Tankless water heater for hot tub idea

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Old 04-28-20, 04:17 PM
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Tankless water heater for hot tub idea

I'm scoping out an idea to use a gas tankless water heater to heat our small inflatable hot tub outside. These units take days to heat up and use alot of electricity to keep heated. I've read that tankless heaters are more powerful and natural gas is a fraction of the cost of propane (and less of a hassle to have it directly plumbed to natural gas).

Originally was thinking of paying to have a gas line run outside. But then was wondering if I could just installed it inside, next to our regular tank water heater. And run it outside from there. Not as efficient but less upfront cost?
 
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Old 04-28-20, 04:19 PM
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if I could just installed it inside, next to our regular tank water heater.
Maybe.

It would depend on the size of the gas line run to that area and what each heater needed to run properly.
 
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Old 04-28-20, 04:31 PM
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Thanks for the reply Pete. I have a small, inflatable 4 person hot tub. People have used models like this for the same project https://www.amazon.com/Eccotemp-L5-P.../dp/B01MXDZCKM

Also while I was at it figured I'd have them extend it a bit to my BBQ grill area. Buy a propane to natural gas kit and kill two birds with one stone.

Figuring the run would be about 50'-65' to the hot tub area.
 
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Old 04-28-20, 05:21 PM
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Maybe for simplicity of installation I change and go for an electric tankless heater. I do have access to a 240v outlet nearby. Figuring the ongoing costs of electricity would be higher than natural gas (need to figure out exactly) but installation I could do myself. No need for a gas pipe plumber.
 
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Old 04-28-20, 05:38 PM
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Each device has a btu rating on it.
A gas water heater..... typically 30k btu's.
A BBQ..... typically 20k btu's.

AT 3.5WC..... you'd need a minimum of 3/4" pipe at 50' for just the above two.
 
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Old 04-28-20, 05:52 PM
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Ok so how about switching to electric tankless? Maybe I need to head to the electric forum to research this approach? This is the make and model I'd probably get. I have direct access to an open 220v outlet right nearby.

https://www.ecosmartus.com/product/s...ric-spa-heater
 
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Old 04-28-20, 06:14 PM
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The cost to heat water is the same whether you use a lot of electricity to heat it fast, or a little to heat it slowly. So converting a small heater to a larger one will certainly heat it faster, but use more or less the same amount of electricity.
Looking at some BTU calculators online, it looks like the 5.5KW heater you listed would heat a 10x10x4' hot tub about 5.6 degrees F per hour. (assuming no heat loss, which of course you'll have some). Do you know what size (watts) your current heater is?

Gas will most likely be cheaper (per BTU) than electric, but will likely have a higher installation cost too. But you'll also have some loss (gas heaters are probably 80-90% efficient) as opposed to electric heaters which are pretty close to 100% efficient.
 
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Old 04-28-20, 07:12 PM
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Thanks. My curre t heater is 1300w and the tub is about 300 gallons. But takes really long to heat and Cant keep up when the cover is off or bubbles are on. Great point about efficiency. The mfr claims like 98%99% efficiency which will save alot. This I could install on my own once I confirm my 220v outlet is sufficient at the breakers.
 
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Old 04-28-20, 07:37 PM
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You mentioned you have a 240v line available.
It would need to be at least #10 wiring and on a 2P30A breaker for that heater.
 
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Old 04-28-20, 08:15 PM
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Heres a picture of the circuit I have available to use. Will this work?

 
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Old 04-28-20, 09:02 PM
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whats make and model of hot tub?

I assume its 120 volts.. most can be converted to 240..

that should fix your issue..
 
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Old 04-28-20, 09:52 PM
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The tub is an Intex 28409E. But I don't think that matters. This heating solution im thinking of would be completely separate from the hot tub. The hot tub heater would still be in place but probably not ever turn on.

So if the circuit breaker pictured above would work for this unit below, I think that's my solution. I emailed the manufacturer to get more details on the electric requirements in addition to what's on their site.

https://www.ecosmartus.com/product-details

 
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Old 04-29-20, 06:51 AM
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I think you will be investing a lot of money into putting lipstick on a pig. After all it is said and done you will still have a cheap, very inefficient spa that will have a short life... and a DIY heating system. I would consider using your current spa as it came from the manufacturer and save any money you'd spend on your heater system and put it towards a higher quality spa when the time comes.
 
