The benefits of EPIV valves explained
Having just got used to PICC valves, the market is now faced with EPIVs - so what's an EPIV? Peter Lowther explains
An EPIV Is a Belimo Electronic Pressure Independent Valve, a valve that continuously modulates in order to provide the correct water flow rate by electronically monitoring the actual water flow rate through the valve and adjusting its position accordingly. It has no mechanical pressure independence cartridge because it does not need one. Whatever the flow, whatever the pressure, the valve will adjust to obtain the correct water flow in order to meet the duty requirement as defined by the control strategy.
Ability has spent the last few months trialling these valves in conjunction with various Ability controls strategies and can now offer a number of available EPIV options.
So how does this actually work?
The Ability strategy knows, at any point in time, the water flow rate required. This might be the water flow rate required to satisfy an operational duty or it might be the design max water flow required to satisfy the commissioning process.
Either way, the valve adjusts, based upon its flow rate feedback to achieve that value.
The flow meter section of the valve sends a flow signal to the Ability controller and the control strategy decides if the valve needs to open, close or stay put to achieve the water flow requirement at any time. Water flow tolerances are now two values held within the Ability strategy and the valve will only be satisfied when the measured flow sits within the customer-defined flow tolerance range. Obviously, if something in the system that alters the system pressure, each of the individual valve flow meters immediately notices the change and readjusts the valve to suit the new pressure keeping the flows in line.
The valve is not affected by the hydraulic pressure being applied; it simply and continuously adjusts to maintain flow irrespective of pressure. Thus, the valve does not need a pressure equalising cartridge, which in turn removes the need to maintain such a high minimum pressure within the system simply to ensure correct cartridge operation. This has both obvious and hidden benefits. The absence of a pressure cartridge means the valve itself is more simple mechanically and the chance of blockages and debris build-up are removed. Also, unlike with ordinary PICC valves, there is a far reduced system pressure requirement, which reduces the load on the main pumps and reduces the electrical consumption of those pumps.
Ability's own strategy can continually poll all the fan coils on a project to identify the greatest need (flow and pressure) at any time and then, through the BMS, optimise the pump speed to satisfy the maximum demand and no more.
Commissioning is a vastly simplified affair. Through either the BMS, the supplied software or a physical switch on the unit, all the fan coils are instructed to open their valves to their design water flow positions. Given that there is enough total water being provided to the floor or the branch and given a few minutes to settle, the fan coils will reliably achieve flow and if need be, readings can be taken and confirmed. The intention for this system ultimately is that commissioning in the conventional sense will not be required.
How accurate is accurate?
Every valve / flow measurement assembly is calibrated before it leaves the Belimo factory and if any adjustment is required, the valve is fine-tuned electronically at that point. As valve signal outputs from any controller can also have a small variance, they are likewise auto calibrated by the Ability controller strategy itself on start-up. The combination of these two actions ensures that flow rate accuracy of the valve set can be set to always achieve or surpass the normal CIBSE / BSRIA guideline tolerances.
Each valve flow metering section has no moving parts and there is only a small probe within the water flow itself. Therefore, there is little chance of a blockage in the flow meter section of the valve and the flow measuring equipment itself cannot get coated, scaled or degraded over time. Also, the device is impervious to all flushing and cleaning solutions commonly in use.
This new EPIV feature can be applied to all the Ability ranges of fan coil unit including EVO (Standard ECs) and the Ability Matrix ranges. As a complete system it has been trialled in Ability's own in house fan coil installation and proved effective and robust.
Over and above the ease of commissioning and energy savings, this product can play a major role in any Soft Landed offering. Since the flow rates are set and maintained electronically, they can just as easily be adjusted electronically. Most Ability products can report into the BMS various temperatures and values that enable occupiers or their FM team, to establish whether the air conditioning is performing as per the design intent. If it is, then all well and good but if changes are required, be they minor or wholesale, Ability fan coils can be retrained, reset or completely reconfigured without going anywhere near the actual unit. This means that Soft Landings with Ability products are not intrusive or disruptive to the new occupants of any building with all interrogation and adjustment being made remotely. There is no point in listing the variables that can be changed on an Ability soft landed project because they can all be changed. Set points, flow rates, air volumes, set backs, scheduling, all of them.
The Ability control strategy, which can include the new EPIV, has now been listed on the Energy Technology List which means any owner may benefit from the enhanced capital allowances available for all products bought from this list.
I am pleased Ability leads the way in innovative fan coil technology. Rather than the fan coil being an element within a static air conditioning system, our products are intelligent, intuitive and play a major role in the provision of environmental comfort and energy effectiveness.
Seasonally variable design water temperatures Recently, the CBCA (Chilled Beam and Ceiling Association) produced a report that suggested that Chilled Beam systems are up to 17 per cent more energy efficient than VAV (variable air volume) EC fan coils. One premise for the claim is that chilled beams utilise higher temperature water at 14F/17R and at those elevated temperatures the main plant is running more efficiently. However, amongst other things, what the CBCA report omits to mention is that fan coils can also be selected at these elevated temperatures and avail themselves of these same efficiencies.
The Ability EPIV product, goes one stage further. Because the design water flow rate is a programmed value held in the Ability controller, it is a programme value that can be changed; it can be changed seasonally, daily or even hourly. So, should a designer believe that he might like to run his building system at different water flow temperatures to take advantage of seasonal savings, he now can. Ability EPIV fan coils can continually re-adjust the ir design water flows to suit a new design flow temperature seasonally, daily or even hourly.
It should be noted that there will soon be another report on the relative efficiencies of chilled beams and fan coils but this time filling in some of omissions of the first CBCA report relating to fan coils, the innovative ways that fan coils can be applied and the further energy savings these methods bring. Ability fan coil strategies are ETL listed which is a status only applied to the most efficient products.
// The author is the chairman of Ability Projects LTD //
3 March 2014