Thermalec 12THR, 36THR, 24THR, 72THR, 120THR Installation, Operation And Maintenance Manual
INSTALLATION, OPERATION AND MAINTENANCE
BEFORE YOU BEGIN INSTALLATION READ THE
MANUAL CAREFULLY
WARNING
Only qualified personnel, should install and maintain this equipment.
Unauthorized alteration or improper maintenance of this unit may release
the manufacturer from any warranty claims.
Check all electrical connections to all components within the heater for
tightness. Connections can become loose during shipment and handling,
this can cause electrical components to burn out.
CAUTION
The heater must be installed in accordance with the country/regional
requirements & regulations. In any event the work must be carried out by a
suitably qualified electrician, who will provide a certificate of conformity
upon the completion of work. The power supply must be fitted with an RCD.
IMPORTANT SAFETY INSTRUCTIONS
When using this electrical equipment, basic safety precautions should always be followed, including the
following.
1) READ AND FOLLOW ALL INSTRUCTIONS.
2) TO REDUCE THE RISK OF INJURY:
a) The water in a pool or tub should never exceed 40°C (104°F). A water temperature more
than 40°C (104°F) is considered unsafe for all persons. Lower water temperatures are
recommended for extended use (exceeding 10-15 minutes) and for young children.
b) Excessive water temperatures have a higher potential for causing fetal damage during
the early months of pregnancy, pregnant or possibly pregnant women should limit pool or tub
water temperatures to lower than 38°C (100°F).
c) Before entering a pool or tub, the user should measure the water temperature at several
occupant locations using an accurate thermometer since the tolerance of water temperature regulating devices may vary as much as ±3°C (±5°F).
d) Alcohol, drugs or medications should not be used before or during pool or tub use since their
use may lead to unconsciousness with the possibility of drowning.
e) Obese persons and persons with a medical history of heart disease, low or high blood
pressure, circulatory system problems, or diabetes should consult a physician before using a pool
or tub.
f) Persons using medication should consult a physician before using a pool or tub since some
medication may induce drowsiness while other medication may affect heart rate, blood pressure
and circulation.
3) SAVE THESE INSTRUCTIONS FOR FUTURE REFERENCE.
WARNING
DANGER OF HYPERTHERMIA
Hyperthermia occurs when the internal temperature of the body reaches a level several degrees above
the normal body temperature of 37°C (98.6°F). The symptoms of hyperthermia include dizziness, fainting,
drowsiness, lethargy and an increase in the internal temperature of the body. The effects of hyperthermia
include:
a) Unawareness of impending hazards;
b) Failure to perceive heat;
c) Failure to recognize the need to exit pool or tub;
d) Physical inability to exit pool or tub;
e) Fetal damage in pregnant women;
f) Unconsciousness resulting in a danger of drowning.
WARNING--- The use of alcohol, drugs or medications can greatly increase the risk of fatal hyperthermia
in pools and tubs.
WARNING
Only qualified personnel in accordance with the country/regional requirements & regulations, should
install and maintain this equipment. Unauthorized alteration or improper maintenance of this unit may
release the manufacturer from any warranty claims. The installation must be in accordance with the
instructions in this manual and applicable local plumbing and electrical codes.
INTRODUCTION
Founded in 1966, Thermalec® Pool and Spa Products was the first company in Britain to manufacture a
range of electric heaters specifically for public, commercial and domestic swimming pools and spas. In
1999, Thermalec® joined the Meddings Group of Companies to enhance and diversify the latter’s
engineering activities whilst allowing Thermalec® to widen its horizons as part of a larger group. Over the
years, the Thermalec® electric pool and spa heater has been refined and today has an established name
in many areas of the world as the quality heater of first choice. The clever patented design, robust quality
and inherent reliability of the Thermalec® electric heater have earned it a position as the market leader in
Britain. Thermalec® heaters are also exported to the Middle East, the Far East and Europe, where
Thermalec® has gained the confidence of pool builders and operators as a name they can rely on.
Thermalec® pool and spa heaters are designed and built with care at our factory in the South West of
England. Our overriding objective is the application of half a century of experience, delivering to each and
every customer a quality pool heater that will give many long years of safe, efficient and economical
service.
The dedication that we apply to the design and building of a truly superlative pool heater extends further.
