CI Boiler & Indirect DHW & Summertime??

Cyclist77

What would be the lowest boiler temperature I could run based on the above?

Thanks!

hot_rod

What size boiler? How much got water do you want?

HeatFlo and others have high output tanks. HeatFlo shows boiler SWT at various temperature. Boiler supply at 150, for example here. This would give you a 130 return to the boiler to stay above condensing temperature.

The more of faster you want hot water, the more boiler power you need.

With a 120 combi you could get 2- 2-1/2 gpm continuously, if that type of dhw use is what you have in mind.

Also, any boiler could have a plate HX added and make a high performance DHW machine, like EK does.

A mod con boiler with a properly sized HX could produce DHW and condense for 90% efficiencies. A cast iron running 180 will be more like 85%.

But not many folks know how much hot water they actually use. Or need :)

Screenshot 2025-01-15 at 10.25.16 AM.png

Cyclist77

Boiler in mind is a Weil-McClain CGI 5. Just 2 of us in the house at this time.

hot_rod

so about 80,000 output to use. Unless you are at high altitude?

Did you run a heatload on your place?

Probably a 40 or 50 gallon indirect if you want to use the boiler

If you have the right space, a HPWH might be workable for a 2 petson household. Possibly less upfront cost, check for incentives. Probably less to operate depending on fuel cost. Shut the boiler off for 6 months maybe?

Go here to compare operating cost

https://coalpail.com/fuel-comparison-calculator-home-heating

hot_rod

here for rebate program

https://www.dsireusa.org

Cyclist77

My current coal boiler from talking with other is a net of 75k output. Revise the Weil-McClain to a CGa 4.

My current setup with indirect dhw works for us.

I'm back to looking at the "simple " non technical approach!