You may remember that last year in the July issue we discussed installing radiant tubing in a concrete slab. If you can recall, there was some careful prep work done with the manifolds, to get them in just the right place to avoid having to reinstall them.
So now the concrete has been poured, let’s install the boiler. But before we do that, let’s discuss the concrete a little bit.
I met with the concrete contractor and GC after the tubing was installed and prior to the concrete pour. The concrete contractor was a quiet fellow; I don’t believe he spoke a word on his own account. The only way to get anything out of him was to ask him a direct question and stare him in the eyes for five minutes until he begrudgingly muttered a three-syllable reply. I don’t have a problem with people who aren’t big on small talk, but this guy took the cake! I was looking for some reassurance that my radiant tubing wouldn’t get damaged, and I wasn’t getting any. Nonetheless, I explained the necessary procedures from my standpoint. I told them the tubing was under pressure, and if a leak sprang up anywhere, they had to stop and let my guy standing by make the repairs.
I left the meeting feeling a little bit uneasy about the whole thing, but there was nothing I could do about it. The concrete guy was an independent bird, and he was going to do whatever he felt like doing. And he alone knew what that was.
The results of the pour were less than perfect. Apparently, the concrete contractor decided to do all 8,624 SF in one pour and didn’t have the manpower to do it correctly. In some places, the concrete was an inch high, and in other places it was too low. Some of the drains had to have ¾-inch of concrete cut off the top of them and were left with no slope to direct the water towards it. But that’s not the worst of it. A couple of months after the pour, I noticed a fairly wide gap in the expansion joints. The gapping comes from the concrete shrinking as it dries, and this tells me that they poured the concrete to wet. If we hadn’t installed the 6-inch insulation sleeves over the tubing at the expansion joints, the tubing would surely have suffered irreparable damage, rendering the whole radiant system useless before the first heating season.
That sleeve over the tubing saved the day! Which goes to show you can’t afford to leave anything to chance when it comes to radiant tubing in a concrete slab.
But on to more fun stuff. The boiler I selected was a NTI VMAX153P. It is a combi boiler with a firetube heat exchanger. It has a small 16-gallon indirect water heater built into the boiler. It also comes with the boiler pump and primary secondary piping already installed in the boiler. These features save a lot of time on the installation and also cut down on the wall and floor space required for the install. Which is a good thing because space was at a premium. I was granted a 10-foot by 8-foot room for the boiler system, the DHW, the plumbing distribution and, oh hey, we’re putting a bathroom in there as well!
Why do people keep doing this to us?
I guess it’s because we let them. The heating equipment keeps getting more compact and our piping methods keep improving, taking less and less space. Every time we raise the bar with neater and tighter installations, more space gets taken away.
The incoming domestic water comes up from the lower left hand side. This supplies the built-in indirect DHW heater and also the PRV to the boiler system. The DHW then exits the bottom of the indirect and goes to the left and up into the ceiling.
The pic below shows you the radiant manifolds and boiler piping. The manifolds had been fastened to a makeshift fence and pressurized before the concrete was poured. After the building was erected and wallboard installed, all I had to do was attach the manifold brackets to the wall. A little bit of extra time spent measuring and leveling, saved me from having to loosen and reattach all that tubing to get the manifolds situated perfectly.
The system has four zones of radiant; two of them are obvious. Each of those radiant manifolds is a zone. The big manifold has 5/8-inch tubing spaced at 18 inches and covers the largest amount of square footage. The smaller manifold also has 5/8-inch tubing, but those loops are spaced at 15 inches. In the bottom center of Pic B, you see two half-inch loops of black PEX entering the floor. These loops serve the two bathrooms. Each bathroom is its own zone, so to speak. Rather than being controlled with a thermostat and zone valve, like the larger zones are, these zones are controlled with TRVs mounted directly to each loop. The one loop has a direct mount operator while the other has an actuator with a remote mount operator. The remote mount operator is in the adjacent bathroom and is connected to the actuator via a capillary tube.
Using TRVs in this way is a great method to achieve microzoning without short-cycling the boiler. Here’s how it works. The two large zones have thermostats and can send a signal for heat to the boiler. The boiler is running an ODR curve, which means it will attempt to match the building’s heat load requirement by adjusting the supply water temperature proportional to the outdoor ambient temperature. In turn, this means the boiler and system pump will be running for the majority of the heating season, giving the TRV-controlled microzones access to flow and heat. The TRVs measure the room temperature and modulate the flow going through the loop by opening and closing the valve they are mounted on. The TRVs cannot send a signal to the boiler for heat, but, as explained before, the boiler and system pump are on the majority of the heating season anyway.
The TRVs could be considered intelligent, dynamic balancing devices that automatically sync the zone they control, with any other zone that is calling for heat.
