What is cheaper to heat a room, Gas or Electricity?

ConstantineX

I understand that this question has been asked quite a few times but I've been trying to work this out but I cant really be certain of what is cheaper. I live in a house in Scotland with 2 bedrooms, 1 living room, 2 bathrooms and a conservatory. My flatmate and I decided to heat up only one room out of all the house and study there, we picked the conservatory which is the nicest room but I guess not the most efficient one for heating.

We have a small 2kW air heater, a 1.5kW oil filled radiator and a normal central heating gas radiator 1.5m(length)x60cm(height)x8cm(depth) that we can choose to heat up the room.

Which one is the cheapest out of all, with gas prices at 3pence per kWh and electricity 12pence per kWh?

I am guessing the air heater is out of the question. Also if we choose the gas central heating then all other 7 radiators in the house will be turned OFF.

How much gas would a radiator that big use per hour in kWh and how much electricity per hour would the oil filled radiator use(since it turns it self on and off all the time)?

Cardew

If all the other heating is turned off, gas would be cheaper.

It is not possible to work out exactly the differential because it depends on the efficiency of your gas boiler. That can range from 60% for an ancient boiler to 95%.

So if you use, say 100kWh over a set period it would cost £12 with electricity(electrical heating is 100% efficient)

The same heat with Gas would cost from approx £5 to £3.50.

Pincher

ConstantineX wrote: »

How much gas would a radiator that big use per hour in kWh and how much electricity per hour would the oil filled radiator use(since it turns it self on and off all the time)?

But what will turn off the boiler?

Unless you know there is a bypass valve, at least one radiator should be permanently open to provide a return path for the heating circulation. Usually the towel radiator does not have a TRV,
so it cannot shut itself off.

The TRV on the conservatory radiator does not shutdown the boiler, which overheats and shuts down to protect itself. It probably comes back on after cooling, so you think it's working fine,
but that's no way to run a boiler. For a start, overheating means no condensing action, so the efficiency goes down. Even if it does have a bypass valve, it's a failsafe device, not for every time the TRV shuts off the conservatory radiator.

Cardew

Pincher wrote: »

But what will turn off the boiler?

Unless you know there is a bypass valve, at least one radiator should be permanently open to provide a return path for the heating circulation. Usually the towel radiator does not have a TRV,
so it cannot shut itself off.

The TRV on the conservatory radiator does not shutdown the boiler, which overheats and shuts down to protect itself. It probably comes back on after cooling, so you think it's working fine,
but that's no way to run a boiler. For a start, overheating means no condensing action, so the efficiency goes down. Even if it does have a bypass valve, it's a failsafe device, not for every time the TRV shuts off the conservatory radiator.

Pincher,
This is from the latest Myson website: http://www.myson.co.uk/products/1207_1625_ENU_HTML.htm

Automatic Bypass Valve
What is an automatic by-pass valve?
An automatic by-pass valve is designed for use in domestic central heating systems. Its purpose is to maintain constant pump pressure within the system.
Back to top
What are the advantages of an automatic by-pass valve?
An automatic by-pass valve ensures minimum water flow rates through the boiler. It reduces system noise associated with high pressure pumps. It eliminates the need to fit an uncontrolled radiator to act as a system by-pass and it also increases system efficiency.(my bold) The automatic by-pass valve also aids the operation of thermostatic radiator valves.

That certainly is at odds with your expressed opinion above.

I have had my system 22 years without problems and there are TRVs on all radiators and heated towel rails.

There is still 'minimum water flow' even when all TRVs close, which is the design purpose of the ABV

Mine is not a condensing boiler, but as the above quote is apparently current??????

Pincher

Cardew,

All the plumbers I have discussed this with agree it's a safer configuration to have one radiator always open, in case of

1. There is NO by-pass valve
2. By-pass valve FAILURE.

The by-pass valve means the pump has somewhere to push the water, hence "minimum flow". With nowhere to push the water, the pump would overheat and eventually fail.

The by-pass valve does not dump any heat, so if the boiler is still heating the water, the small quantity of water circulating soon boils, and shoots out through the pressure release valve (sealed system, with open vented, it goes into the expansion tank.) This is why you should have one radiator permanently open, acting as a heat dump. The simplest way is not having a TRV, and never close it.

Some people seem to think the hallway radiator should be non-TRV,
so that the room thermostat will shut down the boiler when the hallway temperature rises. This is sound only in so far that there is a heat dump, because you can get a stuck room thermostat.

I have some control engineering background,
and so am particularly sensitive to failure scenarios I have also been in the house when a water heater flow pipe exploded because of a flow sensor failure, so the boiler doesn't know to shutdown when the water wasn't flowing.

People think in terms of how things work, but forget single point and multiple point failure scenarios, and then there is poor installation. The permanently open radiator is a very simple and effective failsafe mechanism.

Cardew

Pincher wrote: »

The by-pass valve means the pump has somewhere to push the water, hence "minimum flow". With nowhere to push the water, the pump would overheat and eventually fail.

.

Pincher,
Agreed if an ABV failed it might eventually cause the pump to fail; on the other hand the same effect would be caused by a TRV 'sticking' closed. That has happened to me on a few occasions and I have had to 'exercise' the plunger.

However a pump failing is hardly a great catastrophy.

Frankly I am happy to take the word of Myson who say that an ABV is designed to operate exactly as it does on my system; and my plumber does not agree with your plumbers.

Incidentally there are scores of websites that all agree with Myson's explanation of the purpose of ABVs and not one(that I have seen) refers to it as a 'fail safe' mechanism.
Each to his own I guess.

P.S.
I don't know where you get a 'small quantity of water soon boils'. There is a thermostat on the boiler that stops the boiler firing when it reaches the set temperature - my settings are approx 55C to 82C.

Pincher

Cardew wrote: »

I don't know where you get a 'small quantity of water soon boils'. There is a thermostat on the boiler that stops the boiler firing when it reaches the set temperature - my settings are approx 55C to 82C.

I think in failure scenarios. If everything works, of course the boiler will shutdown. This boiler sensor is just another failure point. That's why you have the presssure relief valve (8 bar, sealed system).

My builder's van is out of commission right now, because they don't know which sensor has failed. The engine cuts out intermittently, and they are replacing one sensor at a time, until they get the right one. Hardware, hate them. You've been saying modern boilers are prone to failure because they are too complicated yourself.