Pool heating a guide

SELECTING A HEATER FOR YOUR POOL OR SPA.

We have had an extended summer this year …. What do they call it “Indian Summer”? Well it’s going to get cold … Soon I guess. We are always receiving a large number of inquiries from domestic and commercial pool owners on the options available to heat their pool. In this Blog I hope to impart to you some relevant information on what are heater options for your pool or spa.

I don’t want to get into cost analysis in this blog. It will be more to the types of heaters their pros and cons. But by all means contact us or drop in and see us at Billabong Pool Service and Supply.

For 40 years, we have been specifying and fitting heaters to a diverse range of pools and spas. We would be pleased to discuss your heating needs and provide an obligation free quote.

It is apparent to us that there is a lack of balanced information available to allow potential purchasers to understand the basics of pool heating. In many cases, heater selection is being made without buyers being correctly informed on the all important issues of performance expectation and operating costs.

Capital outlay appears to be the main motivating factor for selection, whereas on going energy costs and plant maintenance should be the major area of review.

Our hope is that the information contained in this blog will be of assistance to those considering a heater purchase.

SOME FACTS:

Operating costs

The most cost efficient way to heat a pool is with an electric heat pump.

The second is with gas, providing gas purchase price is competitive.

The third is with electric resistance element. On certain tariffs resistance can be competitive with gas.

SOLAR:

We do not consider solar an option in this guideline, as it is not a stand alone system that can offer acceptable commercial swimming water temperature during winter. Solar is sometimes marketed in conjunction with gas or electric boost. With these systems the following points must be considered:

The boost system must be sized to be a stand alone heater at times when there is no solar input.

In winter operation, the solar system contributes little to satisfying the total heat load. To input any available solar gain there needs to be a control system in place to effect change over of energy sources.

For homeowners, solar should be considered to extend the swimming season in spring and autumn.

If a solar installation is being considered, the purchaser should request that the installer provide a written projection of expected pool water temperature for each month.

POOL COVERS:

These are also a consideration, when talking about pool heating by contributing to heat retention. The subject of pool covers deserves its own blog.

Performance expectation

The industry standard target water temperature for comfortable swimming in commercial pools is 28.0 degrees C. Spas are normally operated at 38.0 degrees C.

If you have installed a heater that achieves anything less than target temperature, the heater is incorrectly sized for the installation and the project is seriously flawed.

Q. At what time of the day is target temperature to be achieved and what is the pool temperature at start of days swimming?

A. It is not a satisfactory situation to have a heating system that, for instance, achieves target temperature at midday.

AVAILABLE HEATING SYSTEMS

ELECTRIC HEAT PUMP:

Available in single and three phase supply and is basically a refrigeration unit working in reverse.

Energy Efficiency:

By use of refrigerant cycle energy efficiencies are high, with averages of (1) unit of energy input to the heater, resulting in (4.5) units input to the pool water.

The input to output ratio is referred to as “The coefficient of performance”. (COP)

Heat pumps are usually rated at Kilowatts / hour output. (KW)

Operation:

An enclosure houses a compressor, evaporator coil, cupro nickel or titanium heat exchanger and fans.The fans draw ambient air over the evaporator coil and heat from the air is transferred to the cold refrigerant in the coil, the resultant cold air is exhausted by the fan.

The now warmer refrigerant flows to the compressor where it is compressed and heated then passes to the heat exchanger where heat is transferred to the pool water flowing through the exchanger.

The now cooler refrigerant passes to an expansion valve, the pressure is greatly reduced which in turn chills the refrigerant to a cold gas. The refrigerant flows into the evaporator coil and the heat collection process again commences.

Heat pumps can be indoor or outdoor located. If located indoors, exhaust air must be ducted to atmosphere or distant from the evaporator coils in the case of large area installations such as car parks.

Because the unit employs refrigeration technology, there is high energy efficiency with resultant low operating costs in comparison to other forms of heating. Both ambient air and pool water temperature determine the efficiency of the unit and hence the heat output is not linear as is virtually so with other forms of heating. Warmer ambient air allows for increased output.

For purposes of model comparison, the Heat Pump Association has set an arbitrary figure of rating heat pump outputs. They are:

(a)Air on to evaporator temperature shall be 15.0 degrees C with dry bulb reading.

(b)Water entering the heat exchanger shall be at 27.0 degrees C.

