[Shop-talk] Whole house tankless heater experience. Was: tankless/instant water heater

[Jim Stone]

Thanks, Dave.  That is an interesting way to put it.  I think I will time the heat and try contacting Rheem.  You never know.

> On Jan 28, 2022, at 8:13 AM, DAVID MASSEY <dave1massey at cs.com> wrote:
> 
> Jim, your plumber may have made that recommendation based on reliability and not necessarily on performance.  
> 
> A coworker of mine installed a tankless heater because he has a wife and two daughters who would regularly empty the 30 gallon tank when showering.  He noted that the heater would delay heating water to the point that the front-loading washer would never draw water long enough to get it to kick in.  My speculation is that the manufacturer programmed in a delay to confirm a good, solid hot water demand in pursuit of their energy rating.
> 
> 15 feet of 1/2 inch tubing will hold about .05 gallons of water.  Most shower heads deliver 1 GPM.  That means it should take about 3 seconds to purge the cold water out of the line.  OK, 6 seconds if you are drawing a mix of hot and cold.  Several minutes is probably the heater control.  Maybe the flow switch is not sensitive enough to detect the flow at that level.
> 
> Dave 
> 
> 
> 
> -----Original Message-----
> From: Jim Stone <1789alpine at gmail.com>
> To: Shop Talk <shop-talk at autox.team.net>
> Sent: Thu, Jan 27, 2022 8:30 pm
> Subject: [Shop-talk] Whole house tankless heater experience. Was: tankless/instant water heater
> 
> I held off answering Jimmie’s question below until the original topic seemed to have played out.  With that now apparently done, here is my experience with full house tankless heaters.
> 
> I have two tankless heaters, one in my garage - which has a small living area adjacent to it and two bedrooms and a bathroom above it - and one in my house.  Both are propane fired, as I live in a fairly rural area and natural gas isn’t available here. The garage unit is a combination DHW and hydronic heating unit (I have heated floors in the shop and downstairs living area) made by a company called Laars.  https://www.laars.com <https://www.laars.com/>. I have no complaints with that unit and love having heated floors in the garage.  (I ran the lines before the concrete was poured.)
> 
> My house is a very small (780 sq ft) ranch house and has a Rheem tankless unit (RTGH-900VLP-2) that was installed when the house was completely rebuilt (as in, new house built on the original foundation) three years ago. The shower is no more than 15ft from the heater, yet it takes several minutes to get hot water to the shower.  It was instantaneous when we had a conventional tank unit, but my community requires new construction to meet specific energy efficiency standards that required us to use a tankless unit.  I complained about the heat when the unit was new and an inspection revealed a faulty mixing valve, which was replaced under warranty.  I was still unhappy and Rheem told me how to bypass the preset maximum temperature of 120º and it is better with the unit set to 130º or 140º, but I have a hard time believing that should be necessary.  As I said, it took a separate small electric unit to be able to get fast heat to the kitchen and there is maybe 40’ of insulated PEX pipe between the heater and the sink. (The temp in the basement is generally around 60º.)
> 
> The Rheem unit was recommended by my plumber and is highly rated, so maybe my unit is just a lemon.  But, I spoke with a plumber before installing the 7.5 gallon unit for the sink and he told me he installs a lot of small ‘point of use’ tanked units in house with tankless heaters, so my complaint can’t be unique to my heater.  Overall, I like the fact that my house is very energy efficient, but I really miss the days when I could hop in the shower immediately and not have to worry about waiting for the water to warm up. 
> 
> Jim

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