We exchange knowledge and experience with our partners worldwide to ensure the total satisfaction of
our customers, both installers and final users. Thermalec® engineers and technicians share their skills,
offering guidance, training and support in heater selection, installation and operation. This is particularly
for difficult applications such as sea water pools, health spas or hydrotherapy pools – areas in which the
performance of Thermalec® pool heaters are especially outstanding.
At Thermalec®, we are justly proud of our electric pool heaters. In the few pages that follow, you will find
outline details of the range and of some of the features that make Thermalec® heaters the natural quality
choice for any size or type of pool or spa. This manual provides installation procedures, operating and
maintenance instructions and a parts list for the Thermalec® Swimming Pool Heater. Your Thermalec®
Electric Swimming Pool Heater has been designed and engineered by British Engineers to provide you
with the most advanced highest quality heating system possible. Its operation is the most efficient and
pollution-free. Our models are available for every size or make of pool. To ensure a long life of troublefree service, your Thermalec® swimming Pool Heater should be carefully installed in accordance with the
instructions given in this manual. Failure to do so may damage the swimming pool heater and the pool
equipment to which it is connected. Only qualified personnel should install and maintain this unit, and, of
course, local plumbing and electrical codes have precedence over these instructions.
DESCRIPTION
The Thermalec® Swimming Pool Heater consists of titanium elements encased in a cast iron heating
vessel, the heaters upper external enclosure contains the electrical heating and control system. To help
maintain the heater to its optimum level, a brief description of its components and their operation has
been added to aid the customer. The cast iron vessel houses the elements. The vessel and heating
elements are the only components of this heater that are in contact with the water and has a unique spiral
flow of water through it, this promotes efficient heat transfer, minimizes scaling of the elements and the
build-up of sediments. The internal design of the heater prevents the direct impingement of cold pool
water onto the heating elements, reducing thermal shock, prolonging the service life. If air gets into the
heater, the unique internal weir and baffle arrangement ensures that the air is channeled harmlessly
across the top of the heater and across the unheated ends of the elements. This avoids possible element
burnout and thermal inefficiency due to wasteful heating of air. The external enclosure is a sheet steel
case totally enclosing the electrical components. The enclosure is coated with a rust inhibiting, powder
coat finish. The electrical system, which is the nerve center of the unit, can be considered as three
separate systems engineered to provide years of service and optimum use of energy. They are as
follows:
a) The heating elements; are mounted via two cold legs through a high-grade PVC plate. These
elements are made from titanium as standard and have an extremely low watts’ density due to
their design.
b) The control system; consists of the pilot switch, high limit thermostat, Pump interlock switch, a
temperature controller, magnetic contactors and sequencer (on larger units only). The controls
are wired into a control circuit designed to control the temperature of the water leaving the heater.
The high-limit thermostat is designed to open the control circuit and cut off the power in the event
of excessive temperature. A pump interlock switch is built-in to prevent the pool heater from
operating without the pump being energized, we use this because we have found flow switches to
be very unreliable.
c) The main current-carrying components; are the contactors. They are wired into the circuits which
carry the full amperage of the elements. The contactors open during a high temperature condition
to de-energize the elements. The heater has a temperature controller adjustable up to 45°C
(113°F) and has one manual reset type high temperature limit thermostat set at 48°C (118°F).
Installation: Location
Thermalec swimming pool heaters are quiet, do not emit exhaust fumes and may be conveniently located
in a shed or basement. Normal positioning of the pool heater should be near the pool filtration system.
Select a location conveniently close to incoming electrical service and where excessively long piping runs
are not required. Thermalec® heaters should never be installed outside where they are susceptible to
water.
Minimum clearance:
12THR
24THR
36THR
72THR
120THR
Front
36 (914)
36 (914)
36 (914)
36 (914)
36 (914)
Left
* * * * *
Right
* * * * *
Top
14 (356)
14 (356)
16 (406)
16 (406)
16 (406)
Back
8 (203)
8 (203)
11 (279)
17 (432)
17 (432)
* Required clearance is dependent on plumbing configuration used.
- Dimensions: Inches (mm)
- Temperature control is located on the front of the unit.
Installation: Plumbing
Pipe the heater as shown in Fig. 1 to the inlet (left) and outlet (right) openings on the side. Connect the
heater in line between the filter discharge and pool. The water line coming from the filter should be
connected to the heater inlet, and the discharge line to the pool should be connected to the outlet. The
pool will not heat properly unless it is plumbed correctly. If plastic pipe is used, it should be suitable for at
least 49 °C (120°F). A plumbing bypass around the pool heater is not necessary unless flow rate though
the heater exceeds the flow rates stated in Fig.2. Lack of sufficient flow will cause the heater to overheat
and trip out. It may be necessary, in larger Olympic-sized or public pools, to use two or more heaters to
obtain sufficient kW capacity. If so, the heaters must be installed in parallel, allowing each heater to take
equal flow.
