20929 Bridge Street, Southfield, MI 48033

20929 Bridge Street, Southfield, MI  48033
20929 Bridge Street, Southfield, MI 48033
4121 Brockton Drive SE, Grand Rapids, MI 49512
6200 Baron Drive, Bridgeport, MI 48722
6910 Treeline Drive, Suite A, Brecksville, OH 44141
Serving the industry since 1927
Phone: (800) 589-6120 - Fax: (248) 354-3710
www.deppmann.com
September 21, 2009 ~ Monday Morning Minutes:
Selecting Laars NeoTherm Condensing Boilers
Over the last several weeks we outlined the use of primary secondary systems for hydronic
heating systems. This article will address the selection of Laars NeoTherm condensing boilers.
The Laars boilers and water heaters are constant flow devices which mean a constant speed
primary pump must be installed. The flow rate required allows temperature rises between 20°F
and 35°F. Let’s look at a selection example. Assume we have 1,450,000 BTUH with a 180°F to
150°F temperature range for a 30°F ΔT . We want to use the Laars NeoTherm boiler which
combines condensing technology with modulating control. At 150°F and 100% firing rate the
efficiency shown on the chart below will be about 86.5% and we require 1,450,000/.865 =
1,677,000 BTUH input. Two NTHB-850s will do the job nicely since 850,000 X 2= 1,700,000
BTUH Output.
We have a 30°F ΔT so each boiler will require a primary pump of about 48.5 GPM. We arrive at
this by taking the BTUH output of 1,450,000 BTUH divided by (500 X 25°F ΔT) for a flow rate
of 97 GPM. The total system flow 97 GPM and each boiler in parallel will have ½ of the flow or
about 48 GPM. The piping schematic will look like the following:
Disclaimer: R. L. Deppmann and it’s affiliates can not be held liable for issues caused by use of the information on this page. While the information comes from many
years of experience and can be a valuable tool, it may not take into account special circumstances in your system and we therefore can not take responsibility for actions
that result from this information. Please feel free to contact us if you do have any questions.
20929 Bridge Street, Southfield, MI 48033
4121 Brockton Drive SE, Grand Rapids, MI 49512
6200 Baron Drive, Bridgeport, MI 48722
6910 Treeline Drive, Suite A, Brecksville, OH 44141
Serving the industry since 1927
Phone: (800) 589-6120 - Fax: (248) 354-3710
www.deppmann.com
This solution allows each boiler to see the cooler return water. As we reset the system in the spring and fall the return temperature
drops and we start to condense and gain efficiency. In addition the control package will modulate the boilers because the efficiency
goes up as we reduce the firing rate. The control will operate one boiler from 0 to 40% of load. After 40% our controller will stage on
both boilers at 20% and operate them together from 40% to 100% of load. Clearly from the figure above if we have, for example, 100
degree water returning and we are 50% load, the efficiency of each boiler at 25% load is 96%. If we operated only one boiler the
efficiency would be about 90%.
Selecting multiple boilers and operating them at part load provides the best efficiency with the Laars NeoTherm Boilers.
Thank you for using products sold by
R. L. Deppmann Company in Michigan and Ohio!
.
Disclaimer: R. L. Deppmann and it’s affiliates can not be held liable for issues caused by use of the information on this page. While the information comes from many
years of experience and can be a valuable tool, it may not take into account special circumstances in your system and we therefore can not take responsibility for actions
that result from this information. Please feel free to contact us if you do have any questions.
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