ASHRAE Journal - January 2021 - 58

COLUMN SOLVING PROBLEMS

secondary application, and some can handle variable
primary application. But they are not all able to do both.
6. The need to provide boiler room ventilation to remove
heat even if the boilers are low temperature direct vented.
7. Vendors will sometimes try and steer your design
down a path that puts their competitor at a disadvantage.
8. Condensing boilers need condensate neutralizers
and a means of occasionally ﬂushing the drain line with
primer water.
9. Regulate the incoming gas pressure right at the
boiler to maintain steady gas pressure.
10. Understand when boiler ﬂue vents can or cannot
be combined, and the four types of vents.
11. Understand the whole HVAC system and how each
element in the building mechanical system should be
considered to meet thermal comfort requirements.
12. Some hot water coil selection software can allow the
designer to lock in the existing coil conﬁguration to run
" what if " scenarios when considering using different
entering water conditions on existing systems.

ASHRAE eLearning
The Complete HVAC&R Learning Experience

Save Travel Costs * Learn When Convenient
Access When Needed * Track Performance
CORPORATE PROGRAMS AVAILABLE

For the complete course catalog visit
ashrae.org/elearning
or contact elearning@ashrae.org

58

ASHRAE JOURNAL

ashrae.org

JAN UARY 2021

13. It can be easy to forget that not all boilers have the
same cost. Not every car owner needs a Cadillac, and
not every facility needs a top-of-the-line boiler.
14. Not all boiler types are piped the same. Learn
how to pipe and lay out the different types of
low-mass, high-mass, and condensing boilers.
The manufacturer's installation, operation and
maintenance (IOM) manual should always be reviewed
by the designer.
15. Most boilers have minimum ﬂow limits to satisfy
ﬂow switch safeties and leaving water high limit
temperature safeties. These are designed by the
manufacturer to protect the boiler from damage. If
ﬂow drops below these thresholds, the boiler will trip
out on low ﬂow or high temperature.

What Are Some Resources Designers Should Use to Correctly Select and
Size Boilers?
1. 2020 ASHRAE Handbook-HVAC Systems and Equipment.
Chapter 32, " Boilers. "
2. Basis of design boiler installation, operation and
maintenance manual from the manufacturer.
3. Peterson's July 2018 ASHRAE Journal " Engineer's
Notebook " column, " Design Tips to Avoid Boiler ShortCycling. "
4. Osman and Lane's September 2020 ASHRAE Journal
article, " Five Design Factors to Help Optimize a Boiler
Plant. "

Is There Anything Else You Think Design Engineers Need to Know About
This Topic?
1. Realize that many heating hot water systems can
spend considerable time operating below 20% load, and
select and size boilers accordingly.
2. Improving boiler efﬁciency for gas-ﬁred boilers is
great, but it still consumes fossil fuel. As some states move
toward decarbonization, alternative heating strategies
should be evaluated where decarbonization is a priority.
3. Work with the start-up technician during start-up to
ensure the proportional-integral-derivative (PID) loop is
tuned to not cause rapid cycling or hunting of the boiler.
4. If glycol is required in the heating hot water system,
it impacts most heat transfer devices,
pumps and the expansion tank size.
5. Remember to review your local
codes for boiler room ﬁre rating and
https://bit.ly/3khhdC5
Rate this Column
exiting requirements.
http://www.ashrae.org/elearning https://www.bit.ly/3khhdC5 https://www.ashrae.org/
ASHRAE Journal - January 2021

Table of Contents for the Digital Edition of ASHRAE Journal - January 2021
