How to choose the right Hot Water Heating Control

In order to choose the appropriate hot water boiler heating control, there are several determining factors for R&D model selection:

Is the boiler a single or multi-stage boiler?

Model Series RD1431, 1432, 1433 can control up to three boilers, or a single boiler with a multi-stage burner or gas valve.  A boiler with two stages is commonly called a lo/hi fire boiler.  All RD1431 series models also  control the main circulating pump.  A relay turns off the main circulation pump when outdoor temperature exceeds the override setpoint, thus saving gas and electricity in mild weather along with pump wear.  Models RD1432, 33 are two and three stage controls and include auto boiler rotation to equalize boiler usage and reduce premature equipment failure.

The Model NR203 is similar toe the RD1430 series, but with the addition of some very useful features.  1) A 32-character LCD display containing information about each item displayed.  2) Room temperature data logging that allows the user to easily adjust setpoints for optimal fuel savings.  3) Optional modem access port.  4) Option to use room temperature measurements to automatically adjust the outdoor reset curve and optimize fuel savings 24 hrs. per day.

The day/night timer schedule on either model switches the boiler out of night setback (for example 5:30AM), and the boiler water temperature is elevated (boost) for 30 to 60 minutes. Boost temperature level varies according to outdoor temperature and the amount of the night setback. Computing the amount of boost based upon current conditions results in a perfect room temperature recovery, regardless of outdoor temperature and the amount of night setback.  Either model can utilize up to two indoor room temperature sensors for monitoring actual space temperatures.

Some boilers (consult your boiler manufacturer) are not safe to operate at boiler water temperatures below 140 deg. F.  If this is the case, both the NR203 and the RD1430 have a minimum water temperature setting preventing damage during mild weather.

When the number of boiler stages reaches 4, Model NR203 -4 will be required. Models CB200 -D4, -D8 operate up to eight on/off or four lo/hi/lo stages.  Models CB200 -B4, -B8 operate up to four full modulating boilers.  (See section for full modulation, staging and mixing valves for steam and hot water).

Does the building have thermostats and zone valves?

Most hot water heated buildings have a single main water loop, and multiple smaller loops that are controlled by thermostats. The main loop passes directly through the boiler or boilers, and the boiler water temperatures can be set as low as 100 deg. F. and as high as 200 deg. F.    Even if the zone thermostats are programmed for a night setback (most don’t have this capability), as much or even more fuel savings will occur by setting the boiler water temperature lower at night.

Does the boiler have modulating burners, 3-way mixing valves or heat exchangers?

See section on full modulating boilers and mixing valves.