Hot Tub Maintenance & New Spa Brands

Hot Tub Heater Broke – Diagnosis and Replacement

Hot Tub Heater with Pressure SwitchIs the hot tub heater broken?

First make sure the problem is actually the heater and not another component or even the main electrical supply.
If you already know you need a new heater, then email us to get the best deal online.

What symptoms are there?  Do you see any control panel error messages?

Inline spa heaters are made by Balboa, Hayward, Pentair and other manufacturers who sell to the spa trade.

Wood Fired Hot Tub HeaterTypes of Hot Tub Heaters

  • Flow-Through Heater
  • Stand-Alone Electric
  • Gas Heaters (natural gas and liquefied petroleum gas (LPG))
  • Heating Oil or Propane Heaters
  • Heat Pumps
  • Solar Heating
  • Wood Burning Heater (coal or wood cords)

Most portable spas use the Flow-Through style heater where water flows through the heater manifold which contains an electric heater element that is immersed in the flowing water.   For purposes of this page, it is assumed the spa has a flo-through heater.

Spa Heater Troubleshooting

Dry Heat ConditionError Codes Can Tell the Story
Newer spas have digital control panels that display error codes to assist in troubleshooting.

Messages such as dr,drY,dY or HEATER DRY SERVICE REQD can point the hot tub owner in the right direction. The “dr” or “HEATER MAY BE DRY WILL RETEST SHORTLY”  This can be caused by lack of water in the heater tube. That can be caused by low water level, a leak in the plumbing, loose unions, semi-closed service valves, dirty or clogged filters, obstructions in the main pump plumbing line or other issue.

With Balboa controls, if the problem is found (for instance a dirty filter), then owner must press any button on the control panel to reset.  Troubleshooting this type of problem/error message may involve checking the water level and filling to the appropriate level, checking for closed valves or other blockage or flow restrictions, bleeding out any trapped air in the heater or locate other issue.

A dry condition in the heater is dangerous and if left unchecked, the heater may start to sizzle and even cause a fire.  Shut the spa off immediately if this is the case and address the issue by checking for
1. Low Water Level.
2. Blocked Suction Fittings or Skimmer
3. Dirty Filter.
4. Too Many Closed Jets or other flow obstruction in the Main Pump Line (Pump 1)
5. Closed or Semi-Closed Service Valves (watch out for slice valves that look like they are open, but may be half-closed or stuck)

Other heater related error messages may include: HFL, HL or HTR FLOW LOW – Heater Flow is Low.  This can also be caused by low water level or air in the heater similar to above issues.

OH – Overheat Condition of Spa Heater

  1. Overheat error may occur if the pump runs for extended periods, especially in hot weathe
  2. Check slice valves or gate valves. Make sure that they are completely open.
  3. Check for dirty filter cartridge or blocked filter path.
  4. Check the alignment of the heater element in the heater housing to make sure it is straight and not contacting the sides which could lead to short circuit.

Balboa control panel error messagesThe OH condition is an overheat condition detected by the water temperature sensor.  When the actual water temperature exceeds 110 degrees Fahrenheit. (43 Celsius) then the circuit board automatically stops sending power to the heater until the water cools.  The only natural way of producing OH without there being a fault is if conditions are just right on a very hot summer day with the ambient temperature above 100F, the heater and pumps running and even a reflective surface nearby.

That combination can send the water temp around the sensor to produce this OH warning and condition.   In that case, wait for the water temperature to cool below about 108F or exit the spa and test later.  The only way to get rid of the message is if the spa water can cool down to safer levels.    OH messages that occur when the actual water temperature as measured with a seperate thermometer is under this maxium temperature, then there could be an issue with the actual sensors or on the circuit board.

Sn messages such as SnS, Snb, Sna, Sb, Sa or similar mean the sensors have an issue or are out of sync.  This may require the replacement of one or both sensors.

Spa Will Not Heat

If the hot tub will not heat at all, is the heater getting power from the pack?  An electrician will measure the heater terminals to see if the heater is getting the required voltage.  If not, there could be a setting issue (such as the spa being in ECONOMY MODE and only allowed to heat during the actual filter cycles even if the temperature drops below the set temperature).  SLEEP mode is even worse.  Always operate the spa in Standard Mode unless there is a specific reason to do otherwise.

Heater Has a Short Circuit

If the heater terminals are corroded, a short can occur in the heater.  Sometimes the heater element is allowed to touch the manifold and that can also cause this condition. In any case, if when the heater tries to come on, the circuit breaker trips, then there may be a problem with either the heater element or the entire heater manifold assembly.  If the heater shows physical signs of corrosion and wear, it is best to replace the whole heater.  Sometimes only a heater element is needed, but replacing the element involves making sure it is mounted exactly the same way as the broken element.

