Fans on radiators, anyone tried them?

The idea is to get more heat out of the radiator, I had one of these for years, but the main difference is control. The old Myson had a variable speed fan set manually, and a thermostat to turn it on/off, and no restriction to water flow, the more modern versions have an automatic 5 speed fan, (ivector) and the speed auto varies depending on how much heat required, but again no restriction to flow.

The problem is the modern boiler uses the return temperature to control output, so if plumbed in parallel then as the fans turn off, hot water returns to the boiler, and can turn the boiler down when other rooms still require the heat.

The non fan radiator has a TRV, this means when not required, the water flow is turned off, and when enough have turned off, the by-pass valve lifts, so then hot water returns to the boiler, and the boiler output is turned down (modulated).

So adding a fan to the radiator means the TRV is still controlling flow. So I tried with mother's house, one of these next to the radiator, with my beer controller, powering it, and the sensor on the return pipe. Failure, return pipe gets hot, fan starts, return pipe gets cold, fan stops, so fan switching on/off all the time, tried to reduce fan size, went to a USB adaptor and a USB fan designed to go on the computer desk, and this still cooled the radiator down too much when it switched on.

The TRV was electronic, so I could monitor if this was reducing the flow, and no, the target was well above the current. With the lock shield valve set so under normal use, the current never exceeded the target, and it would once the room was warm, maintain the room to within 0.5°C of the set temperature, they worked well, the problem was how long it took to heat that room, the radiator was not really big enough, and in a bay window, so not room to increase size, the bay window lost a lot of heat, and on the wrong side of the house, so did not heat the room with the sun, so the idea was to speed up how fast it warmed up, but it was a failure, moving air also resulted in the air heating windows even with thick curtains. So in general it resulted in higher central heating costs.

Now my own house with the Myson, was a different story, the main living room had the Myson fan assisted 3 kW output, a tall double radiator 2 kW output, and a 4.5 kW gas fire on a flue brick, so from the Eco setting of 16°C to the comfort setting of 21°C, it took around 20 minutes, once up to temperature we would turn off fire, and Myson would auto turn off the fan. And the fan did not direct the hot air to the window.

The idea of radiator fans is not new, they have been around now for some time, they clearly need some method to be auto turned on/off, and the return pipe would seem to be the best option, but the lock shield valve seems to be the stumbling block, I could not set it high enough to stop the radiator cooling too fast, yet also stop the hystersis from the TRV as it would over shoot as it reached target temperture.

So has anyone ever got these to work, or are they simply snake oil?

ericmark said:

So has anyone ever got these to work, or are they simply snake oil?

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Not quite the same, but...

We've been away the past week, with our tourer caravan. It is fitted with a blown air heating system, and it works absolutely great, on either gas, electric, or both. You can run it, with or without the blown air, via three distribution ducts. You set the temperature on a wall stat, the temperature sensor for which is mounted elsewhere. The separately controlled blower system, can be set for manual, with fixed speed, or automatic, with it's maximum speed set on a dial.

On automatic, the fan speed varies, from a whisper, to a roar, depending on how hot the heater gets/how much heat needs to be put in the space. When first switched on, you get the roar, then has the temperature settles, it becomes barely audible. The blower, distributes the heat very evenly, making for a consistent temperature throughout, when compared to the very hot, localised heat, at the heater unit.

I had a much older caravan, but still had the ducts, and blower from the main heater. And yes, worked well. But 1978 had a house with hot air central heating, god was I cold when James Callaghan turned off the electric. And we have a labour government again.

The Myson fan assisted worked well also, with an on/off boiler, but with a condensing boiler, there is a problem, it returns hot water to the boiler, which will cause the boiler to modulate, (turn down) so today we need a way to combine the TRV, Lock shield, and fan to work together.

