A project to increase the life of a 15+ year old chillers gave a surprising twist.
Not only was the life of the chiller increased but an amazing energy saving and
greater control were achieved, allowing better usage of people to building ratio.
A multiple package of benefits was demonstrated for the clients of a prestigious
building located at Canary Wharf in the heart of London's Docklands
Extended Chiller Life with
energy savings,
incorporating conversion of
Reciprocating
to Screw Compressor
Many of the buildings around the central hub of Canary Wharf complex were constructed in the late 1980's,
and although some of the more significant buildings have only just opened, many of the earlier buildings are
now some 15 years old. ThermaCom advised on the increase of life of the equipment including the forthcoming
phase out of R22 from 2009, and although presently this gas remains available for use until 2015, availability
after 2009 is certainly questionable.
The principle problems facing the client were ...
1 Equipment age
2 Refrigerant situation - R22 phase out 3 Mode of control
4 Power consumption. At start up, Over cycling of plant, Continuous power draw
5 Increasing unreliability of current equipment
6 Lessons of previous attempts at improvements on nearby buildings.
In selecting the Screw compressor a variable unloading
control mode allowed a very precise matching of cooling
load demand to achieve loads across a wide range of
actual loadings.
By properly commissioning the controller the hunting
problem previously experienced was completely
eliminated from day one also a huge volume of the
high energy voltage spikes.
The remaining functional chiller parts were also renewed
or overhauled. We were careful to select part wind
start mode and strongly advised that it be used.
This provided yet further power reduction.
Hotel Complex
The chillers, providing chilled water for air-conditioning to a Hotel complex used for exhibition etc, were in an appalling condition due to a combination of local exhaust flue gases attacking the coils and manufacture standard not suited to a damp northern European climate. The chillers were only 6 years old and used refrigerant R470c. However, the client was receiving service from as few as 6 of the 16 circuits. Leaks were costing a fortune, both financially & environmentally. The differential leakage of the R470c was knocking out compressors due to highly unstable systems.
We provided, via a large crane, 32 replacement coil panels, all made to suit UK conditions, and with additional epoxy vinyl coating to provide increased resistance to atmospheric corrosion. However, the coils removed were barely 2/3 the weight of the coils we installed - with identical fin spacing the cheapness of the original coil was borne out by the weight of copper tube used.
The project was combined with other upgrades including: provision of service exchange compressors specified for R407c, fan motor overhauls and new metal closure panels to improve the aesthetics.
The refrigeration systems were pressure tested using Helium/ Nitrogen mix. Helium is the smallest nonflammable molecule and to be sure the finished systems was 100% leak tight.
The work was tackled as a rolling schedule, which allowed the Hotel to retain the available circuits in service. Once the first two chillers were completed they immediately saw availability increase.
The Hotel now feels distinctly cold, with outside ambient recently of 31°C.
The overall package of works cost the Hotel complex about £205,000. The replacement of eight chillers would have exceeded £1,000,000.
Cost Comparison
Repair (Actual )
New condesner coils
£148,000
Upgrade compressors
£22,000
Renew system parts
£13,000
Set to work
£22,000
£205,000
New (Estimate)
Project fees
£100,000
Chiller units
8X
£95,000
Installation
8X
£10,000
Pipework
8X
£4,000
Controls
£7,000
Set to work
8X
£3,000
£1,003,000
Case Study
Human Genome Campus
When a Chiller suffers a burst or leaking tube within the evaporator the resultant water logged refrigeration circuit represents the most severe compound failure any chiller can suffer. The water destroys the compressors. The chiller cannot function again until every last vestige of water and dirt has been thoroughly removed. The affects of corrosion renders all modulating parts useless.
Because the chiller concerned was already suffering condenser tube failure, due to poor original manufacture, the client had to seriously question whether this particular chiller was worth while repairing.
The simple arithmetic to affect a cost and time comparison clearly showed that despite the severe failure, a repair was still considerably the better option ...
The chiller concerned was a 580 kW triple circuit unit. The resultant failure had filled two circuits to the brim, but remarkably the third circuit was still operating 'On Line' when the failure was discovered.
The project required 2 compressors re-manufactured, re-tube of the evaporator,
new condenser coils, new TEVv's & Solenoid Vv's, etc., 'In situ' dismantling & assembly of components, thorough dehydration and full set-to-work
procedure.
The project cost the client £36,000 net, and 3 months from decision to stand alone operation. Yet, a new chiller would have been 6 months & with installed cost estimated at £150,000. The chiller was 9 years old and the client can now, subject to proper servicing, reasonably expect to receive the remaining 11 years of service from his chiller.
