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Hot Tub Heater Repair

Hot Tub heaters and parts from Hot Tub Outpost
Replacing a Hot Tub Heater - Spa Heater Troubleshooting

Hot tub spa heater for sale at Hot Tub OutpostSpa heaters usually last a long time.  Some things like improper water chemistry can shorten the life of heater elements as well as seals, orings and other hot tub components. 

That is one of the reasons it is important to maintain pH between 7.2-7.6 and to check the water with test strips or a test kit regularly.

The hot tub heater is a metal cylinder connected to the hot tub plumbing and spa pack which contains a flow-through heater element inside and a metal sheath or manifold on the outside. 

Other heater types in addition to flow-through type heaters include trombone style and even external gas powered heaters. 

Horse Sense
Warning: Working on your own appliances, cars, covered wagons and hot tubs as well as anything else electrical or mechanical carries with it severe risk of injury or property damage. These tips and suggested procedures are free and for informational purposes only. Proceed at your own risk. It is best to use the services of an electrician or tech. Hot Tub Outpost is not liable for any damage or injury that may result.

This article is about the Balboa flow-through electrical spa heater. Before making any heater repairs or testing the heater or electrical components, make sure the POWER IS TURNED OFF at the main breaker.

hto heaters spasTwo posts with mounting nuts which are encased in epoxy on the top of the heater tube are connected to the circuit board in order to power the heater.  The spa electronics give the circuit board a signal when it can apply power to the heater terminals.  

Hot tub heaters also have either internal or external sensors which monitor the water temperature and possible overheat conditions.  Older style spas may have an external pressure switch that is sometimes mounted to the heater tube. Newer style heaters such as the Balboa M7 type have these two sensors mounted inside the heater, eliminating the need for an external pressure switch.

Heater failure can cause the GFCI or breaker to trip.  A service technician will disconnect the heater terminals (with the spa powered down and the circuit breaker off) to see if a tripping GFCi may be caused by a short circuit in the heater.

Caution: These two heater terminals have full voltage and can cause shock, so it is recommended to only allow qualified persons to work on a spa and also that the power is off and the breakers also turned off.

Hot Tub Heater Brand List - Hot Tub Outpost Has 'Em All

  • Balboa
  • Brett Aqualine
  • Cal Spas
  • Gecko
  • Hayward
  • Hydro Quip
  • Jacuzzi
  • Sundance
  • Therm Products
  • OEM-Generic and more...

 See all of our hot tub heaters.

Replace your hot tub heater with the same kilowatt rating / voltage and plumbing size.

Although we also sell the individual heater elements, it is recommended to change the entire heater manifold when in doubt, or if the heater is more than a few years old as changing out heater elements can cause issues at the epoxy seal, or it can come in contact with the metal sheath creating a short. Changing out the entire heater tube including the heater element is an easier process and eliminates the guesswork of troubleshooting a heater element that visually looks ok but may not properly fit the existing heater manifold and installation. 

When switching out the heater manifold, be sure to remember the o-rings/gaskets that go on both sides of the heater. These 2 gaskets (one on each side) help avoid leaks at the heater union that connects to your spa plumbing.  Typically for 2 inch inner diameter plumbing, the 2 inch heater gaskets are:

2 inch heater gasket with oring (actual width 2 15/16" od) - for flow through heaters ad the 1 1/2 inch one is

1 1/2 inch heater gasket with oring (actual width 2 3/8" od) though it may vary depending on heater type.

Heater Repair Tips 
If you are removing the heater from the plumbing, do not remove the screws that may be on the heater union.  It is also a good idea to replace the heater gaskets when closing the heater tube back up.  If the heater union is leaking, tighten the union to see if leak stops, but do not over-tighten to avoid cracking the union.  Also inside each side of the heater union (plumbing part that connects the heater tube to the hot tub plumbing), there is a heater gasket (see above).  This may also need to be replaced if the union is leaking.

Spa electrical and heaters should only be worked on by qualified persons as working on any appliance can be very dangerous and lead to electrical shock or other injuries.  This article provided for information purposes only and is not intended to be a comprehensive how to guide.  Call a qualified tech if you need assistance in repairing your spa. Qualified techs may use this information as a primer on some things that can go wrong with hot tub heaters.

The heater is often coupled with the spa pack such as many of the newer Balboa heaters and spa packs. When accessing the heater, the power pack door is opened by removing the top 2 screws on newer Balboa packs.

Tripping GFCI

One of the number one causes of a tripping GFCI or hot tub heater failure is that a drop of water may find its way onto the heater post between the insulator and the post causing a short circuit.  If that happens, the GFCI trips for safety reasons.  A test to see if the heater is causing the GFCI to trip is to remove power from the heater to isolate the problem.  Note that there are many causes of a GFCI tripping including a problem with the spa pump, ozonator, blower or other spa component.

