Boiler Aquastat & Switching Relay Upgrade???

[BostonDan]

Hi - I was wondering if my old boiler can be modified to be more energy efficient by swapping out the Aquastat and Switching Relays with 'smarter' units.

Currently my system is an old Utica PGB150A Boiler that is controlled by a HoneyWell Aquastat type L8148J (*Zone 1*) paired with two Switching Relays, White Rodgers 829A-832(*Zone 2*) and Honeywell RA832(*Zone 3*).

Would swapping out the Aquastat and Swiching Relays with a 'smart' Aquastat and 'smart' Switching Relays make a noticeable difference in energy consumption? Aquastat & Switching Relay recommendations?

In advance, thanks….

 

[Dana]

Most boilers with aquastat controls can indeed be retrofitted with a heat purging economizer such as the Intellicon HW+ or Hydrostat 3200 or 3250, etc. The amount of savings depends a bit on your oversize factor, radiation size(per zone, if zoned), and operating temperatures.

The PGB150A has an output of about 115,000 BTU/hr which is enough boiler to heat my antique 2400' house io Worcester down to about -125F. It's probably more than 2x oversized, maybe more than 3x oversized for the heat load at your 99% outside design temperature. The 99% outside design temp for Boston near the water is +12F, but using +10F isn't insane if you're bordering the eastern 'burbs where there is slightly less local ocean water tempering.

On a single zone system that can emit the full ~115K, at 3x oversizing for the design heat it's as-used efficiency will be about 65-70% instead of about 75-80%, but a heat purging economizer control properly set up would bring it to within a few percent of it's steady-state efficiency, saving about 12-15%. If the house is broken up into multiple zones or doesn't have sufficient radiation to emit the full output of the boiler and 3x oversized for the whole-house load the savings can exceed 20%.

To get a handle on your oversize factor, if you have a few wintertime fuel bills with exact meter reading or fill-up dates it's possible to use the steady-state efficiency of the boiler and fuel used to infer the heat load at the 99% outside design temperature for your location. The methodology is explained in this bit of bloggery

Switching out the zone relays doesn't really buy you anything in efficiency, but if re-doing it putting it all on a single zone controller can simplify the wiring.

 

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[BostonDan]

Dana - This is exactly the type of information I was hoping for. - Thank you very much.