Rinnai Tankless Water Heater Installation in Frisco, TX

Rinnai keeping a full non-condensing line alongside its condensing models is the reason the brand keeps coming up in retrofit conversations, and the reasonable next question is what you give up by taking one. The honest answer is that the efficiency gap is real and the money attached to it is far smaller than most people assume. A non-condensing gas tankless unit generally sits around 0.80 to 0.85 UEF. A condensing unit generally sits around 0.93 to 0.97. Thirteen percentage points sounds enormous until you multiply it by the amount of gas a household actually burns heating water.

The arithmetic is simple enough to do on the back of the quote. Raising a gallon of water by one degree Fahrenheit takes about 8.33 BTU. Frisco inlet water swings from roughly 80F in August to roughly 50F in January, so delivering water at 105F averages out near a 47F rise across the year, which is about 390 BTU of delivered heat per gallon. Multiply that by daily hot water use and by 365, then divide by the efficiency rating to get the gas actually consumed. A therm is 100,000 BTU.

At North Texas delivered gas rates that difference is somewhere in the region of ten to thirty dollars a year. Over a twenty-year service life it adds up to real money, and we are not arguing that efficiency does not matter. We are arguing that it is not the number that should decide the model class, because the venting difference on the same job routinely swings a thousand dollars or more in one direction or the other. Efficiency is a tiebreak. Venting is the decision.

Where the non-condensing Rinnai earns its place is a house that already has a usable vertical chase and no sensible sidewall route. Listed Category III stainless costs several times what plastic costs per foot, but a short run up an existing chase is a short run, and there is no condensate to drain, neutralise or route to a receptor that may not exist near the heater. Where the condensing unit wins is anywhere the vent has to travel: plastic is cheap by the foot, lighter to support, and the allowable equivalent lengths are generally far more generous.

Minimum activation flow

The lowest flow rate that will make the unit's flow sensor call for heat. On most residential gas tankless units it sits somewhere around 0.4 to 0.6 gallons per minute. Below that threshold the burner simply does not light, and the water arriving at the tap is whatever temperature the pipe happens to be.

This is the single most common source of the complaint that a new tankless unit gives lukewarm water at the bathroom sink. Nothing is broken. The tap is not open far enough. Current WaterSense lavatory aerators run at 1.5 gallons per minute or less, and plenty of them are 1.0 or 0.5, so a tap cracked a quarter turn for hand washing can genuinely sit below the activation threshold. On a storage tank this never came up, because the tank did not care how slowly you drew from it.

The related behaviour is turndown. A high-output unit can fire at close to 199,000 BTU per hour, but its minimum firing rate is nowhere near zero - typically somewhere in the low tens of thousands of BTU depending on the model. In August, when inlet water is already near 80F and you only want a 25F rise at a low flow, the unit can find itself unable to modulate low enough. It fires, overshoots, cuts out, waits, and fires again, which the user experiences as the temperature hunting up and down. It is a control-range limitation rather than a fault, and it is worse on oversized units, which is one of several reasons we do not simply specify the biggest model in the catalogue by default.

• Open the tap further rather than cracking it - most low-flow complaints resolve at the fixture
• Lower the setpoint in summer so the required rise is larger relative to the unit's minimum output
• Keep the inlet filter screen clean, because a partly blocked screen drops flow below the activation threshold at fixtures that used to work
• Consider a model with a small internal buffer if short, low-flow draws are the dominant use pattern
• Check the pressure reducing valve if flow has fallen off across the whole house rather than at one tap
• Do not fit an aerator smaller than the fixture needs purely to save water at a sink you use for thirty seconds a day

Rinnai supports manifolding multiple units into a single staged system, and it comes up more often in Frisco than it does nationally because of the size of the housing stock here. Work out your realistic simultaneous peak before deciding. A modern showerhead is about 1.8 gallons per minute, a kitchen tap about 1.5, a dishwasher under 1, and a freestanding tub filler can be 4 to 7 on its own. Two showers and a kitchen tap is roughly 5.1 gallons per minute, which a single high-output unit covers at a winter 55F rise with very little margin. Add a tub filler and you are asking for 9 or more, which no single residential unit produces at that rise.

The case for two units is not only capacity. Staged systems fire the second unit only when the first cannot carry the load, so most of the year each unit is running closer to the middle of its modulation range rather than pinned at maximum. You also get redundancy that a single appliance can never provide: if one module faults, the house still has hot water at reduced capacity, and you are not without hot water waiting for a part. Servicing is easier too, because one unit can be isolated and descaled while the other carries the household.

