Lennox at your disposal in order to save electricity!

15% savings achieved through the eDrive™ variable speed pump, proposed for the Lennox range of chillers (Neosys and Ecolean)


eDrive™ Technology variable speed pump - Lennox
Source: Lennox

Saving electricity

When professionalism is aiming by all means at improving the energy efficiency of chillers, one should point out that in the public water networks the pump is one of the major elements of power consumption. A proven and economical solution is the use of frequency converters to adjust the pump speed.

If obtaining a high efficiency class "A" for a chiller helps reduce energy costs, it must be done at the best cost to do not risk the prolongation of the investment repayment period to a considerable extent. This is the problem. Obtaining a high EER at full load requires manufacturers to increase the exchange surface and the chillers' cost. Is it true what we know that 97% of the time the chiller runs at part load? Wouldn't it be better to find all potential economy sources in operation at reduced load?

Noting that the energy cost of pumping may exceed 20% of the total energy of a cooling group, Lennox thought about using a variable speed pump to reduce the flow when the building's demand is fulfilled.
The variable speed pump technology is one of the few that offers a depreciation/amortization of less than one year. Energy savings are generated to the extent of 75% on the "pumping" position. This economical solution developed by Lennox can now offer chillers (Neosys and Ecolean) with the option of variable speed pump.

Cost distribution of a chiller after 15 years of life
Source: Lennox

Indeed, to date, two types of hydraulic systems were available for chillers: "direct" circuit with constant flow or primary-secondary "off"circuit, with primary constant.
Some chillers now offer a variable speed pump and work in a third type of possible hydraulic system: "direct" circuit with variable primary flow (DPV).

A little explanation is necessary. After many years, manufacturers encourage users to maintain a constant flow through the vaporizer, in order to avoid any problem. Indeed, the groups controlled by the basic functions do not provide reliable operation and reduced water flow through the vaporizer and they are at risk of vaporizer freezing or other break-down. This should prevent the risk of operating in laminar flow in the vaporizer.

The design of a reliable plant with variable water flow requires special attention in the group design. Due to the new regulatory generation, Lennox chillers can nowadays maintain a desired temperature of the water with a flow variation from 60% ?? to 100%, thus allowing the achievement of up to 75% energy saving per year used for pumping.

Remember, the relationship between variables such as the consumption rate, the rotation speed and power consumption may be the so called laws of affinity. This applies to both fans and pumps. Thus, the theoretical energy consumed by the pump varies with the cube of speed.

P1/P2 = (F1/F2)3   or P = engine power and F = engine speed

40% speed reduction = Energy consumption reduced by 80%

Electricity consumption of a variable speed pump on a chiller
Source: Lennox

Earnings: low installation costs and environmentally responsible technology

The potential reductions of the installation cost should be addedd to the energy saving. Indeed, the "direct" circuit with variable primary flow (DPV) is cheaper than a primary-secondary "off" circuit, because it does not require a main pump and the primary-secondary hydraulic decoupling system can be removed. You will have to add the elimination of water flow control valve, because adaptation to the real needs of the installation is done electronically.
 

NEOSYS chillers

Source: Lennox
Contact:
Delphine CASERTA, Lennox Group Communication Officer.
LENNOX HVAC Europe
ZI les Meurieres, BP 71,
69780 Mions (France)
email : delphine.caserta@lennoxeurope.com
Tél. : +33 6 11 95 28 60