Rapak electric heater problems

jholbey

Member
Hi everyone, I’m new here and have a Rapak E3T 11kw 240volt spa heater that I can’t get the heaters to come on. I have a existing main service that is 200amp 3-phase I’m coming out of with a 70amp double pole breaker with #6 building wire going 90ft. to a sub panel with a 60amp double pole breaker. I’m showing 208volts at the heater across phases. I have 24gpm showing on the display and no error codes. The heater has to have 15gpm to turn on automatically after 1min. Of confirmed flow. This heater display also shows present water temperature. The heaters will not come on and this unit has me scratching my head why. Does anyone have any ideas or thoughts as to what the problem might be. Any ideas would be much appreciated thanks.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
1. The #6 is too small for a feeder on a 70a breaker.

2. The spa may have a voltage switch for the control circuitry.

3. When you say "I’m showing 208volts at the heater across phases. " if that's at the heater element terminals (its contactor is pulling in), then the element must be bad.

4. Are you giving it enough time to raise the water temperature? How are you sure it's not heating?
 

reast

Member
Agreed, #6 on a 70 amp breaker is too small, unless terminations on both ends are rated 90 Degree which they are likely not.

You said you measured 208 volts across phases, but this unit is a 240 volt heater. This unit does not seem to have an error code for when voltage is too low, but I suspect that is the issue. 208 is probably enough to turn on the electronics, but not enough to run the heater elements effectively. I found the manual and it says this under the troubleshooting section:

"It takes a long time to heat the spa. Cause:
  • Low input voltage
  • Defective heating element. For the 11kw, resistance across the element should be 5-5.8 ohms.
When you say "I can't get the heaters to come on", are you determining this by the fact that it doesn't heat or are you measuring something. If it's simply not heating, I would suspect the low voltage to be the cause.
 

jholbey

Member
Thanks for your reply Larry... 1 looks like I going to have to go with #4 wire.
2. I will have to check for a voltage switch if it does I will see if it’s closing.
3.I have 208volts at the terminals for the heater not at the elements. This heater doesn’t have a contractor it’s electronic controlled.
4. I have let the system run several times for 1/2hr to 1hr and the display shows no change in water temperature and there is no warm as I feel the water pipe out of the heater. Thanks so much for your help. I will bump up the wire size maybe even go to #2
 

Dennis Alwon

Moderator
Staff member
208 is probably the high leg reading to ground. 208 is not across the terminals, I presume. If it is then something is amiss
 

jholbey

Member
Agreed, #6 on a 70 amp breaker is too small, unless terminations on both ends are rated 90 Degree which they are likely not.

You said you measured 208 volts across phases, but this unit is a 240 volt heater. This unit does not seem to have an error code for when voltage is too low, but I suspect that is the issue. 208 is probably enough to turn on the electronics, but not enough to run the heater elements effectively. I found the manual and it says this under the troubleshooting section:

"It takes a long time to heat the spa. Cause:
  • Low input voltage
  • Defective heating element. For the 11kw, resistance across the element should be 5-5.8 ohms.
When you say "I can't get the heaters to come on", are you determining this by the fact that it doesn't heat or are you measuring something. If it's simply not heating, I would suspect the low voltage to be the cause.
Thanks again Larry for your reply... yes I measured 208volts at sub panel between phases and at the terminal connections on the heater unit. This unit should show a code if low voltage it has that capability but no codes of anything is coming up. I will also check the resistance at both elements for the 5.- 5.8 ohs. I don’t have the voltage across the heater elements when measured. I’m thinking you are right about the low voltage but in a 3-phase panel all you can get is 208volts according to the schematic on the main service panel unless you use all 3-phases of the 3-phase power. I will not get 240 off 2-phases of this 3-phase panel I think.
 

texie

Senior Member
The manual says max/min 2 pole breaker of 60. Just change the breaker. The wire size is fine. This is a 240 volt unit. Are you connected to 240 volt system?
 

jholbey

Member
208 is probably the high leg reading to ground. 208 is not across the terminals, I presume. If it is then something is amiss
Thanks for your reply Dennis.. I’m getting 208volts across the sub panel going to the heater. I measure 208volts on my main service between phases a-b,b-c,a-c. The panel shows have to go to all 3-phases to get 240volts
 

hillbilly1

Senior Member
Even at 208 it will heat, just not as fast. They must be using scr's to control the heaters if they don't have a contactor. Check the amp draw while heating, that will tell you a lot, whether the scr is working or the element(s) are bad.
 

jholbey

Member
The manual says max/min 2 pole breaker of 60. Just change the breaker. The wire size is fine. This is a 240 volt unit. Are you connected to 240 volt system?
Thanks texie for your reply Yes I have a 60amp double pole breaker at the sub panel for the heater and a 70 amp feeding it from the main. My main service 3-phase 200amp shows I can only get 208volts on 2-phases. Not the 240volts the heater is requiringI would think 208volts would work maybe I’m missing something. Thanks so much for your help
 

jholbey

Member
Even at 208 it will heat, just not as fast. They must be using scr's to control the heaters if they don't have a contactor. Check the amp draw while heating, that will tell you a lot, whether the scr is working or the element(s) are bad.
Thanks hillbilly for your reply... I have checked the amp draw with a amp clamp on amp meter and there is no amp draw. This is a brand new unit but the scr may not be working
 

texie

Senior Member
Thanks texie for your reply Yes I have a 60amp double pole breaker at the sub panel for the heater and a 70 amp feeding it from the main. My main service 3-phase 200amp shows I can only get 208volts on 2-phases. Not the 240volts the heater is requiringI would think 208volts would work maybe I’m missing something. Thanks so much for your help
A 240 heater running on 208 will give 25% less output but in most cases should work. There could be something in the controls not allowing operation at 208 though. Depends on the design.
You sure it was not "dry fired"? Check to see if there is resistance thru the elements.
 

hillbilly1

Senior Member
Yes unless you use all 3-phases then the schematic on the main panel shows you can get 240volts. I have a pic of this schematic off the main
If it is a standard wye, you will get 208 volts regardless. If you want 240 volts from a standard wye, you will need buck boost transformer(s). Because they are autotransformers, they will work with the gfci breaker, but not if the neutral is required for the load because the line to ground voltage is also increased.
 

jholbey

Member
A 240 heater running on 208 will give 25% less output but in most cases should work. There could be something in the controls not allowing operation at 208 though. Depends on the design.
You sure it was not "dry fired"? Check to see if there is resistance thru the elements.
Thanks again for your reply texie... you may be right about the controls not allowing the 208 to work. No there was no dry firing on the elements... I will check the resistance on the elements thanks
 

jholbey

Member
If it is a standard wye, you will get 208 volts regardless. If you want 240 volts from a standard wye, you will need buck boost transformer(s). Because they are autotransformers, they will work with the gfci breaker, but not if the neutral is required for the load because the line to ground voltage is also increased.
Thanks hillbilly... I was just looking at the buck-boost transformer. This should work then because it doesn’t have a neutral for load. Thanks so much I was wondering if that boost would work.
 

Little Bill

Moderator
Staff member
@jholbey
You have 208V across two phases, adding the 3rd leg wouldn't give you 240V. You have a 208/120V 3Ø service.
You said you showed no current flow, either your heaters are bad or the control board is not calling for heat, or is just a bad board. I believe the unit would work on 208V but you may have to check with the mfg.
Speaking of mfg, you said this was a new unit, I think I would be calling them under warranty.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Last tub I wired had an automatic start-up procedure and warns not to interrupt it.
 
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