Solar Water Heater and Tankless

One of our readers is working on installing a domestic solar hot water heater in conjunction with a tankless.  They were going to go with a Rheem tankless to offset any additinonal temperature increase that was needed over the solar gains.  Unfortunately they found out that the particular unit that they were planning on using senses the incoming water temperature, buy ‘ignores’ water that is within 40F of the target temp (ie. the unit won’t cut on to work). This has caused them some problems because:

1) The max output on any residential line is 120F (49C) (this is canadian law it cant be any hotter than this in a residential home).
2) If the solar heated water comes in at 100F (37C) or warmer, the unit will not kick on. This means the output is 37C, a cold shower to be sure.
3) If you go to the commerical unit, the max temp is 180F. This much too hot for residential use (think of someone turning on the hot water at the sink to do dishes), but it would work from the 40F differential standpoint (ie. if the water is 60C or colder, then the unit will fire, anything warmer than 60C doesn’t matter as it would be warm enough for a shower).  Again this is illegal in Canada as the Max allowed Temperature is 120F.

The best solution is to more to a Rinnai Tankless water heater as this unit only requires there to be a 20 degree farenheight differentiation between water to be heated and heated water.  Therfor your shower will at the very least be 100 degrees farenheight which is plenty warm enough.

These co-heating water heating systems are quite complicated so its important that you talk to a prefessional regarding any plans that you have for your home or cottage.  Feel free to send us an email if you have any questions.

Related posts:

1. Solar and a Tankless
2. Environmental Water Heater
3. Heating Water with a Tankless in Ontario

Follow this company back and it is basically leads you to the founder of the modern day water heater “Edwin Ruud”. There is definitely a lot of history here and the company has several locations throughout the world. Rheem is the largest manufacturer of water heating units in North America. Rheem has a number of residential tankless hot water units to suit the various home water demands

Rheem RTG2-42

This system is rated at 4.2 gallons with a 45 degree Fahrenheit temperature rise, it would best suited for smaller applications. Rheem suggests that this tankless be installed in homes with only one bathroom.

View Specifications Sheet – Click HERE

Rheem RTG-53 Series

There are 3 tankless systems in the 53 series but they’re all able to provide the same amount of hot water. Should you have a 45 Fahrenheit temperature rise this tankless would provide 5.3 gallons of hot water per minute. The difference in the three systems is the way they are vented; indoor direct vent, outdoor, and indoor power vent.

View Specifications Sheet – Click HERE

Rheem RTG-66 Series

There are 2 tankless systems in the 66 series, you can select either an outdoor model or the indoor direct vent. This tankless hot water heater is able to provide 6.6 gallons per minute at the standard 45 degree Fahrenheit temperature rise. This a new tankless series introduced by Rheem, they recommend these units for 2-3 bathroom homes.

View Specifications Sheet for the Rheem RTG-66 tankless – Click HERE

Rheem RTGL-74 Series

This series of tankless water heaters is recommended for homes with three plus bathrooms. There are 3 different venting options and thus 3 different models. The 74 series tankless can provide 7.4 gallons per minute of hot water with the 45 degree Fahrenheit temperature rise.

View Specifications Sheet for the Rheem RTGL-74 tankless – Click HERE

Notes

All of the aforementioned models can be equipped with up to 3 remote temperature controllers enabling you to change water temperature from any room.
These units are also expandable; Rheem offers what they call an easy link cable enabling two units to be connected together doubling the amount of hot water produced.

Rheem also has several commercial Tankless water heaters but that’s for another post.

Related posts:

1. Navien Tankless Water Tank
2. The Tankless Hot Water Myth
3. Commercial Applications of Tankless Water Heaters