The TRV needs time to respond, and the lock shield valve adjusts the time it takes to heat up the radiator, without the lock shield valve, we end up heating one room at a time. The room with the easiest path to the boiler heats first, as the TRV closes, it pushes the water to the next easiest, and so on, once the whole house is warm, the TRV heads will control it A1, but due to the return water causing the boiler to turn down, recovery time gets very long. In practice, there is often a wall thermostat which turns off the boiler before it has chance to heat up all rooms.

If we had so sort of by-pass, around the lock shield when the fan was running, it could work, my electronic TRV heads cost me £15 each in 2019, so clearly electronic by-pass valves could be made, allowing fast recovery times.

But all the energy saving devices cost money, and to get a device cheap enough to be worth installing seems to be a problem.

ericmark said:

The idea is to get more heat out of the radiator,

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They are a novelty gimmick item, and while they may allow a bit more heat to be extracted from some ancient undersized radiator, the real solution would be to replace those old radiators with new ones of the proper heat output.

flameport said:

They are a novelty gimmick item, and while they may allow a bit more heat to be extracted from some ancient undersized radiator, the real solution would be to replace those old radiators with new ones of the proper heat output.

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I wish it was that easy, I would think the existing double panel radiator is around 1 kW output, and is about the largest which would fit in the space, the Myson fan assisted at 3 kW would work, but then a problem getting UPS power to the radiator, and I remember my old house, and the noise, OK if only there to boost output when first turned on, but when used as only heating, we had to turn up TV sound when it cut in.

Looked at a few and can't really see them working, but if it only switched on when it reaches a set limit, then once the TRV is modulating the radiator output maybe it will not switch on? But when it does switch on, the radiator will cool, so the switch off temperature would need to be a lot lower. Even at £50 it is a bit expensive for what is a computer cooling fan, the thermostat I use for my beer brewing does allow the slewing temperature to be set (difference between on and off) but all my fans are too big, and loathed to buy one just to test.

ericmark said:

The Myson fan assisted worked well also, with an on/off boiler, but with a condensing boiler, there is a problem, it returns hot water to the boiler, which will cause the boiler to modulate, (turn down) so today we need a way to combine the TRV, Lock shield, and fan to work together.

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Myson fan assisted, used to be simple on/off, probably still are - the beauty of my blown air system, in my caravan being that, the hotter the heater, the higher the demand for heat, the faster the fan ran, to distribute the heat around the space.

I used one these at the bottom of the radiator, pointing up through the radiator, it certainly seems to heat the room quicker:

...and, of course, this:

Harry Bloomfield said:

Myson fan assisted, used to be simple on/off, probably still are - the beauty of my blown air system, in my caravan being that, the hotter the heater, the higher the demand for heat, the faster the fan ran, to distribute the heat around the space.

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I looked at the new model, the ivector and that has a 5 speed auto changing fan, the old one had a huge rheostat to manually adjust speed.

StephenStephen said:

...and, of course, this:

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Sorry forgot asked same question last year. The ebay link was what I was considering.

My central heating was in a mess 5 years ago when I moved in, also some poor double glazing, and repairs needed to the floor, which once done could carpet, so each year we have done a little more, being aware how one improvement may affect the requirement for another.

Location of the wall thermostat was a problem, cured by fitting two in parallel, and using a hub which I can link TRV heads to as well, only have one linked TRV head at the moment, but each year there has been an improvement, the problem now is recovery time, the micro bore does seem to slow how fast the radiators respond, but could be down to some by-pass valve never found, the double garage under the house was converted into a flat, and we have no idea what is hidden behind walls and ceiling.

The idea was to arrange a sequence, so each room heated with a short delay, before the next, so radiators get hot to start with, but the delay needs to be short, or the boiler will turn off first. Moving from gas to oil, and modulating gas to on/off oil has resulted in what I had worked out worked well with gas, being found not to work so well with oil.

Also, the change in house design, never lived in a house before with so many outside doors, 3 standard size, and 3 patio size doors, yet the draft problem found with last house, does not exist with this one, in spite of an open fire. The latter has a board in front of it with a hole to take the porable air conditioners pipe with a lid on it. It has never had a fire lit in it since I moved in.