Fig. 1
The maximum flow rates are only recommended flow rates to minimize scale formation and to reduce
wear on the elements. The heater is fitted with a pressure relief valve set to lift at 2 Bar (29 psi). Maximum
flow rates throughout your system will depend on your system configuration.
Flow Rate
3 kW
4 kW
6kW
7.5 kW
Hard water maximum
- use bypass above this rate
- minimise scale formation
2000 gal/hr
152 l/min
2000 gal/hr
152 l/min
2000 gal/hr
152 l/min
2000 gal/hr
152 l/min
Soft water maximum
- use bypass above this rate
- improves element life
1000 gal/hr
76 l/min
1000 gal/hr
76 l/min
1000 gal/hr
76 l/min
1000 gal/hr
76 l/min
Minimum
60 gal/hr
4.5 l/min
80 gal/hr
6 l/min
120 gal/hr
9 l/min
150 gal/hr
11 l/min
Flow Rate
9 kW
10 kW
12 kW
Hard water maximum
- use bypass above this rate
- minimise scale formation
2000 gal/hr
152 l/min
2000 gal/hr
152 l/min
2000 gal/hr
152 l/min
Soft water maximum
- use bypass above this rate
- improves element life
1000 gal/hr
76 l/min
1000 gal/hr
76 l/min
1000 gal/hr
76 l/min
Minimum
180 gal/hr
15 l/min
200 gal/hr
16 l/min
240 gal/hr
20 l/min
Fig 2.
DRAINAGE: A method of draining water away from the heater and other equipment is provided. The
heater should be flushed at the end of each swimming season. During flushing or servicing, water may be
spilled and could cause damage to the floor or other equipment. A drain valve has been fitted to the
vessel to aid you.
Flow direction through the heater is left to right, allowing the temperature controller to sense the
temperature coming from the pool. The direction may be changed by reversing the probes of the control
thermostat and the safety thermostat, as follows:
a) Switch heater circuit breakers to OFF;
b) Switch main power supply and pump interlock supply to OFF;
c) Remove main cover;
d) Reverse two probes. Controller probe is situated at the left-hand end of the element
plate; the safety thermostat probe at the right (marked with a short length of white
sheathing);
e) Reinstate the top cover before reconnecting connecting electrical supplies.
Pipe connections are stub flanges to suit 1 1/2" (12kW) nominal bore pipe (uPVC or ABS). If using ABS,
the solvent jointing compound must be suitable for both materials. Reducers may be fitted to suit smaller
pipes. It is not necessary to fit unions either side of the heater as the stub flanges are easily disconnected
from the heater, by removing the nuts securing the aluminium backing flanges to the heater. In very tight
installations, the studs themselves may be unscrewed. It is advisable that isolation valves are fitted either
side of the heater to allow easy removal of the heater without water loss.
Electrical Installation
a) Check heater label for rating to insure the heater matches your electrical supply.
b) CHECK ELECTRICAL CONNECTIONS TO ALL COMPONENTS within the heater for tightness.
These can become loose during shipment and handling.
c) Check components for any moisture, rust, or dust which may have accumulated during shipping, and
clean or dry where necessary.
All pool heaters covered in this manual have integral thermostats, contactors and sequencers where
required.
Wiring diagrams included show internal wiring and required field connections for various models. Consult
your local electrical code for proper wire and conduit sizes, and other local requirements.
Do not connect the pool heater to, or operate at a voltage other than the voltage rated on the heater label.
Wires of adequate size are to be fed from a fused disconnect switch or circuit breaker with an ampere
rating of 125% of the ampere rating shown on heater label. Connect power conductors to the power
distribution block inside the heater. All other internal connections are completed and tested at the factory.
Overcurrent protection must also be provided in the form of a Miniature Circuit Breaker (MCB). Due to
the continuous high load that will be drawn, MCBs should be rated at least 20% higher than of the current
shown below.