If you are comparing quoted model outputs this is the figure to look for, energy outputs stated at other air temperatures or wet bulb, are not comparable.

Noise Level:

As a rule of thumb, standard build heat pumps operate with a noise level of around 68dba @ 3.0 metres. This noise is generated by the compressor and fans.

You should be aware of the following

In the near future, all new air conditioning and heat pump installations will be checked for conforming to local authority noise guidelines before commissioning.

Noise complaints must be investigated by local authorities and owners of noisy machinery can be directed to comply with regulation or shut down. Such complaints usually come from neighbours, holiday guests or permanent tenants and can arise at any time in the working life of the heater. To attenuate an existing installation can be expensive and in some cases most difficult to achieve.

At point of ordering there are a number of options available to specify a heater with an operating noise level less than 68 dba.

If considering a heat pump purchase, close attention must be given to the potential for noise complaint, particularly if the property:

(a) Has a limited choice of locations for siting the unit.

(b)Is located in a quiet neighbourhood away from traffic noise.

(c)Building is positioned around the pool area with rooms above.

All of the above factors will determine whether the site is suited to a heat pump, they also set the available operating hours to achieve target temperature and consequently the energy input needed to heat the pool in the available time frame.

Good Points:

By far the most economical form of pool heating.

Price stable source of energy.
Clean on site operation.
No tanks to refill.
Minus Points:

Highest capital cost of any heating system.

Operating noise level.
Physical size.
More mechanical components than other types of heaters.

Considerations:

Correctly sized and located heat pumps are excellent pool heaters even though capital outlay is high, costing can usually be amortised over two to four years, by virtue of the available high energy efficiencies.

GAS BOILER SYSTEM (LPG):

They can be outdoor located or indoor with appropriate fluing. In certain indoor installations mechanical ventilating may be needed.

Energy Efficiency:

Generally, pool heater boiler efficiencies are around 50-80%. This means that (1) unit of energy put into the heater results with (0.5-0.8) units being input to the pool water.

Gas heaters are rated in mega joule/hour input (fuel energy consumption) and usually in kW output.

Operation:

These are a simple heater with a set of gas burners, surrounded by heat insulating material. Heat from the burners is directed up over a finned cupro nickel heat exchanger through which passes the pool water. The components are typically contained in a galvanized steel Colourbond enclosure, which also houses the necessary thermostat control systems and displays. Pool water flow across the heat exchanger is automatically modulated at the heater inlet header.

Good Points.

Relatively compact. Easy to site in tight locations

Physical size of heater does not appreciably alter for the model range across the energy output spectrum.
Silent in operation.
Relatively low capital outlay.
Can be economically upsized in specification to offer higher outputs.
Mechanically simple.

Minus Points .

Less stable price of energy. (Consistent with world oil pricing)

High operating costs as a product of existing energy pricing and heater efficiency.
Small quantities of carbon monoxide exhaust.
Hot to touch cabinet. Has shorter working life than heat pump and resistance heaters, especially in outdoor locations.
Requirement for bottle or tank placement on site and ongoing refill requirement.

Considerations:

Still the most used form of commercial pool heating, particularly up to 120.0 kW. Widely used on spas where a quick temperature recovery rate is of benefit.

Most popular in geographical areas with access to natural gas.

GAS HEAT EXCHANGE SYSTEM (LPG)

These are relatively new to the market in Queensland but have been fitted to a many commercial properties in Victoria and New South Wales for a few years now. There are number units installed in commercial properties on the Sunshine Coast.

Energy Efficiency:

These offer efficiencies of around 100%. Installed systems are proving to offer considerable savings on gas consumption over conventional pool LPG heating. Indications are that the running costs are approximately 40% less than those of conventional pool heating. These places the heat exchange systems are better placed to compete with Heat pumps for low operating costs (depending on the LPG price).

Operation:

This system works via a closed circuit of water being heated by a Bosch 32 ‘commercial’ instantaneous water heater and being circulated through a heat exchanger. This is then plumbed in line to circulate the pool water through the heater, which transfers the heat from this circuit to the pool water.

Good Points.

More economical form of pool heating than standard LPG boiler

Small footprint compared to heat pumps. Physical size allows fitting in tight locations
Silent in operation.
Mechanically simple.
Minus Points .

