Holdfast Training Services Trial Blog

I blogged a while back about the potential for dispensing with the need for generators by instead utilising the existing grid connected electrical infrastructure to power a winter environmental control solution for the ‘East Wing’ (Convective heaters and dehumidification units). The spare capacity in the infrastructure is due to the reduced footfall and activities on site a la COVID, with some quick analysis of the Building Management System data it was found that there would be sufficient capacity to provide most of the temporary heating electrical demand.

The cost of generators on hire and the fuel as well as the noise and the associated carbon footprint are undesirable given the cheaper and cleaner (carbon footprint per kWh, getting better and better) supply of elecricity from the grid.

Essentially the ‘East Wing’ has two zone distribution boards at the North and South end, both of these boards have 400 A three phase incoming supplies, therefore each distribution board can theoretically draw 276 kVa based on 400 A per phase loading with a phase to line voltage of 230 V. There are 6 floors to provide environmental control to with each floor having different loading requirements due to ‘high risk’ areas in terms of conservation etc.

We toyed with the idea of setting up a system whereby generators would be joined in parallel with the existing electrical infrastructure, the idea being you would maximise the grid capacity from the distribution boards and use generators to ‘top up’ any additional power requirements in the event of surplus demand. We were informed by contractors that to parallel generators up with the grid requires DNO (District Network Operator such as UKPN) permission, takes a long time and costs a fair amount of money (there is also no guarantee that the DNO will provide permission).

Therefore it was decided to match specific ‘high-use’ floors to the distribution boards which turned out to be the groundfloor, principal floor and second floor and the remaining floors would be supplied by dedicated generators. It has already been noted that the kVa demand of each floor has been based on no diversity i.e worst case scenario that all convective heaters and dehumidification units are turned on simultaneously. It has been confirmed that there are spare ways on the Medium Distribution Units to the three floors just mentioned which gives us flexibility if it becomes apparent that the diversity assumption is ‘overkill’ and we can extend the provision of grid power safely across more of the floors.

Also worth mentioning the ‘East Wing’ has been split into North and South zones for geographical convenience in terms of cabling and voltage drops from the zone distribution boards.

Potentially a blog post soon looking at the temperature and humidity levels in the building and the optimisation of the solution, just waiting on access to the environmental monitoring database (temperature and humidity sensors positioned across the floors).