BXProject

Nothing to do with cars, we have a dehumidifier in the house that (unsurprisingly) sees a lot of use. Problem is, it no work any more.

Managed to trace the fault to the control circuit, which is seeing the correct input from the tank float switch, and seeing a plausible resistance from the thermistor on the evaporator. But the relay operating the compressor isn't switching, and it's not seeing a signal from what seems to be some kind of processor (MC68HC705P6). Now I can build or buy a simple circuit that simply closes a relay whenever the thermistor resistance goes over a certain value, but I'm guessing that if it could be that simple, they'd have made it that simple. There is a 555 timer on the board too, so I'm not sure why that's needed.

The manufacturer is no help, so I'm thinking about trying to make a replacement circuit. But I need to understand a bit more about the circuit design! Or are they available 'off the shelf' as control modules from someone who works in a related industry?

Is it a refrigerant based system or not? If it is then i would expect a pressure sensor in there. That might well be the issue, if it has one, and you can find it.

The 555 is likely configured as a timer, but it could be configured as a philip pholop or any number of fun things.

TBH its more likely a chiller than a full blown HVAC system. It likely has a processor because of eu legislation, dont turn on if it is a tuesday, dont turn on if the greeks are in debt yada yada.

I assume it isn't an EBAC unit, there customer support is normally shit hot.

Can you simply run the compressor from a thermostat? More than fucking likely is my bet. Worst case, it blows up and makes a faint pop.

Why do you need one Mat?

It is a refrigerant based system - simply draws air through the evaporator and then straight through the back to back condensor. No pressure switch input to the circuit, but there may well be one on the compressor itself.

Running just from a simple on/off thermostat is what I was thinking, but was wondering whether there was a good reason why the circuit was more complicated! I.e. to limit the compressor on time when the temperature of the evaporator was above setpoint perhaps?

Philhod wrote: Why do you need one Mat?

Just because it rains so much, therefore the days we can hang washing outside are limited, we don't have a tumble drier so have to hang it up in the house. Plus there's always wet coats to dry off. Also we don't have a damp proof course, so the atmosphere) is naturally on the damp side (although a lot less than you'd think).

Ah! I have said tumble dryer with a pipe to outside. Wouldn't have no DPC though, they are a bit essential. Quite often you can't get a mortgage on a house without one.
My house had none when I bought it but I did an injection one. 4" inside and 9" deep outside. I hired the drilling jig and the injector and stuff

Philhod wrote:Wouldn't have no DPC though, they are a bit essential.

Are they?The only visible damp patch in the house is where it backs onto the hillside and the inside floor level is lower than outside. That wouldn't be solved by a DPC. The house has existed for 200 years without one, so I don't think the structure is affected by not having one. The only reason we feel like we need a dehumidifier is I guess because we're not as tolerant of a damp atmosphere as the previous occupants were in years gone by.

It would cure the back as the injection type spreads up 1 meter and joins the inner and outer injections.
Damp rises from the floor, not necessarily showing on the lower walls but keeping the atmosphere damp

The house where I was born was like that , it had flag floors which were lower than the outside all round
The place always smelled damp but mould never seemed to appear exept in about 3 places.

Philhod wrote:It would cure the back as the injection type spreads up 1 meter and joins the inner and outer injections.

Would it? That would not be in compliance with building regs anyway because not only should the damp course not be bridged, the outside level needs to be at least a prescribed distance below it.

It depends on the preparation. If you have gone down inside and put a plastic membrane below the concrete you can come up quite a way provided you do a 4" at inside ground level.
Like when you come up against a party wall your last drilling upwards will be around 3 ft. All my outer drillings are 6/7" above ground level, drilled down at 45°. Its 35 years since I did mine and there has never been any interior dampness anywhere.

Way2go wrote:That would not be in compliance with building regs

Might not be in accordance with MODERN building regs, but as the 'house' was probably build as a shed, and 200 years ago, i suspect building regs weren't quite so strict?

I think the stuff Phil is talking about isn't your usual plastic injected DPC but modern injected mortar plasticiser. It pretty much turns the mortar to plastic, and gets into all the pours in the masonry, it does an amazing job of sealing, it can permeate normal house brick completely, so will completely join with existing DPC. Problem is, i dont think it can get through slate.

Thinking about it, the only way to stop damp completely in that building is to wire it to the mains. Water molecules are positively charged, if you charge the house it will repel the moisture. And i'm not being stupid, its how historic building like NT places are done.

That is the stuff Vanny. I couldn't remember what it's called. Does all that and more. Don't forget you do all the interior walls as well. This means that ALL the plaster in the ground floor has to be removed from each side of EVERY wall, to a height of 1 meter, left for 2/3 weeks then re plastered and skirting fitted.
Mine came with a 50 year guarantee.
I would be surprised if Mats doesn't have a slate DPC, TBH. They have been putting a line of slate in Welsh houses for over 200 years and judging from where Mat is...........

It won't penetrate slate Vanny, but slate does start to go powdery after a well, very long time. This stuff will then re seal any breaches that may have occurred over time.