Doin’ the math

By Paul Rohrs, Radiant Expert
Biggerstaff Radiant Solutions, Lincoln, Neb.

Ask me what my least favorite class was in school and without hesitation I would answer math! (Yet, here I am 25 years later doing math.) At the onset of any hydronic job I always do the math. I start with the heat loss, boiler sizing with minimum and maximum radiant loads, what my labor and materials costs are and what to charge for the project.  Math, pure and simple. It would be hard to complete a successful boiler change out, let alone a new install without some form of math being successfully completed. Okay, let me modify that last statement a bit: It would be tough to be profitable without doing the math.

 

So, what now Paul? I can hear the snickering, “That Rohrs guy is on his soapbox about math. Big whoop.” I couldn’t agree more; but what if we can add a couple of components that will save us time and money? Bear with me and let’s do the math together.

 

I hate air in hydronic systems. My disdain for air-bound systems ranks right up there with, well, math. I know several articles from multiple authors have discussed air-removal and air-separators, but let’s talk about components that we can incorporate that will give us an immediate payback. Before I get to the math, let me pose a scenario to you.

 

Have you ever been in an apartment complex with fin-tube baseboard heat-emitters? You finish the install, re-pipe, or change out and then need to bleed air from each apartment zone. You get your empty plastic Folgers coffee container and your radiator keys and head up to start the bleeding. With no apartment manager on-site, you knock on the first apartment door. Grandma Jones answers and welcomes you in and offers you cookies, tells you about her arthritic knees and tells you that her kids never call. Before she gets to the grandkid stories, you politely kneel down at the first fin-tube access cover to NOT find the radiator 90 with integral bleeder, or the radiator vent. On to the next room in search of the elusive bleeders. Right behind Grandma Jones’ stash of Elvis Presley albums, you find the first bleeder and you are well on your way to finishing the first apartment. Twenty minutes — not bad — and three more apartments to go.

 

Apartment 2, I knock. “Who’s there?” comes from behind the door.

 

“Orange,” I say.

 

“Orange who?”

 

“Orange you going to let me in so I can bleed your baseboard emitters and get you heat!” After exchanging pleasantries with the tenants, I knock out units 2 and 3. One more apartment to go. No one home in unit 4. Now what? Call the apartment owner/manager again to get access or come back later when they are home. You get the picture, and after one hour of bleeding apartments 1-3, you are unable to finish your task and get on to the next service call.

 

I have spent an hour bleeding fin-tube and I am still not done. Why not consider changing the game plan? Let’s add some ball valves, fittings and boiler drains so that we will never again have to enter a tenants apartment and we can purge all air from the mechanical room. Figure 1 shows some essential fittings that can be easily incorporated into most hydronic heating systems.

 

NIBCO makes a C5C5FIP Tee that will make it very easy to solder in and then screw in a boiler drain. If you are a ProPress shop, Viega and others make a Press5Press5FIP tee that installs even quicker. We are not going to look at cost savings of ProPress versus sweat fittings in this article because that could be an article unto itself. So responsibly adding these fittings can enhance a system so that you can purge very easily. In a very basic zone valve system, with the zone valve on the supply and a drain and ball valve on the return, you can purge each apartment from the mechanical room. Manually close the zone valve, close the ball valve on the return, and open the boiler drain to successfully purge each unit.

 

Okay, let’s look at the math for our 4 unit apartment complex. For a baseline, I am going to use $100.00 an hour for labor.  This was on a service call so we also bill for our trip charge.

 

Now with three of the four units purged in one hour and still one more unit to go, this set up is starting to look more and more attractive. Now factor in the next service call at this location when a zone valve goes bad or we have an issue in an individual unit. This has now more than paid for itself in reduced labor costs in the eyes of the owner, and they will be thanking you.

 

We can look at this from another angle, as well. You will note that properly designed floor heat systems do not have bleeders on individual loops like radiators or fin-tube baseboard emitters. What to do? We incorporate our purge drains on the supply and return with isolation flanges on our zone pumps and ball valves on each return as illustrated in Figure 2. In addition to providing a positive form of air removal in individual zones, the added bonus is that we have isolated the boiler loop with its typical 30psi relief valve. This means that we can use line pressure to fill and purge our floor heat zones, which takes a lot less time. This was new construction so it was easy for me to include this in my proposal.

 

Before any hydronic system is commissioned on start-up, it is air-bound. It is hard to put a price tag on frustration, but the hours of trying to purge a system can easily be calculated as labor rates dictate. Do the math for your own company in adding a few extra purge fittings, factoring in your specific labor rate and trip charge, material costs and the amount of time you estimate for bleeding air from systems. I suspect you will find that the math will be justifiable and your end users will appreciate the extra attention to detail that has enhanced their systems.

 

Paul Rohrs welcomes your comments. Contact Paul at paul@biggerstaffradiantsolutions.com.