Specific Electrical Supply
3 kW
4 kW
6 kW
230V – Single Phase (UK)
13 Amps
17 Amps
25 Amps
Two Phase / Split Phase
L1
L2
NA NA
13 Amps
13 Amps
220V – Single Phase (Euro)
14 Amps
19 Amps
28 Amps
Specific Electrical Supply
7.5 kW
9 kW
10 kW
12 kW
230V – Single Phase (UK)
32 Amps
38 Amps
NA
50 Amps
400V – Three Phase (UK)
11 Amps
13 Amps
NA
17 Amps
Two Phase / Split Phase
L1
L2
21 Amps
11 Amps
25 Amps
13 Amps
NA
34 Amps
17 Amps
220V – Single Phase (Euro)
35 Amps
NA
46 Amps
55 Amps
380V – Three Phase (Euro)
12 Amps
NA
16 Amps
19 Amps
Connect Pool Heater to Power Supply
To connect to the power supply, your installer needs only protect the main supply lines with an RCD.
The size and specification of the cable to the heater should be decided by consulting the Local
regulations. To minimize the effects of volt-drop, the plant room should be located as close as possible to
the main electrical supply.
The supply cable enters via the removable plate at the back of the heater. The plate should be drilled out
to suit the size of cable gland used. Under no circumstances should cable be installed through the metal
plate without the use of a gland. To access the terminals, remove the heater cover and the plastic
terminal cover.
Single-phase. All 12THR heaters are delivered configured for single-phase operation. It is vital that all
wires are firmly terminated into the appropriate terminal (L+, N or E). Ensure that the cable is of sufficient
diameter to ensure a good clamp is made. After termination, check all the cables for tightness and
replace both sets of covers.
Two-phase or Split-phase. Heaters with ratings 3 or 4kW cannot be configured for these supplies.
The standard 6kW heater can be configured to operate on these supplies by carrying out the following
modification:
a) Remove brown wire from contactor pole L3 and reconnect to contactor pole L2
b) Connect first phase wire to contactor pole L3
c) Connect second phase wire to terminal block L+
The standard 7.5, 9 and 12kW heaters can be configured to operate on these supplies by carrying out the
following modification:
a) Remove a brown wire from between L+ terminal block and contactor pole L3
b) Connect first phase wire to terminal block L+
c) Connect second phase wire to contactor pole L3
d) Ensure that filter pump and associated items are supplied from second phase which has
a lighter load
Three-phase. The standard 7.5, 9 and 12kW heaters can be configured to operate on three-phase by
carrying out the following modification:
a) Remove brown wire from between L+ terminal block and contactor pole L2
b) Remove brown wire from between L+ terminal block and contactor pole L3
c) Connect L1 incoming phase wire to terminal block L+
d) Connect L2 incoming phase wire directly to contactor pole L2
e) Connect L3 incoming phase wire directly to contactor pole L3
It is vital that all wires are firmly terminated into each terminal. Ensure that the cable is of sufficient
diameter to ensure a good clamp is made. After termination, check all the cables for tightness and
replace both sets of covers.
The heater will not operate without a pump interlock supply that switches 220/230V ON when the filter
pump is running. The live of this supply should be connected to terminal A and the neutral to terminal B
of the heater. The supply must be taken from the last device switching the pump to ensure that the
heater will switch off at the same time as the filter pump.
This pump interlock supply can also be used to further control the operation of the heater. A time switch
can be fitted to interrupt the supply to terminal A; ensuring that it can only come on during specific periods
of cheap electricity. This is detailed on drawing APH 1319, together with arrangements for an override
switch allowing the filter pump to be run continuously.
Startup Procedure
a) Make sure that the pump is on and that there is at least the minimum flow of water through the
pool heater (IAW Fig.2). The heating elements will burn out if allowed to operate without sufficient
water flow.
b) Ensure heater breaker/switch is turned off. Check temperature control setting is turned down,
also, examine wiring for loose connections, etc.
c) Turn on power at main supply switch.
d) Turn up the heating controller to desired level.
If the high temperature manual reset switch shuts off the heater, disconnect power at the supply and
determine the cause before resetting.
The Control Panel
The control Panel has 6 to 8 indicating lights depending on heater model. The lights are as follows:
Heater Status Lights
Light
Description (when illuminated)
Right Hand Red
Heater has power
Left Hand Amber
Pump Interlock Supply OK
Left hand Red
Heater Turned On
White
Excess temperature Not Tripped
Right hand Amber
Pump Interlock Relay Energized
Green
Heating Elements Energized
FAULT – FINDING
Safety Warning. The electrical supplies to the heater are potentially lethal. All maintenance and repair
operations should be carried out by trained personnel, supported by appropriate safe systems of work.