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Old 04-29-20, 09:22 AM
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@Pilot Dane, you are spot on. Totally agree, in a perfect world :-) Of course there are caveats. First this spa is for my wife, she loves it. Some day when the kids are older and we're empty nesters we will invest in a real hot tub. This makes her happy. Second, we also have a 10' diameter 30" deep infllatable swimming pool. Wife also loves it. Im hoping to tee this setup so I can, at times, warm up the swimming pool. This will be out pool and hut tub setup for many years to come. So if when the pool or hot tub break, spring a leak we'll probably drop another few hundred bucks for new ones until the time is right to put in a real spa. This tankless heating setup would be in place to serve them.

Plus this seems like a cool DIY project, how can I resist the idea!
 
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Old 04-29-20, 10:29 AM
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Do you keep your spa heated all the time or do you just heat it before use?

The 5.5kw heater mentioned previously can not be on your 20 amp 240v spa circuit. You will need a new, dedicated circuit for a heater of that size.
 
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Old 04-29-20, 12:13 PM
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I'd like to keep it to a high temp (say 90F) all of the time, and then when ready spend an hour or two getting it up to 100-102. RIght now the current heater can't do that.

On the circuit, yea. I confirmed with the MFR that I'll need a double-pole 30 amp dedicated circuit. The one pictured above is dedicated but only 2-20 amps. I've never done this before but I wonder, if the wiring gauge is correct (10g?) if its just a matter of me switching out the breakers with 30A?
 
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Old 04-29-20, 01:12 PM
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5-10įf rise in temp per hour is quite fast so you will need some horsepower if you want it so fast. My spa generally does about 2įf per hour.

Whether you go with gas or electric for your auxiliary heater I think you should run a separate pump to supply the heater. Do not rely on the spa or pool's pump. This will also make it easier to use the system on your pool. If you have a dedicated heater, pump and hoses then you could just drop the hoses into the pool or spa and heat it without having to mess with tools and unhooking hoses.

You can run 30 amps on 10 amp wire. You will also have some other wiring regulations to follow since you are mixing electricity with a pool and spa. You're doing something unusual but I assume it will need to follow the spa wiring requirements.
 
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Old 04-29-20, 03:40 PM
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Ok yep. Planning on getting a dedicated pump for the heater for exactly as you say. So really the crappy intext pump will be for bubbles.

Ok thanks so much all! I've decided to run a new dedicated 30A 240v circuit for this. Something I've never done but excited to try! Gonna post it over in the election forum.
 
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Old 04-29-20, 03:44 PM
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Installing a new 240v 30A breaker

Hi folks,

Iím planning to install the below tankless electric heater for a small hot tub. Specs call for 220-240V and 30A breaker. Iíve never installed a new breaker before but have done some reading and would love to try this.

First My design.



For the space I have to work with the wiring has to run about 75í indoors through my basement from my panel to the outside wall. Then through the wall, and along the wall about 10-15í to where I want to place the heater.

The heater will be mounted outside on the wall. This one should be more than fine for my small 300 gallon spa.

Link to the actual heater:

https://www.ecosmartus.com/product/smart-spa-5.5kw-electric-spa-heater

Specs


New Breaker- looking at my panel


Would this breaker work?

https://www.amazon.com/Eaton-BR230-Breaker-240V-Type/dp/B0064OFC9A/ref=sr_1_5?dchild=1&keywords=eaton+30A+240v+breaker&qid=1588195797&sr=8-5

Wiring Ė can I use Romex and just encase the outside run in PVC? Or do you need something special like THHN?


I would turn off the power to the entire house/panel when installing to the breaker for sure.


Any problems, suggestions with this project?

 
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Old 04-29-20, 03:56 PM
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Threads combined.

We asked you if the wiring that was currently in place was #10.
Is it correct we an assume it is not #10 wiring ?

The device you are connecting is 240v only. That would require 10-2 NM-b w/ground.
However you cannot run NM-b wiring outside.....even in conduit.
You could use 10-2 UF outside cable and sleeve where necessary.
 
