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Stephen Follows12/04/2022 22:23:26
89 forum posts
3 photos

My workshop gets very cold in winter so when I heat it during use anything metal gets wet through condensation. It would cost a small fortune to keep it heated 24/7 so i'm thinking of building a heated cupboard for precision tools.

Has anyone tried this? I figure a small thermostatically controlled heater would be off most of the time the cupboard was shut.

Tris12/04/2022 22:56:03
6 forum posts

Little 30w tube heaters are ideal, think you may want a little ventilation top and bottom to let moist air out.

Paul Lousick12/04/2022 22:57:13
2043 forum posts
722 photos

The drawings in our design department (old days when we had drawing boards) would go mouldy in winter and we installed a small strip heater at the bottom of the storage cabinet. It only drew about 50 watts of power but stopped the mould.

Even an incandescent light bulb should be enough to keep your cupboard warm. ( 2 bulbs in series will produce heat but not as much light)

Hopper12/04/2022 23:04:24
6421 forum posts
335 photos

Old refrigerators make excellent insulated and sealed storage cabinets in a wet environment.

Stephen Follows12/04/2022 23:06:08
89 forum posts
3 photos

Like the light bulb idea but don't think incandescent lamps are sold now....

peak412/04/2022 23:24:23
1714 forum posts
183 photos
Posted by Stephen Follows on 12/04/2022 23:06:08:

Like the light bulb idea but don't think incandescent lamps are sold now....

They still are, but so are vivarium and home brewing heaters, both of which often

have the advantage of built in thermostats.


not done it yet13/04/2022 05:11:18
6812 forum posts
20 photos

While a small heated store may be needed, can you not insulate your workshop? Incandescent light bulbs are not to be recommended - high voltage, they can fail. Proper, safer heaters would be far better.

Are you using open fuel-burning heating while you are in the workshop?

Can the workshop be draught-proofed - and run a desiccant dehumidifier to lower the humidity on a regular basis?

Reducing the humidity and maintaining the workshop above zero Celsius most certainly helps protect machinery.

I’m now using one of the chinese diesel air-heaters, when needed, to warm my workshop when I am in residence. Generally cheaper than electric heating and does not produce any unwanted moisture.

AdrianR13/04/2022 07:38:36
583 forum posts
36 photos

Instead of heating the cupboard, you could dehumidify it with something like this

Just remember you will need to make the cupboard air and moisture tight. So plastic lined and seals on the door.

Nicholas Farr13/04/2022 08:40:36
3361 forum posts
1543 photos

Hi, in my old job of many years, we used to have an old small steel electrical cabinet with shelves made from cable tray, which had a one hundred watt bulb in the bottom, this was used to keep welding electrodes dry. OK, we didn't have to pay the electric bill, but the cost wasn't even peanuts for the company with all the machinery used in the factories and I was once told they used four megger watt hours a day of electric 24/7. Never had any damp issues with the welding electrodes.

Regards Nick.

Martin Kyte13/04/2022 09:06:39
2756 forum posts
48 photos
Posted by Stephen Follows on 12/04/2022 23:06:08:

Like the light bulb idea but don't think incandescent lamps are sold now....

Google Rough Service light bulbs and pick what you want.

regards Martin

DMB13/04/2022 09:20:15
1312 forum posts
1 photos

I am using Android, have got an app called Barometer. Just checked and it's saying it's 92.9% humidity outside. Nearly an hour ago it was 98. something. This gives me a rough idea how 'bad' the damp atmosphere is outside, down here on the South coast, having had a fog/mist weather forecast this morning. At least it's giving an idea of surroundings so if a shed/ garage being used as a workshop, you have an idea of how much it's being affected by conditions outside. I have gentle heat on 24/7 most of the year. 4 off, 60W bulbs in brass battenholders, connected in series encased in a 3-ply box produce low light but importantly, low wattage heat. Wiring is protected against possible shock risk. Workshop entry routine, switch off heaters, switch off lights. Still use stock of new bulbs for reading indoors but when they get a bit tired, pension them off as workshop heaters. I believe that total wattage is around 15, so X 168/wk = just over 2.5 units a week, x 25p (+ VAT, =30 p) up to recently, =75p. Leccy now jumped to 45 p + (VAT = 54p), total now £1.35/wk. Still very low compared with all else that's going on. That's for one of my mills, under plastic shroud. Tubular heater back of myford drip tray, on thermost. Just large plastic bags over Dore-Westbury mill and Fobco drill and workbenches. Enough heat escapes to warm whole 10 X 8' wooden shed which is heavily insulated.

Edited By DMB on 13/04/2022 09:26:15

Bazyle13/04/2022 09:53:26
6325 forum posts
222 photos

The quick solution, today, is an old cotton sheet over the machine then a blanket over that. (the sheet keeps the fluff off the oil). You must have a few old incandescent bulbs around you can swap for LEDs eg in the attic and cellar to put under the machine, This provides a microclimate although obviously not sealed it is a quick helper improvement. Don't use plastic sheet and cotton/wool is a lot better than man made.

Often in abandoned workshops and even in houses one sees metal items that have the top surface rusty and the undersides better. This is because dew forms even inside at a tiny level and falls down, maybe from the coldest air near the ceiling that has radiated its heat into the night sky. This can happen when the conditions are not such that a cold machine attracts the condensation onto all its surfaces. So cover metal with a cloth whenever possible.

Samsaranda13/04/2022 09:54:26
1430 forum posts
5 photos

Insulate the workshop, it’s amazing what a difference it makes, I have a small dehumidifier working at night on economy seven tariff and a small oil filled radiator on a very low setting, solves the problem. Dave W

Tim Stevens13/04/2022 10:07:01
1598 forum posts

If you get condensation when you start to heat the space, it is likely that the heating process produces damp air. For instance, a paraffin heater - simply because burning anything with hydrogen combined in it produces water vapour.

