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Green Building Bible, Fourth Edition
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    • CommentAuthorGotanewlife
    • CommentTimeOct 17th 2016 edited
    So my Aircycle 1.2 has stopped going in to boost when the humidity is high. Manual boost works fine and over run is correct (frost function has always operated irrespective of the temp from new but I didn't do anything about it). Brookvent have finally decided that the new version of their PCB will work in my old machine and a new PCB is £40 plus as yet unspecified delivery to Italy.

    The unit is still in warranty but then I am obviously not going to trash the airing cupboard where the MVHR unit is and then pay for delivery to NI in order to comply with the warranty T&Cs. So whilst they agree it is propbaly the PCB, it is at my risk and i have to pay for the PCB. C'est la vie.

    However, it has always irritated me no end that the humidity control is a tiny 'pot' that requires gut instinct to set having no gauge/setting markings etc and that I have to climb a ladder, take off a load of sound insulation unscrew their not at accessible access plate (set between the 4 vertical 125mm pipes, which are obviously all lagged up) in order to fumble around with an utter guess as to what RH I am setting. I generally do this twice a year as with 3 bathrooms feeding the thing the RH setting seems to need to be reasonably close to the avg ambient to kick in (in the normal situation of only one bathroom being humid at a time), so close in fact that the summer winter RH are too far apart to work all year around. If I don't change the thing it will either not boost or stay on boost.

    Sooooo. See below a dead cheap (£20!!) digital humidity sensor with inbuilt 5A relay and hysteresis function - it says temp corrected humidity, which I assume means %RH as opposed to absolute Humidity. If I am correct, I can parallel wire this in with my manual boost switch, set %RH accurately and, since it will be mounted on an accessible shelf in airing cupboard, change it really easily as per the weather. The only downsides seem to be that it is cheap Chinese electronics, I haven't yet found a solution for delivery to Italy yet and the instructions are so badly translated it takes a while to understand how it works. Here it is:

    I would be really grateful for advice on my idea/alternatives. Especially as it is sooo cheap and MVHR manfs seem to charge a ridiculous (in comparison) amount for the Humidity function or stand alone humidity switches (like this one from Brookvent - note no details/spec on product at all, just pay them £70!!)

    Am I missing something?
    • CommentAuthorCWatters
    • CommentTimeOct 17th 2016
    I've only looked at the Amazon page but it looks ok to me.

    It looks like it will switch the boost on when humidity exceeds a high humidity setting and stays on until the humidity falls below a low humidity setting (eg Hysteresis).

    Not quite sure what "delay protection" is. Probably a minimum boost time setting so once triggered it will stay on boost for a minimum time.

    If I am correct, I can parallel wire this in with my manual boost switch, set %RH accurately and, since it will be mounted on an accessible shelf in airing cupboard...

    It says it has remote temperature and humidity sensors so they could be located in the same place as the existing sensor with the control unit somewhere better. Check max length of sensor cable? I'm not sure I would put the control unit in the airing cupboard. If gets humid in there that might effect how long the unit lasts.
    • CommentTimeOct 17th 2016
    I don't see anything obviously wrong with it. Most humidity sensors also include a temperature sensor, so I'm not sure why it has a separate one? As Colin says, check the lead length.

    In trying to find more details, I came across this rather remarkable page:


    Thanks chaps. :smile::smile:

    I would insert both the temp sensor and the humidity sensor into the appropriate pipe just before it enters the MVHR unit. Some careful cutting with my multi tool will do it and seal the hole with foil tape so it is removable. The 'airing cupboard' is actually a linen cupboard that happens to have the upstairs radiator and H/C water manifolds in it - no damp clothing ever goes in there. The cables only need to be 1m long to give the perfect position for the control unit ie fitted to the underside of one of the shelves.

    I just can't get my head around how cheap, or rather, how expensive off the peg humidity controllers are. Usually when things are too good to be true....

    So why are MVHR and even single room fans using those stupid, stupid little pots to adjust the %RH when the retail cost of the linked controller above is £20? Bizarre!

    Oh well best I start looking for one I can get shipped here then. (weird page djh!)
    • CommentAuthorRedDoor
    • CommentTimeOct 17th 2016
    I have two units that look very similar if not the same. They're connected to in-line fans that ventilate shower areas. I did this as an upgrade to the analogue rh sensor that I built into a plenum above a shower area - always disappointed by the slow reaction time (on and off) of that set-up.
    You can position the sensor remotely to the actual unit - I think the wire is a metre or so. The chinglish instructions were laughable but there's a website with a blogger reporting on his home-made curing cabinet which helped me with the wiring connections.
    I'm not sure about a temp sensor on the same unit. There's a near identical unit that controls temperature - indeed some of the buttons on my units appear to be more relevant to it's use as a temp sensor.
    • CommentAuthortorrent99
    • CommentTimeOct 18th 2016
    If you're going down the DIY route, you could get 2 (or more) RH sensors, one for indoors, one for outside, and use something like a Raspberry Pi (or Arduino) to make some intelligent decisions about when it should turn on th efans.
    Thanks red door. The different versions have been driving me a bit crazy and it is even worse for the temperature controllers as there are more versions of that - all in the same container, all with similar looking connections. Basically I can't get the one linked in Italy at less than 3x the price than in the UK but I can get the slightly cheaper version that doesn't have a temp sensor - it says...but then how can it know the RELATIVE humidity without knowing the temperature?????