This is a great control option to use in houses as well. Especially for those small bathrooms that really need their own temp control but are too small of a zone to be allowed to turn on the boiler and run independently.
The only caveat is this: one must be careful to maintain the smallest, reasonably achievable Delta-T possible on radiant floor heating loops. This is a comfort issue. The tighter the Delta-T across the loop, the more consistent the floor temperature will be. Running a wider Delta-T may cause unevenness in floor temperature that can be felt when walking across the floor in bare feet or even with slippers or socks on. This is why it’s critical that the supply water temperature is being controlled with an outdoor reset control. That allows the TRV to remain open further, increasing the flow and narrowing the Delta-T, thereby heating the floor with a more consistent surface temperature.
Techniques such as using TRVs for microzones will help the longevity and efficiency of the heating equipment and also clean up some piping clutter. It will save the customer a lot of money over alternative methods, such as installing a buffer tank to deal with microzones. It’s not a catch-all and doesn’t work in every scenario, but it’s an invaluable tool to keep in your arsenal of hydronic knowledge.
While we are discussing tips and tricks, here are a few more that will help you speed up your installs and do a neater job to boot. A neat and professional-looking install makes all the difference to the customer. If it is a mechanically sound install but looks chaotic, the customer will not write your check with the same goodwill as they will when you give them a neatly piped clutter-free install
Take a look at the pic below. The horizontal red line you see is actually a laser chalk line. There are several manufacturers that are making self-leveling lasers that shoot both horizontal and vertical chalk lines onto the wall. This is an incredibly useful tool for lining up pipes and keeping everything level and straight.
If you don’t have one on your truck yet, go to Home Depot or Lowes and get one! You’ll thank yourself for doing it.
On to the next tip.
I see a lot of boiler install pictures, and I also see a lot of installs in the field. The one thing that is often missing, in my opinion, is pipe angles. The vast majority is plumbed with almost all, if not all, 90-degree angles. Now I have absolutely nothing against 90-degree angles, but there are so many places where using a 45-degree angle will both save on piping and fittings and also make the project look better.
I’ll admit, if you don’t know the formulas or have the right tools, doing some of those angles can be cumbersome. The first thing to remember is that all the piping measurements should be taken from the centerline of the pipe.
So, here’s what you do to find the length of the pipe when you are doing a 45-degree angle. First, envision a square. Then draw a diagonal line from one corner of the square to the other corner. This splits the square into two identical right isosceles triangles. A right isosceles triangle is one where the one corner is 90 degrees and the other two corners are four degrees. This triangle is one of the easiest geometry shapes to deal with mathematically.
In order to find the run of the triangle, which would be your diagonal line (the length of your 45-degree pipe), all you have to do is multiply the length of one leg of the triangle x 1.414. Take the result of that exercise and subtract the take-offs for the fittings at each end. Then you are left with the perfect length to cut your pipe, and all you had to do is take one easy measurement. The take-offs for the fittings is the distance from the intersecting centerlines of the fitting to the seat where the end of the pipe will stop inside the fitting.
Most manufacturers publish their fitting dimensions which will have all the take-offs in them. I use Microsoft OneDrive, which is a cloud-based file storage system. Among the many other technical documents I keep on there, I also have multiple catalogs of fitting dimensions from various manufacturers. Charlotte Pipe and Viega are some of the main ones I use. Since they are in a cloud-based filing system, I can access them from my smartphone while on the job. You could also download them, print the catalogs, put them in a binder and keep a copy in your truck. We all have our own way of handling these things.
Let’s take another look at Pic B and calculate the length of the 45-degree angle 1-1/4-inch pipe on the boiler return that connects the vertical return going up into the boiler, to the horizontal return coming back from the system.
Let’s say the distance between the centerline of the horizontal and vertical pipes is 12 inches.
12 x 1.414 = 16.968
Now we have to subtract the takeoffs. On the one end, we have a 90-degree fitting; and on the other end, we have a 45-degree fitting.
The takeoff for the 90-degree fitting is 1.28-inches.
The takeoff for the 45-degree fitting is .58-inch.
12 x 1.414 = 16.968
16.968 – (1.28 + .58) = 15.108
So our exact length for that pipe is 15.108.
Since our tape measures read in fractions, we now must convert results to something we can use. Typically, I convert to 1/16-inch fractions.
.108 x 16 = 1.728
Round up or down to the nearest whole number.
1.728 = 2
Which makes 2/16 inch or 1/8 inch.
Which ends up with 15-1/8 inches as our exact length to cut the pipe.
Once you are used to it, this is the fastest and most precise way to do piping with angles. There are also some apps you can use on your smartphone to make the calculations fast and painless. I use one called Quick-Plumber.