If you use electric heating, you won't get this problem - but you could still get condensation if, for example, you return to the garage after a frost (which cools everything down) and the day is warm (so the air that comes in with you can include a lot of moisture).

Removing the moisture using a de-humidifier will help in both cases - and delivers de-ionised water for all sorts of useful jobs (topping up car radiators, lead-acid batteries, etc).

Regards, Tim

SillyOldDuffer13/04/2022 10:30:35
8699 forum posts
1967 photos
Posted by Martin Kyte on 13/04/2022 09:06:39:
Posted by Stephen Follows on 12/04/2022 23:06:08:

Like the light bulb idea but don't think incandescent lamps are sold now....

Google Rough Service light bulbs and pick what you want.

regards Martin

Reasons for not misusing incandescent light bulbs as heaters:

  • Shock and Fire Hazard
  • Short filament life due to overheating in an enclosed space
  • Bakelite bulb holders go brittle due to overheating
  • No temperature control, wasting electricity, frying insulation, cooking anything heat sensitive in the cupboard, and maybe starting a fire.
  • Glass Bulb easily broken
  • Light spilling out can be a nuisance

Although these problems can be partly fixed with a guard, ceramic holder, thermal cut-out, and silicon wiring, it all costs time and money. And at the end, light-bulbs aren't designed to run hot - they normally have plenty of ventilation. Better, I suggest, to cough up the precious and buy a Tubular Heater. One with a thermostat would save electricity. You can get small ones intended to warm equipment enclosures rather than airing cupboards, but I don't know of a supplier.


Peter G. Shaw13/04/2022 10:32:13
1421 forum posts
44 photos

My workshop is a draughty cold single skin garage with absolutely no insulation, and depending on the wind and rain, can leak!

I use some self regulating heaters from RS Components, in my case Part No. 360-4059.

These are mounted, two on the underside of the lathe, and one on a large piece of thisk ali sheet and wedged in the bottom of the base of the milling machine. I also use a cover, not sure of the material other than it's woven, and a plastic sheet on top. This effectively keeps the two machines that bit slightly warmer than the ambient. Hey presto, no rust.

The downside is that although mine are rated at 10W, in fact they draw the equivalent of 19W: this appears to be correct according to the spec., hence the running costs may now-a-days be a bit two much. (As far as I am concerned, since it saves the lathe and milling machine from rusting, it's worth it, but your opinion may differ.)


Peter G. Shaw

Tim Stevens13/04/2022 10:36:52
1598 forum posts

But, SoD - the OP says he uses brass bulb holders, and four bulbs in series. So many of your concerns do not apply here, surely?


Stephen Follows13/04/2022 11:15:25
89 forum posts
3 photos

The workshop is draught proof but built of heavy duty blocks. Another project this year is to clad the outside with treated shiplap, there goes £1000 +.

I have a dehumidifier but it stops working below 5 degrees. I could get a desiccant type but the running cost would be too high.

I heat with a fan heater when I'm using the shop. I used to use a convector with a thermostat permanently on but the electricity use was far too high. The cold itself isn't a great problem but when I do heat the shop even small metal things are so cold that they get wet through condensate pretty rapidly. I've lost a digital caliper set through the electronics getting wet.

Mike Poole13/04/2022 11:22:22
3344 forum posts
74 photos

Would I be right in thinking that heating only needs to exceed the dew point or a de humidifier only needs to dry air to avoid condensation at dew point temperature? Dew point sensors seem to be rather a lot of money but the calculation seems to only need to know the temperature and humidity so maybe an arduino could do the calculation and control equipment to keep the workshop safe. The worst situation seems to be a cold spell followed by a warm wind coming in, my workshop could look like it had been hosed in that situation.

not done it yet13/04/2022 11:38:35
6812 forum posts
20 photos
Posted by AdrianR on 13/04/2022 07:38:36:

Instead of heating the cupboard, you could dehumidify it with something like this

Just remember you will need to make the cupboard air and moisture tight. So plastic lined and seals on the door.

Silica gel will typically only reduce the humidity to 20%, at best(and over time), so the cupboard will still need to be maintained above dew point.

Posted by Tim Stevens on 13/04/2022 10:36:52:

But, SoD - the OP says he uses brass bulb holders, and four bulbs in series. So many of your concerns do not apply here, surely?


Did he? I used to use fluorescents under honey buckets to warm them - they were low wattage, but Watts are Watts - and mine were cumulative as the lamps were in parallel connection.🙂 While less likely to fuse at reduced wattage (lamps in seies) if one fails the whole string fails.🙂


I don’t care how low the humidity might be, if the interior drops below freezing point, any/most remaining moisture in the air will likely/possibly condense - dehumidified or not - somewhere.

I’m like Dave, my (desiccant) dehumidifier runs for a couple hours during the night on E7. The dehumidifier adds about 0.75kWh of heat over those two hours. If extremely cold weather I may leave two dehumidifiers running - or if I am away they run for an hour apiece, just in case one gives trouble - or the water collection receptacle fills up.🙂

SOD is right on most of his points. Even with my efficient fluorescents, the light was absorbed inside the box and converted to thermal energy. I’ll add that the heater must be installed low down, because heat rises, so needs protection,

As per Peter, above, I am happy to spend the money on protecting my machines and all the other items in my workshop - but I installed good insulation and efficient draught-proofing in order to reduce my day-to-day heating costs. It is so efficient that in the summer, I often have to keep my workshop door closed to avoid over-heating!

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