Crofter Posted May 15, 2017 Share Posted May 15, 2017 Today was the big unboxing of the MVHR unit which has languished in its box in a corner for the last couple of months. Have the sparky onsite at the moment and he was keen to take a look. Having looked at what I've got, and had a quick call to the seller, I'm now left somewhat dissatisfied and unsure how to proceed. I paid a bit extra to upgrade to a fully automatic humidistat controlled unit. The problem is that the humidistat is integrated into the controller itself, and this can obviously only be in one place. The recommendation is to put it in the kitchen. But what about when someone has a shower?? The seller said that it is possible for a sparky to add a relay to create a second boost capability, but that the system is designed to only talk to the one controller, as supplied. The controller is in the supply and feeds the appropriate level of power to the unit, so in theory all I have to do is intercept that and over-ride it with a second basic manual switch (it would be nice to have something slightly fancier here, e.g. a switch that cuts out again based on humidity and/or time- but for now I will just call it a switch). How big a project would this be? In hindsight I wish I had asked a few more questions when I purchased the unit, but it's a bit late for that. Link to comment Share on other sites More sharing options...
Calvinmiddle Posted May 15, 2017 Share Posted May 15, 2017 What MVHR brand and model is it? Link to comment Share on other sites More sharing options...
Crofter Posted May 15, 2017 Author Share Posted May 15, 2017 19 minutes ago, Calvinmiddle said: What MVHR brand and model is it? It's from 'Boulder Developments', model DHV-15B Link to comment Share on other sites More sharing options...
ProDave Posted May 15, 2017 Share Posted May 15, 2017 Do you have an electronic copy of the manual you can upload? I have to say it seems bonkers to put the humidistat in the controller. I have always heard of the humidistat going in the extract duct so it senses the humidity of the air it is extracting. If you can find a manual we can look at, we might be able to suggest something. Link to comment Share on other sites More sharing options...
Stones Posted May 15, 2017 Share Posted May 15, 2017 12 minutes ago, ProDave said: Do you have an electronic copy of the manual you can upload? I have to say it seems bonkers to put the humidistat in the controller. I have always heard of the humidistat going in the extract duct so it senses the humidity of the air it is extracting. If you can find a manual we can look at, we might be able to suggest something. That's certainly the way ours works (Vent Axia). Does seem a very odd way of configuring it... Link to comment Share on other sites More sharing options...
Crofter Posted May 15, 2017 Author Share Posted May 15, 2017 Manual for the unit (in Pidgin English) is top of the page, and the controller is the DCS-2H https://www.boulderdevelopments.com/downloads/ Link to comment Share on other sites More sharing options...
ProDave Posted May 15, 2017 Share Posted May 15, 2017 A quick scan of that lot reveals a manual barely adequate ro connect it an use it, even less so for understanding the technicalities of how it works or how to do anything fancy with it. When using the controller you have, it appears to use the terminals HF, LF and MF (high medium and low fan?) to select the speed. There is also mention of a manual 3 speed control using the terminals L(1) M(1) and H(1) * Are these in fact the same terminals,. just referred to by a different name to put us off the scent? * (I am not entirely sure what's in the brackets, you zoom in and the resolution of the image is too poor to be certain) I think it's going to be a case of stick with the controller you have, or forget it (at least as control goes, perhaps just keep it as a display) and configure your own controller. I doubt you will ever need 3 speeds. you will need a trickle speed and a boost speed. Once you know which one is going to be your boost speed then a changeover relay contact will switch speed for you. you then need either a boost timer or your own humidistat system to command the relay. Link to comment Share on other sites More sharing options...
Crofter Posted May 15, 2017 Author Share Posted May 15, 2017 I'm glad I didn't pay any more for this, it's not particularly impressive kit to say the least. For the same money I could have got a unit without bypass or any automation, from a more reputable source. Anyway, a bit late for buyer's remorse. Would it be unworkable to physically 'hack' the controller and make the humidistat a remote unit? Putting one in the exhaust duct sounds like the correct way of doing it! In theory it would be be a case of identifying the humidistat inside the controller, removing it from the PCB and adding a length of cable to connect it. But maybe everything inside is going to be tiny, delicate, and unidentifiable? Perhaps more practically, if I install a relay, will the controller 'know' that the fan is now being controlled on a different supply/ circuit? Link to comment Share on other sites More sharing options...
PeterW Posted May 15, 2017 Share Posted May 15, 2017 26 minutes ago, Crofter said: Putting one in the exhaust duct sounds like the correct way of doing it! In theory it would be be a case of identifying the humidistat inside the controller, removing it from the PCB and adding a length of cable to connect it. But maybe everything inside is going to be tiny, delicate, and unidentifiable? It's a blue DHT11 from memory on the back left as you look at the unit .... I had one of these by accident as I ordered the proper Mitsubishi unit from them (£110) and they sent me that ..! They had none of the Mitsubishi ones in stock at the time and the cherub on the end of the phone thought they were the same ... take a photo and post it - I'm sure @JSHarris will spot it a mile off ..! Link to comment Share on other sites More sharing options...
ProDave Posted May 15, 2017 Share Posted May 15, 2017 The DHT11 is a 4 pin digital sensor but only 3 pins are used.. The datasheet is here http://www.micropik.com/PDF/dht11.pdf If you can desolder it and rewire it in the exhaust duct, I can't see why it won't work. The data sheet mentions cable lengths up to and over 20 metres so I can't see why it would not work. Link to comment Share on other sites More sharing options...
