All about static and automatic hydraulic balancing

On the same heating circuit, the simultaneous presence of rooms that are too hot and rooms that are poorly heated is symptomatic of the very common lack of balancing.
Whatever the true origin, be it faulty hydraulic balancing, sizing errors, operation of heterogeneous insulation, etc., the problem can be corrected by adjusting so-called balancing valves, as long as these are correctly distributed and sufficiently accessible.

Figure n°1: Adjustment tee and volumetric valve IMI Hydronic

The adjustment to be made is to throttle the taps of the favoured aerials in such a way that their flow decreases, and that of the unfavoured aerials increases.

The principle of regulation is therefore easy to understand, but its implementation is much more complex. This document details the conditions under which a hydraulic balancing operation will be carried out correctly, particularly on existing installations.

In general, a heating water distribution existing can only be easily balanced if balancing valves have been provided accessible, outside the occupied premises.
If the installation is not too old, this will normally have been allowed for by the design offices during the installation's conception by the installation of so-called 2-way taps.^th balancing level, located in basements, crawl spaces, or even stairwells and in any case outside occupied premises.

Figure 2: Taps (valves) for 2^th Balancing level

Circuits that only have balancing valves installed on the radiators are difficult to balance, as concurrent access to all of the rooms is very difficult to arrange if they are occupied.

In this situation, the distribution should be studied by a design office or a balancing expert to determine the possibilities of installing accessible taps of 2^th level.
It should be noted that the balancing of the circuit will be all the more effective, the greater the number of emitters «controlled» by the taps of 2^th The level will be moderate with an optimal number of 5 to 10 units.

As a general rule on existing installations, the only adjustment of the 2^th The balancing level (and higher levels) is sufficient to obtain a correct result. If disorders were to persist on a few particular antennae, it will always be possible to carry out additional local balancing. This can be done correctly because the corresponding group of emitters will have previously been normally supplied by the correct setting of its 2 valve.^th level.

If the installation of 2-way balancing valves^th given that the level is not achievable, a difficult access plan to all premises will have to be considered.
Since we're going with this expensive solution, we might as well also have the latest generation of thermostatic valves studied for installation, which will also provide «dynamic» balancing, the benefits of which we will study later.

Figure 3: Hydraulically dynamic thermostatic radiator valves Danfoss

Finally, it should be noted that setting these valves, like all balancing valves, requires precise initial hydraulic adjustment.
As we shall see later, if balancing is achieved by adjusting flow rates, determining these rates will require the involvement of a design consultancy, in the absence of records for the existing installations.

 

Three generations of balancing valves exist side by side.

1^Era Balancing valves (static and non-volumetric).
These taps do not allow for the measurement of circulating flow rates.

Figure 4: Non-volumetric balancing valves

There are two methods for settling them:

• Hydraulic simulation of distributions
• Standardisation of antenna return temperatures to balance

Hydraulic simulation of distribution systems requires a detailed survey of the network (section lengths, diameters, etc.), determination of the hydraulic behaviour of installed valves, and calculation of the flow rates to be set on each branch.
With existing installations, gathering all this data is complex and the uncertainties generated limit the chances of easily achieving a good result.

When facilities are equipped with this type of tap, the best solution is to proceed by Standardisation of water return temperatures for balancing the antennae.
This recent method will be presented further on.

2^th Generation: Static and volumetric balancing taps or valves.
These taps allow for the measurement of flow rates in circulation.

Figure no. 5: Volumetric balancing valves Oventrop and Company

Three methods allow for their settlement:

• Hydraulic simulation of distributions
• Setting and control of flow rates by on-site measurement
• Balancing water return temperatures of heating circuits

If we set aside the first solution due to the difficulties it presents on existing installations, we note that working by adjusting flow rates also requires the intervention of a design office to determine the flow rate to be adjusted on each antenna to be balanced.
On existing installations, the simplest solution remains to proceed by standardising water return temperatures.

3^th generation: Dynamic balancing taps or valves
Latest generation balancing valves, they are intended to be installed on variable flow circuits such as those fitted with thermostatic valves.

There are 2 types of taps to distinguish:

• Balancing taps or valves« Differential pressure regulators »

Figure n°6: Differential pressure control valves Honeywell and Danfoss

On a distribution system equipped with thermostatic radiator valves (TRVs), when they «close», the supply differential pressure (DP) of the circuit increases. This DP increase then opposes the closing of the TRVs and leads to an increase in flow in the emitters whose thermostatic radiator valves have not yet closed.
In this situation, the differential pressure control valve registers the DP increase and «closes» to restore it.

Some models, such as those pictured above, are not volumetric and therefore do not allow for the measurement of regulated flow rates. Their adjustment or the control of their adjustment will have to be carried out by measuring the return temperatures.

