Radiator Booster - any thoughts?

Dave_Fowler

jamesd wrote: »

The downstream would be receiving cooler water because the upstream radiator would have removed more heat from it.

Unless your radiators are connected 'in series' then all radiator inputs are from the same supply pipe. The output pipe of one is not connected in any way to the next input. Some of the old large-bore gravity fed systems did use this type of connection, but this system is unlikely to be used in any modern central heating system.

Dave F

Cardew

Dave_Fowler wrote: »

Unless your radiators are connected 'in series' then all radiator inputs are from the same supply pipe. The output pipe of one is not connected in any way to the next input. Some of the old large-bore gravity fed systems did use this type of connection, but this system is unlikely to be used in any modern central heating system.

Dave F

Not so(IMO)

Obviously they are not connected in series, but in a central heating system all the radiators(the system) must be balanced.

As jamesd indicates, this balancing is to ensure that the 'upstream' radiators don't get all the hot water to the detriment of the radiators further 'downstream'.

This balancing is achieved using the 'lockshield valve' on each radiator and thus reduce the flow of hot water. See:

http://www.telegraph.co.uk/property/propertyadvice/jeffhowell/8278429/Home-improvements-What-is-radiator-balancing.html

The whole point of a fan booster is to increase the output of a particular radiator, thus it needs more hot water to enter.

zeupater

Cardew wrote: »

...
The whole point of a fan booster is to increase the output of a particular radiator, thus it needs more hot water to enter.

.... or, of course, the same flow rate maintained with a lower exit & boiler return temperature ...

HTH
Z

jomknight

I have just set up my booster for a third year and it reminded me how incredibly quickly the room warmed up as a consequence. It is on a radiator in quite a large lounge & I turn down the thermostat very soon after the fan starts. The electricity consumption is detailed at http://www.radiatorbooster.com/ but i am sure it must save in payback that but more importantly make the radiator more effective. The fan kicks in when the radiator reached 30 deg and will go on for some time after you turn down the thermostat. The adapter does get warm and so if the radiator is not to be used it is best to switch off the booster at the mains. Sometimes the fan makes an intrusive noise but if I move it slightly it quietens down.

zeupater

jomknight wrote: »

I have just set up my booster for a third year and it reminded me how incredibly quickly the room warmed up as a consequence. It is on a radiator in quite a large lounge & I turn down the thermostat very soon after the fan starts. The electricity consumption is detailed at http://www.radiatorbooster.com/ but i am sure it must save in payback that but more importantly make the radiator more effective. The fan kicks in when the radiator reached 30 deg and will go on for some time after you turn down the thermostat. The adapter does get warm and so if the radiator is not to be used it is best to switch off the booster at the mains. Sometimes the fan makes an intrusive noise but if I move it slightly it quietens down.

Hi

Could that be a placebo effect ?? ... We've looked at the potential for increasing radiator efficiency and/or moneysaving with a 1.2W fan before ...

zeupater wrote: »

Hi

In theory, partially - but here's the reality ....

From what I've seen, the units which are available retail seem to have a single 12V/1.2W 50(ish)mm fan built into an extruded plastic body approximately 0.7m long.

Looking at the first source available for a ~50mm 12V DC fan rated at ~1.2W (http://www.maplin.co.uk/brushless-12vdc-axial-fans-1806)we can see that the 40mm unit is rated at 1.92W (12Vx160mA), which is 60% more powerful than the 1.2W radiator booster, but can only force 210l of airflow/minute, so let's be (very) generous and say that a 1.2W unit would be rated at 180l/minute, that's 10800 litres/hour (10.8 cubic metres) ....

.... follow so far, so let's look at the volume of air naturally convected by just a small radiator ....

A typical small single panel type11 800(ish)mm radiator is rated at around 900W at a 50C differential temperature to the ambient air, and due to the extended transfer area provided by the fins, let's say that 60% of the heat is provided from the rear of the radiator and that the average convecting air temperature is raised by 25C above ambient, therefore somewhere around 45C (((70-20)/2)+20),

.... follow so far ...

We now need to look at the specific heat capacity of air raised by 25C in order to calculate the approximate convection rate to provide 900W of cooling to the radiator ... for simplicity, let's just leave thermal expansion and relative humidity aside and work on 1cubic metre of air having a mass of 1.1kg at 45C (raised 25C), air to have a specific heat capacity of 1.005 kJ/kg per degree C temperature difference, so 27.6kJ/cubic metre of airflow (1.005x1.1x25), therefore multiplying by this 0.000278 gives us energy expressed in kWh .... that's 0.0077kWh/cubic metre of convective airflow.

.... Okay now for the final bit in the calculation ....

Taking into consideration that 60% of heat is being convected from the rear of the type11 (single panel finned) radiator airflow is obviously cooling the radiator by 0.54kW (0.9x0.6) .... which must be achieved by ~70cubic meters (0.54/0.0077) of airflow at the rear of the radiator per hour.

Looking at the above we can see that the natural convection from the radiator is forcing 70 cubic metres per hour into an obstacle which is able to cope with 10.8 cubic metres of forced air throughput per hour, therefore, rather than enhancing airflow the booster will restrict it, with natural convected air simply spilling out around the sides & edges of the booster because it physically can't cope. The booster, not being able to mechanically provide significantly more airflow than natural convection achieves little (/no) more than a passive deflector such as a radiator shelf ..... remember, this exercise is based on a small type11 radiator, so just think about the airflow through a type21 radiator, or even a type22 .... :whistle:

HTH
Z

Although I've tried, I simply can't see any technical or logical reason how a low powered fan (~1.2W) attached to a plastic tube sat on the top of a radiator, which actually acts as an airflow restrictor, could be any more efficient than disrupting the linear convective airflow by simply placing a shelf a couple of inches above the radiator. Have a look through the exercise referenced above as it places the relative airflow into context and then look at the typical positioning figure in the marketing literature (http://www.radiatorbooster.com/) ...

... you'll see that the natural convection from the radiator is far higher than the 'booster' can possibly cope with therefore it would simply be overwhelmed ... also, read the savings claims carefully in order to understand what the claims actually say, not what they seem to say, paying particular attention to the advertising disclaimer "Savings will vary considerably ..."

To me it looks like the claimed savings are due to reducing the room temperature by up to 3C, not from the added efficiencies afforded by the fan-powered unit ... something which anyone could do anyway ...

HTH
Z