Hot Tub Conversion?

[bskaggs32]

Hello, newbie on the forum... lots of great info here...

Someone gave me a nice large hottub because the heating element died and it had a small leak somewhere.
The previous owner said he was also tired of the increased electric bills.

So... I am going to pull out all the electric heat and replace it with some type of heat exchanger. I have read (in my lurking about various issues) several people on this forum have hottubs heated with boiler power.

My questions are:
What type of exchanger is appropriate for hottub?
How do you regulate the temperature?

I put in my own side arm on my water heater, but that requires no real regulation of temp, aside from maybe an optional anti-scald.

Thanks

[Al_Smith]

Well they are expensive to operate ,that's a fact .

I'd kind of tread lightly changing it over to a form of heat exchanger with safetys etc else you could inadvertantly cook someone like a lobster ,not good .

Keep in mind you have to be very mindfull these things require a pretty good filtration system and anti bacterial provisions also .Without same you or the Mrs could get some type fungus among us you wouldn't care to get .Especialy the Mrs without getting graphic about it ,neither she or you would care for that .

[thecfarm]

I use my OWB  to heat my. Bought a device,no idea the name of it now, it has alot of holes about the size of a pencil in it,$400 about 4-5 years ago. Took some guessing to hook it up,electricity wise to control the hot water, I'm not the best with guessing,but it's works,I think. I still use the controls for the hot tub. Same idea as a thermostat in the house.

[bskaggs32]

thanks for the responses...

I do plan on using eletricity to control the temp and the pumps. It will be a closed system with a heat exchanger. I will either use a chlorine based system, or salt seperator system, so no worries there.

I was just looking to see if anyone had a head start for me. The existing computer sends a start signal to the relay for the electric (and costly to run) water heater. My plans are to use an electric valve of some sort to add in the heat from the boiler via closed system heat exchanger.

[sprucebunny]

To control temperature in a loop off a furnace they use a series of high/low limit switches.  Pipes must be monoflow ( directional discharge) for circulation to work because tub pipes are 1.5" and feed to heat exchanger is 3/4? so some water will bypass while some heats.
You will need standard zone valve or circulator to heat exchanger which is plumbed as a seperate zone.

Master plumber here right now has done this. He says the heat exchanger was $800. Maybe you can make one cheaper.

[bskaggs32]

I think i have  the mechanism figured out... on to the heatexchanger...

From what I have been reading, most electric heat element in large hot tubs are 5.5 kw (wow thats pulling juice)
which is less than 20,000 btu...

Does that sound right? Sounds small to me...

I use my OWB  to heat my. Bought a device,no idea the name of it now, it has alot of holes about the size of a pencil in it,$400 about 4-5 years ago. Took some guessing to hook it up,electricity wise to control the hot water, I'm not the best with guessing,but it's works,I think. I still use the controls for the hot tub. Same idea as a thermostat in the house.

Do you know aprox dimensions and how many plates are in your exchanger?

I guess I am looking for a sanity check...

Thanks again

[thecfarm]

It's in the root cellar all covered up in 2 inch styrofoam,so this is all by memory. It's probably 8 inches square by a foot long with just holes in it the size of a pencil. As many holes as you can fit into a 8X12 box. A very pricey box I felt.

[Taylortractornut]

A few years ago I was hosting a friends 3 phase tig welder in my shop in exchange for using it.         I saw a picture of a Cedar wood fired  hot tub.    I had another friend that had an  inground pool with a seperate hot tub that shared a filter systems with it.    My friend had an old keg and  we cut the end out of it and  made an intake pipe for air  that came in near the bottom of the   keg and  one at the top.      We  welded on  som anchors to  secured it  to the back wall of  the  tub.  We also  made a cedar stand off gate around the front of the  heater to  keep  skin away from it.     It worked really well for several years.     One adaptation to our  set up was on the intake side we put a 3 inch pipe to it   from a  110 3 inch portable ventilation squirrel cage.    You could fill the heater up and turn the blower on and really heat the water up in a hurry. 

They used a termometer and thermostat to  run the fan and also an over temp light for safety.  If it was over  115  it shut the fan off and  turn on a red light and buzzer to keep folks out. 

[Gravityman]

 hello bskaggs32 and everyone
I just found this wonderful forum and saw Bskaggs topic.
I just finished converting my electric hot tub to run off my wood stove.
I cut a hole in the top of my favorite wood stove and put an old boiler on it's side,so the flames would go through the pick up pipes.
Then I piped it into my oil furnace,that circulates hot water for heat.
The wood stove keeps the boiler from coming on most of the time, but if the fire in the wood stove gets low, the boiler next to it just kicks on.

I added a heating coil to the old boiler that I put on top of the wood stove and it heats my hot tub, which is about 15 ft. outside the house.
The pipe is pex and runs underground to the hot tub.
Real fun stuff, but yes it takes time.
Let me know if you are interested, and I can post photos.
Note; It ain't too pretty but the electric bill is gone with burning wood to heat the tub.

The whole thing is sort of like an indoor outdoor wood furnace. All the heat loss is inside the house as the wood stove, and boiler are in my basement surrounded by concrete foundation walls very safe this way.

[Ironwood]

I just got a 6-7 person hot tub that was "hit by a voltage surge". The guy said I coudl have it. It only looks a few years old, and I have a pump and filter here from another unit. I am contemplating using something other than electric to heat it. I dont run a wood burner that often. I wanna follow along here.


Ironwood

[Gravityman]

Sounds good!
Maybe consider solar hot water conversion. If you have a south facing view of the sun for 6 hours,(or more) you can heat it free.
Yep you have to build it or pay for a production line unit.
I suggest building your own, or building it into your heating system. Hopefully you do not use electricity for heat, or you are in a warm climate.

[beenthere]

Ironwood
Reminds me when a kid. If I wanted a warm bath, I had to build a fire first. I didn't have a choice on the bath, but did have a choice as to the temp of the water.  
Same with the hot tub?  ;)

[Ironwood]

Beenthere,

That's what I am thinking. I had/ have a stainless milking parlor tank that I was gong to "retro fit" but seemed  a bit "medical" looking and would lack comfort. Also had a Snorkel wood tub here, needed some bottom repair, gave it away. So this one looks good, molded. looks comfy. I have some pumps and filters here, also spare wood burners I can "plumb" into the line feeds. We have a friend off the grid up on the Laural Ridge who has a "tub" outback that he heats with wood., so I am familiar with some of this.

Ironwood