If removing the heater strap from the heater, hold the part with a wrench to avoid breaking the heater post.  Newer Balboa systems such as the BP2000 series have a dedicated heater connector that can be unplugged instead of opening the heater strap connection. 
Techs are now replacing the old Balboa copper heater straps with heater output cables 9920-401161.

To isolate the heater from the pack, the power to the heater is removed.  If the breaker resets, then the problem is with the heater and it may need to be replaced. Some may decide to try to replace just the heater element, but the epoxy that holds the heater post in place as well as the actual placement of the heater element makes this an exercise not recommended. It is best to replace the entire heater.

Multimeter measures hot tub heaterHeater Testing

Resistance Tests - Heater Continuity
There are several multimeter readings that can be taken from the heater posts to determine what a problem might be with a spa heater.

Heater Test 1):  Place the 2 measuring probes of the multimeter on each of the 2 heater posts.  The resistance reading for acceptable heater ohm ranges are:

  • 1kw heater @ 120 volts          9.4-11.5 ohms
  • 4kw heater @ 240 volts          12.96 - 15.84 ohms
  • 5.5kw heater @ 240 volts       12.96 - 15.84 ohms

If the multimeter shows a 1 or OL then there is no continuity and the heater will need to be replaced. Find a new spa heater at Hot Tub Outpost.

Heater Test 2):  Place one multimeter probe on the left heater post and the other on the metal heater tube sheath/manifold. The meter should read 1 or OL to show there is no conductivity between the outer sheath and the heater terminal.
Repeat this test for the right heater post and make sure there is no conductivity between the right heater post and the metal heater tube.

When the tests are complete, connect the heater again.

Insulated heater clamp test for testing a hot tub heater.Voltage Tests

Before setting up the voltage test be sure the POWER IS OFF AT THE BREAKER. 
Use insulated clamps to clamp onto each of the two heater posts.  Be certain that each clamp is not touching the other one.

Set the multimeter to read AC voltage.

Once the heater probes are attached correctly and not touching each other or anything other than the heater post, turn breaker on to get power to the control panel and spa.  With the hot tub powered up, be sure the panel is in standard mode and raise the temperature so that the spa calls for heat.  This should normally apply power to the heater and there should now be the full operating voltage across the heater. This may be about 120v, 230v or 240v depending on how the spa is hooked up.

After the voltage reading is taken, power down the circuit breaker and spa again and then remove the test clamps.

Amperage Tests

An ammeter is required to test the heater for amperage.  The ammeter clamp is placed around one of the heater supply wires.

According to Balboa Instruments (aka. Balboa Water Group), the acceptable heater amperage draw ranges are:

  • 1kw heater @ 120 volts          7.58A - 9.26A  (120v amp draw)
  • 4kw heater @ 240 volts          7.58A - 9.26A  (120v amp draw)   or    15.15A - 18.52A (240 volt amp draw)
  • 5.5kw heater @ 240 volts       10.42A - 12.74A (120v amp draw)   or    20.83A - 25.48A (240 volt amp draw)

 Ammeter Test Hot Tub Amperage

Other Spa Power Issues
Another issue is the 0.3 amp system fuse on the circuit board which could render the entire spa in a non-operating state.  Nothing will work including the topside control panel if the 0.3 amp fuse has blown.  Whenever work is being done on the power pack, be sure the electricity is off/disconnected and breakers are off for the safety of the techician or anyone else working on the spa.

For assistance on getting a new replacement heater or other spa parts, contact Hot Tub Outpost USA.

See our spa heater section for the current line of inline hot tub heaters.

Here is a video for electricians to see how the flow through heater is replaced and also shows adding a pressure switch.

See the complete replacement spa heaters, heater elements, pressure switches and heater parts.

Spa heaters at Hot Tub Outpost

We also offer flow through heater elements and pressure switches.

Heater Mechanical Failure

Still readin'? Well this is all you never wanted to know about how heaters operate and why they can fail. 

Mechanical failure is often caused by improper handling which can destroy the Epoxy Seal end, and also breaking or twisting the Cold Pin off.  Now the Electrical Terminal is welded to the Cold Pin that passes through the Epoxy End Seal to get to the Heating Element or Coil inside the heater manifold.  If the Electrical Terminal is separated or broken from the Cold Pin, then there is an open circuit and no electricity can flow.  There is no repair for this.

problems with sealAnother type of failure happens over time with degradation of the Epoxy Seal. Then moisture gets inside the element and wicks into the MGO filler which eventually can cause an electrical short circuit. Then whenever the spa calls for heat and energizes the heater and heater element, the breaker may trip.  This can be a short circuit between either the electrically charged Cold Pin or heating element/coil - and the electrically grounded outer sheath of the heater manifold.  If properly installed, the GFCI in the system will open the circuit preventing a very dangerous condition that can result in someone getting shocked.

