Hot Spring Grandee- heater issue help!

[scoobywagon02]

I just put in a new heater and both sensors. I got it up and running Thursday night and it is now Sunday and the tub is at 85 degrees. I am in the northeast and temperatures have been in the single digits. I am assuming the water going in was around 35 degrees. Does this seem like it is not heating fast enough. I have read some places that at the given temperature it could only rise about .5 degree per hour. This is a 4kw heater. I just don't know if the amount of time is on par with the current temp of the tub given the ambient temp. The tub is 500 gallons.

[Ryan VSO]

should be at least 4 degrees per hour

[Isaac-1]

Are you getting good flow from your circulation pump, and what was the reason for replacing the heater?

[dunecritter]

Did you replace the heater with OEM parts or aftermarket? Is your circulation pump flowing correctly? If the circ pump is not flowing correctly I'm not sure you will ever get that tub up to temp in single digits. If the ozonator is hooked up and the Circulation pump is working correctly you should see a fair amount of bubbles coming from the bottom round vent grid in the foot well. It should be a steady heavy flow of bubbles....If not I would say your Circulation pump is not happy or the replacement heater is not correct. I have no experience in that extreme cold weather but I would still think you should see a 3-4 deg rise in temp per hour.

[scoobywagon02]

It is a oem heater direct from Hot Springs 4kw. It is pushing out alot of bubbles from the discharge at the bottom of the tub which leads me to believe the circ pump is operating correctly. The only other thing I can think of is that the heater relay board is bad. I tested the power coming from the box before I replaced the heater and I got power which makes me even more puzzled. I think its a far stretch to think the heater is bad. If the circ pump was not operating correctly I would think it would trip the high limit sensor? I am just unsure of how long it should take given that the water was so cold and the ambient temp being so cold. Any other ideas??