The costs are real and they are mostly outside the equipment. Two 199,000 BTU units is close to 400 cubic feet per hour of gas demand before you count the furnaces, the range and the dryer, which in most existing Frisco houses means a serious pipe upgrade and a conversation with the utility about meter capacity. You need either two listed vent terminations or a manufacturer-listed common vent assembly. You need wall space and service clearance for both cabinets. And every maintenance item doubles.

Frisco water runs roughly 8 to 11 grains per gallon, which puts annual descaling firmly in the required column rather than the optional one. If isolation valves were fitted at installation - and on our installations they always are - this is a job a reasonably practical homeowner can do without calling anyone. We would rather tell you that than have the flush skipped because it felt like it needed a plumber.

1. 1

   Shut down and isolate

   Turn the unit off at the controller, close the gas shutoff, then close both isolation valves so the unit is separated from the house plumbing. Leave the power on if the model requires it for the flush mode, otherwise switch it off at the receptacle.

2. 2

   Connect the hoses

   Washing machine hoses on the two service ports, one from the pump discharge to the cold port and one from the hot port back into the bucket. Open both hose bibs on the service valves.

3. 3

   Circulate the descaling solution

   Three to four gallons of ordinary white vinegar, or a descaler listed as safe for the appliance. Run the submersible pump for 45 to 60 minutes. Do not use hydrochloric or sulphamic mixes intended for boilers unless the manufacturer names them.

4. 4

   Rinse thoroughly

   Drain the solution, then open the cold isolation valve and let mains water push through to the hot service port for five to ten minutes until it runs clear and does not smell of vinegar.

5. 5

   Clean the inlet filter screen

   With the water still isolated, remove and rinse the cold inlet screen. This is the cheapest and most frequently skipped step in the whole procedure, and a clogged screen mimics half a dozen more expensive faults.

6. 6

   Check the condensate side

   On a condensing unit, confirm the condensate trap and drain run freely and inspect the neutraliser media. Spent media is a common cause of a condensate blockage fault a few months later.

7. 7

   Restore and verify

   Close the service ports, open both isolation valves, restore gas and power, then run a hot tap and confirm the unit fires and holds temperature.

A pump, bucket and hose kit costs well under two hundred dollars and lasts indefinitely, and the vinegar is a few dollars a year. If you do this yourself, keep a dated note of each flush, because manufacturers commonly make heat exchanger coverage conditional on documented maintenance and hard water damage is a routine exclusion. A photograph of the date on your phone is enough.

What a service visit adds beyond the flush is the part you cannot do with a bucket: inlet gas pressure measured under full fire, a combustion check, burner and flame rod inspection, a read of the stored fault history, and a look at the vent terminal for nesting and debris. If the unit is behaving perfectly and you are flushing on schedule, an annual professional visit is a sensible habit rather than an urgent one. Call us on (972) 430-9024 if you want the flush done for you, and equally if you just want to be talked through doing it yourself.

Every major manufacturer builds freeze protection into indoor and outdoor tankless units, and on essentially all of them it is electric - resistance heaters and, on some models, burner cycling. That means it protects the unit only while the unit has power. February 2021 established that a hard freeze and an extended outage can happen together in this part of Texas, and a tankless unit with no electricity in a 15F garage is an unprotected assembly of small-diameter water passages.

1. 1

   Before a forecast hard freeze, insulate first

   The exposed water piping to and from the unit freezes before the unit does. Pipe insulation on the inlet, outlet and any recirculation return costs very little and solves the most common failure point.

2. 2

   If an extended outage is likely, drain the unit

   Close the cold isolation valve, open a hot tap in the house to break the vacuum, then open both service port bibs and remove the unit's drain plugs so the exchanger empties. Leave everything open until power returns.

3. 3

   Do not rely on a dripping tap

   Leaving a fixture trickling protects the pipe run to that fixture. It does not necessarily move water through the heat exchanger, and on a unit below activation flow it certainly does not warm it.

4. 4

   Refill deliberately

   Close the drains, open the cold valve, purge air through a hot tap until flow is steady, then restore power and gas. Firing a unit with air in the exchanger is how people turn a freeze scare into a repair.

On warranty generally, we would rather set expectations than quote figures we cannot stand behind. The common structure across the category is a longer term on the heat exchanger than on other parts, a shorter term again on labour if labour is covered at all, reduced terms when a residential unit is put into a commercial application, and conditions attached to professional installation, product registration and documented annual maintenance. Terms change between model generations and between regions. Confirm the specific terms against the current manufacturer documentation for the model you are actually buying rather than trusting any web page, including this one.

What we do control is the paperwork on our side. We register the unit in your name with the correct installation date, leave the installation and operation manuals with the equipment rather than in a van, and note the model, serial and install date on your invoice so that a warranty claim years from now is a five minute phone call rather than an archaeology project.