Heating elements can fail for many reasons.  Scale accumulating on the heater element can raise heating costs and is especially caused by running the spa under a high pH condition.  As calcium carbonate is allowed to precipate into the water, it can build up on heater elements and other spa components.  This is another reason why a used spa my be less efficient than when it was new.

Ohmmeter hot tub heater measurementUsing a volt/ohm meter, the resistance across the heater terminals (with power off and heater disconnected from pack) should be somewhere between 8-20 ohms depending on the heater.  If the measurement shows 0 resistance between terminals, there is a short and the heater will need to be replaced.  This short is what is causing the breaker to trip when the heater tries to come on.   If the ohms are in the acceptable range, then there is resistance and the heater element should be working.


Replacing a Heater Element

Universal Bowtie Heater ElementWhen exchanging a heater element, be sure to turn the power off and also the breaker.  If the spa is drained it is easier to do a heater replacement than relying on the service valves, but they also may work.  To exchange the element, the heater will have to be unhooked, unscrewed and removed from the spa pack or plumbing.  There are 2 bolts on the heater manifold that hold the element in place. Be sure not to damage the wiring or terminals.

If the heater has sensors in it, they will have to be removed in order to get at the element.  Just be careful of the 2 posts where the spa pack wire hooks on to as that is where a short can occur if they are mishandled.

If the heater had a pressure switch on it, then replace the pressure switch at the same time, or order the heater with a pressure switch. If you need to mount the new pressure switch, it is a threaded connection in the heater manifold, so screw it in carefully (using a layer of teflon tape around the threads), then connect back up the 2 sensor wires to the pressure switch.

If the sensors are located inside the heater, then you don’t have a pressure switch.  You will need to know if you have a pressure switch mounted on your heater or not before you order the replacement heater to assure you get the right type. Also match the same wattage as the heater you are removing, as well as the size.   The hardest part about replacing just the heater element is getting it in without bending the terminals and be sure not to overtighten the nuts on the 2 posts to avoid cracking anything.

replaceheaterelementWhen replacing a complete heater, be sure you get both of the gaskets that go in each side of the unions that connect both ends of the heater to the plumbing.  The old gaskets should be in there, but new ones will assure a good seal. Also don’t overtighten the heater unions as they can crack when forced with a wrench.

Get a good replacement heater or heater element online. Order the same rating (how many kilowatt). Post distance is usually 1 1/4″ between post elements.

Epoxy Heater Posts Hot TubThat is important so the new element fits in the existing manifold.  Never crack the epoxy around the 2 heater posts.



 Replacing a Complete Hot Tub Heater

If the spa is more than a few years old, and there is an issue with the heater, it may be best to replace the entire heater manifold rather than just the heater element. Not only is heater element replacement trickier, but an incorrect attempt at a heater element replacement may crack the epoxy seal around the heater terminals, not be seated properly causing a short circuit or otherwise damage the heater during installation.

To replace a complete heater manifold which already includes the flow-through heater element inside, make sure to order the correct wattage rating to replace the existing heater (for example replace a 3kw heater with another 3kw heater), make sure the voltage is specified (120v or 230v) because a 1kw heater at 120v turns into a 4kw heater at 230v.  Also make note of the connection size (usually 2 inch connectors, but sometimes 1 1/2″ or other size).  Be sure to specifiy if the replacement heater needs to have a pressure switch mounted to it (or has a threaded hole for a pressure switch to mount to), or if it is the type that has the sensors built into the heater (in which case it does not use a mechanical pressure switch).

Replacement heaters usually come with the 2 gaskets needed that are in the heater unions to connect back up to the existing plumbing connectors.  Be sure power to the spa is off and disconnected before handling the 230v wires attached to the heater.  The spa should be empty or the service valves, if available, completely closed left and right of the heater to avoid water leaking during the repair.  It is often best to have the spa empty.

To replace a heater manifold, power is turned off and verified in the off state to avoid shock, the wires connected to the heater terminal are disconnected, if the heater has a pressure switch, those wires are removed from the pressure switch as well. The unions are loosened on both sides of the heater and any bolts attaching the heater to the spa pack are opened.  See this video for some heater replacement tips.

Nothing on this site is intended to be a service guide or how-to instructions on fixing your own spa. Those not qualified to work on electrical appliances should leave the work to a spa technician, electrician or other person capable of troubleshooting and repairing electrical appliances and equipment.  Incorrect repair procedures can damage equipment and lead to serious injury.
If you are in his area, call John.
or Buy a replacement hot tub heater online in the U.S

Heater Availability Update 2018

Well a lot has happened in the hot tub heater industry since this article was first published.   Therm Products has gone out of business and revived by a new company. Others are also stepping in to fill the void.   Casualties include many Therm Products heaters including a lot of the low flow heaters which are still not available.  Some of the 3 inch heaters and short heaters are also not being made.  But as the new heater manufacturers step in, perhaps some of these hard to find low flow heaters will become available again, at least as a generic replacement that may require some re-plumbing.

Contact one of the heater vendors above for the latest.