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Old 04-22-2012, 10:10 AM   #1
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Need Advice about Tankless water heater

HI Everyone,
Few weeks ago i bought a Jayco GreyHawk with a tankless heater, every time i want to take a shower the water is cold 80% of the time and hot the other 20%. It seems to be impossible to adjust, i took the MH to the dealer and i was told it functions fine! !!...but it really doesn't....does anyone have this problem? any suggestion? are tankless heaters a piece of junk? thanks in advance.

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Old 04-22-2012, 11:29 AM   #2
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Well? If I had a tankless water heater and it worked part time or sometime I would dig out the owners manual and start there. I f no possitive results I would contact the maker of said WH and get some advice/guidiencefrom them if possible.... After that I would be looking for a replacement preferable a 10 gal. Elec/Gas one....
Best of luck with your tankless WH...... Great idea if it works, never ending hot water..

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Old 04-22-2012, 03:08 PM   #3
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Sounds like a flow rate issue to me.. Tankless water heaters are started by a flow switch (like a sail switch on a RV furnace) when water flows the switch closes.

If the flow rate is "on the border" the switch may not be closing.

NOW: over time lime and other minerals may build up on the switch and cause it to need more flow to activate. Or other things can cause it to become less senistive. This is easily fixed, Locate the switch, remove and clean . Reinstall, or replace.
Home is where I park it!
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Old 04-23-2012, 04:08 AM   #4
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The tankless water heaters Jaycoi has been installing are Girards. The Girards have been popular for installation by RV manufacturers because they are less expensive than any others. While they do work well when set up and used properly (I've seen one in operation), to keep the price down, Girard used minimal control valving and circuitry. Because of that, they operate differently than other water heaters, tankless or otherwise.

To control water temperature at the point of use, one does not blend hot and cold water as one would do with other water heaters (the symptoms the OP described can be caused by trying to blend hot and cold water). Instead, one controls the temperature by varying the flow rate of the hot water, using the hot water valve only (the cold water valve stays off). The slower the water flows, the hotter the temperature. The faster it flows, the lower the temperature.

As wa8xym pointed out, flow rate is critical. A certain amount of water has to be flowing to just to get the water heater to fire up. If the maximum water flow is too slow, then the water will always be too hot. When I attended the seminar Girard did at an RV show I was at about a year ago, the Girard rep mentioned that modifications to the RV's water system often has to be made. Many shower heads have flow restrictors that will prevent an adequate flow of water to enable full temperature control. Shower mixing valves sometimes will restrict water flow. Sometimes pumps have to be upgrade to one that puts out more volume. Water filters and pressure regulators reduce water flow enough to cause problems.

Because water temperature is dependent on water flow, a drop in water pressure while using will cause the temperature to rise. Turning on a hot water faucet while someone is showering will cause a temperature drop in the shower. Turning on a cold water faucet or flushing a toilet while someone is showering will cause an increase in water temperature in the shower. If incoming water pressure drops because a neighbor starts using water in a park with inadequate pluming, that could cause a sudden increase temperature.

There are five propane fired tankless water heaters approved for use on RVs available. Only the Girard has the minimal valving and controls. While it does work, it is sensitive to operating conditions and its operation is not intuitive. The other four (two by Awood and two by Precision Temp) have more sophisticated controls and valving that permits them to be controlled the same way a conventional water heater is controlled. The Atwoods are too new to have a track record yet but the Precision Temp RV 500 has a reasonably good track record (they have a new model that was just released that doesn't have to be installed on an exterior wall because it vents throgh the floor; it's also too new to have a track record yet).
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Old 04-23-2012, 05:50 AM   #5
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We just installed a new Rinnai Tankless system at our stick house. I read the complete manual. The system allows you to set the temperature of your hot water. Mine is set at 125 by the installer. A section of the manual said that if I had problems getting hot water to the destination, it might help to lower the temperature that I was calling for to match the temperature that I wanted at the destination. The theory would be that I would be mixing LESS cold water at the destination and keeping the flow rate from my tankless system higher. So, they did say that a problem could exist with the flow rate not activating the heater, but the way to fix it is to adjust the heater to a lower temperature.

Hope this makes sense and that it may help you.

Pat and Judy, Molly and Emma
2000 Monaco Dynasty-1999 Sebring Convertible
Winter S/W Florida....Summer Eastern Tennessee
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heater, water

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