OP
dennis2011
I have read the whole of this thread and found it fascinating. I am not an electrician but have a scientific background. It occurs to me that with a maximum saving of only around 50p per day, during the summer months, the level of sophistication you need with any system depends not only your HW usage but also what kind of installation is possible at an economic price.
We have a recently installed 3.92 kW SE facing PV system, with a newly acquired ‘freebie’ display unit. (Referral gift). There are only two of us in the house most of the time. We are retired and are at home quite a lot especially in the winter. Our ‘background’ power usage is around 300w. We probably use more than half of the electricity we generate during the winter. We heat hot water using gas CH boiler linked to a DPS Pandora Heatbank system which gives mains pressure HW to all taps and showers.
We have no immersion heater whatsoever. There is not even a power point in the airing cupboard; neither are there any spare ‘ways’ on the consumer unit. Changing this for a larger one would be quite expensive. However looking on the bright side, when I ordered my thermal store a few years ago I had the cost of a standard immersion heater deducted of the bill and they fitted a blanking plug instead. The tank is 150 litres in capacity and does have an immersion heater point half way up the tank – so a short 280mm heater, like the ones from the SureJust range, (probably go for 1000w), could be fitted horizontally and heat half the tank at least. I have checked with DPS and they see no problem – so just drain, fit heater, refill, add inhibitor and plumbing side of job done.
I have checked for a suitable method of getting power to the airing cupboard and the utility room below has power sockets on a 32A short ring main serving just the utility, dining room and one bedroom – so I propose to take a spur from one of the sockets then to a switched FCU and then up the wall, through the ceiling and up through one of the floorboards into the airing cupboard finishing with a twin 13amp socket on the inside of airing cupboard wall.
I need some advice please as to what I put in between the FCU in the utility and the twin socket in the airing cupboard.I am thinking along the following lines –
from the FCU go to a socket box mounted timeswitch, like Grasslin 24 hr, then next up to something like Legrand 20A dual bath/sink immersion switch. This could both isolate the immersion heater (irrespective of timeswitch setting), and also divert the electricity supply direct to the immersion heater, 1000w, in the ‘bath’ position or alternatively to the next box up on my wall container a ‘power halver’ which would operate at 500w, in the ‘sink’ position. I am still waiting to hear back from Abeltronics but my wife is hoping for the sake of appearance/neatness that I can put the ‘power halver’ in something like a galvanised cooker back box, 47mm deep, mounted vertically and covered with a standard brushed steel blanking plate. (Drilling ventilation holes top and bottom if needed)
My way of operating this proposed ‘system’ could only generously be described at ‘semi-automatic’. I would set the time clock to come on say 1 hour after dawn and go off say 3 hours before sunset. The system would start each day on 500w and when the inverter was producing over 1500w then manually switch the heater to 1000W. If it became cloudy then manually back down to 500w. If we went out for the day unless certain to be cloud free would leave on 500w.
You might be wondering why the twin socket in the airing cupboard and not simply a wired in connection. Am I correct in thinking that immersion heaters 2000w or less can be fitted with a 3 pin plug and run from a plug socket? I may use the other plug socket for circulation of water in the tank so that the immersion heater could possibly heat the whole tank.
Due to several bad admin errors when I ordered my DPS system I had fitted on the input side of my heatstore cylinder a ‘quick recovery system’ instead of the more usual indirect coil. As compensation I was not charged extra for this. It is basically another plate exchanger on the input side operated by a Wylo pump. DPS say they see no reason why I couldn’t utilise this pump, if needed, to circulate the HW heated electrically. Whether I need to this I don’t know yet as I could run the top part of the tank at 85 C if needed and it would still come out at 50 C through the mixing valve and this might give us enough hot water.
So what do you think of my system? The inputs of Mr Robinson and Mr Heath are quite evident! but I am somewhat ‘snookered’ in that I can’t easily install a fully automatic system, at least I can’t at an economic price.
What I like about my design is –
I will have for first time an emergency use immersion heater
Total installation cost is quite cheap
I can control it from down stairs without having to use my savings towards buying a new stair carpet!
What I don’t like about my system is –
Too many sockets/boxes on the wall
Need to change time clock at least every month to allow for different day lengths.
Danger of leaving set at end of day in 1000w position so starts next day at 1000w! Could really do with a warning light when in 1000w ‘bath’ but nothing in 500w ‘sink’ position.