    Ahhh finally found the same one in Italy and it's Prime too - bargain!!https://www.amazon.co.uk/gp/product/B00GNT1NJY/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A2I0KD4PFXY56D

    RedDoor, Did you look for a chassis for the thing; they must exist because there are about a zillion choices out there using the same box?
    • CommentAuthorEd Davies
    • CommentTimeOct 18th 2016 edited
    Posted By: Gotanewlifebut then how can it know the RELATIVE humidity without knowing the temperature?????
    More likely than not the sensor measures something pretty close to relative humidity anyway. If a temperature probe is needed then it'll just be to improve the accuracy of that rather than to convert an absolute or specific humidity into relative humidity.

    Since you'll likely be using it over a fairly narrow temperature range and the exact humidity isn't so important I doubt it's too critical to you.
    • CommentTimeOct 18th 2016
    • CommentAuthorRedDoor
    • CommentTimeOct 18th 2016
    I have the MH13001. It does not appear to have any temperature sensor capabilities. Confusingly, they arrived in boxes clearly marked "digital temperature controller". It senses the environment, has a digital read-out like a de-humidifier, and will switch a fan (load) on or off depending on set points that I enter with the potential of a timer over-run. The instructions include "3. The humidity control host machine cannot be installed in the place where is dripping water, or the elderly, children could be touched;".
    I tried to source a suitable chassis but gave up. I took a dremel to a faceplate and drywall back box (there was an unintentional prototype !) and it all fits into a stud wall.
    I was helped by the blog of Ben Starr:
    but that features a similar looking unit that does have temp and humidity sensor connections.
    Ta everso - that helps!........and I love the idea of curing my own meat, which a lot of my nieghbours do the old fashioned way :wink:

    Another GBF problem solved.
    • CommentAuthorwookey
    • CommentTimeOct 21st 2016
    That is a fine page djh (once I work out to get rid of the 'login' box so I can see the page).

    Looks like you can have a humidity sensor plus relay on a board for £2! Which would do gotalife's job. Although I guess some power will need to be arranged.
    • CommentAuthorGotanewlife
    • CommentTimeOct 21st 2016 edited
    So it cost me about £20 incl delivery and it is amazing - tiny thing under door frame below MVHR unit - displays current humidity and so you can see what's going on and set the limits and hysteresis very quickly if the ambient conditions change. ALL MVHRs should have one!!!! Only shame was that it is parallel wired up to the boost switch (one of the switches on the 2 gang light switch to the right of the cupboard) and the boost switch has a 15 minute over-run time as standard but a trivial point (the controller has a user adjustable min run time). I just don't understand why for such an incredibly cheap item all MVHRs don't have a controller on a fly lead - completely changes the usability and frustration factor of boosting via humidity.
    • CommentTimeOct 21st 2016
    Posted By: GotanewlifeI just don't understand why for such an incredibly cheap item all MVHRs don't have a controller on a fly lead - completely changes the usability and frustration factor of boosting via humidity.

    Where do you sense the humidity? I suspect the average humidity in the extract duct into the MVHR won't change enough to be a useful signal, which would mean running separate sensors in each wet area. I've got some additional sensors I mean to fit to measure such things, but ....
    Actually the average humidity across the 3 extract rooms (all bathrooms) does change enough for this to work - but no way you could get the required level of accuracy with a 'pot'. Those colored wires going up the front of the MVHR are the sensor wires and I just drilled a 12mm hole to pass the sensors through (once I had opened up all the sound insulation!). The built in humidity sensor operation never worked properly (even when it functioned) so this is mildly revelational and I am offended that this level of sophistication is unavailable as standard in MVHRs when it is patently so inexpensive.
    • CommentTimeOct 22nd 2016
    Ah, your system is simpler than mine. Maybe that is the secret of success. I have six extracts: kitchen, utility, bathroom, 2 x shower rooms & plant room; same number as the supply vents. So I doubt that extra humidity in any one would be likely to trigger a single humidity sensor. Fortunately we don't suffer much and misty mirrors are cleared just by opening the shower room door. So I haven't tried humidity boosting yet.
    If you are sensing the humidity in the extract side of the MVHR does this mean that you are running the unit 24/7, or do you have it on a timer?
    When I first set it up I 'understood' that MVHR was supposed to be on 24/7, now of course others on here have made clear they have theirs on a timer. I had considered the effort of putting it on a timer (all the electrics just a bitch to work on so not a simple thing!!!!) but whilst this unit only covers the top floor (bedrooms and bathrooms) we have showers all over the shop time wise so I just don't see it working on a timer.
    The simplest timer is one that goes between the socket and the plug. (plug the timer into the socket and the unit into the timer) this allows fixed times through the 24 hours which perhaps could set the unit to come on for some hours around the time(s) of high demand with the humidity sensor managing the boost for higher loads.

    BTW any news on replacing the fan bearings (other thread)
    Posted By: Peter_in_HungaryThe simplest timer is one that goes between the socket and the plug
    Yes I know, I have loads of them. However, my MVHR is hardwired. But anyway, with 4 adults in the house all the time plus one grown up kid at college (with girlfriend who showers here whenever possible) there really isn't a way to do a timer that wouldn't leave a shower room full of steam.

    I'll try and update the other thread.
    So you would need a humidity sensor in each steamy place (at £20 a pop) wired back to the MVHR unit.
    Hmm... lots of wiring and a cost / benefit calc. first
    • CommentTimeOct 23rd 2016
    Posted By: Peter_in_HungarySo you would need a humidity sensor in each steamy place

    Maybe we could just fit one sensor at Steamy's place and then all access it over the intertubes? :bigsmile:
    • CommentTimeOct 24th 2016
    Easily done.
    It is always 100% RH here :devil:
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