• 2^th types of dynamic balancing valves: Automatic balancing valves (also called self-balancing, supply pressure independent, PIBCV or flow regulators)

Figure n°7: So-called «automatic» balancing valves» IMI Hydronic

These taps have been designed to allow the adjustment of a single terminal unit as a heating coil for a CTA or fan coil unit.
They can be motorised, thus allowing the unit to be regulated under optimal hydraulic operating conditions.

They are sometimes used to ensure the balancing of aerials comprising several emitters fitted with 2-way control valves such as radiators fitted with thermostatic valves. Automatic balancing valves then replace the differential pressure control valves normally intended for this scenario.

This situation was not originally foreseen and is not mentioned in the manufacturers' technical specifications. Indeed, the functioning of the automatic balancing valve is not entirely optimal in this case and resembles that of a static balancing valve.

We can study this operation by consulting the article: «Automatic balancing, the conditions for success»

It is worth noting in the comments at the end of this article the points of view of two major manufacturers.
Therefore, IMI-Hydronic clarifies:
«Regarding the installation of automatic valves (PIBCVs, i.e. flow regulators) on variable flow rate systems (e.g. domestic premises fitted with thermostatic radiator valves), our positions as experts or as manufacturers specialising in hydraulics require us to maintain a technically irreproachable discourse. Even though the installation of PIBCVs at the entrance to domestic premises is undeniably increasing, we cannot ethically encourage this practice.»

More pragmatically on the same topic, Oventrop states even if there is a technical concession on hydraulics, the general regulation obtained with automatic valves is still much better than that obtained with static valves and pressure-regulating valves, as the latter are, most often, poorly or not at all regulated.

Indeed, the adjustment of differential pressure control valves often leaves something to be desired, particularly on non-volumetric models. If we do not work by return temperature measurements, their adjustment can only be carried out on the basis of a hypothetical pressure drop calculation. If we wish to balance by flow measurement, it is essential to opt for volumetric models, and several brands offer adaptable volumetric valves.

Figure n°6 bis: Adaptable volumetric tap with a differential pressure regulating tap Oventrop

It should be particularly noted in conclusion that one must not confuse «tap installation» with «tap adjustment», regardless of the generation of the models installed.

As with previous generations, dynamic balancing valves must undergo rigorous initial adjustment. This adjustment can be carried out by simulation and/or flow measurements and/or return temperature measurements. The subject will be developed in the following section.

On the existing collective heating installations, three methodologies of initial adjustment of balancing valves are used today.

• 1^Era Method: Simulation of hydraulic network behaviour

On existing installations, it is theoretically possible to carry out the surveys necessary to estimate the flow rates and pressure losses of circuits, in order to deduce the pre-setting of the balancing valves by calculation. However, this is a difficult «whodunit», unless distribution plans, which are rarely available, are used.

This possibility particularly developed by Mr Pierre Fridmann requires the ability to subsequently verify the result of all the preset adjustments made, either by measuring flow rates or by measuring return water temperatures.

This method is more suited to new or recent installations that do not yet present unforeseen fouling and for which all necessary calculation data is available.
It can notably be used to determine the pressure differences to be set on «differential pressure regulators» fitted with pressure unit adjustment scales.
The simulation result allows for the pre-setting of the taps before the actual water flows or return water temperatures obtained on-site are then checked and adjusted.

• 2^th Method: Calculation, setting and control of flow rates to be conveyed

The methodology involves calculating and adjusting the flow rates to be conveyed. It naturally requires the presence of volumetric, static or dynamic valves, which allow for the measurement of flow rates.
It is therefore not applicable to non-volumetric taps such as simple adjustment valves installed on radiator outlets, but also at the base of risers and, crucially, on the return of underfloor heating circuits.

Let's also recall that some differential pressure regulating valves are not volumetric. Their adjustment or the control of their adjustment will therefore only have to be carried out by measuring the return temperatures.

On existing installations, for the determination of flow rates to be regulated, a design office will have to carry out the necessary surveys to estimate the heat losses corresponding to each of the heating emitters to be treated.
For this, it will have to calculate the heat losses for standard rooms and for particular rooms (under a terrace, against a gable wall, etc.). Then, what is often very tricky, it will have to assign them correctly to each of the antennas to be adjusted.

Adjusting the flow rates requires the use of a measurement kit and, if the taps are not dynamic, a specific methodology.
One can acquire one of these methods on L'Eformation Xpair or on Simulator.

Figure n°9: Source Flow Control Oventrop et mallette de mesure IMI Hydronic

If the regulating valves are of dynamic type The flow rates can be adjusted more easily, without the use of a particular method, other than checking that the most disadvantaged tap has sufficient supply differential pressure.

