Hydroseparator, Part 1

By Paul Rohrs
Radiant Expert

The new kid on the hydronic street corner is a component called a hydroseparator or low-loss header. This is the first of a two-part article that will look at the practical application of this component, how it is employed with modcon boilers, and what value it brings to the hydronic table.

The hydroseparator keeps connected hydronic circuits separate from each other. You are probably saying to yourself that sounds like the basic primary-secondary piping that can be achieved with closely spaced tees. The hydroseparator functions a little bit differently by creating a zone of low pressure loss so that the primary and secondary zones will remain independent of each other. Why do you need this component then? It is a potential time and material saver. In addition to isolating primary and secondary flow, it provides air-elimination out of the top and sediment removal from the bottom. Let's look at a few models that are currently on the market.

Figure 1 shows a hydroseparator -- the 548 series -- from Caleffi. Figure 2 shows a model available from PHP (Precision Hydronic Products). Viessman also has a low-loss header (LLH) on the market, and it is my understanding that Taco is soon to introduce a model into their line of hydronic wares.

Installing a hydroseparator with a single boiler or single heat source might not be the best use of time and money, unless you are considering adding optional heat sources in the future. Multiple modcon boiler installs or multiple heat source applications are really where the hydroseparator's functionality starts to shine, as it can increase profitability by reducing the amount of time and materials needed.

Previously, multiple modcon boiler installs were piped in a reverse return or parallel primary fashion. This piping arrangement ensured equal return temps to each boiler and was ideal for establishing the heat sources for a primary-secondary system. You can see that it required a lot of time and material to correctly pipe this arrangement. Figure 3 shows the same four-boiler setup piped with the hydroseparator.

Let's take a second look at the value of the hydroseparator. It provides air-elimination and sediment removal, gives us a platform for true primary-secondary piping, provides for reduced labor and material for hydronic systems and can simplify the future addition of heat sources or secondary zones. If you remove the cost of your air-separator, wye-strainer, additional pipe and fittings and the labor to install, those savings will go a long way in offsetting the cost of installing a hydroseparator of your choice.

It is always appropriate to address concerns about utilizing space in mechanical rooms, which are getting smaller. Space is at a premium right now, and architects are trying to provide as much useable office or living space as possible. I can't blame them for that. It does present a problem for contractors, in that hydronic contractors are being asked to provide more heating options, more bells and whistles and to assemble them all in much smaller spaces.

The hydroseparator is a great building block for assembly in small areas. We usually start our mechanical rooms by locating the boilers and making sure that the venting will conform to the "total equivalent length" requirements if a modcon boiler is being installed. After that, mounting the hydroseparator seems to make our installs flow very smoothly.

One key aspect to be concerned about when sizing hydroseparators is the total flow rate. Check the literature and specifications prior to purchasing a unit, so that you can ensure that total secondary flow rates, often higher than primary side flow rates, can be met.

This would be a good time to discuss ever-advancing hydronic heat sources, coupled with existing sources. Geo-thermal, solar, solid-fuel (wood, wood pellet, corn) boilers, and modcon gas or LP-fired heat sources can all take on a plug and play a role, as a hydroseparator allows ease of installation and integration.

Hydronics have truly moved into the 21st century, as significant advances have been made in the last five to ten years. There can be 22nd-century advances lurking right around the corner that will have end-users looking to integrate these advances as soon as they hit the wholesaler's shelves. The hydroseparator would significantly simplify the new addition, which we will take a more in-depth look at in next month's article.

We have addressed the basics of the hydroseparator this month, with the emphasis on piping of modcon boilers. Next month we will look at advanced and hybrid systems that integrate multiple heat sources on the primary side, as well as at how the hydroseparator can be utilized with atmospheric boilers that require minimum return temperatures to prevent sustained flue gas condensation.