My Tub Does Not Maintain 104

[ne_skier]

I usually leave my tub set at 104 through the colder months (in New England, as you may have guessed from my username). The temp always shows 104 when I flip the cover open but then it drops while we're in it. It varies with outside temp but if it's in the 30's or maybe upper 20's, it'll drop to ~102 after a couple jet cycles. And obviously the colder it is outside the farther it drops (I saw it get down to 98 once last winter when temps were in the low teens. Needless to say, 98 degree water doesn't raise your body temp so exiting was frigid!)

Anyway, the tub is on 220/50A power. The "heating" indicator will be on, regardless of whether jets are on or off, but it seems like the heater just doesn't keep up. Is this typical?

[spatech (the unreal one)]

I usually leave my tub set at 104 through the colder months (in New England, as you may have guessed from my username). The temp always shows 104 when I flip the cover open but then it drops while we're in it. It varies with outside temp but if it's in the 30's or maybe upper 20's, it'll drop to ~102 after a couple jet cycles. And obviously the colder it is outside the farther it drops (I saw it get down to 98 once last winter when temps were in the low teens. Needless to say, 98 degree water doesn't raise your body temp so exiting was frigid!)

Anyway, the tub is on 220/50A power. The "heating" indicator will be on, regardless of whether jets are on or off, but it seems like the heater just doesn't keep up. Is this typical?

To some degree its typical though not all spas are alike so others with different brands and in different locations will have varying results. With the top off its not really about how well the sides/bottom are insulated but more a function of what kind of heater you have (not all spas use the same KW element and therefore are not pouring heat into the water at the same rate) obviously how long you are in it, how long you are using the jets (huge since a hot cup of coffee cools much quicker when you stir it)... Nothing you wrote leads me to believe your particular spa is not functioning as it was designed to.

[ne_skier]

To some degree its typical though not all spas are alike so others with different brands and in different locations will have varying results. With the top off its not really about how well the sides/bottom are insulated but more a function of what kind of heater you have (not all spas use the same KW element and therefore are not pouring heat into the water at the same rate) obviously how long you are in it, how long you are using the jets (huge since a hot cup of coffee cools much quicker when you stir it)... Nothing you wrote leads me to believe your particular spa is not functioning as it was designed to.

Thanks for the reply spatech. Your point about side & bottom insulation having minimal impact on heat loss when the tub is uncovered, and especially when jets are on, was exactly my hunch.

So I did an experiment last week. I uncovered the tub but did not run the jets at all. The temp was set to, and showing, 104. The tub had been covered for at least 24 hrs before this which I assume is plenty of time for all the water to get evenly heated. I uncovered the tub and just went back inside the house. I rechecked the tub after ~1 hour and the temp was showing 102. This was during the daytime, outside temp of 27F, zero wind. Jets were off the entire time, but the tub does have dedicated cutculation pump. Does the temp loss in this case still sound normal?

Im a bit surprised that all spas don't necessarily have "enough" thermal capacity in the heating mechanism. But then I don't really know anything about the manufacturing of spas so I don't know how much those parts factor into the bottom line cost...

Is it possible that there's some sort of heater-output dial inside the tub that I could turn up? (Like maybe something that gets set at the factory to calibrate the thermal output for unit-to-unit variations and to prevent some units from being overheated??) MAybe Im grasping at straws...

I spent an hour in a friend's tub last night and it never dropped below 103, even with jets running. (outside temp was ~30F). You know that great feeling of stepping out of a tub in the winter but not feeling cold for a minute or 2, and when you go inside you're sweating for 20 mins all because your body is superheated Yeah... I got that with my friends tub. I don't get that with mine. I'm reallllly hoping my tub's performance can be improved. :-(

If it's helpful, my tub is a 1 year old Master Twilight 8.3 situated on a purpuse-built deck whose surface is ~1 ft above ground. My friend's tub is a ~11 year Calspa on concrete.

I appreciate any info/suggestions/thoughts etc!

[masanori]

To some degree its typical though not all spas are alike so others with different brands and in different locations will have varying results. With the top off its not really about how well the sides/bottom are insulated but more a function of what kind of heater you have (not all spas use the same KW element and therefore are not pouring heat into the water at the same rate) obviously how long you are in it, how long you are using the jets (huge since a hot cup of coffee cools much quicker when you stir it)... Nothing you wrote leads me to believe your particular spa is not functioning as it was designed to.

Thanks for the reply spatech. Your point about side & bottom insulation having minimal impact on heat loss when the tub is uncovered, and especially when jets are on, was exactly my hunch.

