#steam

Tech Tips:

With cold temperatures right around the corner, it is a good time to brush up on our steam now, and there's no better way to do that than by reading an article by Dan Holohan. This article was written by Dan Holohan and published at HeatingHelp.com HERE. It has been reposted here with permission. This […]

Boiler Basics Part 4 – Piping

Please note: There have been some legitimate questions about a few of the points in this article and the diagrams. While Justin Skinner is an experienced tech and totally qualified to write this article, we will be specifically looking into the question of the best location of the circulator pump and addressing the “point of […]

Boiler Basics Part 3 – Steam

This article was written by Senior Boiler Tech Justin Skinner. Thanks, Justin. Steam plays a very important part in all of our lives, whether we know it or not. Virtually every article of clothing and accessory you are wearing right now relied on steam for either manufacturing or packaging. Hospitals use large steam boilers for […]

Redux – The Lost Art of Steam Heating w/ Dan Holohan

In today's podcast, Bryan talks with legendary Hydronics author and trainer Dan Holohan about the history of steam heating and some practical applications of old ideas. Recently, Dan has been working on more novels, having published two of them over the past few months. Steam heating is a “lost art” nowadays; it has become […]

Pumping Away & More w/ Dan Holohan (Podcast)

Dan Holohan speaks to Bryan about his background and journey as a writer. He also dives into his book, Pumping Away, and describes classic hydronics as he does in his book. Bryan and Dan also briefly discuss the difference between search and research. Dan is a prolific writer, and one of his most famous works […]

How to Evacuate an AC system, Full Vacuum Procedure

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In this short podcast episode, Bryan talks about heat exchangers and temperature rise in gas furnaces, especially 80% open-combustion gas furnaces.

Temperature rise is the difference between the return air temperature and supply air temperature; in cooling, we usually refer to this difference as a delta T or temperature split. The manufacturer sets a target range on the data plate; high-efficiency furnaces tend to have lower temperature rise targets than mid-efficiency or older furnaces. We want to heat the space and not waste heat on surfaces (like duct surfaces). For that reason, the goal is to stay in the middle of the temperature rise range or slightly on the lower side for peak efficiency, better heat transfer, proper airflow, proper venting, and protection of the heat exchanger.

In mid-efficiency furnaces, we don’t want the temperature rise to be too low, as cooler gases can condense. High-efficiency condensing furnaces have a dedicated condensate system, but 80% furnaces do not. That condensation can corrode the heat exchanger, which makes it vulnerable to cracks. Cracked heat exchangers may also happen when the temperature rise is too high, and they are dangerous due to carbon monoxide (CO) leaks; check for abnormal flame movement and color. Lower-temperature air is also uncomfortable if the registers are in locations where blowing air on people is inevitable.

We can reduce the temperature rise by increasing the heating airflow, which can sometimes be done by re-tapping constant-torque and PSC motors or changing ECM settings. However, restrictive filters and ductwork may also cause that problem, and they need to be addressed.

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