IET logo
 
IET
Decrease font size
Increase font size
Topic Title: warehouse heating options
Topic Summary: Any ideas
Created On: 21 December 2012 11:29 AM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 21 December 2012 11:29 AM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1090
Joined: 04 November 2004

Hi

I have been asked to quote for installing some heating in a small storage warehouse.

I was thinking of either ceiling hung electric fan heaters or wall mounted heaters with ceiling hung destratification heat recovery fans.

The warehouse volume is approx 1575m3. L 15m w 15m height 6-9m (apex roof)

Gas is available but I'd rather not go down that route if possible flues roof works etc.

Has anyone got any recommendations?

Thanks and Merry Christmas everyone.
 21 December 2012 11:40 AM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19900
Joined: 23 March 2004

If gas is available then use it

Do you need to heat the whole volume (and the contents) for environmental reasons

Will heating the occupants suffice

That should decide if you need convective or radiant systems (with or without destratification fans)

big convective system could be a gas fired AHU with recirc, or combat type heaters at high or low level. You could use the gas direct or apply it to LTHW and use that.

If radiant is a better solution then direct gas fired black tube radiant heaters or "frenger" type panles running off LTHW (or MTHW)

If you must use electric then quartzray radiants as a direct system for occupant comfort or electric water heaters for panel radiant or combat heaters.

You could also use direct electric combat heaters and destraification fans.

I wouldn't go electric if gas is available - but you can do both radiant and convective systems replacing heater coils etc with electric elements - but with the obvious energy financial and carbon penalty.

If you have reasonable insulation you could use roof mounted refrigerant air source heatpumps in heat recovery mode. Basically, a windcatcher chimmney affair with the condensor and evaporator contained within, taking heat from the external air and injecting it down into the space - at least you'd get a reasonable annual COP to mitigate the electrical burden

regards

OMS

-------------------------
Failure is always an option
 21 December 2012 01:36 PM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1090
Joined: 04 November 2004

Thanks OMS

Apparently they had condensation dripping from the ceiling last week in the extreme cold weather, the warehouse is currently unheated.

It's used by a touring orchestra company as storage only, so I don't think radiants would be the most suitable. It's a typical 80-90's shed.

I don't want want to risk making the condensation worse by heating the area though, I hoped the fan covectors and destrat fans would help prevent that?

Thnaks again.
 21 December 2012 02:07 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19900
Joined: 23 March 2004

Yup if you lift the temperature then the dew point condition changes.

I simply can't remember the firm I used on the last small shed I did

they had a unit that from outside looked like a monodraft roof chimmney and inside it was an air source heat pump that took some fresh and a big proportion of recycled air and ran it over a DX coil that gave heating and cooling as and when required (which is probably ideal for instrument storage)

Just a simple roof ridge penetration and of course, it's also providing destrat by default. I think they could do about 25 - 30kW of heating per unit.


I'll continue to rack my brains and post if it comes back to me - I'm not near my design files at the moment so perhaps one for google.

I agree radiant would be less useful to you in the unoccupied space

Regards

OMS

-------------------------
Failure is always an option
 21 December 2012 07:39 PM
User is offline View Users Profile Print this message



lyledunn

Posts: 652
Joined: 13 August 2003

may be heating the space is not the answer. it might even exacerbate things with warm air condensing on cold structural elements. We had a similar problem. by accident someone left a supply air fan on and it seemed to do the trick. perhaps just moving the air around might be worth a try before embarking on major expense. Dehumidifiers might be worth trying. Would you be kind enough to let me know how you end up resolving things?

-------------------------
Regards,

Lyle Dunn

Edited: 22 December 2012 at 09:16 AM by lyledunn
 21 December 2012 09:29 PM
User is offline View Users Profile Print this message



peteTLM

Posts: 3234
Joined: 31 March 2005

Look at Combat heaters. Basically a huge gas/ oil powered cube blasts heat out over a large area.

I dont think any kind of electric heating would have the impact necessary unless they do a huge fan heater type deal.

Unless the warehouse roof is insulated, i wouldnt bother as the losses will be enormous.