Heaters are not the only reason why a GFCI will trip, there are many components in the spa that can have short circuits including pumps, circulation pump, blower, ozone generator or even those pesky rodents a'chewin away at the wires.  Nuissance tripping is a whole nother page, but if a heater is shorting and the GFCI is tripping when the spa calls for heat, then it is time to replace the heater.

Sort of Working Heaters

Well now if the condition above happens and there is moisture inside the element, but it is allowed to cool off, then perhaps air is getting in through any crack and the next time the heater element gets power, wa la - it works. So the GFCI is reset  - problem solved - or not so fast.  The problem will then recur and trip the breaker again - so a tech will check the Cold Seal carefully.

Never bend, tug, push, pull or twist the Electrical Terminal. A tech will always use 2 wrenches to tighten or loosen the Terminal Nut.  1 wrench holding the Terminal Hex to keep it from turning and one on the Terminal Nut to do the loosening or tightening.

Dry Fire Condition

Allowing an air pocket in a partially full heater manifold can cause heater failure and a dangerous condition.   Normally when water completely fills the heater manifold/tube, then the temperature of the Incoloy Outer Sheath of a heater will only be a few degrees above the hot water temperature. For example if the set temperature is 102 degrees F, then the outer sheath can be about 110 degrees F and all is well.

But in a dry fire condition, one of three things can happen.  The water flow slows down too much, or the water flow stops, or the heater is turned on without the heater tube being completely full of water.  In this case, the Outer Sheath temperature can rapidly rise to 200, 500, 1000 or even 1500 degrees Fahrenheit very quickly - in a minute or two.  Now the melting point of the Sheath is about 1700-1800 degrees F and the temperature inside the heater and at the sheath can approach that critical temperature very quickly.  Most times the spa circuit board or safety device such as the high limit switch will sense this temperature anomaly and shut down power to the heater and the circ pump producing an OH message or similar.

Damage that can occur includes the Outer Sheath splitting open - the Heating Coil wire hanging out in all directions and the MGO filler can be cracked, smashed and blown away.  The element is destroyed and often the Stainless Steel housing can be damaged as well.

If the damage is not that extreme, there still could be one or two holes that are blown through the Sheath and this destroys the heater element.

If no holes are visible, but the walls of the Sheath are bulged outward in spots, the normally smooth surface of the Sheath is now bumpy and has become discolored. Inside of the element the Heating Coil may be broken; or it might be electrically shorted against the Sheath. Or both.

Pressure Switches can also be destroyed by a Dry Fire Condition

HIGH LIMIT PROTECTION – the primary job of the High Limit Switch in the finished product is to prevent scalding water from ever reaching the people using the product.

Normally the Thermostat should shut the heater off long before the point at which the High Limit Switch is needed, but Thermostats, like everything else,can also fail.

Will the High Limit do its job? It hasn’t had to operate for months or years. Is it in the right place to do the job? If the High Limit is not sensing the water temperature close to the heater element, and the pump suddenly quits – its dry fire time in just a minute or two. The element will boil the water in the heater housing – and create its own “dry” condition. Following that, the service technician arrives and finds the heater assembly full of water again, and claims it couldn’t have been a dry fire. This goes back to not replacing heater elements in the field, but just replace the complete heater assembly.

Check that High Limit. FLO/PRESSURE SWITCHES – Various types of devices are used to detect whether there is any water flowing through the heater assembly. Unfortunately, when these things fail, they generally fail in the closed position and there is no indication that they are not doing their job. In most cases a spa system will work just fine with a stuck pressure or flow switch – until there is a need for it. If a full-scale dry-fire destroys the flow or pressure switch along with the element, it’s impossible to determine which went first; but one thing is certain – the heater was doing its job. It isn’t very smart – it just makes heat.

Another cause of heater Failure is Corrosion

badelementThere are different corrosion types such as galvanic corrosion, chemical pitting, intergranular corrosion, stress corrosion cracking, corrosion fatigue, electrochemical corrosion - we even have a strain of bacteria: Ferrobacillus in the Siderocapsaceae family, also called "iron eating bacteria," to contend with.  But one takeaway here is that LOW pH (below 7.0) is one of the worst offenders that can cause deterioration of heater elements and corrosion.  Acidic, low pH water will eat away at metals.  If the element has craters in it, then it could be because of a chemical imbalance in the water and lo pH.

High pH can, on the other hand, cause SCALE and coat heater elements so it becomes harder for the water to be heated efficiently.

If there is a slippery brown coating, then there could be iron eating bacteria, so the water would need to be treated with sanitizer such as chlorine or bromine, then drain and refill.

Use Ahh-Some to purge biofilm from the water if the water balance got out of hand and there are deposits in the plumbing.  This is a good idea anyway once a year to purge the plumbing lines.

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