Economy 10 and 3 phase - feasible or not? ..CONCLUSION: Yes but E7 simpler & cheaper

macspud

FAI wrote: »

Hello HappyMJ,

In all honesty, I do not know what % we will consume overnight. That is why I like Scottish E7 as the break even % with the non E7 version of the same tariff is at approx 12% overnight usage and any increase on that is a saving.

Our collector pipes are between 1.5 and 4.5 metres down and the ground temperature will not change significantly overnight. The warmth is supposed to also be provided by water in the soil aswell as the differential with air. The GSHP return feed warms an 800litre buffer tank to 35 deg C to subsequently circulate through the UFH, and the intention is to ensure that this buffer tank is up to temperature by the end of the night. After that, yes we will have usage in the day; and our ground is south facing so that will help.

Once the GSHP has been commissioned, we will be tuning the running of it to get the highest COP (coefficient of performance) i.e. availble heat in kW from running the pump, aswell as the lowest energy bill. It is definitely trial and error, but based on some good heat calcs for the total building....

I'm not sure if you've already settled on and committed to one particular GSHP supplier but have you looked into Kensa?

Quote from the web site:

"Kensa are the only UK manufacturer of a 24kW Single Phase Ground Source Heat Pump - The Largest Single Phase Unit in the UK Market.

Due to the constraints of the UK National Grid there are a number of large properties with single phase electricity, where the upgrade cost to 3 phase supply can be extortionate. This rarely happens on the continent as 3 phase supplies are readily available, so importing manufactures have had no need to develop large single phase heat pumps, this is why most current suppliers can only provide units up to 11-12kW.

Kensa are the only UK manufacturer of a 24kW Single Phase Ground Source Heat Pump - The Largest Single Phase Unit in the UK Market.

Due to the constraints of the UK National Grid there are a number of large properties with single phase electricity, where the upgrade cost to 3 phase supply can be extortionate. This rarely happens on the continent as 3 phase supplies are readily available, so importing manufactures have had no need to develop large single phase heat pumps, this is why most current suppliers can only provide units up to 11-12kW.

As Kensa manufacture our heat pumps in the UK we understand this issue and have developed our award winning product range to suit, featuring single phase twin compressor heat pumps from 16 to 24kW.

The twin compressor unit has ‘soft start’ fitted as standard, and the compressors will stage start to ensure peak starting load is minimised."

I am running a ASHP on Scottish Hydro Electic (SSE) Economy 10 (RHT) in the Scottish Highlands. The Economy !0 tariff means there is no option for competition and having looked into it thoroughly again this week find that there has been no benefit costwise over using a standard rate tariff, and actually if I'd been on a standard rate tariff there is some options for competition which would have saved £75-£100 per year. Whatever the anwer is to spend money on insulation and getting the house airtight, using under-floor heating and a heat recovery system. That way the actual heating cost are mininal. Some Scandinavian and Canadian systems need no heating right down to minus 35 degrees celcius. Depending on the design of house that you're buiding a single phase system could be capable/suitable and would have advantages in some areas.

Regards,

Iain.