Question about Rheem Paloma PTG-74XN / RTG-74XN Natural Gas Outdoor

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What can cause Hot/Cold spikes on an RTG74-XN

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Crossover, low hot water flow, low water pressure, sediment in water lines or heater, heat exchanger needs to be de-limed, water filter needs to be cleaned, water heater temperature set too high, incoming water temperature too high or too low depending on model, MUD or PUD districts with pressure spikes, dirty faucet aerators, loose wires, bad sensor, faulty PD-board, bad venting, dirty burner and combustion parts, etc.

Crossover
http://waterheatertimer.org/Crossover.html
Clean water filter monthly, de-lime tankless yearly
http://waterheatertimer.org/pdf/Tankless-maintenance.pdf
http://waterheatertimer.org/pdf/Rheem-De-lime-tankless.pdf
No error code:
http://waterheatertimer.org/pdf/No-Error-Code.pdf
Overcoming fluctuating temperatures:
http://waterheatertimer.org/pdf/Bosch_Overcoming_fluctuating_temps.pdf
Resources:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Posted on Sep 21, 2011

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Posted on Jan 02, 2017

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Why does my hot water go hot and cold on my gas hot water service


When water feels cold at tap, check water heater TP valve and drain valve to see if water is hot at top and bottom of heater
Maybe you have bad single-handle faucet cartridge
http://waterheatertimer.org/Crossover.html

Another possible cause is bad dip tube
http://waterheatertimer.org/Water-heater-dip-tube.html

Gene

Water Heater Timers Save Money

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Mar 14, 2015 | Water Water Heaters

1 Answer

T and p valve leaking and i replace it and pressure pushes out hot water


It sounds like it's doing it's job, by not letting your water heater turn into a missile, or exploding....The "T" in T&P stands for temperature. When it gets too high, the valve will open. The "P" in T&P stands for pressure. When IT gets too high, the valve will open. When they both get too high...you know the rest...The condition can be caused by many factors.
1. The house "pressure reducing valve" is letting in too much pressure. Any more than 80 lbs. is too much. 50 to 75 is good.
2. Hot water expansion in a closed loop system...no "prv" or "water meter" bypass...To fix, you can install a small "expansion tank" above the water heater. It will allow the extra bit of water to go somewhere temporarily, Letting the T&P valve stay closed. Installation is always on the hot outlet side, because high efficiency water heaters use a "check ball" in the factory installed cold water inlet nipple, which also doubles as a dip tube. (lets cold water into the heater at the bottom)
When a gas fired water heater turns on, there is a pretty fast spike in both temp. and press.
3. The gas control valve itself, has a non resetting 190 degree, "high limit" safety shut off feature. IF that were to fail, the control would run away temperature wise, but I have never heard of one failing.
regards!

Dec 06, 2014 | Rheem 40 Gallon FVR NATGAS Low WATER...

1 Answer

Sunbeam hot/cold water dispenser is leaking from looks like copper tubing that goes to tank. Model # ylr-5-87h3 what could my problem be


Broken solder connection.
Continual expansion and contraction of metal due to hot and cold extremes will cause metal fatigue. The most vulnerable place is at the join. Other places can fail, but usually the solder join will fail first.
Buy another one and support economy.
Make sure next unit is connected to cold water line, and not hot water line. If hot water dispenser is connected to Hot line, then it will cause water heater to run each time water is drawn through dispenser because cold water immediately enters tank.
http://waterheatertimer.org/Water-heater-dip-tube.html
http://waterheatertimer.org/How-to-install-under-counter-water-heater.html#h-c
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html#pot
You might also consider installing small tank under counter. Tanks are less glamorous than hot water dispensers but tanks are more reliable long term than instantaneous water heaters.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

May 28, 2013 | Water Heaters

1 Answer

On demand hot water heater gets cold for a short while during showers.


