Out with the old. In with the new.

27 February 2017

Gisborne Girls High School needed a more efficient way of heating the school as their existing boiler was unsafe and inefficient in providing adequate heat. That's where ElectriServ comes in ...

Case Study: Boiler Replacement at Gisborne Girls' High School

Client: Ministry of Education
Engineer: Darrington Slater Architecture
Principal Contractor: ElectriServ, Whakatane
Technical Specifications: Installation of two new high-efficiency condensing boilers

The Problem

Gisborne Girl's High School was heated via a large, old, oil-fired boiler that was converted to gas some time ago. The heat was distributed via the heating hot water infrastructure pipework which was installed when the school was built back in 1956.

When carrying out their initial inspections at the school, ElectriServ discovered asbestos rope which was visible and uncontained around the boiler combustion door seals. This meant the old boiler would need to be completely removed and the option of temporary recommissioning would not be permissible. 

Old boiler with asbestos

The existing pipework was above ground and well insulated and was therefore deemed to be in good serviceable condition by the ElectriServ technicians.

Proposed Solution

ElectriServ proposed to remove the old boiler and replace it with two new high efficiency condensing boilers with would sit side-by-side in the old boiler house. The efficiency of old oil boilers which have been converted to gas sit around 40%, whereas the new boilers ElectriServ would install are close to 100% efficient, resulting in an expected saving of around 50% on the school's heating costs.

The two new high efficiency boilers would each provide slightly more than 50% of the maximum building heating demand.  ElectriServ recommended installing two boilers rather than one, due to the benefit that if one boiler is out of commission for any reason the remaining boiler should provide enough heat for the school. Although supplying and installing two boilers is more costly than only one, ElectriServ believed that when considering the remote location of Gisborne, it would be prudent to have the security of 50% standby heating capability if one boiler was out of service.  

The ECO C330-280kw boilers ElectriServ proposed to use are manufactured in France and weigh 364 kg each. As there was only one in the country at the time, they proposed to install the one available boiler and then return to install the other boiler, when it arrived from overseas.  In order to ensure the best and quickest method to install a heat source in the school, in the shortest timeframe, this phased start up was recommended to the school as being the best option. The single boiler was expected to fulfill the heating requirements for the school down to an external ambient temperature of about 10C.  

Gisborne Girl's High School liked the proposal for the two boilers presented by ElectriServ and the fast turnaround times that the work could be completed in - a start date of 5 days from acceptance of quote, heating at the school within 4 weeks of the start date and both boilers operational within 10 weeks - and therefore ElectriServ were awarded the contract.  

Application of Proposed Work

The first task entailed decontaminating the existing boiler and storing it for removal at a later date; due to health and safety concerns, the removal needed to be carefully planned and executed at a time when no students or members of public were on the school grounds. To this end, ElectriServ waited until the winter school holidays and removed the boiler and flue on July 21st 2016.

Removal of the boiler and flue was a colossal task, as the boiler weighed around 2.8 ton and the existing flue tower was 13 metres tall. This required a crane with a lifting hook and a man-cage to remove it. The structural connections at the base of the flue tower were cut and then the flue was lifted directly onto a truck for transportation and disposal.  

Removal of flue

Removal of boiler

Once room had been made for the new boilers, the ElectriServ technicians fabricated the pipework from the existing boiler system to allow for the two new boilers to be placed in the boiler room. 

They replaced the circulating pumps and re-wired the pumps and boiler temperature probes.

Three new secondary zone pumps were installed along with one new boiler primary pump.  These pumps and boiler duty would be controlled by the boilers' intelligent operating system that is programmed to use the most effective energy saving operation.  The flow temperature is kept as low as possible, according to the outside temperature, as high efficiency condensing gas boilers save the most energy when the return temperature is 54C or less.

The boilers also required a new gas supply, control regulators and over pressure vents. They were piped to sanitary drainage, due to the fact that when they are operating efficiently a large amount of liquid condensate is produced. Also, a new stainless steel uninsulated boiler flue was installed that exited through the side wall and terminated in a vertical position 500mm above the roof surface.  

As the existing vent system was an open vent system, meaning the level of oxygen that attacks steel pipework in the heating water is high, ElectriServ converted the system to a sealed system type and installed a large expansion vessel in the plantroom.  

Also, as the existing system was old and had a very low corrosion inhibitor level (according to the water sample test they carried out) ElectriServ technicians installed a special cyclonic dirt and air separator into the system and a chemical dosing pot to enable anticorrosion chemicals to be added to protect the radiators, pipe system, new pumps and boilers.

Services rendered from ElectriServ included plumbing, electrical, gas-fitting, drain-laying, concreting ... and they also re-painted the entire boiler room as well.

Once the work was completed, the boilers were fully commissioned and the radiators were balanced to ensure that every radiator in the school received the same amount of heat.

New boilers

The Outcome

The work completed by ElectriServ was delivered on-time and within the quoted budget and, according to the Principal of Gisborne Girls' High School, Jan Kumar, was to a very high standard.

"The completed work was to a very high standard - both the installation of the boilers as well as how they left the building both inside and out. The way they completely painted the full room as well as how they treated the flue remains was excellent. The boilers are working very efficiently - they will be a great asset for my school and they provided a warm school through the winter."

Principal, Jan Kumar, was very impressed with the work ethic displayed by all of the ElectriServ technicians and would happily recommend them to others.

"They were all very friendly, professional and great to work with. They kept me fully informed about the progress of the job and always turned up as expected. They were excellent and I was very impressed."