On certain dynamic taps graduated for flow rate, presetting can be carried out without measurement, but this will not exempt from the final measurement of the flow rates obtained when all taps have been pre-set.
On models that are not graduated in flow rate, particularly differential pressure regulating valves, flow rates cannot be adjusted without their actual measurement (if they are of the volumetric type, moreover).

Once all dynamic valves have been adjusted or pre-adjusted, if they are of the volumetric type, a serious balancing will conclude with the measurement of all circulating flows to ensure that the hydraulic interactions between the branches have been properly managed.
Indeed, let's recall that it only takes a few disadvantaged aerials to cause the rest of the distribution to overheat, and the hydraulic behaviour of circuits, especially existing ones, often holds many surprises.

• 3^th Method: Measurement and standardisation of return water temperatures during the heating season

This more recent solution, known as the «EQUILOG method», involves, with the heating installation running and the flow temperature stabilised, measure water return temperatures antennas to balance and standardise them such that all antennas to be adjusted are «as hot» as each other.

The process, which appears «simplistic», has been, and continues to be, criticised, quite naturally, by its competitors. You can read more about this «Hydraulic balancing: what's new for a simple method. However, it can be observed that across several hundred sites, more than 80,000 housing equivalents have been dealt with to date under favourable profitability conditions.

After calibration, the antennas will show comparable return temperatures and round-trip temperature differences. (*).

Figure no. 11: Equalisation of water temperatures in a heating circuit

(*) Where the hydraulic distribution allows, it is of course possible to set differentiated water temperatures for each aerial unit, in order to take into account local isolation operations.
However, it is noted that on buildings that have undergone homogeneous thermal renovations (replacement of all openings, insulation of all exterior vertical walls), the balancing initial or posterior achieved by standardising water temperatures is sufficient to obtain a good result.
Heating power can then be adjusted by simply setting the water temperature at the boiler outlet (heating curve adjustment).

The process applicable to all types of taps has been optimised thanks to advances in infrared thermometry and research carried out by the GMTI94 – GEFEn.
We can study its principle on L'Eformation Xpair or on Simulator.

The main advantage of the methodology is that it bypasses all heat loss calculations or installation surveys on normally sized networks. It is therefore particularly well-suited to existing circuits where records are rarely available.

Experimentally implemented in the 2000s, this procedure was patented in France and more recently in 15 European countries.
The «EQUILOG» method is notably implemented by « MAPSEC company »(*) on behalf of various operating and installation companies (Dalkia, Cofely-Soccram, Idex, etc.).
MAPSEC 80 rue de Paris 93100 Montreuil Tel: 01 48 59 06 05 – www.mapsec.fr

Figure no. 10: Source water temperature control Mapsec

Let us finally note that in the article on dynamic balancing valves as already mentioned in the preceding paragraph, the Oventrop engineer states in the comments at the end of the file.
«For existing systems, balancing by equalising return temperatures is also, in my opinion, the best method, provided the chosen temperature drop is correct.
Despite this, this method is time-consuming and difficult for specialist residential installers to accept when it has to be carried out manually.
There are taps that do this automatically, but the price isn't the same.»

Indeed, balancing by equalising return temperatures used to require long thermal stabilisation waiting times, but recent advances now make it possible to overcome this, and the duration of operations has become very competitive.

Alternatively, we could indeed consider the automatic implementation and long-term maintenance of balancing through the equalisation of return temperatures. However, with the current state of technology, this would require the installation and electrical supply of motorised automatic balancing valves connected to a programmable logic controller or a building management system.
From an economic perspective, this remains difficult to envisage for now, at least on existing installations.

It is particularly important to clearly distinguish between descaling activities (when necessary) and those of installing balancing valves, from the actual initial adjustment of them.

Indeed, whatever the type of tap, it is tempting for an installation or descaling company to include the commissioning task in its proposal without always being able to define all the parameters.

Obviously, it is possible to imagine that a single company could handle an entire rebalancing operation, but it must then have teams with very different practical and theoretical skills.

In general, it will therefore be necessary to be extremely careful in choosing a company to undertake an balancing action. It is a difficult technical specialty and underperformance is common because verifying the quality of the work carried out is difficult to ascertain.

Even if this were to lead to an additional cost, we will therefore not hesitate to separate the interventions so that the study and/or development phases are carried out by subject matter specialists.

A good way to select one will be to ask, during the consultation, for the type of method that will be used, and to ensure that the data that will be returned after the operation is clearly specified.
Any vagueness or hesitation in the answers provided on one or both of these two points will undoubtedly be a sign of a poorly executed performance.

