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Old Jan 14, 2010, 09:45 AM
Donwill
Donwill
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Re: Heating a workshop/garage

David Littlewood wrote:

> In article <7r82crF173U1@mid.individual.net>, Donwill
> <Donwill.seesig@invalid.invalid> writes

>> Peter Parry wrote:

>>> On Wed, 13 Jan 2010 10:48:38 +0000, Donwill
>>> <Donwill.seesig@invalid.invalid> 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.
>> Don

>
> Don,
>
> Warming the air automatically reduces its relative humidity, so it
> does not need to be cooled first.
>
> David

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.
Don