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Is it cheaper to run your heating continuously or not? How does insulation change that?

The level of insulation can make a big difference to the “difference” in energy usage between running a system 24hours a day vs just when needed and it can certainly reduce the energy usage per hour of maintaining a particular temperature. It does not, however, change the fact that a building at a temperature above ambient will always be losing some energy to its surroundings and therefore some energy must be introduced to maintain that above ambient temperature.

When a building’s internal temperature is the same as it’s external temperature no energy is being wasted and therefore every hour that the building sits cold (and heat is not required) it is performing at 100% efficiency. When the building’s internal temperature is higher than it’s external temperature some energy will be being lost and the level of insulation only affects the rate at which that energy is lost. The point here is that a building’s efficiency only drops when there is some higher than ambient internal temperature, the rest of the time it’s performing at the maximum possible efficiency.

The more insulation a building has the less time the building spends with its internal temperature being the same as its external temperature. Therefore the difference in cost between running the heating system continuously or as needed decreases as insulation increases.

A building which is very well insulated and cools back towards ambient temperature so slowly that it doesn’t reach the ambient temperature in the time when heat is not required therefore is continuously losing energy at a constant albeit low rate. Therefore the heating system will be no more or less efficient if it is set to be on continuously or only as needed because the building never cools to ambient and so it always has some energy to lose every hour. It would not be possible for continuous operation to become cheaper than only heating when required because that would imply that you are actually creating energy, and as we know it is not possible to create energy.

It may certainly be more convenient to always have the heating turned on and I’ll acknowledge that with some really good insulation the financial cost of running your heating continuously may be very low especially if you have solar panels or some other “free to run” energy gathering systems but it still wouldn’t be cheaper (though it also wouldn’t be any more expensive) than running your heating on demand.

Here are three examples using some hypothetical numbers:

Assumptions:
1. The exterior temperature is 10C (degrees centigrade)
2. A comfortable interior temperature is 15C – 20C
3. The thermostat turns on the heating system when the temperature falls below 15C and turns it off when the temperature reaches 20C
4. We’ll assume no delay in heat being produced and that heat reaching the thermostat (i.e. no overshoot)
5. Numbers may be somewhat unrealistic in order to make the mathematics easier.
6. The temperature drop (energy loss) is linear over time.
7. The heating system increases the temperature by 1C for each kWh used.
8. The occupants get up at 7 am and leave the building at 8 am.
9. The occupants return to the building at 6 pm and go to bed at 10 pm.
10. The occupants only require the building to be at a comfortable temperature when they are awake and in the building.
11. A poorly insulated building’s internal temperature drops by 5C per hour
12. A medium insulated building’s internal temperature drops by 1C per hour
12. A well-insulated building’s internal temperature drops by 0.5C per hour
13. Energy (kWh) can come from multiple sources e.g. gas boiler, solar panel, sun trap, etc and some of these energy sources are cheaper than others.

 

If the system put on a time clock to be active only during hours of occupancy in a poorly insulated building:

At 7 AM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 8 AM the building has dropped to 15C and the system is turned off
At 9 AM the building dropped back to 10C

At 6 PM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 7 PM the temperature has dropped to 15C and the system uses 5kWh to bring the temperature back to 20C
At 8 PM the temperature has dropped to 15C and the system uses 5kWh to bring the temperature back to 20C
At 9 PM the temperature has dropped to 15C and the system uses 5kWh to bring the temperature back to 20C
At 10 PM the building has dropped to 15C and the system is turned off
At 11 PM the building has dropped back to 10C

Over a 24 hour period, the system would use 35kWh to maintain the temperature

 

If the system put on a time clock to be active only during hours of occupancy in a medium insulated building:

At 7 AM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 8 AM the building has dropped to 19C and the system is turned off
At 5 PM the building dropped back to 10C

At 6 PM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 10 PM the building has dropped to 16C and the system is turned off
At 4 AM the building has dropped back to 10C

Over a 24 hour period, the system would use 20kWh to maintain the temperature

 

If the system put on a time clock to be active only during hours of occupancy in a well-insulated building:

At 7 AM the temperature of the building is 13.5C and the system uses 6.5kWh to bring the temperature to 20C
At 8 AM the building has dropped to 19.5C and the system is turned off

At 6 PM the temperature of the building is 14.5C and the system uses 5.5kWh to bring the temperature to 20C
At 10 PM the building has dropped to 18C and the system is turned off

Over a 24 hour period, the system would use 12kWh to maintain the temperature

 

If the system is active 24 hours in a poorly insulated building:

At the beginning of each hour, the system will use 5kWh to bring the temperature from 15C to 20C and over the course of the hour, the building will drop back to 15C. On average each hour the system will use 5kWh to maintain a comfortable temperature.

