2006 Vanguard, confused on heater replacement (4kw vs 6kw, & thermistor threads)

[clh42]

I have a 2006 Vanguard.  The heater sprang a leak (still heats, just leaks badly), so I'm trying to replace it.

The SN of my tub is VV2H2940.

I searched on multiple online hot tub parts supply stores, and they all say that based on my serial number, the heater replacement I need is part #76227, which is a 6kw heater.  So I ordered this from someone.

The new heater arrived so I went to remove the old and install the new.  I ran into a few issues.

The OLD heater is a 4kw heater, not 6kw.  If I read it correctly, the part # on the old heater is 70332.  I did have the heater replaced under warranty once 7 or 8 years ago, so it possible my local dealer installed the wrong heater with the warranty replacement?

Am I safe to install the 6kw heater if that's what every web site I check says I should use?  I did find this other thread here from a few years ago, https://www.whatsthebest-hottub.com/forum/index.php/topic,20421.0.html, that talks about needing a 60 amp main and 30 amp subpanel breaker for the 6kw heater.  I double-checked mine and my main is a 50 amp, and the subpanel has a 30 amp and a 20 amp breaker.  I know one is for the jets and one for the heater, but I forget which is which.  But this is what I was told to install by the dealer when I first bought the tub.

If I need the 4Kw heater, why would every web site I check, including talking to a dealer directly on the phone checking himself, tell me that I need the 6Kw heater for my serial number?

My second main issue is that one of the thermistors, the larger diameter one that screws into the "Inlet" side, will not screw into the new heater.  It's like the threads are different (like trying to screw a 24-thread bolt into a 32-thread nut, or vice versa).  If I can the threads to bite at all (which takes significant effort), the thermistor starts to turn sideways in the hole instead of screwing straight in.  Did those threads change between heater models?  Do I need a new thermistor that will have matching threads for the new heater?  (Or back to the above, do I need to get the 4k heater instead?)  (Side note, the smaller diameter thermistor that screws into the Outlet side screws into the new heater just fine.)

The last, and most minor factor, the new heater came with spade connectors on the main power, but my old one just had bare wires that were pushed into spring terminals on the control board.  Am I safe to just clip off those spade connectors and connect it the way the old one was?

Thank you!  I'm exasperated at this point.  I've already pulled the old heater and still not able to install the new one, so I've had to let the tub drain, and it's starting to freeze at night here.

[castletonia]

When I run your serial number in my Hot Spring service portal, it shows as a 2006 Vanguard that uses a 6kW heater, part number 76227.  As long as the 30A breaker is powering the heater, then you should be fine.  If the heater is on the 20A then you need the 4kW heater, part number 76228.

Just cut the spade connectors off and strip the end of the wires.  Every heater I order comes the same way and we remove the spade connectors on each one.  The thermistors are the same regardless of which heater you have.  Is it possible that when your dealer replaced that original heater that they cross-threaded the thermistor?  I wouldn't force it in because if it causes an issue, I doubt whomever you purchased the heater from will cover it under warranty.

I think your dealer installed the wrong heater, but hard to confirm without being onsite.  I will say that prior to running your serial number, I thought your hot tub originally came with a 4kW heater.  If you cannot get a heater installed ASAP, I would make sure you blow out the plumbing lines and winterize the hot tub.  Last thing you want is freezing issues.

[clh42]

Thanks!  I'm getting desperate.  The tub is drained, but I haven't blown out the lines yet.  At least it's still above freezing during the day here.  Still hoping to get the heater installed soon.

I called my original dealer today to ask for the history on the tub and repair.  They did confirm that they installed the 4kw heater when they replaced it under warranty in 2010, and that they THINK it had a 6kw heater originally.  Though they couldn't explain why they installed the 4kw heater under warranty.  (That said, I never had any issues with the 4kw heater not being able to keep up.)

I'm also pretty sure I've verified that the 30 amp breaker is for the heater.  I remembered, and double-checked, my refill instructions and it says that after filling to turn on only the 20 amp breaker and run the jets for 15 minutes, turn off the jets and check for bubbles from the floor drain, then turn on the 30 amp breaker.  So that must mean that the 20 amp is the jets and 30 amp is the heater.

My dealer also couldn't explain the issue with the thermistor.

The threads on the thermistor, and the old heater, don't seem to be marred or anything like that to indicate that it was cross-threaded in the old heater.  I can also still screw in the thermistor in the old heater most of the way by hand.

Should I just order new thermistors at this point, and if the new thermistor still doesn't fit then it means I got a defective heater?

