Bosch fine adjust - drying targets

[mrlaundry1011]

Hi, I was wondering if anyone knows more about Bosch’s +1/2/3 fine adjusting system. Would this just be a timed phase ran after the relevant drying target is reached or is it actually an adjustment of the sensor like Miele dryers? I’ve noticed diff cycles add different amounts of time for each +1 for example cotton adds 8min and mix adds I think 5. I’ve also noticed that cotton cupboard +2 is estimated as being longer than cupboard plus +0. Therefore was wondering if you’d be better off selecting cupboard dry plus +0 rather than cupboard +2 if it is a timed phase vs actually sensing to the higher plus drying target if that makes sense.

 

[logixx]

With my previous Siemens condenser dryer, it would just add time to the cycle. Once the LCD icon switched to the target drying level, the dryer would run for 5, 10 or 15 minutes before entering cool down.

I haven't found out how BSH do it now. As you've said, adding two increments to the Cupboard
Dry drying level, will give you a longer (estimated) cycle than selecting Extra Dry in the first place.

My Serie 8 will add 12 minutes when selecting Cupboard Dry +1. However, once the Cupboard Dry icon lights up, the dryer will jump from eleven to three minutes remaining. Huh? I am confusion! I feel like the, say, Cupboard Dry light won't come on, unless the added time has elapsed as well.

And don't even get me started on that wonky timer. The time will fluctuate down and up again by five minutes for like an hour, only to then drop to 30-something minutes once clothes are iron dry.

Henrik, where you at? Oh, and kindly also explain to use what Gentle Dry does (besides adding time). It surely doesn't decrease the temp on my dryer.

 

[henene4]

Gentle on the heat pump models changes the target temp where the fan comes on and off, lowering it.

That fan is the only way to control temp on the single speed heat pumps.
But given how basic some of the BSH dryer operation is I almost bet that even the inverter heat pump models just change the fan behaviour.

The dryness fine adjustment is just timed and as far as I know not load based.

Where it adds the drying time I can't tell you - neither how and when it senses.

Only that there is only moisture sensing, no load size detection beyond sensing if there is anything.

The most advanced there is AEG actually at this point, with it actually sensing moisture AND load size by weight.
Knowing load weight and residual moisture gives you pretty exact prediction abilities.

They are also the only ones scoring well on residual time display accuracy in the current Stiftung Warentest testing.

Miele - last I checked and owned mine - right now also just adds time if you change the dryness setting.

 

[logixx]

Next time I'll do laundry, I'm going to spend some time observing the dryer. However, I could swear that Low Temp did not change the behavior of the fan (didn't come on before oron dry and then only intermittently).

 

[henene4]

Depending on cycle, there are 3 fan behaviours.

Either temperature dependent, on continuously or timed.
Delicate lowers the temperature the fan comes on at.

The documentation however AFAIK does not state which cycle does what.
I'll check when I'm back at work, but I'm on holiday for this week and next week so we'll see.

 

[logixx]

Henrik

I dried a roughly 4kg load of clothes today using the Low Temp option. The fan didn't come on until the time dropped and the clothes were about to be iron dry - which is normal. It cycled on for 15 seconds and remained off for 20 - again, this seemed normal. At that point the air temp was 42C. The duty cycle remained unchanged through the cycle and even into the anti-crease phase. At the end of the cycle (Cupboard Dry with one +) the temp was 62C. Don't know if that is supposed to be low or...?

 

[henene4]

62C is - by laundry care standards definition - low temp.

65C was as far as I am aware the reference temp for low temp drying.

 

[logixx]

Well, today's victim was a large pillow. Had it on Timed Dry for an hour with low temperature. Towards the end of the cycle, the temp had reached 68C in the lint filter. I stopped the cycle, as 68C is clearly above 65C and the fan never came on, ever. Started another Cotton cycle with low temp and the temp rose to 68C again, at which point the timer jumped to 1 minute and the cycle ended. Tried again on Delicate with low temp: exact same result.

What I did find interesting (not that a 70C Delicate cycle isn't interesting) is how quickly the temp in the filter drops. After three minutes of tumbling without the compressor on, the air temperature had dropped by almost 10C - although the temp did eventually stop rapidly falling at around 50C.

