Adding A Heater To An Existing Pool
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Before we can even start to answer this question first I should answer the question "can you add a heater to an existing pool?" and the answer is yes. It is absolutely possible to add a heater to an existing swimming pool. In fact there are likely a few different heater options available to you and it will come down to how much heat you need, how much you want to spend for the installation of this heater, and then of course how much this heater will cost you to operate day to day. I should also add in a very important point that you should be asking if you want to add a heater to an existing pool and that is whether the new heater will meet your expectations of function.
There are different kinds of pool heaters and each of them will perform differently. Natural gas and propane heaters output the highest amount of BTU's while electric heat pumps output typically less, perhaps one third or so the BTU's of gas heaters, but they potentially provide more efficiency with this low-and-slow approach to pool water heating. Of course there are also solar pool heaters which utilize the sun for a free heat source. This form of pool heating is the lowest BTU output (depending on the size / square footage of solar collectors you use) but it does cost the least to operate day to day. The conventional logic for pool heaters is that gas heating provides heat any time of year, but at great expense. Electric heat pumps cost less to run, but lack the power to heat enough during the cooler shoulder seasons. The same goes for solar heaters. So gas heating for extending your swimming season to colder months of the year, and electric heat pumps / solar heaters for improving the regular in-season water temperatures. At most extending into the fall a little but typically not enough to heat the water early in the year when the pool is so cold.
Adding a gas heater to an existing pool - When you add a natural gas heater to a swimming pool you should have your gas meter inspected by the local utility to see if it can accommodate the large demands of a new gas fired heater. At 150,000 BTU ranging up to 400,000 BTU a large pool heater will burn as much fuel as 10 family sized BBQ's all running on maximum temperature at the same time. This means that gas line sizing and gas meter sizing are critically important to a successful heater installation. Of particular note is that you want to locate the pool heater close to the gas meter. It is expensive to have gas lines run and the closer you can get the heater to the gas service the better. If you have to run the plumbing from the location where the pump and filter are to another location for the pool heater I would definitely consider doing this. Ideally the pump, filter and heater will all be installed on the same equipment pad, but since a heater needs so much clearance room around it you might not have enough room on your equipment pad since you are adding this new heater to an existing pool installation. In addition to spacing requirements directly around the heater you will also have venting requirements. This means that pool heaters can not be placed below, next to or even near windows or doors which could allow harmful fumes into the home. Check with your local code requirements for the heater installation specifications in your area, but for now be aware your heater can not be located near or under a window. This often limits the options for where you can install a heater, especially on an existing swimming pool. If you want to add propane heating be aware that the massive fuel consumption of these heaters necessitates the use of large propane cylinders. Usually you would have a large, permanent tank installation for propane heaters. Your local propane utility can provide an estimate for locating one of these tanks for your new pool heater.
Adding an electric heat pump to an existing pool - Electric heat pumps represent one of the most efficient ways to heat swimming pool water, though your mileage may vary depending on where you live as the climate of your area and cost for your electrical service will determine whether your pool is suitable for an electric heat pump or not. Supposing it is, the biggest concerns when installing a new electric heat pump on an existing pool are the availability of electricity in the main electrical panel of your home, the cost of installing the electrical service to the heat pump, the cost of the heat pump itself (they are more expensive than other types of heaters) and how much it will cost you to run since heat pumps need to run for long hours to heat the pool with this low and slow approach. From an installation perspective it is important to note that a heat pump performs best when it has long hours of direct sunlight exposure and room to breathe on all sides. Additionally electric heat pumps can sweat up to 5 gallons of water per hour! That is a ton of condensation that you need to account for with adequate drainage when you install an electric heat pump on an existing pool system. You probably do not have the drainage you need, nor the room or direct sunlight access on your existing equipment pad, unless you are very lucky, so again it is not uncommon to have the heat pump located remotely from the pump and filter location, such as to limit the length of the (large) electrical service these units require. Be sure to double check your existing electrical service can accommodate another 40A to 60A as this is how much a typical residential electric heat pump requires for the electrical service. It is not uncommon to need to upgrade the main service and main electrical panel for your house to allow enough amperage for a new heat pump.
Adding a solar heater to an existing pool - If this is a ground level solar heater installation then there is little in the way of concerns other than if you have the space needed to install enough square footage of solar collectors. In general you should have half the square footage of your pool in solar collector grids for optimal performance. It is when solar collectors are installed on the roof that you need to be more concerned with your pump and whether it will be able to deliver water to the roof or not. The solar collectors themselves add resistance to flow to a system. If you put them on the roof this will cause some pumps to operate far from their best efficiency point, and some medium head pumps might lack the power to lift to the solar at all. Commonly a high head pump is used for pools that include a solar lift. Look up the performance curve for your existing pool pump to see what it performs like when there is higher resistance to flow. A regular inground pool might be 30' to 50' of head (resistance to flow) but a pool with a solar lift might be 70' or 80' or more. Some pumps will fail to operate with this much resistance to flow. If you oversize the pump to account for this then you can also risk moving too much water or overdriving your pool filter when the solar lift is bypassed. Sizing of pumps and filters for solar heaters is one of the most challenging aspects of adding a solar heater to an existing pool since the original equipment was selected before this additional resistance to flow was added to the system.
Adding an electric heater to an existing pool - Electric element style of water heaters, like you would find in an electric kettle for example, are rarely used in swimming pool installations. This is due to electric element style heating being inefficient when compared to the other options, but also because the amount of heat BTU output of these heaters is very low. Or perhaps more accurately they BTU output is low based on the availability of input voltage / current. You will see electric element style heaters on commercial applications more commonly, where 600 Volt systems and unlimited current potential are available. In residential applications it is usually only spas and hot tubs, and the smallest of swimming pools which can use electric element style heaters. If you want to explore electric element style heating be sure to look into Coates Heaters as they are the gold standard for electric element style heating for pools and spas: www.CoatesHeater.com.
It is cost most commonly that limits you from adding a pool heater to an existing pool, but if you want to swim in warmer water and you have the money to spend then almost certainly you can add one (or more) of these pool heaters to your existing pool system. Even if it means remotely locating the heater from the pump and filter equipment pad, this can often help to limit or reduce the installation costs of running gas and electrical services to your existing equipment location, as well as help to satisfy safety and code requirements for clearances etc. with your new heater installation. For information about heater sizing for pools you can read this article: What size of pool heater do I need?
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Swimming Pool Steve is an award winning, second generation swimming pool specialist from Ontario Canada and one of the most trusted voices in the swimming pool industry. With over 20,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the Pleatco Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print. Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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