Posted by Harold Kestenholz - Hydronic Network on June 07, 2001 at 10:06:55:
In Reply to: american standard boiler M#wo451 posted by paul donovan on June 07, 2001 at 08:10:23:
To get the maximum amount of hot water from an oil-fired boiler with a tankless coil, set the high limit to 220F, the low limit to 180F with the differential to 20F. These is the old-time settings; they can be dangerous as water temperatures leaving the coil can be over 200F on starting flow and can remain over 160F.
A tempering valve to reduce the possibility of scalds on the domestic how water line is highly recommended, if not mandatory. The tempering/mixing valve will also mix in cold water with the outgoing hot water to make even more hot, sub<130F water. 3 gpm can then become 5 gpm. The mixing valve also means you can leave the settings the same year-round. Get the mixing valve checked, cleaned, and serviced along with the yearly cleanup.
Some hot water tank engineers are so angry with the high possibility of scalds that a tankless coil boiler can produce that they close down schools that even mention how they work or what they were set at in the past. Changing to a heat exchange tank that contains 30 or 40 gallons of 120F hot water is far safer.
To examine the difference between these two methods of providing hot water, visit the free lessons at http://www.hydronic.net