So I did an experiment last week. I uncovered the tub but did not run the jets at all. The temp was set to, and showing, 104. The tub had been covered for at least 24 hrs before this which I assume is plenty of time for all the water to get evenly heated. I uncovered the tub and just went back inside the house. I rechecked the tub after ~1 hour and the temp was showing 102. This was during the daytime, outside temp of 27F, zero wind. Jets were off the entire time, but the tub does have dedicated cutculation pump. Does the temp loss in this case still sound normal?

Im a bit surprised that all spas don't necessarily have "enough" thermal capacity in the heating mechanism. But then I don't really know anything about the manufacturing of spas so I don't know how much those parts factor into the bottom line cost...

Is it possible that there's some sort of heater-output dial inside the tub that I could turn up? (Like maybe something that gets set at the factory to calibrate the thermal output for unit-to-unit variations and to prevent some units from being overheated??) MAybe Im grasping at straws...

I spent an hour in a friend's tub last night and it never dropped below 103, even with jets running. (outside temp was ~30F). You know that great feeling of stepping out of a tub in the winter but not feeling cold for a minute or 2, and when you go inside you're sweating for 20 mins all because your body is superheated Yeah... I got that with my friends tub. I don't get that with mine. I'm reallllly hoping my tub's performance can be improved. :-(

If it's helpful, my tub is a 1 year old Master Twilight 8.3 situated on a purpuse-built deck whose surface is ~1 ft above ground. My friend's tub is a ~11 year Calspa on concrete.

I appreciate any info/suggestions/thoughts etc!

I have D1 amore bay and it was 6f last night. I keep my temp 102f we stayed in the tub 10min and my tub stayed at 102f. Note We did not run the jets we just relaxed

[JimKW]

I keep my 2005 Sundance Optima set at 103. It usually reads 102 or 103 when I get in. I stay in for about 1/2 hour and it will be 101 or 102 when I get out. I run the jets about half the time I'm in. When set at 103 I have never seen it dip below 100, 101 is usuaally as low as it goes. I agree that 98 is not a good temp when it's below freezing outside.

[Roger]

To some degree its typical though not all spas are alike so others with different brands and in different locations will have varying results. With the top off its not really about how well the sides/bottom are insulated but more a function of what kind of heater you have (not all spas use the same KW element and therefore are not pouring heat into the water at the same rate) obviously how long you are in it, how long you are using the jets (huge since a hot cup of coffee cools much quicker when you stir it)... Nothing you wrote leads me to believe your particular spa is not functioning as it was designed to.

Thanks for the reply spatech. Your point about side & bottom insulation having minimal impact on heat loss when the tub is uncovered, and especially when jets are on, was exactly my hunch.

So I did an experiment last week. I uncovered the tub but did not run the jets at all. The temp was set to, and showing, 104. The tub had been covered for at least 24 hrs before this which I assume is plenty of time for all the water to get evenly heated. I uncovered the tub and just went back inside the house. I rechecked the tub after ~1 hour and the temp was showing 102. This was during the daytime, outside temp of 27F, zero wind. Jets were off the entire time, but the tub does have dedicated cutculation pump. Does the temp loss in this case still sound normal?

Im a bit surprised that all spas don't necessarily have "enough" thermal capacity in the heating mechanism. But then I don't really know anything about the manufacturing of spas so I don't know how much those parts factor into the bottom line cost...

Is it possible that there's some sort of heater-output dial inside the tub that I could turn up? (Like maybe something that gets set at the factory to calibrate the thermal output for unit-to-unit variations and to prevent some units from being overheated??) MAybe Im grasping at straws...

I spent an hour in a friend's tub last night and it never dropped below 103, even with jets running. (outside temp was ~30F). You know that great feeling of stepping out of a tub in the winter but not feeling cold for a minute or 2, and when you go inside you're sweating for 20 mins all because your body is superheated Yeah... I got that with my friends tub. I don't get that with mine. I'm reallllly hoping my tub's performance can be improved. :-(

If it's helpful, my tub is a 1 year old Master Twilight 8.3 situated on a purpuse-built deck whose surface is ~1 ft above ground. My friend's tub is a ~11 year Calspa on concrete.

I appreciate any info/suggestions/thoughts etc!

If you could tell us what KW heater you have it would be helpfull. A 5.5 KW heater should be able to keep temp maintained, or close in a 350-450 gallon tub. On the other hand in a bigger tub it may struggle. A 3 KW heater may not do so good. When your running your pumps does your heater work?

