Hi, new to the forum - looking for advice on thermostats

[rsk289]

Hi all, I was pointed over in this direction from the plumbing forum for advice on thermostats.
I have a couple of wall-mounted Calorex dehumidifiers in my workshop which have built-in 2kw heaters to keep the dehumidifers working in cold weather. The Corgi remote thermostats supplied for these are rubbish, one coming on at 12°C and below whatever it's set at, and the other not coming on at all at any setting.
I'm looking for a good quality thermostat to connect up instead, just for frost use (I don't want to heat the building apart from keeping the dehumidifiers working). I've seen some Honeywell ones that look good but am not sure about the spec. needed - they need to be two-wire connections and volt free (I believe). I don't think Honeywell make such a thing - does anyone have any suggestions for this?
Thanks, Roger

 

[Spoon]

Welcome to the forum mate.
How about one of these..

 

[Wilko]

Hi RSK and Welcome to the Forum
Can I ask what the model number /pic of the existing ones? Have you got a wiring diagram for the system? Did it ever work properly, or might there be an installation fault too?

 

[rsk289]

Hi chaps, Spoon - was it the Drayton Digistat you meant? Looks promising.
Hi Wilko, Calorex did supply two very cheap thermostats with the dehumidifiers but these switched the heaters on at anything below 12˚C and I racked up an electricity bill last winter of over 3K. Ouch. I'm afraid I have no record of what those stats were. I had a couple of Corgi STTRFSN-C volt-free thermostats fitted instead, as they have a range from -5˚ to 10˚C so I assumed these would give me better control. I don't need the heaters to come on until the temp drops to around 3-4˚C ideally. These are also bimetallic strip jobs by the look of them with the cover off, and are just as inaccurate as the originals - one doesn't seem to come on at all unless I stick it in the freezer for 30 mins (dial set to 10˚C), the other isn't much better. I've also noticed that they seem to be wired backwards - i.e. the one that does work switches the heater on when I turn the required temp dial down, not up. Calorex give no wiring diagram, just a schematic with wires going to boxes, no detail. I can't find one on the net either.

 

[Wilko]

Hi - Which Calorex unit are they attached too?

 

[static zap]

A tricky balance is to be had ,
more warmth = faster job.
(if de-humidifiers already make some heat-Need to keep that in !--Like asbestos guys )

 

[Spoon]

Hi chaps, Spoon - was it the Drayton Digistat you meant? Looks promising.

Hi mate. U wasn't pointing you at any specific one. I don't know how good they are.
I just gave you a few potions. See how much you want to spend and what specs you want.

 

[rsk289]

The dehumidifiers are Calorex DH30AXP.
I've got things working as they should now, but the thermostat temperature range is terrible. If the room temperature is 9˚C, verified by a good quality thermometer, one of the Corgi units is switching with the dial set to 1˚C, the other is switching when set to -4˚C. They are sitting next to each other and have been in the room for 6hrs.
If I could find a good quality thermostat that would work with the DH30AXP I'd be happy. Calorex don't offer a different unit option.

 

[Wilko]

Looking at the installation manual it does just need a switch (volt free). Here's a pic of the control wiring and what may be the Corgi frost stat. I tried to find the recommended one but crashed and burned. Anyway, perhaps check they're wired as they should be?

 

[rsk289]

Thanks for that - unfortunately nothing seems to come up on those part numbers. Best bet is probably to talk to Calorex technical about it. I can get hold of a Honeywell T4360A so will try that. Hopefully it's a 2-wire.