If the company works by flow measurement or hydraulic simulation, it will be possible to request that the proposal includes the final discount:

• Detailed calculation of heat loss in correspondence with each tap to be treated and leading to the establishment of the amounts to be paid. This will ensure that the amounts targeted are not the result of rough estimates.
• From a grid certified measured flows upon adjustment of all taps (and not just rely on the theoretical flow rates). This will ensure that the hydraulic interactions between the antennas to be adjusted have actually been taken into account and, if necessary, allow for control.

If the company works by measuring return temperatures, it will be possible to request that the proposal include:

• Some corresponding references or, better still, communication of at least one detailed report of a previously carried-out operation. This will allow us to ensure the candidate's experience, because if the principle of the method is old, it has only really been mastered recently.
• The return of a graph certified, complete and detailed return temperatures measured, Before and after balancing, indicating the stable starting temperatures at which these readings were taken. This will allow us to ensure the quality of the work carried out.

It is not easy to predict the energy saving to expect from a balancing operation.
Indeed, if in the hypothesis of a perfectly achieved balancing, it can be estimated from a mapping of initial ambient temperatures, this is in reality very difficult to interpret.
In any event, if this estimation method is chosen, it must be based on recordings made during very cold periods and in the absence of any free input (sunlight, electrical appliances, etc.) and not on instantaneous measurements.

Fig 15: Example of ambient temperature readings affected by free heat gains

However, an even more delicate consideration is the placement of balancing valves that can actually be adjusted. In fact, on existing heating systems, balancing is generally only carried out on the accessible valves from 2^th level (see 2^th As a consequence, the more or less successful implementation of this 2^th Level is an essential parameter for estimating expected energy savings.

On this point, the company MAPSEC uses a methodology known as REQUILOG which allows, from a mapping of water return temperatures measured at the adjustable taps, to assess the extent of the imbalance that can effectively be treated.
Also, where possible, balancing operations entrusted to him are preceded by a diagnostic operation including this assessment, which allows the decision-maker to better judge the interest of proceeding or not with the operation.

Finally, it should be noted that the energy saving resulting from a balancing operation will require the subsequent involvement of the technician responsible for adjusting its regulation.
Indeed, if balancing were ultimately to involve bringing the initially less well-heated premises back to the situation of the better-heated ones, it would not be energy savings that would be achieved…

Overall, it appears that the average % energy savings following the rebalancing of heating distributions are in the region of 7%, with a payback period of around 2 to 3 years, provided the system requires little or no replacement of valves.

Until December 2014, these projects could be included under the Energy Saving Certificate scheme at a flat-rate energy saving percentage of 10%.
The corresponding BAR and BAT SE 04 sheets are currently being modified. They are expected to reappear under different names in the next ministerial order concerning CEEs.

Finally, to conclude, one certainty: balancing operations are generally perfectly profitable if carried out rigorously.

The best proof of this is the work carried out by Dalkia's balancing department in IdF(*) created about ten years ago to exploit the EQUILOG method and currently managed by Mr Christophe Tillay.
On Xpair, you'll be able to read a report on one of his achievements in the article «Operation for balancing by equalising return temperatures.

Dalkia Ile-de-France, Service Equilibrage, 28 Boulevard de Pesaro, 92 751 NANTERRE CEDEX Tel: 01 55 67 68 97

The hundreds of balancing operations carried out by this service have been exclusively on property portfolios managed by the company under MF (fixed price contract) or MT (temperature contract) agreements. Under these types of contracts, which are not sufficiently widespread, the client pays the operator an annual lump sum (or adjusted for degree days) in return for the assurance of optimal heating.

The fuel supply is then entirely the responsibility of the operating company. Its primary interest is therefore to reduce it within the limits of correct heating for the customer, since all energy savings made will accrue to them.

This type of case naturally encourages the provider to manage the installation in the best possible way and to assign their best teams to it. From an ecological point of view, the situation is therefore optimal.
For their part, at no extra cost, the customer is guaranteed long-lasting and well-regulated heating, and the ability to recover, at the end of contracts generally lasting 8 years, an installation that has been maintained as well as possible.

The balancing carried out by Dalkia IdF's Balancing department was therefore financed with own funds and amortised over a few years by the energy savings generated.
The maintenance and development of this service over 10 years is undeniable proof of the profitability of this type of operation.

Reducing the energy consumption of our existing district heating systems relies on insulation, proper combustion tuning, regulation, and balancing.

Despite its major influence on the tuning of regulation and the efficiency of condensing boilers (and combined heat and power units), the latter item was until now the weak link.

After a very long pause, the issue has never been as relevant as it is now.

Recent advances in tapware and development should allow for better exploitation of one of the largest remaining available energy saving deposits.