Before removing the top cover ensure that, both the main power supply and, the pump interlock supply,
are both isolated.
Excess Temperature Trip. If all lights are on, apart from the white, amber and green, and the
temperature controller does not engage the heater; this could indicate that the excess temperature
thermostat has tripped. Before resetting investigate why heater has overheated.
Controller Drift. The calibration of the controller drifts over time, requiring the value set on the dial to be
gradually increased to maintain the same actual temperature in the water. Please contact your heater
supplier to adjust this.
Contactors Frequently Switching. Switching of the contactors every few minutes indicates that the
direction of water flow could be incorrect. The flow of water is designed to travel from left to right in the
heater. Consult instructions on how to reverse the flow.
Protective Devices on Supply Trip. If RCD has tripped, first check that other equipment in the
installation has not caused the trip, then check heating elements for insulation resistance. If MCB has
tripped, check it is correctly rated.
Noise. Excessive “buzzing” when heating indicates small amounts of rust on the pole faces of the
contactor. Electrical contact cleaner should be applied to the affected area.
Pool Not Reaching Desired Temperature. If the status lamps are lit as described on the previous page
and the contactors can be heard engaging, then the heater can be said to be operating correctly. If the
pool does not reach the required temperature after an appropriate number of hours, then the current
drawn by the heater should be checked using a clip-on ammeter. An alternative method is to set the
temperature control several degrees above normal and use the main supply meter to check how many
Units (kWh) the heater consumes in an hour. This figure should be slightly above the kW rating of the
heater, allowing for the filter pump and other domestic equipment on the same supply. If the consumption
is less than the rating of the heater then the issue is elsewhere in the system, for example:
▪ Low voltage supplied to the heater, indicating that cable diameter is too small or run is too long.
▪ Inadequate mixing of the warm water from the heater with the cooler water in the pool, leading to
a layer of warmer water forming at the height of the inlets. To cure, alter the direction of the pool
inlet jet downwards.
▪ Incorrect setting of any time switches fitted to heater or filter pump.
▪ Time switches are not synchronised with the main electrical supply meter.
▪ Lack of water flow caused by insufficient pump head, or blockages in the pipe-work.
Annual Cleaning
Yearly, before winter, the pool heater should be drained and cleaned. More frequent checks may be
required if pool water contains sediment or any amount of foreign matter.
a) Switch heater OFF.
b) Switch main power supply and pump interlock supply to OFF.
c) Remove main cover and check main and contactor terminals for tightness.
d) Apply Electrical contact cleaning spray (or similar) to all electrical components, particularly the
contactors.
e) Close heater isolation valves.
f) Empty vessel using drain valve.
g) Remove drain valve locking screw and check for debris at the bottom of vessel with 6mm
dowel rod.
If rod cannot be fully inserted, then consideration should be given to opening the vessel to remove debris.
If the pool is to be kept in semi-operation during the winter, then the heater may only be left full of water if
the filter pump is fitted with a frost-stat.
Warranty. The heater is guaranteed for two years against faulty workmanship or materials. This
does not cover damage caused by incorrect commissioning & maintenance or by other neglect of
the heater.
The manufacturer will replace or repair, at its discretion, any faulty units or components returned to
the company for inspection. Proof of purchase may be required. The manufacturer will not be liable in
cases of incorrect installation of the heater, inappropriate use or neglect of the heater.
Water Quality
The water quality must be within the following limits:
PH. 6.8 - 8.0, TA (Total alkalinity) 80 - 140ppm (parts per million)
Chloride Content MAX: 150 mg/litre
Free Chlorine: 2.0 mg/litre
Total Bromine: Max 4.5 mg/litre
Total Dissolved Solids (TDS) / Calcium hardness 200 - 1,000ppm
Thermalec® heaters are suitable for use with salt water pools with a salt concentration up to 8000ppm
(8g/litre).
Water chemistry is complicated if in doubt seek expert advice.
RoHS Compliance Statement
Meddings Thermalec Limited certify that our Electric Swimming Pool Heater Range complies in
accordance with RoHS Directive 2011/65/EU on the restriction of hazardous substances. Waste of
Electrical / Electronic Equipment
This product complies with EU directive 2012/19/EU. Do Not dispose of this product as unsorted
household waste.
By ensuring this product is disposed of correctly you will help prevent potential negative consequences
for the environment and human health, which could otherwise be caused by inappropriate waste handling
of this product.
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