Who is in control around here?

Beyond piping, integrated systems present some challenges

By Bob “Hot Rod” Rohr


You take a few steps backwards, snap a few “glamour” shots and send your piping pics around the globe. It is a common practice these days to share mechanical room piping on the various chat rooms and social media sites. Some incredible piping can be found if you have time to search around. Perfectly piped, gorgeous back wall treatment, even custom lighting and unique artwork is sometimes included. There is no doubt the industry has been elevated with all the articles and training on best practices for boiler or mechanical room piping.

I am particularly enamored with the clever blending of piping and connections. Back in the day threaded steel pipe and copper sweated together was the method used by most all fitters and installers. While those piping materials still are the go-to materials, an array of connection types are now being used. Press and grip fittings are working their way into piping systems of all types of pipe and tube. PEX and PP piping materials are also becoming more common for boiler room piping.

The industry seems to have a good handle on the mechanical and piping component of hydronics. Equally important is how to control the piping “Picasso.” We will continue to see more blended mechanical systems. By this I mean a combination of heating and cooling components piped together.

It is not uncommon in parts of Canada and the U.S. to see multiple boilers piped to take advantage of the best energy rates. Electric boilers, for example, can be piped with a fossil-fuelled counterpart. The electric boiler takes advantage of off-peak or desirable lowcost KWs. The oil- or gas-fired components will take over when the cost of operating the electric source increases. This toggling between the two or more heat sources could be done with a simple time of day clock, manually, or by a smart control attuned to the changing energy rates.

The movement away from strictly fossil-fuelled systems is underway. Fossil fuel is no longer available in several jurisdictions for new construction installations. The obvious option is a heat generator and DHW source that is powered by electricity. Uncertainty of the reliability and cost of an electricity only powered home has some designers and installers providing a hybrid option.

Perhaps leaving the fossil-fuelled devices in place and connecting an electric powered partner makes better sense. The electric side could be a straight resistance style, or one of the updated heat pump options.


Things get complicated

The challenging part of these systems will be the controls. For the most part, the typical hydronic installer understands and can correctly pipe a hybrid system together. Many, perhaps most, hydronic technicians and/or plumbers are not wired to design elaborate hybrid control systems. A basic zone control or pump control relay box is within the comfort level of most hydronic technicians and plumbers. When microprocessor-based controls, digital signals and programmable logic controls (PLC) come into play, things can get complicated and sometimes frustrating.

Which of the multiple electrical components will take charge of a hybrid, multi-fuelled, multi-component system? Will a sophisticated relay box be adequate? Which manufacturer’s controls are provided to onboard a modern boiler? Would a microprocessor-controlled heat pump have enough understandable logic to run the show? Does a smart thermostat have enough intelligence and outputs to take charge? Should a stand-alone control system be considered? What about a PLC custom designed with a software program by the installer?

I’m not sure there is one answer to these questions. It depends. In any or all cases, you would be well served to take a manufacturer’s class to understand what the device, be it the heat source or controls package, is capable of. In my experience the mechanical tradesperson struggles with complex control design, installation, commissioning and troubleshooting.

Very often complex control systems are scrapped by the next technician to work on the system. This could be due to a lack of documentation; or the number of hours required to reverse engineer the existing wiring and controls; or because of obsolete control components; or because of incompatibility with the new hybrid components being upgraded.

There are a handful, although a small handful, of excellent control manufacturers in Canada and the U.S. with hydronics experience which have evolved with hydronics and continue to raise the bar in control options and product offerings. I would recommend enrolling in their training classes to see if there is a fit in your system offerings. For less complex systems, a relay box control may be able to successfully integrate multiple heat sources along with some zoning control and outdoor reset functionality. operates a boiler for Domestic Hot Water, set point load, boiler zones, and backup for the heat pump.


Mild to wild controls

Boiler manufacturers are offering more and more options for advanced controls and multi component integrations. Here again, I would recommend manufacturer or rep presented training as a first step. Many rep firms offer hands-on training at their locations.

Time spent in front of a simulator can make control understanding and installation much less frustrating. Some savvy contracting shops build simulators or training walls and provide in-house training. There will be a movement towards hydronic cooling in residential applications with various heat pump offerings, both geothermal and air to water. Cooling control does offer some unique challenges. It is not just temperature control … dewpoint comes into play with chilled surfaces or emitters. Fluid temperatures need to be tightly controlled to prevent condensation. In many cases, some air movement will be required and that needs to interface with the control system as well.

If you are creative and capable, there are plenty of components available to build from-mild-to-wild controls. I have seen it done with basic relay mash ups or more complex PLCs. A wood boiler chat room that I visit has some clever owner-built microprocessor-based control discussions. The same challenges are present when integrating a wood-or pellet-fired boiler with a fossil-fuelled partner. Or try throwing solar thermal and buffer tank control into the mix.

I have seen unique German-built PV controls that dump excess generation into a thermal tank to store the excess PV production. That may be a better approach than giving it back to the utility for a thank you, or maybe even a utility fee added when you push back your generated surplus. Decide early on in the job if you are in control of the system, or if the system will be controlling you.