Since I included a fully finished basement in the design of my new house, I decided to also ask my GC to install a radiant heating system in the floor. The topic of this article is what I learned about radiant heating systems after my house was completed. Before the house was built I didn’t know enough about how these systems work. Perhaps this article can help serve as a cautionary tale.
In my case the general contractor decided to leave everything up to XYZ Plumbing (name changed for purposes of this article). This was the company that the GC awarded all of the plumbing work to as part of the construction of the house.
XYZ Plumbing laid out all of the radiant tubes on the foundation floor. Cement was then poured over the tubes and the cement was leveled. The company had spent some time figuring out the zones and they based their zones on what would physically be in each area. Zone 1, for example, was dedicated solely to the three bathrooms in the basement and the laundry room. These were the rooms that would each have tile flooring. The bathrooms were on a single zone and the thermostat for that one zone could be set to make the tile floor feel nice and warm to bare feet. The other rooms would all have wood flooring.
As mentioned, all the radiant tubes were laid out and then buried in cement. The tubes all ran to four different radiant manifolds, specifically four TruFLOW manifolds manufactured by Uponor.
Four temperature sensors were also laid into the floor which in turn talked to four thermostats placed on the south wall of the mechanical room. When a floor sensor gives a temp reading lower than the set point on the thermostat, the thermostat talks to a relay (a TACO SR504 4-Zone Switching Relay) which in turn tells the corresponding circulator (a Taco Integral Flow Check Cartridge Circulator with 1/25th horsepower) to start pumping hot water over to the Uponor manifold.
It’s all relatively simply except… Once the system was initially installed, the plumbers figured “Hey, this part of the job is complete, let’s move on to the next part. Nothing more to do here.” The problem of course is that eventually the house construction is completed, the keys turned over to the owner, and here you go sir thank you very much. The plumbers head off to the next job. The owner is shown the four radiant thermostats on the mechanical room wall and he can play around with them to his heart’s content. He can adjust the temperature settings up and down and 6 or 7 hours later he’ll feel the result of his adjustments via new temperatures in the floor.
What the new owner does not know is the following:
– What specific area does each thermostat control?
– Where were the floor temperature sensors buried?
– Did each manifold get flow-adjusted so that an even temperature spreads across the surface of each particular zone?
Incredibly, XYZ Plumbing’s business is not set up to provide this level of reporting for clients. (I say “incredibly” because this company is one of the major plumbing companies in Southampton. In fact they are probably the largest such company in the area.) The plumbing company technicians fly through their work and perhaps assume the owner is too dumb to know what to ask for about radiant systems. And the general contractor, P Construction, they are so disorganized they have no clue that they should track down the above information for their client. Perhaps P Construction has been lucky enough to have clients who are not sophisticated enough to know anything about radiant systems. And certainly the owner, Mr. P, is not going to waste his time to do any of this work. In fact he seems to have no clue that this is something he should even consider doing. And so the owner is left blowing in the wind and hopefully is too clueless to know what he or she is actually missing.
And so, back to the list of what was missing and my efforts to track all of it down …
While having house guests at my apparently completed house, the guests mentioned they noticed the floors were warm in two of the basement bathrooms but cold in the third. Hmm, how do I fix this? I checked the radiant thermostats and they were all set to the same temperature. Okay, why is one bathroom floor so much colder than the others? I called XYZ Plumbing to ask which thermostat governed which bathroom. They had no idea. They would have to track down whoever did the work and get back to me. They did. That person came over to check but he couldn’t remember. He would need to check with someone else. This set off a long chain of events that resulted in me going from knowing relatively little about radiant heating to learning everything I could about radiant systems from scratch. (Thank you YouTube videos.)
I learned the following:
– You’d better get a map of the radiant zones. At a minimum, print out the architect’s floor plan of any floor that has radiant heating and get the plumbers to write from memory where they put each zone.
– You also better know exactly where each tube runs to from each manifold. What exact room does that tube govern? (More on this later.)
– It’s a good idea to invest in a handheld laser infrared thermometer (they’re cheap!) because you’re going to need this to manually check the temperature of each floor in each zone.
– After you take delivery of the house, the installing plumbers must return to adjust the flow at each manifold so that heat is distributed evenly across that specific zone. (XYZ Plumbing blew this off hoping I would never know about this. Heck, why do work you don’t have to do if the owner has no clue it needs to be done? And P Construction never followed up with the plumbing company because that kind of service is not in their business model.)
– As the owner, it’s a good idea to learn where the temperature sensors were embedded in the floor because a decade or two from know they may fail and where in the world does that wire run to that’s coming out of the thermostat? It’s all hidden and buried behind the walls. Good luck finding the plumber who did it when it’s 20 years later and he’s retired in Florida. Have fun opening lots of walls. And guess what, you’ll never find them anyway.
After going back and forth with the plumbing company, a technician arrived who provided me with a map of the zones. The zone numbers were wrong on the map (thermostat one did not govern zone one etc), but the document gave me a starting point I could use to see what rooms were tied together from which manifold. Next the technician began the work of adjusting the hot water flow at the manifold that governs the bathrooms. The manifold receives pumped hot water from the mechanical room circulator and the manifold has adjustable valves called balancing valves that allow a plumber to adjust the amount of flow through each tube running down to the floor. Oops, let me back up… The manifold has two parts, the supply side and the return side. It’s the supply side that receives the hot water from the circulator and then sends the water through tubes into the floor. Those tubes do their loop in the floor and then “return” to the return side of the manifold to go back to the mechanical room where the circulator is. The plumber can adjust balancing valves on the supply side of the manifold to pressure balance the system and allow more pressure to go through loops that are longer than other loops coming off the manifold. This is very important. Obviously more pressure is required to send water a longer distance and if this adjustment is not made you end up with wildly different temperatures in a single zone (as happened at my house).
Okay, so the plumber finally made these adjustments. First and foremost he had to figure out which loop had the longest run. This was not obvious to him because neither he nor anyone else had written this down during installation. He had to turn all the loops off and by using a process of elimination he then opened one loop at a time and waited to see what which bathroom warmed up. This took lots of time because he needed to wait for the floor temperature to actually change and this is a slow process. Over the course of two days he figured it all out and was able to successfully make the adjustments.
Because I was curious, I called Uponor’s main phone number and asked to speak to technical support. I now love Uponor because incredibly they connected me to a tech support rep fairly quickly. The tech support person told me that the supply manifold valves should be adjusted such that each supply line coming out of the manifold ends up being 10 degrees warmer than the corresponding return line for each loop. You can shoot the laser thermometer right at the plastic tubes coming out of and coming back to each manifold to get these readings. Wow, cool.
Okay, so the XYZ Plumbing plumber pressure balanced the manifold and thereby created a far more uniform temperature across all the tile floors in that zone. Great. But then the plumber took off and didn’t think I would want this process repeated on the other zones. The other zones are covered by wood floors, but the same process needed to be repeated for each zone, and so I got him to come back to finish the job. Also, I got him to show me on the architect’s floor plan for the basement where he had originally placed the temperature sensors.
Lastly I created my own map. I took the architect’s floor plan and added the zone numbers, the sensor locations, the manifold locations, and the thermostat locations. Below is a rendering of that map. If you have a good general contractor, they will make this map for you. If you have a bad one, my guess is they won’t have any idea that they actually should make this for you.