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Old 04-29-20, 04:04 PM
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Thanks for combining the threads!

Guess I should've address the question you're asking about...

So I "thought" I had an open 240v receptacle but can't seem to confirm that for sure. I have a breaker in my box labeled as such, but when I go to the where I thought it comes through it doesn't look like I'd expect. I expected to see two hots (black, a red) and neutral (white). Instead I see just a black and a white wire. Telling me something is not right. It's def wired to the breaker I have pictured above.

EDIT: or is the breaker I have pictured above (2-20 AMP) not a 240v double pole but something else?
 
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Old 04-30-20, 07:27 AM
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"...I "thought" I had an open 240v receptacle..."
I do not understand what you mean. Do you actually mean a 240 volt receptacle/socket like you'd have for your dryer or stove or do you mean two empty/available slots in your breaker panel?

"...where I thought it comes through it doesn't look like I'd expect."
Do you have the cover off of your breaker panel so you can see and trace the wires coming out of the breaker? If not where wires come out the side of the breaker box has no relation to where the breakers are located inside the box. Your 20amp breaker may be in the bottom of the panel while it's wires emerge from the top.

The breaker in your photo is a 240v 20amp breaker. You can tell because it's twice the width of a single (120v) breaker and the two levers are connected together. A single pole breaker (120v) will only have one wire connected to it while a double pole (240v) will have two wires connected to it.
 
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Old 04-30-20, 08:39 AM
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Thanks for keeping me focused Pilot Dane :-) So let me go back a bit...

So when I said I had an open receptacle it's really a wall heater for one of the finished rooms in my basement that we never ever use. So I considered it "open" meaning I was gonna remove the heater. Its only about 15 feet away from the outer wall right where I want to install the tankless heater. So plan was going to be to extend that circuit to the wall.

Now I know the double breaker pictured above powers this wall heater. Where I'm confused is I opened up the connection to the heater and on see two wires coming in. A Black and a White. Assumed that was hot and neutral. Was expecting to see a black, red, white or two blacks and a white powering the wall heater. Hmmm.

So today I removed the cover to the circuit panel to see exactly what's coming out of that double breaker. And I see two wires, a black and a white, coming out of the double breaker. So two Hots, right, feeding the wall heater. I guess I was expecting to see a neutral wire somewhere in there?

Either way, in the end, these wires do NOT look like 10 gauge, which is what I'd need for a 30Amp run, right?
 
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Old 05-01-20, 11:13 AM
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So, you were looking at the wiring at the heater. It is common for 240v to be run with "normal" Romex which has a black, white and bare copper ground. Done properly both ends of the white wire should have been wrapped with black electrical tape to indicate that it is a hot wire and not a neutral. Hopefully there was also a ground conductor there that you did not mention.

With some 240v circuits, especially older ones there is no neutral. You only have two hots and a ground. That is why older stoves and dryers had three prong plugs (hot, hot, ground). In some applications code now requires a neutral so there would be four wires/conductors and is why modern stoves and dryers use four prong plugs (hot, hot, neutral, ground).
 
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Old 05-01-20, 11:23 AM
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There are special electrical requirements for hot tubs, spas, pools, etc. for any electrical connections within X feet. I suggest you post your question(s) regarding the electric on our electrical forum.
 
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Old 05-01-20, 11:32 AM
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Hi Grady it was suggested by Mods that it stays here.
 
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Old 05-01-20, 11:40 AM
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Ah on thanks pilot Dane. Didnt know tha . Big update next. Should we keep this here or move to electric forum?

Anyway Big updateI totally forgot but 15 years ago when we had out basement finished we had out contractor pre-wire for a hot tub someday. Weíve never used it. Its not wired to the breaker panel, but thereís a feeder wire of 6/3 all ready from the box to an outside receptacle! So, changes my plans a bit...

Since I was going to have to run a new circuit and install a new double pole breaker on the panel, I was thinking of upgrading to a more powerful device. And also heat a small 1,200 gallon above ground pool nearby.

The model is an 11KW heater, with a 54 a draw, needing 6 gauge wire, 60 amp breaker. This wiring should suffice. It runs along the basement to a box already installed on the outside wall (it has 50amp breakers so will have to replace those). I will branch off that box right to the heater about 15í feet away.