[castletonia]

The 4kW heater will heat slower, thats it.  It would still heat to the same temperature as the 6kW.  Since your current thermistor doesn't work, I would get a new one since they are cheap enough.  I honestly have no idea how it couldn't work since I'm not aware of any changes from 2006 to now in terms of the thread diameter.

[clh42]

Thanks much!  I will say, it's not so much that the thread diameter is different.  It's more like the thread "count".  Like if you have a 24 thread count bolt and trying to put it into a 32 thread count nut of the same diameter, or vice versa.

The only other possibility I can think of is that the threads on the new heater itself are cut wrong, and thus essentially a defective heater.

One last follow-up question.  Regarding the main black and white wire hookup of the heater to the control panel, is it okay to hook these up in either order?  Looking at a couple of YouTube videos of replacing a HotSpring heater, one of them shows the black wire in H2 and the white in H1, and the other video has it backwards (white in H1 and black in H2).  When I pulled out the old heater, it had white in H2 and black in H1.

Thanks again!

[castletonia]

As long as the thermistor goes in and you have the o-ring to make a tight seal, I would think it would be fine.  I've only been a Hot Spring dealer for a couple years so I'm not aware of all the changes over the years.  I wouldn't be surprised if the thermistors were changed a bit over time either to be more accurate, reliable, or for cost efficiency.

To my knowledge, the heater wires are not interchangeable, but I don't know that for fact. 

[clh42]

Thanks again!  So which way are the heater wires supposed to go? I didn't get any instructions with the new heater.

[clh42]

Ugh, well, now I've got a new problem.  Don't know if you can help me with this or not.

I got concerned about the tub freezing so I decided to reinstall the old heater and get it running again.  Not sure I mentioned, the old heater still heats.  The reason I'm replacing it is that it leaks.  But a leak is better than having it freeze.

So I got the old heater reinstalled last night, filled it, powered up, and it ran for a little over 2 hours.  Then I left the house for about 4 hours and when I came back the whole tub was dead.  No power at all.  (I had checked it RIGHT before I left the house and it was still working then, which was about 2 hours after I got the old heater reinstalled and the tub powered up.)

The breakers (neither the sub-panel nor my house main) had NOT tripped.

I verified that I have 240 for both circuits coming into the main connections on the heater board.

Looking at the heater board I do see a bit of charring on the "black" spade connector that connects to the main board.  There is a bit of charring on the back too, but it's just around that spade connector, nothing else looks fried.  I checked continuity and there is still continuity from the block terminal to that spade connector. and that wire to the main board has connectivity.

And I verified I have 240 on the white, black, and red wires that go from the heater board to the main board (120 between each of the black & white and red & white, and 240 between black and red.  So it would seem power IS getting to the main board.

And the main board looks okay, no charring anywhere on the main board, front or back.

I have pictures of all this stuff (including the original thermistor issue), but I can't figure out how to add pictures to posts here.  Or maybe this forum doesn't allow pictures?

[castletonia]

On my display model hot tubs, black goes to H1 and white to H2.

I have no clue how to upload pictures, so I can't help there.  I'm not a service tech and without having one onsite, I can't guarantee this, but I'm guess the heater relay circuit board is bad, especially if there is evidence of charring or burn marks.

[clh42]

Well, the power issue is resolved and the old heater is operational.  I found Backyardplus.com and their help desk ticket system.  They got me working.  Turned out it's my spa light.  That seems to have shorted out which kills the whole spa.  Simply unplugged both connections from the spa light from the main board and everything works again.  Awfully coincidental timing.  I can only guess that the freezing got to the light during the period I had it drained.

Luckily I can run the spa without the light.  I see it's pretty pricy and just not ready to spend that much on top of the heater right now.

So at least I've bought time to get the thermistor issue with the new heater figured out.

[clh42]

Just thought I'd give a final update in case anyone else runs into the same issue(s).

All is well.  New 6 kw heater installed and working great.  Albeit now without a working spa light.

As I mentioned in a previous post, my local dealer confirmed that my spa likely did indeed come with a 6 kw heater originally, but when they replaced it under warranty they replaced with a 4 kw.  My local dealer says all they stock is 4 kw heaters as replacements.  They've never used 6 kw heaters as replacements.  (I didn't ask, and they didn't say why.)

Regarding the threads on the old thermistor not matching the new heater, that was indeed the case.  I ordered a new pair of thermistors and they fit in the new heater just fine.  So Watkins did indeed change the threads on that thermistor (and corresponding heaters) at some point.