[latestgood]

I redid the plumbing and installed a new tankless water heater. The problem is hot water only kicks in if two faucets (shower/sink) are on. Also if both facuets for hot water are open about 20%, no hot water. There needs to be about one full facuet and 25% of second facuet to be on for hot water. If only one facuet is used, no hot water... And it looks like it's not related to cross over. Certain amount of water that needs to be used for a tankless to activate.

Could someone come with a couple of hypothesis for my problem? I'm stumped.

 

[jmon]

It's brand new, call rheem directly and ask them what the problem could be.

Looks ok. I would of used service valves for easier maintenance in the future and installed a pressure only relief valve with an air gap. But that wouldn't have anything to do with your problem just an observation.

Hope you get it figured out and working right soon lastestgood. Stand by others will be along soon with other suggestions.

 

[JLawrence08648]

Rheem is great for their customer service and warranty. I've diagnosed and fixed electric tankless hot water heaters so I can only apply my knowledge from those. With those, there's two sensors, one in the beginning for the incoming water temperature and one at the end for how hot the water is. Could be those, could be the circuit board. Did you install it yourself? Do you have a multi meter?