A repost from "the epoxy floor guy".....
BTI
A few Pointers though. SPEND a extra few bucks and purchase a 'pump relay' it is simply a relay that you hook up to a t-stat to turn your pump on and off.
The beauty of a Seisco boiler is that it SELF REGULATES. It regulates the elements based on the temperature difference between the output and the input sensors. If the set point temp is 100 deg. and water coming in is 65 degrees it will probably run at 100% the output temp will not be 100 deg, maybe only 80. As the unit runs for a while it will gradually increase both the input and output temps.
GENERALLY they will only add 15-20 degrees. THIS IS OK. Lower than 10 degrees you have TOO high volume a pump, higher than 20, you may have a restriction slowing your flow. BOTH are not FATAL flaws. But will cause issues. Worst being restricted flow, this can be by loops being over 300 ft (for 1/2" pipe MAX, 250' recommended) This will cause 'cold spots'. If one loop has a much higher restriction than the others you will end up with little to no flow in that loop. To fix this you need to add needle valves to the other loops to increase the pressure in those to even out the flow.
A quick way to determine this is to using a temp gun or by hand determine which loops are the hottest. apply slightly more pressure, let unit run at least 15 mins, recheck.
WOW, I got way off. But you can use the seisco and run it continuously. The boiler will ONLY turn on when it detects a drop in temp. You will wear out pumps quickly though.
The systems I have installed use MOSTLY RA-14's I do have ONE RA-28.
** MONEY SAVING TIP. If you are not going to have to have this unit inspected, the ONLY difference between RA-14 and SH-14 is a HIGH TEMP overlimit switch in the first chamber. This is a lower limit for domestic hot water. They will never see 90 degree water at the input. The SH units have a 120 deg limit switch in stead of 90 degree I think. What happens is when the pump shuts off it takes less than 2-3 seconds for the unit to react.
sometimes the water stops DEAD the element is still firing at full blast and instantly heats up that pint of water in the chamber to above that limit switch. That's it. So swaping this out will save you upgrading. IF you are going to have to have your installation "inspected" the RA-14 is not "Rated" for space heating applications. The additional cost is to cover the 'testing and rating' process that Seisco had to go through to get the units rated for space heating. SO Pay the $7-10 for the HIGH LIMIT limit switch swap it out with the first limit switch in the unit and you have the SAME THING.