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 21 December 2012 11:41 PM
User is offline View Users Profile Print this message



peteTLM

Posts: 3234
Joined: 31 March 2005

http://www.cehltd.co.uk/products_cuh.php

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 22 December 2012 09:02 PM
User is online View Users Profile Print this message



aligarjon

Posts: 2926
Joined: 09 September 2005

i would tend to agree with Lyle, heating it might make it worse unless they want to spend a fortune. better ventillation and air movement would be a better option.

Gary

-------------------------
Specialised Subject. The Bleedin Obvious. John Cleese
 23 December 2012 10:55 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11786
Joined: 13 August 2003

Do think about insulation - I was chatting to some spray insulation people a while ago and it seems that a lot of their work is spray insulating the inside of barn roofs and similar buildings - primarily to stop condensation dripping down.
- Andy.
 24 December 2012 01:08 PM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1090
Joined: 04 November 2004

Thanks everyone for your replies.

It was a simple inquiry asking for a price to increase the temp in the warehouse.

As it's just being used as storage you wouldn't think much water vapour would be produced so the relative humidity should be fairly low, but they park one of their touring trucks in the warehouse, that has it's AC kept on all day and night so the exhaust air from that will be contributing.

I like OMS suggestion of the windcatcher heat pump set up or a AHU with heat recovery, but as everyones mentioned without an upgrade of the roof insulation the heat loss may be too great.

I also thought about a couple of largish heat recovery fans in the external wall, I will check again whether the condensation is the main concern or if they definitely want to increase the temp for the instruments being stored. It maybe that for 95% of the time the temps fine and condensation doesn't occur either.

I've had look at CIBSE guide A this morning and apparently, the thermal bridge effect of the warehouse roof results in a lower than the acceptable critical value of surface temp factor (fRSi), this is worked out from.

fRsi=1- U Rsi

U = U value of element
Rsi = internal surface heat transfer coefficient.


According to the guide the critical temp factor for the storage area needs to be above 0.3, to prevent condensation from forming on the cold internal surface of the roof.

Merry Christmas to you all.
 24 December 2012 01:15 PM
User is online View Users Profile Print this message



aligarjon

Posts: 2926
Joined: 09 September 2005

That might be a way forward. a smaller scale i know but the roof in the back of my van(seperated from the front) is often hanging with condensation yet the front where the roof is insulated there is never a problem and its pretty warm in there when its parked up on a cold night.

Gary

-------------------------
Specialised Subject. The Bleedin Obvious. John Cleese
 24 December 2012 09:39 PM
User is offline View Users Profile Print this message


Avatar for dg66.
dg66

Posts: 1676
Joined: 11 January 2008

solar wall ?

-------------------------
Regards

Dave(not Cockburn)
 08 January 2013 02:12 PM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1090
Joined: 04 November 2004

Originally posted by: OMS

Yup if you lift the temperature then the dew point condition changes.



I simply can't remember the firm I used on the last small shed I did



they had a unit that from outside looked like a monodraft roof chimmney and inside it was an air source heat pump that took some fresh and a big proportion of recycled air and ran it over a DX coil that gave heating and cooling as and when required (which is probably ideal for instrument storage)



Just a simple roof ridge penetration and of course, it's also providing destrat by default. I think they could do about 25 - 30kW of heating per unit.





I'll continue to rack my brains and post if it comes back to me - I'm not near my design files at the moment so perhaps one for google.



I agree radiant would be less useful to you in the unoccupied space



Regards



OMS


Hi OMS

If you get a chance could you let me know the manufacturer of the roof mounted heat pump system you mentioned.

Thanks
 08 January 2013 03:15 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19900
Joined: 23 March 2004

Hoval

Roofvent TwinPump - TWP 9 is the DX version.

We had 4 of them in a space providing climate control. Ridge mounted via a bit of bespoke secondary steelwork (to carry about 700kg each) and some flashing details.

Effectively, we were looking to minimise condensation (via vent and some heating) and to limit summer temperature primarily by fresh air ventilation with limited cooling.

