Tankless hot water heater install/conversion advice

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Taylorjm

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When you say a double 50amp breaker is powering the lower half of the box, that doesn’t mean there’s 100amps. Just because it’s a double pole breaker doesn’t double the capacity. There’s only 50a powering the lower half of the box. You are talking about using two 50a double pole breakers for your water heater. That’s 100amp draw when someone’s calling for hot water. I highly doubt your panel and service can handle that along with any other loads. It would be easy to have the stove on, dryer and need hot water. Plus if it’s cold the heat pump can go on. Now you’re talking about drawing at least 180amps. No way your panel can support that. Plus you don’t have a main circuit breaker to trip if you exceeded the panel capacity because that panel is very old. That style was modeled after the old federal pacific or cutler hammer panels. If you tie your hot water heater into that panel you are asking for a fire. IMO
 

doc1623

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When you say a double 50amp breaker is powering the lower half of the box, that doesn’t mean there’s 100amps. Just because it’s a double pole breaker doesn’t double the capacity. There’s only 50a powering the lower half of the box. You are talking about using two 50a double pole breakers for your water heater. That’s 100amp draw when someone’s calling for hot water. I highly doubt your panel and service can handle that along with any other loads. It would be easy to have the stove on, dryer and need hot water. Plus if it’s cold the heat pump can go on. Now you’re talking about drawing at least 180amps. No way your panel can support that. Plus you don’t have a main circuit breaker to trip if you exceeded the panel capacity because that panel is very old. That style was modeled after the old federal pacific or cutler hammer panels. If you tie your hot water heater into that panel you are asking for a fire. IMO

I appreciate the info. Yeah, that makes more sense on the lower panel. Thank You for the correction. Based on that, it should mean that between the internal and external heat pump units the maximum is 80amps (the external CB DP 30, internal CB DP 50). I don't trust the AC guys that did the install because they lied on some things and you can see from the panel they are the ones that used the wire nuts rather than getting longer wire. So, maybe those will need to be corrected in the future. I'm guessing it's a 200amp panel but I don't know, someone correct me if I'm wrong. I will put a larger panel in eventually, but it may be at least 6 months. I may start by putting sub-panels in the rooms. Over the years, there seems to have been some strange wiring done. So it wouldn't hurt to redo it all. Besides some computers and a stereo, I don't draw much. I'll try and figure it out. Tips for that would be appreciated.

Currently with the upper CB the maximum draw for the house (with your correction) is 280 but it's probably a 200amp panel or possibly 150, I'll try to look it up some more. Can the size of the incoming wires be used to determine which panel between those two. I don't .

The bottom can only take 50 max, and I've moved the dryer CB there; so the worse thing the dryer can do is maximize that 50amps or trip the breaker, right? So the only other thing that could be a problem is the stove. For me, currently, I can not use the stove when any hot water is running. I rarely use it anyway. Normally, I use a small airfryer. That only leaves the 30amp for the external heat pump unit . So 280 for all possible CB (forgetting the max of the panel at 200 or 150) minus 50 for the stove leaves 230 including the new HW heater. So, it's maximum overage if the panel is 200 is the 30 amps. I think, if I don't run the dryer, I'll probably be okay, but I will double check before leaving the new HW circuit breakers switched on. I'll try to calculate my draws (amperage), and I'll check on what exactly the incoming wires are (to the panel). I'm thinking those and the two bars are what might be the limitations (in other words the panel); now if it's 150 watt panel it was overloaded before. I will also try and what the maximum amperage is for the external heat pump unit.

I appreciate all the help. At, least I know where I'm about at now. I will try and find all the information, I talked about, including the panel.
 
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doc1623

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You are right... I was thinking about the one inch space per pole. Alternate 1-inch positions connect to different hots, and a 2-pole breaker takes up two spaces.

I was right about the tandem breakers... that is what they call them. Two independent breakers for independent 120 volt circuits fit into one 1-inch space.
Yes, from my understanding that's correct. From what I can tell, I only have the one. It's usage that's doubling as a dual-pole, is a question I need to answer though.
 

doc1623

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Split Bus Panel https://waypointinspection.com/split-bus-panel/ describes Split Bus panels.

