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...

 

[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...

 

[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...

 

[henene4]

For fun I checked my dryers temps today.

I ran a single, big, heavy mattress cover through a extra dry cottons cycle on the speed setting.
Thet cycle was just about an hour and used 0.8kWh.

The exhaust temperature climbed to just above 55C.
Interestingly, it did cycle the cooling fan on that cycle.
Checking the temperature of the duct on the back, it cycled the fan on when that temp registered about 60C and off at 55C.
That points at target intake air temps of 70-75C on the speed setting.

My dryer has (at least) 3 NTCs - 2 on the compressor circuit and 1 in the filter area.

 

[wholelottared]

a question to henene4

Hi henene!! Glad we have informed people with access to service documents like you on the forum.

I saw that you said if we tell the device model, you can give us information about it such as the temperatures, how the programs behaves and how the fan works, etc. I really wonder about these all.
I also wonder how the additional pump that washes the second condenser in the back (which is special to AutoClean models) works, does it automatically work at the end of every cycle or do we have to start the cleaning program, etc.

My model is WTX87EH0TR (in Germany it's WTX87E40 / WTX87E90) basically the Home Professional dryer that's being sold right now.

I would be really happy if you can check about this model and tell me about any interesting thing you found, thank you so much.

 

[henene4]

I can actually tell you the self clean story from memory.

There are 3 self clean systems - the basic self clean system for most dryers.
Then there are the 2 upper line SC systems. Those have the condenser cleaning. (Condenser as in the technical term, meaning the "hot" heat exchanger. Refrigerant condenses there, releasing heat.)
The 3rd tier is the full AutoClean system which has no main fluff filter, only the trap in the bottom you have to clean every now and then.
So - technically - you can have condenser cleaning without the full AutoClean system, but I don't know of any model implementing that.

The 2 systems that also flush the condenser don't use a second pump.
They use a thermal actuator that just diverts the flow from the first path which just flushes the evaporator to the secondary path to the condenser.

The condenser rinsing is triggered based on total operating time - I think every couple dozen hours.

More interesting is actually the alarm for cleaning the lint collector on the AutoClean models.
It uses several mechanisms to check for how full the trap is.
First is if a certain total operation time has passed. Second is if a certain number of cycles have run. Third is if after flushing the lint collector, it takes to long for the water level in the water collection area to rise. The thicker the fluff layer, the longer it takes for the water to get through it.

And it goes even further than that. Apparently, during testing, the concern arose that customers don't like to handle soaking wet fluff.
Thus, if the dryer senses the need for the trap to be cleaned, it actually waits for the next cycle to complete and does not run a rinsing stage during that cycle.
That leaves the fluff much dryer, making removing it easier.

I'll check the rest tomorrow when I'm back at work.

 

[wholelottared]

thank you henene4, can't wait for additional info

Wow thank you for the info!!

It always makes me happy to hear interesting inside info and facts from you, it's so cool. Can't wait to hear the details you'll share tomorrow.

Btw, from what I know, all the Self Cleaning Condenser devices washes the first condenser, yes, but only the AutoClean devices washes the both condensers, the one in the front and on the back.

I saw a Russian video in YouTube and someone was inspecting the insides of an AutoClean model, and they were actually showing the additional piece that washes the second condenser in the back. How does it divert the water to that part? That's what I was wondering.

Here's the link to the video i'm talking about, you can see it on 0:36 :

Will be waiting for the other infos you'll share about my model, thanks!!

 

[wholelottared]

addition to my last reply

and oh also, there's something i really wonder a lot. during the AutoCleaning phase, right after it flushed the condenser, sometimes the drum stops and wait for like 2-3 minutes until it continues. sometimes this doesn't happen and the drum continues to spin right after flushing. why does it happen? what determines the drum stopping for like 2-3 minutes or continuing right away? this part behaves differently literally anytime i run the machine (sometimes the drum stops sometimes it doesn't) so i think maybe it has something to do with the temperature? maybe it stops the drum when the clothes are too hot, so it can be like a cool down? idk. let me know if you know anything about this please. if you can't understand what i'm talking about, i can take & share a video.

 

[logixx]

Judging by the parts diagram, the condensate pump is connected to a diverter that switches from pumping the water up into the tank, to pumping the water through this short hose onto the condenser.

 

[henene4]

Some corrections

So actually, yes, the main pump is used for flushing.
The diverter I had in mind is situated in the drain pump, makeing a total of 2 thermal actuators down there max.

The SC2 system has automatic filter flushing but NOT condenser flushing, so I switched that up.

 

[henene4]

Unfortunately, both your dryers have revised cycle charts that do not list target temps.

The 2 examples are both A+++ dryers, one with Inverter one without.

The compression on here isn't doing it any favours, but should be doable if you zoom in enough.

 

[henene4]

Actually, Logixx, going to through stuff, you dryer has actually an old cycle chart available and lists 65C NTC temp as limit.
You dryer should be KI-index 12, so WTWH7540/12.

On all other dryers, there's a testing document for end-of-line and service testing that shows power consumption depending on temperature.