Jandy JXiQ

The JXiQ is Jandy's newest gas pool heater, which Jandy calls the next generation of its compact JXi line. It comes in 200,000, 260,000 and 399,000 BTU, on natural gas or propane, in 16 model numbers once cupronickel and ASME versions are counted.

The 400 is 399,000 BTU/hr in every Jandy document: the brochure, the product page, and the rating label printed in the manual. The name rounds it up.

What the Q adds over the JXi is sensing. Jandy's list is a low gas pressure switch that stops the heater lighting on too little gas, a sensor that measures the temperature rise across the heat exchanger, auto-sensing 120 or 240 V power, a sacrificial anode, a larger display that estimates heat-up time, and Bluetooth diagnostics for service technicians.

Reading the model number

• 200, 260 or 400 is the size.
• N is natural gas, P propane.
• K is the standard heater, with VersaFlo and a poly header.
• NNK and PNK are the 400 with a cupronickel heat exchanger. Only the 400 comes that way in the standard range.
• C and S are the ASME versions of the 260 and 400, with bronze headers, copper or cupronickel respectively, and no VersaFlo.

So JXiQ400NK, the model this site shortlists, is the 399,000 BTU natural gas heater with a copper exchanger and VersaFlo.

Small, and what that saves

Jandy says the JXiQ fits on a 2 × 2 ft pad and is 38% lighter with a 28% smaller footprint than popular competitor models. The standard heaters weigh 117, 120 and 126 lb. The cabinet is the same for every size, about 22.9 × 22.1 × 26.5 inches.

The top panel lifts off and rotates 180°, which moves the water connections from the right side to the left. That matters on a crowded pad, but it also moves the service clearance: with the top reversed, the 18 inches normally needed in front is needed behind instead.

VersaFlo, and why it decides the warranty

VersaFlo is an integrated bypass. When the heater is not firing, a gate in the header sends most of the water around the heat exchanger instead of through it, which cuts the head loss through the heater. When it fires, the gate swings back. After the burner shuts off, the gate stays in the heat position for about a minute before bypassing again.

It also protects against freezing. With the heater control off but its power left on, the bypass senses the air, and as it approaches freezing the gate closes so water keeps circulating through the exchanger.

And it is what earns the long warranty. Jandy's five-year heat exchanger warranty applies only to non-ASME models with VersaFlo. The ASME models do not have it.

Flow, and the valve that shows you the water

The JXiQ takes 30 to 100 GPM. Above 100, a manual bypass valve goes between inlet and outlet, set and then left with its handle removed. In hard water, Jandy recommends 40 GPM or more to help prevent scale. Heater failure caused by insufficient flow is not covered by the warranty.

Inside, a thermal regulator valve balances how much of that water passes through the exchanger. Jandy treats it as a gauge of water chemistry: inspect it before every season, and replace it if it shows scale or corrosion, because either one means the water is out of balance.

The heater connects to 2-inch PVC or CPVC through Jandy unions, hand-tight, with no thread tape. The top inlet takes Jandy's Versa Plumb sweep elbow, which carries an exclusive interface for Jandy's AquaLink RS temperature sensor.

Gas supply is where installations go wrong

• Supply pressure, measured while the heater is firing, must be 4.0 to 10.5 in. WC on natural gas or 4.0 to 14.0 in. WC on propane.
• On a 400, the minimum natural gas line is 1 inch for up to 20 feet, 1¼ inch for 95 feet and 1½ inch for 215 feet of equivalent length, adding 3 feet for every elbow. A ¾ inch line is allowed only for the last 5 feet before the gas valve.
• A sediment trap is required, even with a flexible connector.

The low gas pressure switch will not let the heater fire on inadequate pressure, and shuts it down if pressure sags while firing. The manual notes that when the delivery system is the problem, utilities typically upgrade it at no charge.

