I had a Bosch Aqua star GWH 2400es-ng tankless water heater installed last May 2010 by an general contractor. I have already noticed a few issues. First off while in the shower the water will cycle between hot and cold, even when no other water source is used. It irritates me to have to fine tune this throughout my shower.

Secondly, when drawing water from the bath faucet it never gets as hot as the shower head. How can I correct this? I called Bosch tech support and was asked how high I had my heater set at (126 deg) and was told it was too high and they suggested setting to 118 deg, as bath water is normally 105 deg range. They explained that my system has been cycling because of this, as it's trying to reach that desired temp. I am not certain how it would cause it to cycle, but I did lower it to 118 deg. I have not seen any changes since turning it down. And while in the shower my water turned completely cold because the sink faucet was being used! Since my tankless water heater should support two major appliances I was very upset about this. I was told that this is d/t low water pressure, and that it needed to be 2 1/2 ppm.

How do I check my water pressure?

Also, while investigating this I performed another test to see if I had a plumbing crossover... and I do :( I have single faucet handles on both my downstairs sink & stand up shower and single faucet handles in my kitchen and upstairs bath. The only double faucet handle I have is the upstairs bath vanity. Would this be part of the issue?

Is fixing a plumbing crossover difficult? Expensive?

Please help!

Shan

Hi Shan...

You said, "I performed another test to see if i had a plumbing crossover...and I do"...

Please tell me how you know this as you did not say how this was made clear to you, OK? In fact, a defective mixing valve could be the whole problem you are having and not the Bosch system at all... maybe?

Back to you...

Mark

PS: To check pressure go to home depot or Lowe's and get a hose bib (also caled an outside faucet) pressure gauge and attach it to the outside faucet, turn the faucet on and that should give you an accurate pressure reading.

Attached Images

  

We turned off the cold cold water, and then turned on all the hot water faucets... waited 15 minutes... and there was still water flowing from the faucets. According to the Bosch manual this is a plumbing crossover and needs to be fixed to properly operate the unit.

I will purchase that water pressure measuring gauge. Thx for letting me know how to do this! If the water pressure is below 2 1/2 ppm how do I fix? Any further advice on fixing the existing crossover? I appreciate your help Mark :)

Shan

Mark,

Also, when measuring the water pressure am I supposed to crank the outside faucet as high as possible to get the best reading? And how would a reading of say 90 PSI convert to 2.5 PPM? Thanks

PPM stands for "parts per million" in my area... can't convert that to PSI so something is off there.

Before worrying about that, you need to determine which faucet or valve has the defective mixing cartridge. This is not an easy task because most shower valves can't be isolated so you may be better off bringing in a plumbing contractor in to work through this... ;)

Hope that helped some. I'm off for the night!

Mark

I am referring to pounds per min. Can this be converted using the PSI gauge? A plumber huh? That's what I was hoping to avoid :( do you know about the avg cost is to repair? Thx

We can convert PSI to Pascal, Kpa, Mpa, Bar, Torr, or Atmospheres, but Pounds per minute is related to time so doesn't work here.

You can convert gallons per minute to pounds per minute. Here, take a 5 gallon bucket and measure how many gallons come out for 1 minute and then look up how to convert that to PPM at GOOGLE. Otherwise, you call Bosch technical support back and ask them what they were talking about.

In terms of cost to get a plumber I wouldn't have clue here. Not only do I not know where you are from, but even if I did the pricing is still so different between plumbers that the best I can do is to tell you to get a few plumbers in and see what they offer. Choose the plumber that knows the most and you feel most comfortable working with... not the cheapest... ;)

Sorry I couldn't help more, but crossover issues with tankless and shower valves just isn't something to try over the internet.

Good luck!

OK! I appreciate the advice thanks. I know of a plumber, who I contacted recently about a boiler issue I'm also having. Need to have air bled out from ny gas boiler, the PSI gauge is not even detecting a reading and water as been gushing through my pipes loudly for a few weeks now. He quoted me $130 for the job. Said it would take about 2 hrs. I haven't called anyone else yet to compare prices. I will do that today. I live in central ny by the way :)

NY at 2 hours and $130.00 is very reasonable. See what he thinks about this issue.

Would love an update when you learn more, OK?

Thanks... Mark

Well that is good! I will keep you updated :)

I called that plumber. He can come next week to bleed the air out of the system. Although he said it shouldn't have air in it if it's sealed, which may indicate a leak somewhere. Then I told him about the PSI gauge being below zero so he suspects an issue with this. I forgot exactly what he called it, but something responsible for controlling water self-filling? As for the crossover he was not completely sure but suspects the water not being all the way closed at the main.

You never mentioned the pressure gauge being at 0 PSI... clearly this would be an issue with the air in the system and the system will need to be purged and filled with water.

Keep me posted...

Thanks!

Wow stupid me for not mentioning this, thought I did in my original post. Haha so yeah the PSI gauge is reading below zero! I just hope nothing needs to be replaced or become too expensive. I will keep you posted. Take care :)