High capital cost.
Less stable price of energy. (Consistent with world oil pricing)
Very small amounts of carbon monoxide exhaust.
Requirement for bottle or tank placement on site and ongoing refill requirement.

ELECTRIC RESISTANCE HEATING:

Available in single or three phase power. Units over 6.0 kW are usually three phase.

Energy Efficiency

Resistance heaters have a theoretical efficiency of 100 %. This equates to (1) unit of energy put into the heater results in (1) unit of energy put into the pool water.

Resistance heaters are usually rated in Kilowatt output. (KW)

Operation:

A simple heater consisting of a plastic or stainless steel cylinder with a series of incoloy sheath elements immersed in the pool water that flows through the cylinder. Heat exchange takes place between the element surface and the pool water.

Only suitable for use within a weatherproof enclosure.

Good Points.

Very compact physical size for energy output.

Silent operation.
Clean on site operation.
Price stable energy source.
No tanks to refill.
Minus Points.

Expensive to operate on standard tariffs when compared to other forms of heating.

Elements are susceptible to attack from aggressive pool water and salt.
 

Considerations:

popular and economical form of single phase heating for installations calling for up to 6.0 kW capacity.

Also popular for larger pool and spa heating because of small physical size combined with energy output.
Suits installations where a gas heater cannot be flued because of building restrictions, or gas storage is unwanted / difficult.
Fits in where there is a preference for electricity, but a heat pump cannot be used.

CORROSION:

Heater corrosion in any aquatic location and especially on the Sunshine Coast is a matter of some concern.

Heat Pumps

Enclosure

You should expect an operational life of 10 years plus from a heat pump.

To achieve this, we insist that the heater enclosure be constructed of plastic, stainless steel or aluminum. It is uneconomic to replace an enclosure in service. A heat pump by virtue of its design operates in a damp condensate environment.

Evaporator

The evaporator coils are passing large volumes of corrosive air; coils are constructed of copper tube surrounded with aluminum fin stock. To maximize aluminum fin life, we insist that at a minimum the coils be double epoxy dipped at time of assembly .

Coils subjected to extremely harsh environments should be specified with copper fins.

Gas Heaters

You should expect an operational life of 5 years plus from an outdoor installation and

Somewhat longer from indoor. In service, we find that outdoor installations have the added problem of garden mulch build up around the base of the heater, which retains moisture and accelerates enclosure deterioration.

Most gas heaters have zinc anneal or galvanized steel enclosures and because of their operating temperatures are less susceptible to corrosion than heat pumps. Having said that, most gas heaters on the coast end their service life because of corroded enclosures.

Some manufacturers offer stainless steel enclosures, but taking into account the extra cost against the purchase price of a new heater we find fitment hard to justify.

Heat Exchange (All)

A heat exchange whatever their material make-up are susceptible to corrosion or plating from unbalanced pool water.

It is important for the longevity of the heat exchange that you ensure that the pool water is maintained in line with the recommended saturation index. Pool operators should seek the assistance of a pool shop professional to make the necessary pool water adjustments.

OPERATING COSTS:

There are so many variables to take into consideration, like size of the pool, location, projected bather load, the role the pool will play (commercial pool, hydrotherapy pool, swim school, domestic pool) all of which may have different outcome requirements. The use of a pool cover will also affect the operating costs. With the above information our staff at Billabong Pool Service and Supply can provide you with an accurate (depending upon the information provided) picture of the operating cost you could expect. There are also some very good on-line calculators available but are still reliant on the information provided.

Electric

Electricity pricing depends on best negotiation with the various electricity suppliers.Different Tariffs can be applied after operating times and heating outcomes are taken into account. Contractual pricing should be considered, but with caution.

Gas Heater

Gas pricing depends on best negotiation with the various gas suppliers. Volume users enjoy more attractive pricing and pricing varies between bottle and bulk supply. Contractual pricing should be considered, but with caution.

Billabong Pool Service & Supply Pty Ltd.

Billabong has a preferred product range, but we can supply most brands on request.

We recommend:

Accent Air / Rheem Heat Pumps.

Astral / Raypak LPG gas heaters.

Astral LPG heat exchanger systems

Elecro resistance electric heaters.

We are located at:

7 Kayleigh Drive, Maroochydore Phone 07 5443 2111

20 Rene Street, Noosaville Phone 07 5449 7855

134 Bulcock Street Caloundra Phone 07 5438 1577