[Davidpsalt]

That final point by Spa Guru is what I suspect may be the issue. Check you manual to ensure your tub is set up to run the heater at the same time as the Jet Pumps - if you have two Jet pumps it may only be wired to run when only 1 jet pump is on.

I know that my Hot Spring spa require that you wire the tub from a 30A GFCI for the Jet Pumps and Heater for 220 and another 20A GFCI for the circ pump at 110. This allows for getting full heat while both Jet pumps are on and if there were ever a flow issue and the heater were to trip the breaker the Circ pump will continue and prevent it from freezing.

Check your manual for any wiring options to allow for constant heat with Jet pumps running - or your tub may limit you to only able to run 1 jet pump if you want constant heat.

Look forward to hearing back on what you find out.

[ne_skier]

Bump. On the outside chance that some of the posters here still remember this thread!

First, let me say thanks for the suggestions to check whether my tub's heater actually runs simultaneously with the jets. Very shortly after the previous post I did check this and found that heater will run with 2 or fewer of the tub's jet pumps running, but not with all 3 jet pumps going. That actually explained the 98 degree water chills. As I recall it was a cold night, we had guests in the tub and all jets were running.

Knowing that though, I remain a bit disappointed at the more moderate temp loss we usually see in a tub session on a typical winter day. (falling from 104 to 102/101 within ~15-20 mins, with 1 or 2 jet pumps running.) I realize the heater is probably running at less than max output when jets are also running, due to limited total power. But there're no jets running, it seems like there should be plenty of heating power available.

A service rep at Master tells me my tub has a 4kW heater. I find that a bit surprising/disappointing, since my tub (Twilight 8.3) is rather large and, searching replacement heaters, 5.5kW seems to be a general max. The rep tells me installing a higher-power heater in my tub would be a recipe for blown heaters. I don't know what that means, but I can't help wondering why would a tub manufacturer not spec the highest power heater available for a tub of the largest common size...

Based on previous replies here, I'm going to assume that this slight loss of temp (falling to 102/101, not 98) is somewhere within the realm of normal, even if disappointing.

That said, does anyone have info or experience with swapping in higher-spec heater elements into their tub? Beneficial? Disastrous?

[Roger]

We will need to know how many amps you are supplying to your tub.

[ne_skier]

Hi Roger, thanks again for replying!

My tub is supplied by a 220V / 50A circuit over 6 gauge wire.

[Homer14]

ne_skier,

I've only owned one hot tub, i learned a lot about it due to issues unfortunately. I know with my tub, you can install a 4kw and a 6kw heating element, maybe even a smaller 1.5kw element if on 110v only. The 6kw element keeps the water within 1 degree of temp on 0-5F outside with jets on and me in it. This model lets the heater run when the jets are on (Hot Springs sovereign II 2006) however. what you have described is functioning as normal. Dont feel too bad, some spa's dont allow heaters to be on when jets are on which completely kills the purpose to hot tub longer or have friends in and out of it during a party. See if you can replace your element with a stronger one, maybe a 5.5kw or 6kw one, but only if the one in yours is smaller than that already.

[ne_skier]

Bump. I've subsequently been told that 4kw is the highest heater most new tubs come with these days. As it was explained to me: At some point in the mid-2000's, California passed legislation allowing spas sold in that state to have a max heating capacity of 4kw (presumably for energy consevation). A side effect of that regulation is that most, if not all, new spas sold in the US come with 4kw heaters, because manufacturers don't want to deal with state-specific spec'ing. This is per a guy at my local spa dealer (also the place I bought my tub), who claims to have formerly been a product rep of some sort for a manufacturer.

This is all what was told to me. This is also the same source who tells me that current tubs can be set to 104 max, by federal law. But a poster in another thread claims that he can set his brand new tub to 106 with a bit of special button pressing. So take this FWIW; I don't know what to believe anymore.

When asking different people about installing a higher-wattage heater in my tub, I've gotten a range of answers:

- You'll burn out the heater due to insufficient water flow to absorb the heat;

- You'll burn out some other electrical bits inside the tub due to above-spec current flow;

- You'll be running your supply-line breaker too close to rated amperage and it'll trip frequently, or shorten its lifespan.

The most optimistic answer I've been given, again by my local dealer, is that there is in fact a 5.5kw heater that would fit right into my tub. (Sold for older tubs that predate CA's nazi-legislation.) But he wouldn't speculate on the liklihood of burning out anythnig inside the tub, or whether it would improve cold weather heating performance.

