You can put a filter after the pump and before the heater if you want or combine the systems like shown in the diagram.
SPA heater, what would happen?
- Thread starter Hulaomr
- Start date
Just to be sure, the diagram shows the current implementation. I did it based on the current installation.
I checked the gas pressure as suggested. The pressure were +3.62" and +0.04" as show the pictures below.
| No gas | With gas (heating) |
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After adjusting the offset pressure screw, the value get around -0.2" (varied from -0.19 to -0.24)12. Remove the barbed adapter. Apply joint compound to the NPT plug and replace to seal the vent port.
Ok, let's see if the numbers for gas used, temperature rise overall, temp rise for flow and stack temp are all where they are supposed to be.
@JamesW I saw in the video shared, the pressure was negative with the valve off. Please, let me know if you see something unexpected about this.
Did you have the Low Side (Negative (-)) on the pressure tap and the High Side (Positive (+)) on the T?
I think that the person had the lines backwards.
He puts the High side on the Pressure Tap, which is reverse of the Pentair instructions.
Below the results of the temperature (according with heater display) in the time. Notes: it was a little rain
I will perform another test including the recording of the meter as well.
After adjusting, you are getting about 1 degree per 1.18 minutes.
Before adjusting, the temp rise was about 1 degree per 1.18 minutes.
So, it seems like it did not help.
Before adjusting, the temp rise was about 1 degree per 1.18 minutes.
So, it seems like it did not help.
The pressure test is somewhat confusing because both lines are under vacuum and you are taking a negative differential pressure, so it's like a double negative.
The Pressure tap side is lower pressure (more vacuum) before the gas valve opens because the gas line is closer to the blower impeller.
Once the gas valve opens, the gas pressure pushes the Pressure tap side pressure higher than the vent line side, which makes it read negative since the low side is now a higher pressure than the high side even though both sides are vacuum.
In my opinion, it would be clearer if they reversed the instructions to make the vent the low side and the pressure tap to be the high side and the reading should be +0.2" w.c.
As it is now, increasing the gas pressure makes the reading go more negative.
The Pressure tap side is lower pressure (more vacuum) before the gas valve opens because the gas line is closer to the blower impeller.
Once the gas valve opens, the gas pressure pushes the Pressure tap side pressure higher than the vent line side, which makes it read negative since the low side is now a higher pressure than the high side even though both sides are vacuum.
In my opinion, it would be clearer if they reversed the instructions to make the vent the low side and the pressure tap to be the high side and the reading should be +0.2" w.c.
As it is now, increasing the gas pressure makes the reading go more negative.
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I did another test including:
- Temperature (F) at the heater
- Gas consumption at the meter
- Stack flue temperature
- In around ~3min it get to 333F.
The gas used is about 3.4 cubic meters per hour, which is about 75% of the expected consumption of about 4.5 cubic meters.
You are getting about 0.79 degrees per minute, which is about 68% of the expected temperature rise of 1.16 degrees per minute.
It seems to be working, but not at 100% performance.
Hard to tell exactly why is is not at 100%.
Note that the tests are just estimates and they are not going to be 100% accurate.
Are you sure about the spa volume at 580 gallons?
Note that you will also lose some heat if the spa is uncovered, so that can affect the heating times and it can account for the total heating time being longer than expected.
Try to get a temperature before and after the heater with thermistors to see the temperature rise at 60 GPM.
You are getting about 0.79 degrees per minute, which is about 68% of the expected temperature rise of 1.16 degrees per minute.
It seems to be working, but not at 100% performance.
Hard to tell exactly why is is not at 100%.
Note that the tests are just estimates and they are not going to be 100% accurate.
Are you sure about the spa volume at 580 gallons?
Note that you will also lose some heat if the spa is uncovered, so that can affect the heating times and it can account for the total heating time being longer than expected.
Try to get a temperature before and after the heater with thermistors to see the temperature rise at 60 GPM.
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The Stack temperature is in the acceptable zone, which is good.
It might be working correctly and the gas consumption might not be 100% accurate.
With the correct manifold pressure, the gas supply should be ok.
Maybe an issue with air intake supply.
Inadequate air supply can cause incomplete combustion due to lack of oxygen and the reaction producing some carbon (soot) and some carbon monoxide instead of carbon dioxide.
Make sure that you have adequate air supply and adequate venting.
Improper venting is a serious safety hazard, so get this 100% correct with a qualified gas contractor before operating the heater.
The heating time can possibly be explained by heat loss.
Ok. I calculate assuming two rectangles and the volume get to 2239.71 Liters. Similar to the one reported previously.
The 580 gallons come from drawing the SPA in a CAD software and calculate the volume based on a solid. It must be quite accurate (without the pipes).
The SPA is uncovered all the time. Just has a metal (tubes) pergola.
HEAT LOSS FROM WATER SURFACE AT VARIOUS AIR AND WATER TEMPERATURES AND AIR VELOCITIES AT 70% HUMIDITY.
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