indirect water temp to increase capacity

Jake2010

My homes heat loss is approx 50,000btu, and I have a 40 gallon Weil Mclean gold plus indirect.  If I size my boiler selection to the heat loss I may go with with something like the MPO 84 or Buderus 115ws/3 both at 74,000btu net.  I will want to increase the indirects capacity for our peak demand (2 adults, 3 children) by using a mixing valve.  What is an expected or recommended temperature that I might want to run the indirect.  The Buderus Logomatic has max temp for the indirect of 140deg. Should I plan on using a different control that will allow a higher indirect temp to have some flexibility?

Thanks in advance for any help.

furnacefigher15

What is

the current set up, and does it keep up?

bob eck

higher temp

if you are going with the Burnham MPO boiler you can give the indirect water heater priority. you could also check with WM and see how hot you can store the domestic water at. I believe the WM indirect was made by Triangle Tube and in their units you can store the water at 160* - 180* F but you must use a temp mixing valve to get supply temp to faucets down to 120*F. Also take a look at replacing old shower heads that flow at 2.5 GPM or higher. I have a Alsons 655C model in my house that flows at 1.6 GPM and I have two daughters with very long hair and they never complained to me that the shower does not put out enough hot water. When you reduce your water consumption your water and sewer bills will go down. Plus when using less hot water your cost to heat it will also go down. If you have your own private well and septic system using less hot water will make both of those systems last longer.

Jake2010

The boiler I have now

is a 47 year old american standard oil boiler that is 173,000 gross btu, net is 129,000btu, rated for a  1.7gph, I believe it has a 1.0gph nozzle on it now.  I have enough hot water now with my 40 gal WM indirect.

Jake2010

Indirect temp max

I believe the WM indirect says to not go any higher than 210deg, obviously pretty high.  I am wondering what a good target temp would be to best increase tank capacity without making it too inefficient through increased boiler demand and heat loss from the indirect. If the recommednation is above 140 deg I may have to look for a different controller other than the Logomatic.