Over a 24 hour period, the system would use 120kWh to maintain the temperature

 

If the system is active 24 hours in a medium insulated building:

Every 5 hours the system will use 5kWh to bring the temperature from 15C to 20C and over the course of 5 hours the temperature will drop back down to 15C. On average each hour the system will use 1kWh to maintain a comfortable temperature.

Over a 24 hour period, the system would use 24kWh to maintain the temperature

 

If the system is active 24 hours in a well-insulated building:

Every 10 hours the system will use 5kWh to bring the temperature from 15C to 20C and over the course of 10 hours the temperature will drop back down to 15C. On average each hour the system will use 0.5kWh to maintain a comfortable temperature.

Over a 24 hour period, the system would use 12kWh to maintain the temperature

 

Now I’ll agree that these examples are somewhat simplistic but the principle still holds.

 

Renovating VideoLogic Sirocco Stereo Speaker System

I have had a VideoLogic Sirocco speaker system for about 15 years now, originally manufactured in 1999 my dad bought it to use at a kid’s club he helped run. A couple of years later he was no longer involved and the speakers were not being used – stored in the shed for a while they became a little damaged by the elements with some rust showing on the amplifier cabinet. He then gave them to me as a replacement for an awful set of speakers that I had which had been damaged (i don’t remember how). Since then I’ve hung on to these speakers because they seem to me to be pretty good quality and I love the tone and clarity of the sound that they produce.

damaged cone

Sadly time has taken its toll on these speakers and the original Audax mid range speaker cones which were made of foam and cardboard have now disintegrated. Additionally, the original volume and adjustment potentiometers are noisy (and I have tried cleaning them) and the headphone jack socket which uses a spring to complete the circuit when there are no headphones attached doesn’t reliably maintain the circuit.

Therefore I have decided to renovate these speakers, more because they have a kind of sentimental value to me than because they’re worth the time. After all, I have a couple of sets of Tannoy HiFi bookshelf speakers which I could happily use instead and decent amplifiers are not hard to find. I started this renovation project when I moved into my last house around the beginning of 2015 because I thought before I took the time to wire them in I should get them back into a working state. I ordered the replacement cones around this time but the project stalled after that and personal issues got in the way. I have now moved again and am getting settled, and in going through my stuff found these speakers and the replacement cones. They are vastly superior to the speakers currently attached to my computer so I am going to get this project finished up so I can use them.

To rectify the headphone socket I am just going to remove it and bridge the circuit as if it was there without headphones inserted. This is because I never use it for headphones because I have a separate headphone amplifier for them. I haven’t yet decided whether to place something in the vacant hole left by the headphone jack or to simply leave it.

The potentiometers I am attempting to find like for like replacements.
The volume potentiometer is a stereo A203 (20k Ohm logarithmic) with no detents, a smooth 6mm diameter shaft, 5mm spacing between pins and a shaft length of 13mm.
The sub potentiometer is a mono A103 (10k Ohm logarithmic) with a centre detent and also has the same dimensions as the volume potentiometer.
The attitude potentiometer is a stereo B104 (100k Ohm linear) with centre detent and again the same dimensions as the volume potentiometer.

the pots

While I am resoldering these potentiometers I also want to replace the bright blue power indicator led with a much less bright red led. This is because when watching a video or something in the dark, the blue led is bright enough to be distracting.

To replace the disintegrated cones I attempted to track down the exact same models from Audax but found that they haven’t been in production since around the time that the system was manufactured. So as an alternative I found some Monocor “One” speakers which, from what little I understand about speaker cones, have similar frequency responses and power ratings to the original Audax cones. I also believed that they were of the same size as the ones I was replacing, however, having ordered these replacements and laid them up next to the originals, while the cones themselves are the same size, the replacement enclosure requires an additional 6mm clearance in the cabinet. I have therefore removed the extra material with a rasp and a file. Finally, the spade connectors of the original speaker cones were a different size to the new ones, so I cut off the connectors and soldered the cables directly to the cones.

Speaker cabinet with new cone fitted

I will complete this project soon. I have modified both cabinets and changed both cones over, I have desoldered the existing pots and am just waiting for new pots to resolder and then reassemble the amplifier and the project will be completed.