I suspect you have something smaller than a 200 amp panel. Do the markings at the input terminals indicate that they accept #2 AWG copper or aluminum feeders?
I will post some of pics on an electrician's board or there does seem to be a Reddit sub that is for that. Let me know if you understand any of that from the pics or have a board in mind to ask. Thank You
 

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Yes, from my understanding that's correct. From what I can tell, I only have the one. It's usage that's doubling as a dual-pole, is a question I need to answer though.
I think you have 13 tandem breakers. I was wrong
 
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doc1623

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I think you have 13 tandem breakers.
Sorry No, all the lower breakers are separate .5 inch single throw (come out separately) breakers except for the dryer which is the 30 amp 1 inch tandem, which unlike the pic, is now across two different ..phases (I think that's the term, when it's using both bars) and the top are all dual-pole for the maximum 240 volts. Oh, and the one GFI 1 inch breaker, but the's a 1" single, I believe. I know it's harder to tell from the pic, but you can see the two off in the pics i.e. the 15 and 20amp. I just went out and looked, just to dbl check; they are all separate single throw breakers on the bottom, with the noted exception.

I do appreciate your trying to help. Thank You
 
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Reach4

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Sorry No, all the lower breakers are separate .5 inch single throw (come out separately) breakers except for the dryer which is the 30 amp 1 inch tandem, which unlike the pic, is now across two different ..phases
You are right about the breaker count. I had the wrong interpretation. I will do some editing.

However phases is not the right word for the two legs of our split-phase 120/240 wiring system.
 

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You are right about the breaker count. I had the wrong interpretation. I will do some editing.

However phases is not the right word for the two legs of our split-phase 120/240 wiring system.
Thank You, "legs" was the term, I was looking for, I believe. I'm still learning but I'm working on it and I appreciate all the help
 

Taylorjm

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I appreciate the info. Yeah, that makes more sense on the lower panel. Thank You for the correction. Based on that, it should mean that between the internal and external heat pump units the maximum is 80amps (the external CB DP 30, internal CB DP 50). I don't trust the AC guys that did the install because they lied on some things and you can see from the panel they are the ones that used the wire nuts rather than getting longer wire. So, maybe those will need to be corrected in the future. I'm guessing it's a 200amp panel but I don't know, someone correct me if I'm wrong. I will put a larger panel in eventually, but it may be at least 6 months. I may start by putting sub-panels in the rooms. Over the years, there seems to have been some strange wiring done. So it wouldn't hurt to redo it all. Besides some computers and a stereo, I don't draw much. I'll try and figure it out. Tips for that would be appreciated.

Currently with the upper CB the maximum draw for the house (with your correction) is 280 but it's probably a 200amp panel or possibly 150, I'll try to look it up some more. Can the size of the incoming wires be used to determine which panel between those two. I don't .

The bottom can only take 50 max, and I've moved the dryer CB there; so the worse thing the dryer can do is maximize that 50amps or trip the breaker, right? So the only other thing that could be a problem is the stove. For me, currently, I can not use the stove when any hot water is running. I rarely use it anyway. Normally, I use a small airfryer. That only leaves the 30amp for the external heat pump unit . So 280 for all possible CB (forgetting the max of the panel at 200 or 150) minus 50 for the stove leaves 230 including the new HW heater. So, it's maximum overage if the panel is 200 is the 30 amps. I think, if I don't run the dryer, I'll probably be okay, but I will double check before leaving the new HW circuit breakers switched on. I'll try to calculate my draws (amperage), and I'll check on what exactly the incoming wires are (to the panel). I'm thinking those and the two bars are what might be the limitations (in other words the panel); now if it's 150 watt panel it was overloaded before. I will also try and what the maximum amperage is for the external heat pump unit.

I appreciate all the help. At, least I know where I'm about at now. I will try and find all the information, I talked about, including the panel.
Yes. If you can see the markings on the wire coming in it will tell you the max amperage. Seeing that your service entrance is aluminum, I would be surprised if it was even a 150a panel.
 

Fitter30

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I appreciate the info. Yeah, that makes more sense on the lower panel. Thank You for the correction. Based on that, it should mean that between the internal and external heat pump units the maximum is 80amps (the external CB DP 30, internal CB DP 50). I don't trust the AC guys that did the install because they lied on some things and you can see from the panel they are the ones that used the wire nuts rather than getting longer wire. So, maybe those will need to be corrected in the future. I'm guessing it's a 200amp panel but I don't know, someone correct me if I'm wrong. I will put a larger panel in eventually, but it may be at least 6 months. I may start by putting sub-panels in the rooms. Over the years, there seems to have been some strange wiring done. So it wouldn't hurt to redo it all. Besides some computers and a stereo, I don't draw much. I'll try and figure it out. Tips for that would be appreciated.

Currently with the upper CB the maximum draw for the house (with your correction) is 280 but it's probably a 200amp panel or possibly 150, I'll try to look it up some more. Can the size of the incoming wires be used to determine which panel between those two. I don't .