All comments and suggestions most welcome – and thanks for your time reading this.
We have a recently installed 3.92 kW SE facing PV system, with a newly acquired ‘freebie’ display unit. (Referral gift). There are only two of us in the house most of the time. We are retired and are at home quite a lot especially in the winter. Our ‘background’ power usage is around 300w. We probably use more than half of the electricity we generate during the winter. We heat hot water using gas CH boiler linked to a DPS Pandora Heatbank system which gives mains pressure HW to all taps and showers.
We have no immersion heater whatsoever. There is not even a power point in the airing cupboard; neither are there any spare ‘ways’ on the consumer unit. Changing this for a larger one would be quite expensive. However looking on the bright side, when I ordered my thermal store a few years ago I had the cost of a standard immersion heater deducted of the bill and they fitted a blanking plug instead. The tank is 150 litres in capacity and does have an immersion heater point half way up the tank – so a short 280mm heater, like the ones from the SureJust range, (probably go for 1000w), could be fitted horizontally and heat half the tank at least. I have checked with DPS and they see no problem – so just drain, fit heater, refill, add inhibitor and plumbing side of job done.
I have checked for a suitable method of getting power to the airing cupboard and the utility room below has power sockets on a 32A short ring main serving just the utility, dining room and one bedroom – so I propose to take a spur from one of the sockets then to a switched FCU and then up the wall, through the ceiling and up through one of the floorboards into the airing cupboard finishing with a twin 13amp socket on the inside of airing cupboard wall.
I need some advice please as to what I put in between the FCU in the utility and the twin socket in the airing cupboard.I am thinking along the following lines –
from the FCU go to a socket box mounted timeswitch, like Grasslin 24 hr, then next up to something like Legrand 20A dual bath/sink immersion switch. This could both isolate the immersion heater (irrespective of timeswitch setting), and also divert the electricity supply direct to the immersion heater, 1000w, in the ‘bath’ position or alternatively to the next box up on my wall container a ‘power halver’ which would operate at 500w, in the ‘sink’ position. I am still waiting to hear back from Abeltronics but my wife is hoping for the sake of appearance/neatness that I can put the ‘power halver’ in something like a galvanised cooker back box, 47mm deep, mounted vertically and covered with a standard brushed steel blanking plate. (Drilling ventilation holes top and bottom if needed)
My way of operating this proposed ‘system’ could only generously be described at ‘semi-automatic’. I would set the time clock to come on say 1 hour after dawn and go off say 3 hours before sunset. The system would start each day on 500w and when the inverter was producing over 1500w then manually switch the heater to 1000W. If it became cloudy then manually back down to 500w. If we went out for the day unless certain to be cloud free would leave on 500w.
You might be wondering why the twin socket in the airing cupboard and not simply a wired in connection. Am I correct in thinking that immersion heaters 2000w or less can be fitted with a 3 pin plug and run from a plug socket? I may use the other plug socket for circulation of water in the tank so that the immersion heater could possibly heat the whole tank.
Due to several bad admin errors when I ordered my DPS system I had fitted on the input side of my heatstore cylinder a ‘quick recovery system’ instead of the more usual indirect coil. As compensation I was not charged extra for this. It is basically another plate exchanger on the input side operated by a Wylo pump. DPS say they see no reason why I couldn’t utilise this pump, if needed, to circulate the HW heated electrically. Whether I need to this I don’t know yet as I could run the top part of the tank at 85 C if needed and it would still come out at 50 C through the mixing valve and this might give us enough hot water.
So what do you think of my system? The inputs of Mr Robinson and Mr Heath are quite evident! but I am somewhat ‘snookered’ in that I can’t easily install a fully automatic system, at least I can’t at an economic price.
What I like about my design is –
I will have for first time an emergency use immersion heater
Total installation cost is quite cheap
I can control it from down stairs without having to use my savings towards buying a new stair carpet!
What I don’t like about my system is –
Too many sockets/boxes on the wall
Need to change time clock at least every month to allow for different day lengths.
Danger of leaving set at end of day in 1000w position so starts next day at 1000w! Could really do with a warning light when in 1000w ‘bath’ but nothing in 500w ‘sink’ position.
All comments and suggestions most welcome – and thanks for your time reading this.