I suspect this is becoming a moot issue for me. I'd personally love to try sticking the 5.5kw heater in my tub (**), but my wife absoluetly forbids me to experiment with a $10k purchase. I'll admit she's not being unreasonable, and since she's the one who really wanted the tub in the first place, and I'm the one who's mainly annoyed by the under-heating, well... maybe that's the end of it.

Addendum: A friend has a circa 2000 CalSpa. The difference between his tub and mine is stark, on a very cold winter day. I've advised him to hang onto his tub for as long as possible.

Thanks again to everyone who replied!

[Dr. Spa]

A 5.5 Kw heater will pull 6.3 amps more than a 4Kw heater. Your system may be adjustable to accommodate this, but it would probably need a larger breaker and supply wiring to do so. If it's not adjustable for this, you almost certainly would fry the controller. Generally the reason a manufacturer would use a smaller heater is so that the overall power consumption of the spa (heater, pumps, blower, lights, ozonator etc.) is under a predetermined AMP rating (imagine a spa that required a 150 AMP supply. It would be VERY expensive for most people to install, thereby drastically reducing sales).

The California regulations have nothing to do with size of the heater, but with the amount of overall, total power consumption.

I suspect you're losing a lot of heat from the bottom of the spa. Being build on a deck there's a fair amount of heat loss through the spaces between the boards (as opposed to being on concrete, which would be warmed by the spa, and the thermal mass of it would greatly slow down heat loss.

[ne_skier]

Interesting. Dr. Spa some of your statements directly contradict some of what spatech said in his Dec 2011 reply to my OP.

I find it hard to believe there is significant heat loss out the bottom of the frame. The tub has insulation applied directly to the underside of the shell.

[Dr. Spa]

"I find it hard to believe there is significant heat loss out the bottom of the frame. The tub has insulation applied directly to the underside of the shell. "

how much insulation?

[ne_skier]

"I find it hard to believe there is significant heat loss out the bottom of the frame. The tub has insulation applied directly to the underside of the shell. "

how much insulation?

Hmmm, I'll admit I don't actually know. I'll try to eyeball the insulation thickness next time I have the panels off, which unfortunately may not be until well into the fall due to a yellowjackets nest somewhere inside the paneling.

How expensive is insulation material? Tub manufacturers actually will skimp on insulation material? Wow...

[Dr. Spa]

hahahahahahahaha, Given the opportunity, and if they think they can get away with it (without ruining their reputation), they'll skimp on ANYTHING to save money.

[ne_skier]

I'm not convinced. How expensive is spray foam? Unless it's like $100 per ounce and applying enough would consume a third of the product budget, I find it hard to believe a tub manufacturer would skimp on insulation, to the extent that heat loss through an insulated shell, cabinet and deck surface, would rival heat loss from the water surface, which is aerated, jetted and directly exposed to winter air.

Cite some numbers. What's the unit cost of tub insulation and how many units to well-insulate a shell?

I notice your sig links to a company that sells tubs and covers. Does your company skimp too?

[Dr. Spa]

There's a couple of manufacturers that sell roughly 25,000 spas a year. What is their annual savings by cutting just $4 from the production of each spa? Business is a game of numbers. The higher you're overall volume, the greater the potential for savings. Imagine what coke-a-cola could do if they could save just 0.00001 cents per can of coke.

[PreservedSwine]

Confirm the heater is running 240v. The heater may be mis-wired. A 4KW should not be be losing that much heat, that quickly, even in a poorly insulated tub. Never heard of a 4KW heater being the max size allowed by state law, as many manufactures, even those based in California, use 6KW heaters in their spas.

[ne_skier]

There's a couple of manufacturers that sell roughly 25,000 spas a year. What is their annual savings by cutting just $4 from the production of each spa? Business is a game of numbers. The higher you're overall volume, the greater the potential for savings. Imagine what coke-a-cola could do if they could save just 0.00001 cents per can of coke.

I don't dispute the concept that every penny you shave from production cost gains you a penny of profit per unit sold.

You still have not made a convincing case that my tub (or any tub) would be so thinly insulated, that heat loss through the tub's insulation, cabinetry and support structure would equal or exceed heat loss through 60 square feet of water surface, agitated and aerated and directly exposed to winter air.

This isn't about the icon of "corporate greed" that cynics love to hate on. (I say that as a cynic who loves to hate on corporate greed. :-)

This is about thermodynamics.

[ne_skier]

Confirm the heater is running 240v. The heater may be mis-wired. A 4KW should not be be losing that much heat, that quickly, even in a poorly insulated tub. Never heard of a 4KW heater being the max size allowed by state law, as many manufactures, even those based in California, use 6KW heaters in their spas.

