Engineers & Manufacturers of the Heatsponge Economizer


Hot Water Boiler Condensing Economizers

The HeatSponge SIDEKICK and RAINMAKER line of boiler economizers are a first-to-market product designed specifically to accomodate extremely high water flow rates typically encountered with hydronic boilers without excessive water side pressure drop issues. The signature feature of the SIDEKICK and RAINMAKER is the use of modular, pre-engineered ASME heat exchanger blocks that can be oriented to achieve the required heat transfer in an optimized package. Products such as these could not exist without the unmatched power of our proprietary BRUCE software. While both designs utilize full stainless steel internal construction and 316 stainless steel tubes, the SIDEKICK is our legacy design using stainless steel fins for applicatiosn where the unit will be exposed to oil firing exhaust. For natural gas only use we developed our RAINMAKER hydrid tube technology which incorporates a corrosion-resistant aluminum fin for astonishing performance allowing for a more compact and lower cost unit. Both units are supplied with the same standard warranty.

HeatSponge Efficiency-Match selection software

The proprietary HeatSponge Efficiency-Match software allows our customers to automtaically match a retrofit HeatSponge SIDEKICK or RAINMAKERto a new condensing boiler. Simply select the new condensing boiler you are considering and the existing boiler you wish to retrofit. The E-Match software will calculate the actual effciency of the condensing boiler at the actual return water temperature and water temperature rise based on performance curves published by the boiler manufacturer. Bruce will engineer a SIDEKICK or RAINMAKERto allow the retrofit boiler to match the efficiency of the new condensing boiler. A copy of the efficiency curve BRUCE bases the design on will be included with the proposal.

If the boiler you are considering is not on our list please contact us and we will add it promptly. If you need to manually select a SIDEKICK or RAINMAKERfor a project other than comparing to a condensing boiler at the bottom of the page simply turn the E-Match OFF and manually enter your required flue gas exit temperature and water flow rate.

Your Location

Existing Boiler Make
Select the existing boiler you will install the Sidekick on
Existing Boiler Capacity
This is the capacity of each of the boilers you will install the sidekick on
Number of Existing Boilers One Common Sidekick for all boilers
Individual Sidekicks for each boiler
for Comfort Heating Hot Water Boiler Sizing
Efficiency-Match ON
Efficiency-Match OFF.
If E-Match is turned off you must select a flue gas outlet temperature for the software to target. If left blank the mid-point of the flue gas and water inlet temperatures will be used. deg F
Condensing Boiler to Match
Select the model of the condensing boiler you want your existing boiler to Efficiency-Match. If not using E-Match leave alone.
Entering Water Temperature
If this unit is for a comfort heating hot water boiler application enter the return water temperature otherwise enter the water temperature to be used as basis of design.
Reset ScheduleOptional if using E-Match Reset ON
Reset OFF
Reset Temp 2
Reset Temp 3
Reset Temp 4
Water Flow Rate
If you leave this cell blank and set to GPM Bruce will automatically calculate the flow rate based a deg F temp rise. If set to PPM will calculate water flow as if it was a steam boiler.
Check to allow flow rate to track firing rate.
Current Boiler Supply & Return Temperature
required only if E-Match is ON
Current Supply

deg F - Supply water temperature of the current system.
Current Return

Return will be calculated on inputted supply temperature and temerature rise of system.

Firing Rate Load Condition 1
100 % Firing
Load Condition 2
% Firing
Load Condition 3
% Firing
Load Condition 4
% Firing
Flue Gas Temp Leaving Boiler/Entering Sidekick 100% Firing Required
Flue Gas Temp @ 100% Load is Only Required Entry - Part Load Temperatures are Automatically Calculated if Left Blank
Annual Hours @ Firing Rate
Excess Air % % % %
Flue Gas Recirculation Rate % FGR Taken Before Economizer
FGR Taken After Economizer
Construction Type
Sidekick & Rainmaker
RAINMAKER - 316 stainless steel w/ aluminum fins, 8 per inch, for natural gas only or include optional bypass for #2 oil use - highest performance / lowest price option

SIDEKICK - Legacy design 316 stainless steel with stainless steel fins, 5 per inch, for natural Gas w/ #2 Oil Standby and no gas bypass - NOTE! stainless steel fins could add up to 50% premium to price due to reuced performance fo stainless steel fins compaired to the aluminum used on Rainmakers

Stack Diameter in Leave 0 if diameter unknown
Draft Inducer Not required - use boiler fan to overcome pressure drop
Incorporate fan-assisted draft inducer. Supply by others.
Fuel Price dollars per million btu
Maximum Water Side Pressure Drop PSI
Water Specific Heat for glycol systems
Current Boiler Efficiency Override % - You can override Bruce's calculation of the current boiler efficiency Override OFF
Override ON
Maximum Unit Overall Length (not including piping connections) No length restriction - DEFAULT
3' 10" Overall Length
4' 4" Overall Length
4' 10" Overall Length
5' 4" Overall Length
6' 4" Overall Length
7' 4" Overall Length
8' 4" Overall Length

Only experienced boiler professionals should adjust the data below.

Manual Unit Selection / Bypass Bruce - For Experienced Boiler Technicians Only:
AutoPick ON
AutoPick OFF - Manual Selection below
Experienced boiler professionals may bypass Bruce's AutoPick software and manually select a maximum gas side pressure drop from the selection chart below. Just because a data page will be printed out means HeatSponge confirms that a manually selected unit will work on a given boiler. Excessive backpressure will seriously impact boiler operation.

This feature is also a very good way to compare the performance of a competitive unit to a HeatSponge. If you are comparing units and the competitive unit has a higher gas side pressure drop than our AutoPick selects use this feature to see how a HeatSponge would compare to the competitive selection. Some competitors will try to sell a smaller unit with an excessively high backpressure simply to offer a lower price.
Select Maximum Allowable Backpressure:

Flue Gas Mass Flow Calculation Override - For Experienced Boiler Technicians Only:
Experienced boiler professionals may custom select the flue gas mass or volumetric flow rate. You must both enter the flow rate and units to use as well as check the override checkbox.
Bypass checkbox required

Final unit selection could be affected by other operational constraints. HeatSponge reviews all selections for accuracy prior to placement of any purchase order.