Hot Springs Grandee - heater problems

[JulieMor]

We have a 1993 Grandee that we did a major overhaul on this past summer.  Part of that included replacing the (2) 230V heater elements.  This is the diagram for the heater box components on our spa:


Three days ago the water temp was around 102⁰.  Right now, it's 81⁰.  I noticed the temp dropping two days ago.  I couldn't do any tests then because I had other obligations so I kept my fingers crossed.  Yesterday it was snowing wet snow but I did manage to test the load side of the GFCI breaker in the sub panel before getting soaked, not to mention freezing.  The output voltage is 120v to ground on both legs and 230v between them.  I didn't open the equipment panel yesterday.

Last night it got down to around 9⁰ and I woke early this morning worrying things might have frozen overnight.  I found the temperature still warm and I doubt with this cold snap that the insulation alone could be keeping the temp from dropping more.  So some heating of the water is going on.

From the electrical schematic (attached) it looks like if the heater overload went bad it would shut down the whole thing.  The pumps and light work fine.  So I don't think it's the overload.

I thought maybe one leg feeding the heater went bad and the elements were only getting 120v.  But this morning I was playing with the temp control dial to see if I could hear the relay click in and out as I moved through the dial.  At one point I heard the click, stopped turning, then heard another click, like the relay disengaged, without me moving the dial.  Now I'm wondering if it's the thermostat that's failing or is the coil in the heater relay failing?  Which would be more likely?  Or could it be something else?

It seems the likelihood of both elements partially failing (I do believe there is some heating of the water happening) is pretty slim.  And now that I heard the coil kick in and out I'm thinking the problem is somewhere between the thermostat and the relay.

Any thoughts?

[d00nut]

Hot Spring dealers have access to a program called Detechtive, which spits out possible causes for specific issues.  In this case, low water temperature, but still heating.  This is what it gave me:

SYMPTOM: ERRATIC WATER TEMPERATURE

An erratic water temperature condition exists when the spa's water temperature fluctuates more than two or three degrees without any adjustments to the spa's control thermostat.

Most Common Causes

Dirty or clogged filters

Low flow from the 24-hour circulation pump

Summer Mode Switch activated

Non-operative control thermostat

I put this in for a 1993 Grandee.  It sounds routine, but simply check the top 3.  If that's not the case, the last possible thing, according to detechtive, could be a failed control thermostat.

[JulieMor]

Thank you!

I can eliminate #1 because I just cleaned them.

The flow from the circ pump is fine.  The problem is no hot water coming from it.

I looked but can't find a summer mode switch.  I've had the spa since it was new (18-1/2 years) and have never been aware of any summer mode switch.  I've had the entire control box out of the unit and never saw anything other than the two limit switches and the timer toggle switch.

The fact that I'm hearing the relay engage then disengage immediately tells me it's #4.

I went out to check it a few minutes ago, toyed with the stat dial, heard the telltale relay click and there's now hot water coming out of the vent.  I think it's time to order a new thermostat.

Thanks again!

[d00nut]

My pleasure, let us know what happens!

[Chas]

I would be willing to bet that it is a bad relay or simply a burned wire at or near the heater relay in the control box.



Chas

[JulieMor]

I forgot to answer this...

I installed the new stat and the heater has worked fine ever since.