Client Objective

An FM client required a solution to regain heating and hot water services back into their client’s commercial office building. The existing boilers within their plant room were not functional. The client was looking for a long term rental solution, to create some breathing space whilst a plan was formulated to replace the existing plant room.

As tenants began to occupy the commercial office space, speed of delivery and commissioning became vital. Rapid Energy’s team advised that a full scope of works would be required to design and formulate a plan. Our team arrived on site to determine the appropriate hire solution and followed up with a formal plan of action with the client.

40kW Electric Mobile Boiler

Equipment Required

  • 6 x 40kW electric boilers.
  • 1 x 240kW plate heat exchanger with 2” manifold complete with 12 x 1” flow/return connection points with isolation.
  • 36m of 25mm hose.
  • 20m of 50mm hose.
  • 25m of 185mm 4 Core SWA cable to be connected from the existing 400amp switch in the server room to the boiler room.
  • Installation of a 6-way panel board complete with 6 x 63amp triple pole MCCB.
  • Installation of 6 x 10mm 5 core cables from panel board to the 6 x electric boilers.
  • Connection of existing Trend 963 system to the electric boilers, to sequence the boilers in relation to the return temperature and to provide duty rotation to give even use of the electric boilers.


The client’s existing boilers were located in the basement and consisted of 6 x 50kW boiler modules, with a vertical flue running 6 stories up through an internal stack. The existing boilers fed the primary heating circuit and a 1000L HWS calorifier. With no outside space to locate a boiler externally, it was quickly ascertained that an electric boiler solution would be the best plan of action. Our mobile electric boilers can be installed anywhere in the building, as no flues are required and have the advantage of being very quiet in operation. Ideal for a basement plant room located in central London. 

Firstly, the power requirements had to be addressed. The client’s server room was located down the corridor from the plant room. Our electrical engineer surveyed and concluded that the server room had enough available power to run a supply cable from the server room into the plant room.  This allowed us to power the 6 x 40kW electric boilers, each requiring a 3 phase 63amp supply.

On the mechanical side, we designed a solution consisting of a 2” header manifold running off a 240kW plate heat exchanger. Allowing a total of 12 x 1” IV connection points for the 6 electric boilers to be connected onto. The 240kW plate heat exchanger system, allowed us to separate the client’s system from ours. The secondary side of the PHE would then be connected into the client’s primary circuit via 20 meters of 2” heating hose. Providing the client with 240kW of LTHW at 80 degrees into their system, which also supplies the 1000L calorifier for their hot water services.

Installation and location

Our Solution

Upon instruction from the client, the project was scheduled for the following week. Rapid Energy submitted detailed Risk Assessment Method Statements (RAMS) prior to works commencing for client approval. The electrical works were due to take a total of 5 days with the mechanical works taking a further 2 days to complete.

The electrical works consisted of running a 185mm 4 Core SWA cable on a 25m run. Allowing us to connect from the existing 400amp switch in the server room, to the basement plant room. We then installed a 6-way panel board, complete with 6 x 63amp triple pole MCCB, which the SWA cable then connected into. Following this installation, 6 x 10mm cables were run from panel board to the 6 x 40kW electric boilers. This took our 5 man electrical team a total of 4 days to complete.

On day 5, our BMS controls engineer connected our electric boilers into the building’s Trend 963 BMS system. We did this to sequence the electric boilers in relation to the return temperature and to provide duty rotation to give even use of the electric boilers. Our boilers are rated 40kW each but can be configured to run as two stages of 20kW. This would give us 12 stages of controllable heat output, ranging from 20kW to 240kW, and would also have the advantage of interlocking the boilers with the client’s circulating pumps.

Once the controls were completed, day 6 consisted of our mechanical engineers filling and venting the client’s existing system. Raising the temperatures and allowing heat back through the system.

The following week, a walk-round was conducted with the client to show how the system operates, completing the handover. This system will be in place for the next 12 months to allow the client time to design and install a new permanent boiler system.

From the moment we were instructed, we designed, installed and commissioned a temporary 240kW electric heating and hot water solution. Ensuring the tenants had uninterrupted heating and hot water as they occupied the building.

If you require a temporary boiler or a long term boiler rental solution, complete the form below or call us on 0800 464 7025 to discuss your requirements. We have a wide range of packaged boiler plant rooms and mobile electric boilers within our fleet. Our experienced team of consultants will do their utmost to find the best solution for your project.

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