colder months like right now. I'm currently in their 62F range.

With the talk of the min flow rate differences, I wonder if that .5 GPM to .77 GPM min flow rate is that noticeable? It looks like your average bathroom faucet is 1.2 GPM max.

 

[Micrornd]

Have you been pretty happy with the unit so far? I guess I'd be mostly worried about multiple things running at once.

When I first installed it, we ran a test using 2 showers (no flow restrictors ) and 2 sinks running hot water wide open for 15min.
There was no problem. Endless hot water.
That was 6 years ago and I still use the same test at random to help put a full load on my genset when testing it and we have never had a problem or run out of hot water.
The DHE-24 model I chose was the cheapest of the 24kw units available, with just a dial for setting temperature, instead of the fancy electronic displays. I mean really, how often does one change the temperature of the water heater or even go look at it.
Dial it to 140F and forget it.
Basic just works

This is what concerned me -

my water heater is on a 30A two-pole tandem breaker with my dryer right now. If I swapped to the tankless, the one tandem part of the tandem breaker would be open. Currently, my pool pump is using its own 20A two-pole breaker. Would it be a problem to put the pump on a 30A breaker instead of a 20A? I'd imagine it's fine since it only operates at 7.5A anyway, which means 20A is already quite large. If I could move that to the water heater's spot, that would free up another two spots.

Perhaps you worded it wrong, but were you referring to this for the water heater and dryer - https://www.bing.com/images/search?...ndex=217&ajaxhist=0&vt=0&eim=0,1,2,3,4,6,8,10
Or were you referring to this - https://www.bing.com/images/search?...ndex=165&ajaxhist=0&vt=0&eim=0,1,2,3,4,6,8,10
As far as moving the pool pump, remember the circuit breaker is normally sized to protect the wiring, not the device. Although it may be undersized (by choice), it can not be oversized.

My own home was built in the early '80s and it came with a 10/20 panel so I understand what you are going through/doing.
I rewired it myself, adding circuits and dividing existing circuits, bringing everything up to the then current local code (GFCIs, AFCIs, etc.) while installing a 42 space panel and installing a whole house genset and ATS.
BUT it was all done with the correct permits and was inspected by and under the guidance of a master electrician before it was inspected for the permit.

Just remember rewiring anything yourself without a permit and inspections, not only is illegal (yes, I'm sure many of us, including myself, have done it at some time ) and can leave you liable for future damages, but it WILL void your home owner's insurance if the insurance company finds out about it (regardless of whether the work is done properly or not).
Understand, I'm not preaching or pointing fingers, I just want to be sure you know what could happen if you do the work your self.
In the end the decision is yours alone and whatever you are comfortable with

 

[Aikouka]

When I first installed it, we ran a test using 2 showers (no flow restrictors ) and 2 sinks running hot water wide open for 15min.

Hmm, that's pretty impressive. No wonder my old coworker seemed fairly happy with only a 27kW version when I figured a family of our might go for something a bit higher!

Perhaps you worded it wrong, but were you referring to this for the water heater and dryer

It's neither of those. I can't even find a picture of it online. It's quite literally a SquareD QO tandem 30A two-pole 240V breaker. It takes up two spaces, provides 240V and has two latches for two separate circuits. It has to be old, because I'm pretty sure they don't sell these anymore. That has made me wonder about whether I should still use it, but I can't find any information on these and I've never had any electrician say anything about it.

Although, I can say that I was planning on replacing that tandem breaker if I went the route of using a sub panel.

As far as moving the pool pump, remember the circuit breaker is normally sized to protect the wiring, not the device. Although it may be undersized (by choice), it can not be oversized.

I was planning on rewiring it to handle 30A if I did replace it. I just wasn't sure after I did some research on HVAC breakers after reading my HVAC's info plate. Apparently, you are supposed to size those according to what the info plate says (for example, mine says 50A) due to something about the motor. It's kind of weird too since they say you don't even have to size the wire for the 50A breaker... but rather or the max ampacity rating.

I'd also rewire the 15A outlet circuit (it's for a single outlet below the deck) to #12 if I combine that into a 20/20 tandem. This is all in my crawlspace which is tall enough for me to walk around in, so it's not a huge deal.

Just remember rewiring anything yourself without a permit and inspections, not only is illegal (yes, I'm sure many of us, including myself, have done it at some time ) and can leave you liable for future damages, but it WILL void your home owner's insurance if the insurance company finds out about it (regardless of whether the work is done properly or not).
Understand, I'm not preaching or pointing fingers, I just want to be sure you know what could happen if you do the work your self.
In the end the decision is yours alone and whatever you are comfortable with

You know one thing that's odd about the contractors around here? They actually give you the option to pull permits for jobs, and of course, they make it cheaper (omitting the permit fee) if you don't do it.