Warehouse frost heave protection

[samiam]

I am considering the following options for a warehouse floor to prevent problems associated with frost heave: So far I have used:

a) Electric heater mat.

b) warm glycol pipes.

c) Natural and forced ventilation.



I have used the electric mat and glycol heater pipes before, but not the forced ventilation.



What are you experiences/comments on the forced and natural ventilation methods?



Thanks

[Grizzly]

I am considering the following options for a warehouse floor to prevent problems associated with frost heave: So far I have used:

a) Electric heater mat.

b) warm glycol pipes.

c) Natural and forced ventilation.



I have used the electric mat and glycol heater pipes before, but not the forced ventilation.



What are you experiences/comments on the forced and natural ventilation methods?



Thanks

Samiam.

I have many years experience with Cold Stores and like you understand the benefits and pitfalls of both A and B.
If by Natural you mean floors built on dwarf walls.
With 6 inch Concrete slabs on Insulation slabs.

Thereby having a thermal gap under the floor.
Then I understand and this is by far the most common for Large areas.

But I am not sure what "forced ventilation" is can you explain?

Grizzly

[smpsmp45]

We generally use Forced Ventilation by embedding the pipes below the Flooring.

If you are interested I can send you a sketch as to how we do it.

Electrical mats is expensive proposal though we use that only for Blast freezers for -40 deg C.

We have used elevated floor in few cases, but again that also is expensive.

[Kh1971]

HI,

The ventlation should be done before doing the cold store it self, if you are interesed send me a mail and I well send you the drawing how you can make the ventaltion for the flooring *** note that it is very good way and Iam using it here.

Khalid

[US Iceman]

The forced ventilation system is when a fan blows the air through the underfloor pipes. The static version of this is the natural convection pipes that are open to the outside air.

I think the method you use depends entirely on the location of the cold storage. In areas where the climate is moderate or cold you would want a positive (heat source) method to provide heating for the floors.

In warm to hot climates the natural convection pipes may provide a suitable alternative. In this climate the ground temperature would remain fairly warm year-round so the underfloor pipes with natural convection air currents should be sufficient.

[samiam]

Hi Gents,

smpsmp45 - please add the scketch to this forum

Thanks for the feedback - US Iceman (thank for the expalantion - it is as per my thinking)

Thanks

[riazahmadmalik]

How do you use natural air flow to avoid frost heave? i.e. Using PVC pipes that are slotted or have holes can let the air touch the concrete thus warming it to avoid heave process and let the frost drip inside pipes that are inclined to sides.
What if the pipes are not drilled with holes or have slots? How is heat conducted through these. Metal is a good conductor to use here but is expensive. Concrete pipes are an alternate (in fact a better and second to metal)

[riazahmadmalik]

Mr. Khalid, I am interested to know how you use pipes for natural / forced ventilation. Kindly email at riazahmadmalik@aim.com

[Alexie]

Samiam.
We've been providing low voltage electric heater mats to Ireland and UK for 15 years and in that time we've been the cheapest method by far, compared to glycol or forced ventilation. You can look at our site for more info. look at thermatek uk.

[sterl]

Have had to line bore through (2) foundation walls and 220 feet of frozen ground to retrofit an underfloor heating arrangement. Anyone want to guess how far out of line the bore was by the time it made the far end? And what happens if it drifts up rather than side to side?

Most remediation for a failed sytem after the frost has penetrated involves core drilling from the floor down and installing vertical heating probes...And that is a Very Expensive exercise even before the wiring is powered up.

Glycol circuits can easily use refrig system heat rejection to warm the glycol; and with most forms of food storages, there is always a refrigeration load so there is no intermittent shortage of heat; circuit lengths can be 600 to 1400 feet and more using 1-1/4" OD tubing...Major problem is to ensure grid assembly remains leak tight while rest of building gets built.

Electric in conduit often employed and can be service fairly easily....carefully installed with pull lines etc. remaining. High water table is major difficulty.

Never liked draft systems over 50 or 60 feet building size....Largely because air contains moisture and that stuff condenses out somewhere part way down the pipe when the entering air is near 100% RH. Interior boxes smaller than this do OK though within a food plant, the choice of material for the ducts is pretty critical because of washdown and various vapors and chemicals....Would not use any metal. Would be very careful with selection of polymers.

Forced draft arrangements work OK: Though practicality says that you will end up with a buried duct at one end of the building if the building is large and the climate can get cold. Now concrete drain pipe, end sump and similar become material of choice. Long time ago, one such arrangement had the duct drop from the overhead furnace get ruptured at a duct flange....Set up an interesting battle between the half a million BTU furnace and the Minus 25 F. refrigeration system.

I like low voltage systems. I do not have any specific history with them in a big building but the basic premise extends easily enough.

[Andy]

Samiam.
We've been providing low voltage electric heater mats to Ireland and UK for 15 years and in that time we've been the cheapest method by far, compared to glycol or forced ventilation. You can look at our site for more info. look at thermatek uk.

Hello Alexie

electric heating may sometimes be cheaper to install, but it is always more expensive to run than glycol based systems.
When working on large cold stores, in or climate glycol is always better than electric.

Kind Regards Andy