The bottom can only take 50 max, and I've moved the dryer CB there; so the worse thing the dryer can do is maximize that 50amps or trip the breaker, right? So the only other thing that could be a problem is the stove. For me, currently, I can not use the stove when any hot water is running. I rarely use it anyway. Normally, I use a small airfryer. That only leaves the 30amp for the external heat pump unit . So 280 for all possible CB (forgetting the max of the panel at 200 or 150) minus 50 for the stove leaves 230 including the new HW heater. So, it's maximum overage if the panel is 200 is the 30 amps. I think, if I don't run the dryer, I'll probably be okay, but I will double check before leaving the new HW circuit breakers switched on. I'll try to calculate my draws (amperage), and I'll check on what exactly the incoming wires are (to the panel). I'm thinking those and the two bars are what might be the limitations (in other words the panel); now if it's 150 watt panel it was overloaded before. I will also try and what the maximum amperage is for the external heat pump unit.

I appreciate all the help. At, least I know where I'm about at now. I will try and find all the information, I talked about, including the panel.
Doesn't matter if the breakers add up to more than the panels rated. But it does if water heater is on with other high amp systems. Code is 80% max amps 200 amp panel is only good for 160 amps.
 

doc1623

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Doesn't matter if the breakers add up to more than the panels rated. But it does if water heater is on with other high amp systems. Code is 80% max amps 200 amp panel is only good for 160 amps.
I need to see if I can find info on that panel. I'll keep trying. Let me know if anyone knows where I might find it. I think I did once before, but that may have been a few years ago
 

Taylorjm

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I need to see if I can find info on that panel. I'll keep trying. Let me know if anyone knows where I might find it. I think I did once before, but that may have been a few years ago
Check the service wires. They are aluminum, so find out what gauge they are and that will tell you the maximum amperage your panel can take. Since it's an old panel, it probably wasn't replaced by some handyman who upgraded the panel but not the service wires.
 

doc1623

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Check the service wires. They are aluminum, so find out what gauge they are and that will tell you the maximum amperage your panel can take. Since it's an old panel, it probably wasn't replaced by some handyman who upgraded the panel but not the service wires.
I think you are right and it needs to be replaced, regardless.

I think, I will try to go backwards; i.e. put sub-panels in the house and then do the main panel. Is there a comparable electrical forum? Also, let me know any recommendations for panels and sub-panels. I'm reading and watching vids. I may try and run conduit where possible. Let me know your thoughts.

Currently, I'm replacing the dishwasher and putting and outlet there (it was just a wire coming out of the wall :rolleyes:. It seems to be on the same circuit as the garbage disposal; so I think, I will do a double outlet under the sink. From what I gather, the kitchen has to be on 20amp circuits. Thankfully the wire is 12/2, so that shouldn't be an issue. Again, let me know your thoughts.

I appreciate all the help
 

Taylorjm

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I think you are right and it needs to be replaced, regardless.

I think, I will try to go backwards; i.e. put sub-panels in the house and then do the main panel. Is there a comparable electrical forum? Also, let me know any recommendations for panels and sub-panels. I'm reading and watching vids. I may try and run conduit where possible. Let me know your thoughts.

Currently, I'm replacing the dishwasher and putting and outlet there (it was just a wire coming out of the wall :rolleyes:. It seems to be on the same circuit as the garbage disposal; so I think, I will do a double outlet under the sink. From what I gather, the kitchen has to be on 20amp circuits. Thankfully the wire is 12/2, so that shouldn't be an issue. Again, let me know your thoughts.

I appreciate all the help

Adding a subpanel isn't going to make any difference if your service isn't capable of handling the load. People put in a subpanel because they run out of room. You are talking about adding 100a of constant load with that water heater, it won't matter if you put it in a subpanel or the main panel if the main service isn't capable of handling the load. Did you check the gauge of the service wire to see what it's capable of handling?
 

doc1623

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I know that, but I start with sub-panels, I believe, before replacing the main breaker box. 1 reason is that some hacky wiring has been done in the past and some of the circuits don't make a lot of sense. Also, the subs don't have to match the main or anything else and I think they are cheaper than the main box but I'll have to look.

I do believe you are correct but I can't do everything at once. I now have a cheap clamp meter. I'll have to check it's limitations, but if it's able, I will check the load coming into the main box. I know it needs to be replaced, if nothing else, because of the split panel being old and not as safe, but also because it's doesn't have the capacity I want/need.
 
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