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The HVAC company I work for as a service manager is transitioning into plumbing as well and while i am competent in boiler service and troubleshooting, I am not at all well versed in design and install of steam or hot water. It looks like we are going to possibly get on board with Rheem and install their tankless heaters for most of our water heater replacements.
With being the service manager, and concentrating mainly on service, this isn't a very big transition due to service and troubleshooting not being very much different than any other gas fired appliance, but I do a lot of replacement quotes and engineering when a system is determined to be too costly of a repair.
I have done quite a bit of reading on tankless heaters and I am a little worried about the average water temp here in my area vs the temp rise I am seeing on some of these spec sheets from Rheem.
From what I can tell, unless operating at a VERY LOW gpm flow, I'll at best be providing 100 degree water to my customers! Average water temp here is 45-55 degrees and a typical residence for one of our homeowners considering tankless would be a 3 bed 2 bath home. Assuming a washing machine and shower only running in tandem, you get well above 5gpm and the temp rise drops off to 40-45 degree!
Are we required in this situation to run two tankless heaters in series? Or add an electric booster at the hot water outlet with a relay to energize when the burners fire?
Looking for any input from the guys who install a lot of these... seems to me like a nightmare from a liability standpoint.