Check for crossover.
Bad single-handle faucet cartridge causes cold water to enter hot pipe, so hot never arrives and tankless does not run consistAntly
http://waterheatertimer.org/Crossover.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Apr 13, 2013 | Bosch AquaStar 2400ES-NG

1 Answer

My reliance natural gas water heater overheats causing scalding water to come out of my faucets. I have had authorized service companies come out three times to replace and retrofit different controls and...


Information below is for tank-type electric or gas heater only.

There is a condition called stacking.
This might apply to your water heater or not.
Having authorized service people to your house 3 times suggests more complicated mix of problems.

Stacking is caused when there are repeated short draws of hot water.
As you know, each time any hot water is drawn out of faucet, cold water immediately enters bottom of tank through the dip tube. The dip tube is connected to cold water inlet and runs to bottom of tank.
So all cold water enters bottom of tank close to the gas water heater thermostat.
See illustration of dip tube, that also shows copper thermostat sticking into tank that is connected to gas valve.
http://waterheatertimer.org/Clean-sediment-out-of-water-heater.html#flushelectric

Let's say your water heater if fully heated and burner is off.
A short draw of hot water causes cold water to enter tank.
Another short draw. And then another short draw, each draw happens close to same time as other draws.
Water at top of tank is plenty hot, but bursts of cold water get near thermostat and cause thermostat to turn on burner.
Burner heats water and more hot water rises to top of tank. Water at top of tank becomes overheated each time stacking occurs.

Again, a stacking situation may not be the cause of your problem.
However, remember if single-handled faucet is opened straight upward, then that draws both hot and cold water. And cold water immediately enters tank.
Only when the single-handled faucet is lifted with the handle all the way to the right, does it draw only cold water. Even so, some single-handled faucets have bleed-over between hot and cold sides, so hot water is drawn anyway.

Another possibility is that the dip tube ends at or near thermostat, instead of going all the way to bottom of tank. The dip tube should go straight down from cold water inlet, but dip tubes are made of plastic, and some self-cleaning tanks have a curved dip tube or dip tube with perforations that create currents designed to stir sediments off bottom of tank (although this is not proven to be effective deterrent to sediment formation).

Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Feb 10, 2011 | RELIANCE ELECTRIC WATER HEATER

1 Answer

I am trying to find out why the cold water line leading out of the WH unit is sometimes hot but no hot water coming out of the cold water faucets in the house and sometimes there is no Hot water in half...


Believe it or not one of the sink or shower fixtures is by-passing when closed.Gravity circulation in standby mode(not being used) is the cause.Trace the (warm )cold water pipe to the fixture after no one uses the water for a while.Good luck.

Sep 23, 2010 | Rheem 81VP6S/430126 Water Heater

1 Answer

I have a hot water circulator when i turn on the cold water hot water comes out for about 30 seconds before the cold water will come out. What could be causing this?


This is could be because the system is set up to use the cold water line as the return to the HWH.

Hot water recirculation systems generally consist of a pump, an integrated electronic controller, and a zone valve. When the activation button is pushed, or when another type of control turns the system on, the pump starts recirculating cooled water that's been sitting in the hot water line and sends it back to the water heater through the cold water line.

If you would like..Google "hot water re-circulation theory"...it further explains this senario.

HTH,
Mike....

Dec 01, 2009 | Rheem 40 Gallon FVR NATGAS Low WATER...

1 Answer

My thermostatic concealed shower valve only gives either boiling hot water or cold water, there is no inbetween temperature? the cold is fed from mains and the hot from a combi boiler. the plumber has said...


Hi,

If the hot and cold are fitted the wrong way round then the thermostat on the shower unit cannot operate properly!

Most thermostatic mixer showers have a 'bi-metallic' thermostat, if you supply the hot to the cold and vice versa IT WILL NOT WORK.

It is like wearing the left shoe on the right foot and the right on the left! It doesn't work.

Re-install the hot and cold to the correct supply, and this will sort it.

I hope this helps.

Jul 07, 2009 | Grohe Integrated 1/2'' Shower Thermostatic...

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