 

[mrlaundry1011]

Here’s just 2 examples of mine. A regular cycle and then a timed 20 cycle which didn’t use the fan at all after delicates finished at 52c

 

[logixx]

We love a Bosch fryer... I meant dryer.

 

[henene4]

I still am holiday and sure as hell won't turn my work laptop on during that lol

Next week I'll have access to the service literature again.
If you leave me any model numbers, I can check if the manuals mention any temps.

I know for sure the old BlueTherm model literature mentions specific temps for fan cycling and they used to be in the 60C range.

These newer dryers sometimes don't have the NTC in the air stream but on the compressor circuit to basically check refrigerant temps.
That might lead to a significant difference between air out temp and actual temp readings.

I do think 70C is on the high side for a heat pump dryer - but keep in mind old condensers targeted up to 85C on normal.

 

[logixx]

I found an old German service manual for the Siwatherm dryers - those with the rectangular door. It references the high temperature as 75C, the low temperature as 65C and extra low as 55C. Each of the fine-adjustments would add .5% to the selected dryness level.

I remember when we had these Panasonic dryers...

 

[mrlaundry1011]

Oh and also the allergy plus programme

 

[henene4]

My VZug actually has pretty similar temp targets for delicate to speed drying as Panasonic advertised.

I usually run mine on Eco and it peaks at something like 65C on the largest loads.
But that is with low compressor speed.

Reaching 75C in a heat pump dryer is surprising though - but Allergy has very long post-sensing drying, so makes sense.

Is that an A++ or A+++ model?

 

[mrlaundry1011]

I forgot to say I believe from memory that mine has an NTC sensor just below the door filters. It’s also back to doing its random glitch/bug where at random (depending on where it’s been moved) it’ll consistently run the cooling fan on for about 10-15sec every minute no matter the ambient temp or drum temp, pushing heat out. It done this in my old house in a study room, didn’t do it when moved to another place but has now started doing it again after being relocated in a garage (insulated and temporary, so my sisters Siemens washer dryer doesnt have to be used for drying purposes). It wastes energy as the little heat it produces in the ambient temp of 8c currently is just pushed back into the room instead, it’s temping to just block off the cooling fan vent lol

Not sure if I’ve ever shown her washer dryer on here, but here’s a pic of it anyways. For anyone wondering, intensive dry peaks at around 85c I believe but dries at an average of 75-80. Gentle dry peaks very briefly at 72ish but then cools and averages about 60-65c. Outdoor dries at 50-55c, wool does intensive heat 70+

 

[mrlaundry1011]

It’s a A++ model rated 800w, but has an A condensation rating.

 

[henene4]

The fan cycling depending on location sounds like something the service manuals mention, though, and should be temperature dependent.

Logixx has reported on his "older" unit having condensation issues under certain conditions around the control panel area.
That issue had later been mitigated in some runs/designs with a seperate small fan in the control panel.

The final solution was to actually run slightly different fans in reverse in certain designs.
The fan wouldn't suck air in at the bottom, but would instead blow it out there.

Since no dryer is 100% air/moisture tight the air inside the cabinet is higher moisture content.
(Even an A condensing class model looses like up to a glass or two of water per cycle to the room air.)

When you blow air into the dryer, what would happen was air blowing slowly out of the panel area. The slow movement and high moisture content could lead to condensation under certain circumstances.
If you sucked air out of the dryer with the fan, dry cold air would flow in where it used to flow out.
The airflow straight from the fan into the room is fast enough that no condensation could happen - air would mix to quickly.

 

[logixx]

Yes, my WTWH7540 made in December of 2019 will leak moisture around the control panel in the Quick|Mix cycle that does not use the fan. The fan, by the way, expels air through the front of the dryer.

Not sure where the NTC is in my dryer. It's there, according to the parts list (0527), but it's not anywhere where I could see it (i.e. the filter area).

 

[henene4]

Position 0527 is the NTC that's mounted to the refrigeration circuit and not the process air stream.
That just sense the coolant temperature.

As far as I understand, that location allowed to infer the process air temperature pretty accurately and to monitor the circuit for safety reasons without having multiple NTCs.

The other would be located in the front bulkhead in the filter area.

The service literature says that only HP dryers with a refresher system ("Steam") have that second NTC, but I have seen pretty recent parts diagrams for dryers without that still having the second NTC.

BSHs service literature can be quite a wish wash of semi-correct information...