Does an electric boiler need a tank?
Discussion
I've looked online but there's conflicting information, and most information is biased because it's from boiler sellers.
600 sqft flat, very well insulated, underfloor heating, one bedroom. Would use 2 baths a day at most.
Can I use an electric boiler without a tank?
And if I do need a tank, does it need to hold one unit of water-used-to-"fill"-the-bath?
600 sqft flat, very well insulated, underfloor heating, one bedroom. Would use 2 baths a day at most.
Can I use an electric boiler without a tank?
And if I do need a tank, does it need to hold one unit of water-used-to-"fill"-the-bath?
How many watts is the boiler?
Given that a combi boiler needs to be rated at around 30kW to provide instant heating of enough water for a shower or bath I'd suggest a HW tank is probably needed for an electric boiler as 30kW means 130A @ 230V which is going to be an interesting proposition to say the least.
Given that a combi boiler needs to be rated at around 30kW to provide instant heating of enough water for a shower or bath I'd suggest a HW tank is probably needed for an electric boiler as 30kW means 130A @ 230V which is going to be an interesting proposition to say the least.
From here <<linky
They can be used for heating and hot water. For hot water (e.g. showers) you would want to a 9kW version at the very least.
These boilers work on the same principle as an electric shower - they pass water over a heating element - however the hot water heater has slightly higher (water) capacity than a typical electric shower.
On single phase mains, you can go as high as 12kW.
We have a 6kW boiler (but with a separate hot water cylinder) and the 6kW version is probably just about adequate for our 2 bedroom 77sqM flat (well insulated).
They can be used for heating and hot water. For hot water (e.g. showers) you would want to a 9kW version at the very least.
These boilers work on the same principle as an electric shower - they pass water over a heating element - however the hot water heater has slightly higher (water) capacity than a typical electric shower.
On single phase mains, you can go as high as 12kW.
We have a 6kW boiler (but with a separate hot water cylinder) and the 6kW version is probably just about adequate for our 2 bedroom 77sqM flat (well insulated).
website said:
Our single phase Electric System Boiler outputs are 6kW, 9kW, 12kW with the 14.4kW available for properties that require larger outputs.
All Comet Boilers can be installed for Heating only or Heating and Domestic Hot Water purposes when used with an ‘S’ Plan configuration in conjunction with our Twin Channel Heatpack.
All Comet Boilers can be installed for Heating only or Heating and Domestic Hot Water purposes when used with an ‘S’ Plan configuration in conjunction with our Twin Channel Heatpack.
montecristo said:
Mr Pointy said:
How many watts is the boiler?
Also trying to decide that but they range from 3kw to 12kw, so let's say 12kw.We just switched a small 2 bed flat to full electric, has a small "Potterton gold" heater which powers 4 rads, then a ??? litre tank which does the hot water. Removed the need for gas safety cert for rental.
EDIT: The guy who installed it said the electric combis are rubbish.
pic below:
EDIT: The guy who installed it said the electric combis are rubbish.
pic below:
Edited by z4RRSchris on Monday 4th March 16:06
TonyRPH said:
From here <<linky
What confuses me is that in the link you posted (and in most other places), a tank *is* shown even though the text suggests no tank is needed. Same with the Slim Jim boilers which look like a very thin bar, but are also shown in diagrams feeding from a tank.Warning, maths.
Please correct if I've cocked this up!
- To raise 1g of water by 1 degree c uses 4.18 Joules
- To raise a litre of water by 1 degree needs 4.18kiloJoules
- Assume 100 litres of bath water, raised from 10 degrees to 50 degrees.
- 4000 x 4.18kJ = 16.72MJ = 4.64KWh
- 12KW Boiler,
- 60 * 4.64KWh / 12Kw = 23.2 minutes
Please correct if I've cocked this up!
Mr Pointy said:
12kW is around 52A which is nearing the upper limit of domestic wiring & barely half of a low powered combi so I'd still say you'd need a storage tank. You'd want to be heating the water at night when the cost is lowest so storage is the only way to go.
The boiler will require a dedicated feed, just like an electric shower.A 10kW electric shower draws 42A and will be fed via a 45A (or higher) MCB and suitably rated cable.
Our 6kW boiler is fed by a 40A MCB, and because we also have a separate hot water cylinder, there are two separate 16A feeds for each of the immersion heaters. (see image)
Our boiler is a Heatrae Sadia which has the boiler and hot water cylinder incorporated into the same (massive) unit.
montecristo said:
What confuses me is that in the link you posted (and in most other places), a tank *is* shown even though the text suggests no tank is needed. Same with the Slim Jim boilers which look like a very thin bar, but are also shown in diagrams feeding from a tank.
You are correct - it *is* confusing, especially when you see the attached screen grab from one of their promotional videos.But then I found this << linky
Which states:
site said:
With superior performance and reliability, the Fusion Astro Electric Combi Boiler provides on demand heat and instantaneous domestic hot water. They are suitable for small Properties that have a Shower and Hot Water outlets for sinks. In homes with larger hot water requirements, it can be combined with a hot water storage cylinder via an ‘S’ Plan configuration.
So in other words, if you have demanding hot water requirements, a cylinder will be required.When used standalone, the boiler will likely be adequate for showers, but not for baths (as per the calculations presented above).
This is the "S plan" configuration.
silentbrown said:
FTFY.
A full-on 40KW 3-phase combi would probably just run an acceptable bath.
Yep, hence I said in the following paragraph;A full-on 40KW 3-phase combi would probably just run an acceptable bath.
TonyRPH said:
When used standalone, the boiler will likely be adequate for showers, but not for baths (as per the calculations presented above).
montecristo said:
This is all very helpful.
I currently have a gas combi (no tank) and it runs a bath in 19 minutes at 46 degrees, so if that's what the electric will do, that's OK by me.
I doubt it will though, because you have to factor in the water cooling off in the bath whilst it's still running.I currently have a gas combi (no tank) and it runs a bath in 19 minutes at 46 degrees, so if that's what the electric will do, that's OK by me.
Gas combi boilers in a typical 3 bed home tend to be around 30 to 40kW so capable of significantly greater heat output than a 12kW electric boiler.
Evanivitch said:
Why would you use a electric boiler for heating wet radiators!?
There's no benefit. Just use electric radiators.
Our last flat had electric radiators, the current flat has electric wet heating.There's no benefit. Just use electric radiators.
I'm inclined to think the electric radiators were more efficient, despite the old place having inefficient insulation. (I have detailed consumption statistics for both). Interestingly, the electric radiators seemed to run more frequently than the wet system.
The wet system works just like a gas boiler - it kicks in, heats and then cools off and then heats up etc...
The electric radiators seemed to maintain a more constant temperature.
As the wet heating was already here when we bought the place, there doesn't seem to be any advantage to changing to electric radiators at this time.
montecristo said:
This is all very helpful.
I currently have a gas combi (no tank) and it runs a bath in 19 minutes at 46 degrees, so if that's what the electric will do, that's OK by me.
Hang on just one second - you currently have a gas boiler and you are going to replace it with an direct electric boiler (where cost comparison will be at a minimum of 4 times the £ cost for the same Heat output) or have I missed something I currently have a gas combi (no tank) and it runs a bath in 19 minutes at 46 degrees, so if that's what the electric will do, that's OK by me.
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