New Design


Heres pics of the existing wiring and the box currently mounted on my outside wall. Approx 15 feet from where I want to mount the heater. Again this wiring is not yet connected to my panel. So I'd need to

1) install a new 60 amp double pole breaker
2) upgrade the 50am breaker in the outside box to 60. Or just remove it altogether?
3) install a new run of 6/3 wire from the outside box to where I'm gonna install the heater

existing wiring waiting by my panel





Existing box outside my patio wall meant for a real hot tub someday





 
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Old 05-01-20, 12:52 PM
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I see the existing 50A to be a GFI. Any replacement would also have to be GFI.
 
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Old 05-01-20, 02:29 PM
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An 11kw heater should draw around 46A @ 240vAC.
#6 cable is rated for 55A. You can protect it at 60A.
You don't need a GFI breaker for a fixed water heater. You can replace that with a 60A breaker.
 
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Old 05-01-20, 03:31 PM
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Specifically its an 11.8 KW drawing 54 amps

https://www.ecosmartus.com/product/s...ric-spa-heater

I'll have a 60am breaker at the main service panel. Then do I need a 60am breaker at the outside box? and should it be GFCI?

I'm excited as I think this is gonna work!
 
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Old 05-02-20, 09:31 AM
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Heater purchased! Now I need to figure out what pump to get. I'm fairly versed in pumps and PVC from the 300 gallon reef aquarium in my basement. Need a pump designed for this setup - hot water with chemicals right? The specs for this heater call for 10gpm activation flow. Plus I want to have the option to divert the flow to/from a small above ground pool nearby.

Any ideas or recommendations on makes and models to start with?

 
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Old 05-02-20, 12:13 PM
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10gpm activation flow.


Oh my. .
 
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Old 05-03-20, 05:40 AM
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10 gpm to activate the heater? That doesn't sound right. In a home that would require fully opening four fixtures to get that much flow. I could understand 10 gpm as a maximum flow rate. I would look at your heaters heat rise chart that will tell you how much the heater can warm the water at different flow rates. You don't want a low flow rate that will send dangerously hot water (above 120f ?) to the spa or pool. If your flow rate is high enough the heater will be on continuously for maximum heating power while sending safe, warm but not scaldingly hot water to the spa.

What pump you choose will depend on the flow volume you need (obviously) but also pay attention to pressure. If the hoses connecting to your spa are large diameter and short you won't need a pump that can generate much pressure but a long hose run with fittings and valves can generate decent back pressure. And of course don't forget the resistance through the heater.
 
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Old 05-08-20, 08:43 AM
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Ok I confirmed the pump definitely needs to provide a min of 10 GPM flow. Below is a snapshot of the heating table.

@Mods since my only questions now are around installing the breaker in my panel and running the wiring outside should I start a separate threat for that in the electrical forum? I also just noticed there's a spa forum here too. Maybe it should be moved there?
 
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Old 05-08-20, 11:52 AM
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Maybe I misunderstand but I donít think that table tells you anything about GPM. It just tells you that when that specific heater (there are 2 choices) is activated, after a certain number of minutes the water will be raised a certain number of degrees Ė based on the size of the pool/spa (i.e., based on the constant volume of water in the spa). It will take a certain amount of heat to raise the water temp, irrespective of the pumping capacity. So it is [heater output + time] that is significant, not the pumping capacity.

The 10 GPM is like an ON/OFF switch for that specific heater. If you circulate at 10 GPM or more, the heater is turned ON, otherwise itís OFF.

Isnít that heater supposed to be used with a SPA circulating pump, and donít those normally run between 25-35 GPM? In that case the 10 GPM would easily be satisfied. It seems to me you should be looking at pumps up in that range (25-35). But maybe it would be OK to use a smaller pump and not affect the life of the heater.

I donít have a spa or pool and so the above may be total nonsense, but it seems right to me anyway Ė LOL!
 
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Old 05-08-20, 02:09 PM
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Hi Zoesdad youre right on the size of the pumps from what I've learned. Looking at one thats 40GPM. And its a circulating pump to your point (versus a jet pump). And I posted the heating chart per PilotDane's request above.
 
 

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