Hot Water Reset ON Weil LGB-10W Possible?

Norbert

Folks:
I am the controls contractor, I have an engineer that wants to do hot water reset based on outside air 125@70 and 200@0 degF OAT, with a simple loop, 2 pumps, 1 is standby, just hws and hwr with a dp control valve since rh coils use 2 way valves, pumping out to 15 reheat coils and 2 AHu coils.

He thinks this can be done by simply cycling the boiler, to maintain desired HWS temp. I don't think the LGB will like that.

I believe he needs to redesign into 2 loops and or use a 3 way valve.

Any suggestions?

hydronicsmike

Reset on LGB Boiler

Norbert,

The LGB Boiler is a standard cast iron Boiler and can therefore only be reset between 180°F and 140°F. If I am not mistaken, this boiler is a 2-stage Boiler and I would therefore recommend a tekmar 2-Stage Boiler Control 262. It will cycle the two stages within the boiler to maintain an Outdoor Reset Water Temperature between 140 and 180°F. This is achieved by cycling the boiler, which is standard procedure that increases your Comfort Level and reduces Fuel Consumption.

If you want to go below the Boiler Minimum Water Temperature of 140°F that the Boiler Manufacturer recommends, you'll have to use a Mixing Valve or Variable Speed Pump Injection. However, if the System is already piped, simply stop the reset at 140°F.

Then I would recommend a tekmar 132 Pump Sequencer for the 2 Pumps with one of them being in stand-by mode.

Please call, should you have any further questions or comments. I can be reached at 250-545-7749, Ext. 214.

www.tekmarcontrols.com

Best Regards,



Mike