#pump down

Tech Tips:

There is a lot of misunderstanding about the HSO (hard shut-off) or “non-bleed” TXV (thermostat expansion valve) and what makes it shut off, why it exists, and how it “magically” opens. Once you understand the forces inside the valve, it is quite simple, obvious, and sadly devoid of any magic. The Three Forces The TXV […]

Should I Pump Down or Recover?

During my second year in HVAC, the company I worked for was hired to fix some poor work that was done on a multi-head inverter system. The system used flare connections, and many of them were leaking. The system also had a branch box, which meant there were even MORE flares. So we pumped all […]

Scroll Compressor Pump Down, Megohm Test & Fusite Terminals

This tip will be like an episode of Columbo; we will start with the what and who and then get to the why. Don't pump down a scroll into a vacuum. Don't run a scroll in a vacuum. Don't run a high voltage megohmmeter or Hi-pot test on a scroll (As a general rule, don't […]

Refrigeration Pump-down Cycle

This article was written by Jeremy Smith CM, an experienced refrigeration tech and all-around great dude. Thanks, Jeremy. A very common means of control seen on refrigeration equipment is the pump down control. Why do we use this rather than just cycling the compressor off and on like a residential HVAC unit? Since most refrigeration equipment […]

Changing Liquid Filter/Drier Cores Tip

This tip comes from market refrigeration and controls technician Kevin Compass. Thanks, Kevin! A little tip when changing liquid cores: If you start pumping them down, begin bypassing discharge gas into the shell to warm it up, push out the remaining liquid, and bring the shell above the dew point so that it doesn't sweat […]

Solenoid Facts

Do you know how a solenoid valve works? Really? On the surface, I think we all understand how a solenoid valve works. The coil energizes, creating an electromagnet. That temporary magnetism lifts an iron plunger within the valve allowing refrigerant to flow. But is it really that simple? It turns out that the answer isn't […]

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

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 increasingly uncommon and has been disappearing since the Vietnam War. Many people who understood steam heating either retired or died after the Vietnam War. Many elements of steam heating are difficult to understand or surprising. (For example, steam pressure has a surprising relationship with velocity: low-pressure steam moves through piping much more quickly than high-pressure steam.) So, Dan Holohan is on a mission to revive that knowledge and teach the newer generations about the lost art.

There are many older steam heating systems still operating today, especially in the older large buildings in New York. Dan learned a lot about steam heating when working on these old systems and optimizing them. Most of the time, he optimized those systems by removing unnecessary accessories, not by adding components like steam traps.

Many old boilers used coal as a heat source. Nowadays, many old boilers have been fitted with conversion oil burners with thermostats, but they are still piped for coal. Some systems now have multiple risers or massive vents on the main riser to prevent the thermostats from getting too hot too early and satisfying the thermostat too early. We call that master venting, which reduces pressure and allows steam to move very quickly and efficiently.

Dan also discusses:

The 2-PSI standard
Transportation metaphors for BTUs in steam
Harmful renovations for old boilers
Replacement vs. restoration mindsets
Gaps in steam boiler education
Monopolizing the market if you HAVE the education
Boiler piping and venting
Two-pipe vs one-pipe steam

Find out more about Dan and hydronic heating at HeatingHelp.com.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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