Temperature reading on Raypak 406a heater

[pgershon]

My spa heater has consistently read 2-3 degrees higher than the spa. This is true whether the unit is heating or not. I have verified the spa temperature multiple ways (Jandy system probe, external analog thermometer, temperature reading on salt meter). I changed the temperature probe (009577F)
in the heater today but it did not improve or change the miscalibration. The main board has been changed 3 times in the past year and the temperature reading has consistently been off. I expected the new probe to fix the problem ,but it did not. Any ideas for a solution? I must override the high limit on the spa heater and set to 106 in order to heat my spa to 104. Been this way for at least 6 years on a 10 year old heater.

 

[BassPlayingDude]

Probably just live with it.. you know that you need to set 2 degrees higher. Why worry?

 

[blazer58]

My 406 runs about 4-5 degrees higher then pool temp shows, I have never worried about it and just set heater a little higher

 

[pgershon]

The issue is that I need to override the high limit from 104 to 106 or 107 to get the spa up to 104. My service company frequently adjusts it downward and has warned me not to change the high limit. I guess I live with it - its too bad Raypak doesn't have a calibration feature.

 

[BassPlayingDude]

Hmm .. what did they warn you would happen?

 

[pgershon]

Non- specific. Just said bad for heater

 

[BassPlayingDude]

I am no expert but I highly doubt that a couple of degrees would add much stress to the heater in the ~100F range. It might just make it cycle slightly more often or longer than otherwise.
Does your heater short-cycle often at that temperature?
If the high and low limit are close together, it can cause short cycling which can lead to corrosion via flue gas condensation, as well as reducing efficiency.
I would think that having it run a bit longer to evaporate all the condensate in the flue would actually be better for the heater. I could be wrong.

I think they are just worried about scalding and are not aware that the temperature sensor is off by that much, and don't want to get sued.
Perhaps next time they come for service you can demonstrate the discrepancy for them by using a digital thermometer in the water and showing them the comparison to what the heater is reading.

 

[BassPlayingDude]

From the RayPak Manual:

Before entering the spa or hot tub, users should check the water temperature with an accurate thermometer; spa or hot tub thermostats may err in regulating water temperatures by as much as 4°F (2.2°C).

NOTE: The LCD temperature display may not agree with the temperature reading of your pool or spa thermometer. The heater reads the water temperature at the inlet. Due to the circulation characteristics of any pool or spa, the water temperature at the inlet to the heater may differ from that observed at a given location in the pool or spa.

 

[pgershon]

That last one from the manual is a copout by Raypak- the heater reads two degrees igher than the pool whether ignited or not and all the time. It does not stabilize. Having said that, Raypak customer service got back to me and said I should run the spa at 107 and there is no issue with doing that.

 

[BassPlayingDude]

This is probably because they use a simple thermistor instead of coughing up the $3 per unit for a proper temperature sensor to simplify the design and cut costs.
Personally, I would gladly pay an extra $20 for a unit that reads temperature accurately, or that allowed me to calibrate the sensor reading.
I have both in my electronics hobby parts kit.

 

[pgershon]

This is probably because they use a simple thermistor instead of coughing up the $3 per unit for a proper temperature sensor to simplify the design and cut costs.
Personally, I would gladly pay an extra $20 for a unit that reads temperature accurately, or that allowed me to calibrate the sensor reading.
I have both in my electronics hobby parts kit.

I could not agree more

 

[BassPlayingDude]

For gosh sakes man .. 3 lines of C++

float readTemperature()
{
tempS.requestTemperatures();
return tempS.getTempFByIndex(0);
}

 

[dishwillow]

The issue is that I need to override the high limit from 104 to 106 or 107 to get the spa up to 104. My service company frequently adjusts it downward and has warned me not to change the high limit. I guess I live with it - its too bad Raypak doesn't have a calibration feature.

Im having a similar issue. How did you override the high limit?

 

[ajw22]

Im having a similar issue. How did you override the high limit?

See page 28 in https://s3.amazonaws.com/AWSProd/sites/raypakcom/documents/241236.pdf

Spa Max Temp – Spa Setpoint Maximum Adjustment
Refer to step one above to access the program screen.
Press the MODE button until SPA MAX TEMP appears on
the digital display. Using the UP and DOWN buttons will
change the Maximum Temperature Setting to your desired
value. The control can be set for a maximum of 107°F
(42°C).

Pool Max Temp – Pool Setpoint Maximum Adjustment
Refer to step one above access into the program screen.
Press the MODE button until POOL MAX TEMP appears
on the digital display. Using the UP and DOWN buttons
will change the Maximum Temperature Setting to your
desired value. The control can be set for a maximum of
107°F (42°C).