Crofter Posted May 15, 2017 Author Share Posted May 15, 2017 Ok looking inside the controller I find this: I'm guessing the humidistat will be the little beige box in the 2nd photo? Link to comment Share on other sites More sharing options...
PeterW Posted May 15, 2017 Share Posted May 15, 2017 Yep the cream one but how it's supposed to detect humidity there I've no idea..! The front looks sealed on that. CO2 sensor is the one at the bottom. I think it's a cheap 2 wire sensor - easily removed and extended on a length of ordinary bell wire ....! Just re-read the instructions - does it do humidity based fan control as it seems to say it's only CO2 ..?? Link to comment Share on other sites More sharing options...
Crofter Posted May 15, 2017 Author Share Posted May 15, 2017 There are vent holes in the casing that line up with the sensors. If the big silver one is CO2, is that tiny little black blob on legs for temperature? It is supposed to control via humidity, but the instructions do a good job of obfuscating that! Link to comment Share on other sites More sharing options...
PeterW Posted May 15, 2017 Share Posted May 15, 2017 Just now, Crofter said: There are vent holes in the casing that line up with the sensors. If the big silver one is CO2, is that tiny little black blob on legs for temperature? It is supposed to control via humidity, but the instructions do a good job of obfuscating that! Yep that's a thermistor. Any chance of a photo of the end of the beige block where it meets the circuit board ..? Link to comment Share on other sites More sharing options...
Crofter Posted May 15, 2017 Author Share Posted May 15, 2017 6 minutes ago, PeterW said: Yep that's a thermistor. Any chance of a photo of the end of the beige block where it meets the circuit board ..? Will have to wait till tomorrow. Thanks for all the help on this! Really appreciate it. I'm busy browsing google images and ebay to see if I can spot this component. Is there an easier way?? Short of unsoldering it to see if there's anything written on the reverse side... Link to comment Share on other sites More sharing options...
PeterW Posted May 15, 2017 Share Posted May 15, 2017 Just de-solder that one and extend it with a wire - should be fine if you mark the correct polarity. 1 Link to comment Share on other sites More sharing options...
Temp Posted May 15, 2017 Share Posted May 15, 2017 Pretty sure that yellow/cream/beige thing will be the humidity sensor. I couldn't google up an exact match but take a look at google images.. https://www.google.co.uk/search?q=humidity+sensor&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjznqWW6_LTAhXqKMAKHRrMBEEQ_AUICygC&biw=1340&bih=779#imgrc=_&spf=1494883538482 Look in through the vents, does it look a bit like this inside? Link to comment Share on other sites More sharing options...
PeterW Posted May 15, 2017 Share Posted May 15, 2017 (edited) That looks very "binary"...... Edited to add that I've just looked and these are good to 3% accuracy ..! Can pick them up for £2 on eBay so removing the old one intact may not be an issue. Edited May 15, 2017 by PeterW Added info Link to comment Share on other sites More sharing options...
Crofter Posted May 16, 2017 Author Share Posted May 16, 2017 @PeterW @Temp See closer up pic- looks like you are right on the money. I have an electronics engineer friend who I might enlist for this as he's bound to have a steadier soldering hand than I do! Would it be worth hooking up a little jack socket, or maybe just a wago or chocblock, to connect the extension wire? Link to comment Share on other sites More sharing options...
PeterW Posted May 16, 2017 Share Posted May 16, 2017 I would just de-solder that and get it onto some wire - use something reasonably "chunky" like a speaker wire as these work on resistance so you want to not affect that if possible. You could just use a 3.5mm mono jack for ease - £10 would get you an extension of 10m which should easily be enough to get into a duct. Link to comment Share on other sites More sharing options...
ProDave Posted May 16, 2017 Share Posted May 16, 2017 Just use the small size wago's as good as anything. It's not like you will want to unplug it often is it? If trying to remove that, the tip is a really hot soldering iron as you have to heat the mass of the board and the plated through hole. Heat the solder that's there and one leg at a time pull the component out. Only then use a solder sucker or solder wick to clean the hole out. If it's lead free solder, a little drop of 60/40 applied will make it flow a lot better. If you can't desolder it without messing up the board, just snip the wires as close to the board as you can. Solder the new wires onto the board and there should still be enough on the sensor to solder onto. 1 Link to comment Share on other sites More sharing options...
Crofter Posted May 16, 2017 Author Share Posted May 16, 2017 What about a bit of 0.75 twin core flex? Link to comment Share on other sites More sharing options...
ProDave Posted May 16, 2017 Share Posted May 16, 2017 Sounds good to me. Link to comment Share on other sites More sharing options...
Crofter Posted May 16, 2017 Author Share Posted May 16, 2017 Well this sounds fairly straightforward. What a daft design though, putting the sensors in the controller itself, which is not allowed to be in the bathroom. If they made a version with a remote sensor option they could probably charge an extra hundred quid for it and people would buy it without hesitation. Thanks for the all the help/ideas/suggestions/encouragement- I was a bit worried about the idea of opening up the controller and attacking it with a soldering iron! Link to comment Share on other sites More sharing options...
Temp Posted May 17, 2017 Share Posted May 17, 2017 Not quite sure how they work. Probably the resistance varies with humidity? Perhaps worth measuring the resistance while it's working in case it fails later. Then you know what to order. If you wait till it fails you might not be able to measure it? Just a thought. Link to comment Share on other sites More sharing options...
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