Essentially we had to maintain the shed at a reasonable range of temperatures (10C - 25C against -10C and 32C external winter/summer design day conditions). Insulation was poor in reality - 1980's Bulding regs compliant shed - so not great roof insulation - it was originally designed as ambient storage

Regards

OMS

-------------------------
Failure is always an option
 08 January 2013 03:59 PM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1090
Joined: 04 November 2004

Thanks OMS

The client has now advised that an indoor temp of between 8-9 degress would be acceptable.

I tried the manufacturer of the ceilng fan convectors/destrats Pete suggested, they have advised 2 x 20KW units and 1 x 15KW unit would be required, ouch.

Regards
 08 January 2013 04:28 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19900
Joined: 23 March 2004

Sounds about right - 1500m3 @35W/m3 for a temperature delta T of say 15C (-5C outside to 10C in the shed)

tis why I suggested not using electric - you don't want tobe running 55kw of electric heating direct

I'd go for a simple gas fire AHU firing heated air down the apex line via ducting and jet diffusers and a couple of big bell mouth return ducts at the AHU end of the shed. Mostly recirc with heat recovery run around on the supply/exhaust.

You could use a similar arrangement with a DX heat pump coil as the heating - be about a 25kVA electrical supply but a high cost per kw delivered.

I suspect the hoval units may be a bit OTT for what you need.

Regards

OMS

-------------------------
Failure is always an option
 08 January 2013 05:04 PM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1090
Joined: 04 November 2004

Yes as many of you mentioned this would not be a good idea, I wouldn't want to be paying for 55kw of electric heating and don't think the client would be too pleased either.

I think insulating the roof has got to be the way forward, before any heating or ventilation is installed.

Regards
 08 January 2013 05:35 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19900
Joined: 23 March 2004

Part L2b and consequential improvements is where this is taking you.

This is the first provision of a heating system to a previously unheated space - so you'll be forced to do something - roof insulation would be a good shout.

Raising the internal room temperature wioon't cause condenstation - it'll simply raise the dewpoint of the roof and stop it forming.

It's the latent load interbnally (I don't think you have anything) and the introduction of external air that will give you issues.

Take a look at a psychrometric chart - cold air containing moisture brought in and heated will actually result in a decrease in RH (as the warmer air can now absorb more moisture) - it's why we humidify large building in winter - stops the users getting "dry eye" and shocks from the photocopier.

Do you know what the walls and roof are constructed like - there may be some insulation present (but not much)

A recirc air handler is not likely to create a dew point problem in my experience

Regards

OMS

-------------------------
Failure is always an option
 08 January 2013 06:50 PM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1090
Joined: 04 November 2004

OMS, The useful floor area is less than 1000m2 would consequential improvements still apply?

One of the touring trucks parked in the warehouse has it's internal AC on all the time, I wondered if that was the cause of the condensation I can't see any other producer of latent heat.
The psy charts make my head hurt.

Regards
 09 January 2013 09:08 AM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19900
Joined: 23 March 2004

OK - if the useful floor area doesn't exceed 1000m2 the the CI's won't kick in. You'll still need to achieve the enhanced efficiencis for newly installed fixed building services indicated in the non dom guide.

The truck AC may be contributing initially to the latent load whilst it rinses the moisture out of the air in the truck interior - but asssuming a lot of that moisture is removed during the journy I suspect the amount of condense being produced will be negligible.

What may be happening is the cold discharge from the AC (as it extracts heat to maintian the truck container temperature) is cooling the general warehouse space and leading to the reduced dew point inside the shed.

If you heat, and ventilate the shed, regardless of the U value, you will raise the dewpoint temperature and minim,ise the condensation, particularly if you have the minimum amount of fresh air being used.

Designing a system for this shed won't need significant use of psychrometrics -you just need to find an efficient way to put a bit of heat in there - and highlight the energy implications of doing that in a poorly insulated building.

Does your client own the shed - you may also be heading into both landlords consent and into potential change of use - there is a difference in planning for ambient B8 sheds and those that are substantially treated spaces.

If you are putting in a cost, put a bit in for the design element - plenty of people will knock out a mech design for you (with or without an EPC as required) - £1.5 - £2K should cover it (including drawings)

Regards

OMS

-------------------------
Failure is always an option
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.