Jan 14, 2010, 09:45 AM
Re: Heating a workshop/garage
David Littlewood wrote:
> In article <7r82crF173U1@mid.individual.net>, Donwill
> <Donwill.email@example.com> writes
>> Peter Parry wrote:
>>> On Wed, 13 Jan 2010 10:48:38 +0000, Donwill
>>> <Donwill.firstname.lastname@example.org> wrote:
>>>> To minimise the risk of condensation on machines the temperature
>>>> should be kept reasonably constant but that's expensive if you
>>>> heat to a comfortable working temperature.
>>> If you are contemplating electric heating then start by installing one
>>> or more dehumidifiers. Firstly they (obviously) dry the air but
>>> secondly they recover the latent heat of evaporation so are slightly
>>> more efficient than a 100% efficient radiant heater (you get more heat
>>> out than electric energy equivalent put in).
>>> Another alternative which is much cheaper to run than resistive
>>> heating is an inverter split unit air conditioner. This is an air
>>> source heat pump with air drying. DIY fit versions are available.
>>> Look for the coefficient of performance figure. In heat pump mode
>>> these types of systems typically have a coefficient of performance
>>> (CoP) of about 3. This means that a 3 KW air conditioner uses about 1
>>> KW of power. Conversely a heat pump provides about 3 KW of heat while
>>> using about 1 KW of power.
>> That sounds like the way to go, having done a quick search LG and
>> Toshiba seem to be eminent in the field, do you have any experience
>> with them that you can share? To keep the humidity down AND heat the
>> wksp cheaply seems to be great. :-)
>> Generally speaking, the air passing through the unit needs to be
>> cooled to remove moisture, how does the unit apply heat to warm it up
>> to working temp, is this where the so called "split" system comes
>> in? To cool and then heat the air in principle seems wasteful ?
>> Any info gratefully received.
> Warming the air automatically reduces its relative humidity, so it
> does not need to be cooled first.
You need to reduce the dewpoint temp of the air below the temperature of
the machines in the wksp.
e.g air at 22degC and 60% RH, will condense out at the DP of approx
14degC. If you can reduce the RH of the air to say 48% then the DP will
be reduced to approx 11degC so if the machines are above 11deg C then
water will not condense out on them.