2 Speed Fireplace Fan Switch - Page 1
Forum section: electronics / beginners

author: Larsson55
author_rank: Regular Contributor
timestamp: November 26, 2024, 10:22:20 am
content: I had a fireplace insert for 22 years and was working very good but 2 months ago it developed cracks on the welds and had to replaced with a similar unit. The old and new units have the same fan arrangement and if I knew that I will have a problem with the new one I would have kept the old fan arrangement.The problem with the new fan unit is it has low and high speed settings (like the old unit) but the low speed is pathetic slow and the high speed is very high. Is there anything I can do to get the low speed a bit higher?The attached wiring schematic is wrong, the fan switch has 3 positions High OFF Low.Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: November 26, 2024, 11:06:20 am
content: Probably not. All the speed control is happening inside the fan motor as the external speed switch only selects which terminal to power. Back in the day it was common to use series capacitors (of the motor 'run' capacitor type) to drop the speed of small fractional HP induction motors when very little startup torque was required (primarily fans and non positive displacement pumps). However nowadays its more likely to have electronic speed control with the speed set by some custom programmed, often unidentifiable IC, with no obvious way to tweak the speed(s).If the motor does have a capacitor between the black and red wires (almost invariably mounted externally on the motor frame, maybe in a plastic housing) you can investigate and try a higher value one, which also needs to be of the 'motor run' type (a regular film capacitor or non-polarised electrolytic typically wont stand up to the high RMS current in this application) and of the same or higher voltage rating.

author: CaptDon
author_rank: Super Contributor
timestamp: November 26, 2024, 01:33:10 pm
content: One possible solution is to leave the unit set on high speed and rig up a ceiling fan motor speed controller to your fan. Simple lamp dimmers are usually a bad choice to control motor speed. The ceiling fan speed controllers are different from lamp dimmers and are designed for induction motors. If it is a two wire unit (simply goes in series with the motor, as most are) you could even rig a bypass switch to jump out the speed controller to create the high speed. You did allude to the fact that you thought high speed was too high so perhaps the speed controller will be the best solution, the low you want and the high which isn't hurricane speed. Generally the fan motor speed controllers are significantly higher priced than a lamp dimmer. I seem to recall $30 to $40 U.S.D. You would laugh at my woodstove rig. A modified Leeds and Northrup P.I.D. unit driving a bi-directional motor that drives a fan motor speed controller via a velcro slip clutch. The clutch is a disk of fuzzy velcro driving a disk of fuzzy velcro allowing the drive to slip at the ends of travel. There is a thermistor positioned to sense available heat and if there isn't any heat a comparator circuit turns the fan off. Basically, light the fire and let the controller do the rest. Fan speed is set by sensed outlet air temperature, higher temperature = faster fan speed.

author: Larsson55
author_rank: Regular Contributor
timestamp: November 26, 2024, 02:22:06 pm
content: Somehow I knew it would be impossible / difficult to fix since the assembly only includes the fans, wiring and the switches but I had to ask.My thanks to both,