Output is certified to 4,500 feet. Above that it falls about 4% for every 1,000 feet, but Jandy says its self-compensating combustion system means the heater does not need its rating reduced for altitude.

Where it can go

• 5 feet from the inside edge of the pool, unless a solid fence or wall separates them.
• 36 inches clear above for removing the top, 18 inches in front (24 in Canada), and 6 inches from any combustible surface. Never on carpet.
• Outdoors in an open area, with the top at least 3 feet below any overhang. Not under a deck unless it is installed as a direct-vent indoor heater.
• The vent top at least 4 feet horizontally from, 4 feet below, or 1 foot above any building opening, and 3 feet above any forced air inlet within 10 feet.
• It runs outdoors in air down to 40°F. To operate it in freezing conditions, Jandy says to put it in a protected shelter.
• Natural gas models are certified for indoor installation with the right venting; propane models are not recommended indoors.

Water chemistry, and the salt limit

Jandy's limits for a pool are pH 7.6 to 7.8, total alkalinity 80 to 120 ppm, calcium hardness 200 to 400 ppm, free chlorine 2 to 3 ppm and never above 5, and salt no higher than 4,500 ppm. Fiberglass pools get their own, lower pH and higher alkalinity targets.

Tablets in the skimmer are singled out: they send heavily chlorinated, low-pH water through the heater. Heat exchanger damage from corrosive water or calcium buildup is not covered.

Cold water

The manual's warning is specific. Do not run the heater with water below 40°F, and prolonged operation with water below 50°F can seriously damage it and is not covered by the warranty.

Winterizing

In freezing climates, a technician should shut off gas and power, remove the drain plug and outlet temperature sensor and drain the heater before the first frost, disconnect and drain the copper siphon loop to the water pressure switch, and cover the vent grill so snow cannot build up on the combustion chamber. In spring, the manual has a qualified technician put it back together.

When it shows a fault

A few of the codes, from the manual:

• CHECK H2O FLOW — usually the pump, a dirty filter, a closed valve or a variable-speed pump set too low, before it is the pressure switch.
• LOW GAS PRESSURE — the supply, before the switch.
• TEMP RISE HIGH — water flow too low, or the thermal regulator valve stuck closed.
• TEMP RISE LOW — flow too high, or soot on the heat exchanger.
• FLAME SIGNAL FAIL or WEAK — check the igniter's cold resistance, 30 to 800 ohms at 75°F.
• IGNITION CONTROL LOCKOUT — three failed ignitions in one call for heat. Cycling the breaker resets it.

Jandy recommends a qualified technician for all service and repairs.

Where Jandy's documents disagree

• Efficiency of the 200. The brochure gives the JXiQ200NK and JXiQ200PK 83%; the product page gives them 84%.
• The cupronickel 200. Jandy's product page lets you choose a cupronickel 200 and returns the model number JXIQ400NNK with a 200,000 BTU specification. The brochure lists cupronickel only on the 400.
• Cupronickel model numbers. The manual calls them JXiQ400NN and JXiQ400PN; the brochure and product page add a K.
• The water pressure switch. The manual's water system parts table gives R0457001; its electrical parts table gives R0013203 for a part with the same name.
• Rear clearance with the top reversed. The clearances section says the 18 in. service clearance moves to the rear; the note on the plumbing figure says 12 in.
• The warranty. Jandy's printed warranty names the JXi, not the JXiQ; the five-year heat exchanger promise for the JXiQ comes from its product page and brochure.

Buying one online means no warranty

Not a shorter warranty. None.

Jandy's limited warranty does not apply to Jandy branded products purchased through the internet or other e-commerce platforms, with exceptions only for valves under three inches, parts and accessories. A heater is none of those.

Bought from a dealer and installed by a licensed contractor, the JXiQ gets one year on the heater and, with VersaFlo on a non-ASME model, five years on the heat exchanger. Bought online, it gets neither. The Jandy brand page has the rest of the terms.