I'm not sure how to specifically confirm that, but would my tub even heat (or run) at all if it were not wired correctly? The tub does not have a 120V mode; it's strictly 240V. The power line was installed and connected by a professional electrician. (That job was done twice actually, but that's an unrelated story.) I had the circulation pump replaced about 6 months ago; the repair guy did a general check of stuff while he was in there.

Are you thinking the heater came mis-wired from the factory? But again, I would think the system would be completely non-functional, rather than function weakly, if that were the case, no?

As for regulations and 4kw vs higher, I was just repeating what I was told. What manufacturers are you aware of, that currently install 6kw heaters? I'd be curious to read up on their models.

[PreservedSwine]

Hot Spring Spas is a spa company with their headquarters in Vista, Ca (Though they're sold all over the world), and use both 6KW and 4KW, depending on the model. They're one of the leaders in the industry. Some of their larger tubs use 4KW, the smaller 6KW, the opposite of what you might first think- but it has to do with the size of the jet pumps, and keeping the heater on while the pumps are on. The larger tubs use larger pumps, and there just aren't enough amps available to run two powerful pumps, and a 6KW heater, so they use a smaller heater on the tubs with large dual jet pumps.

Dimension One is another California made spa, that uses 6KW heaters. Both are premium brands sold nationally and internationally.

I've never heard of any special requirements for their spas sold in California.

If your tub uses the same control box across all models, (as many do) they typically can be configured to have the heater run either 120v, or 240v. And sometimes, someone makes a mistake, and the heater is wired 120v even in a "240v" spa. If you're losing several degrees in just 30 minutes while the 4KW heater is energized, something is clearly wrong. You can tell right away the amp draw of the heater with a fairly inexpensive amp clamp.

[Spa_Guru]

The larger the exposed surface area of the water, the greater the heat loss, even a 5.75 kw element may not keep up with the loss at some point (your results may vary) but I can tell you how I solved this problem for a customer whose cabin is in Northern Idaho, and gets hit with -30F temps and sometimes a stiff breeze coming across a frozen lake.

I had an electrician run an additional 50 Amp 240v service to the spa, and installed a compact Hayward CSPAXI11 11KW heater plumbed in after the existing equipment.

I installed an air button and air switch to shut the heater on or off by wiring the air switch in series in the contactor coil circuit, and left the thermostat on maximum.

When the customer wants more heating capacity, he simply hits the switch, when the pump shuts off, the pressure switch in the heater automatically shuts it down.

This gives him 15KW of heating power, which means he can also heat the tub from stone cold in the dead of winter to steaming hot in about 2 hours.

[ne_skier]

Hot Spring Spas is a spa company with their headquarters in Vista, Ca (Though they're sold all over the world), and use both 6KW and 4KW, depending on the model. They're one of the leaders in the industry. Some of their larger tubs use 4KW, the smaller 6KW, the opposite of what you might first think- but it has to do with the size of the jet pumps, and keeping the heater on while the pumps are on. The larger tubs use larger pumps, and there just aren't enough amps available to run two powerful pumps, and a 6KW heater, so they use a smaller heater on the tubs with large dual jet pumps.

Dimension One is another California made spa, that uses 6KW heaters. Both are premium brands sold nationally and internationally.

I've never heard of any special requirements for their spas sold in California.

If your tub uses the same control box across all models, (as many do) they typically can be configured to have the heater run either 120v, or 240v. And sometimes, someone makes a mistake, and the heater is wired 120v even in a "240v" spa. If you're losing several degrees in just 30 minutes while the 4KW heater is energized, something is clearly wrong. You can tell right away the amp draw of the heater with a fairly inexpensive amp clamp.

Hot Spring Spas is nice enough to list heater watt ratings for all their spas on their website, and it pretty much confirms what you wrote. I looked at specs for all their spas and noticed that all the models with 2 jet pumps have 4kW heaters, while the models with 1 pump have 6kW. I didn't see a correlation with tub size; they have big and small tubs with either number of jet pumps. But it was always 1 pump => 6kW, 2 pumps => 4kW. But I think your point stands about total current draw - more pumps leaves fewer amps available for the heater. (That's a very subtle point I bet no first time buyer thinks about. I know which variation I'd go for if I were buying again!) And I take your point about 4kW not being a legislated limit.

Regarding measuring the current draw across the heater; that's a good idea. I'd like to think that test would have been done when I had the circ pump replaced last winter, but I'd have to dig up my papers. I'll reply again if I find that info, or get to do the test myself.