Oz07 Posted January 12, 2020 Share Posted January 12, 2020 First fix sparky tomorrow. I have received seperate boost switches for the MVHR unit. Can I just have the sparky link these to the two lights in the bathrooms? What did you all do in the kitchen? I could either have a standalone switch or is it possible to link to (recirculating) extractor power so when that's in use the boost kicks in? Link to comment Share on other sites More sharing options...
ProDave Posted January 12, 2020 Share Posted January 12, 2020 This is highly dependant on which mvhr you have, they all operate differently. I doubt you can get it to boost when you turn a light on for instance without the use of a relay or two.. For mine I chose to put a timer boost switch in the kitchen and another on the landing. This gives a timed boost. For the kitchen it boosts it to one down from the fastest speed. For the upstairs one for use when showering, it boosts it to the fastest speed. These are the timers I used https://www.tlc-direct.co.uk/Products/SMTGBT4.html These timers give a switched 230V output. Because my mvhr expects a volt free contact for low voltage switching, I use the timer to energise a relay, and the relay contact switches the mvhr. Link to comment Share on other sites More sharing options...
JFDIY Posted January 12, 2020 Share Posted January 12, 2020 What make and model of mvhr are you using? Link to comment Share on other sites More sharing options...
Oz07 Posted January 12, 2020 Author Share Posted January 12, 2020 Dormus there is info and a wiring diagram in there but electrics is over my head. Looks like I'll just opt for 2 gang switch at bathrooms and separate switch in kitchen no major Link to comment Share on other sites More sharing options...
Oz07 Posted January 12, 2020 Author Share Posted January 12, 2020 Dave I think you set the timed boost from the units control panel. Remember reading something about it in the book Link to comment Share on other sites More sharing options...
ProDave Posted January 12, 2020 Share Posted January 12, 2020 31 minutes ago, Oz07 said: Dave I think you set the timed boost from the units control panel. Remember reading something about it in the book MY mvhr is really basic, it can run at 4 speeds selected by some volt free input contacts. Speed 1 is the fastest, used for the bathroom boost mode. speed 2 the next for the kitchen boost, speed 3 is not used, and speed 4 is the normal trickle rate. Actually when I set it up and balanced it recently I find speed 4 is too slow to meet building regs ventilation rates, but anecdotally is fine. If I have to for compliance I can set speed 3 as my normal rate. Link to comment Share on other sites More sharing options...
joe90 Posted January 12, 2020 Share Posted January 12, 2020 1 hour ago, ProDave said: Speed 1 is the fastest, used for the bathroom boost mode. speed 2 the next for the kitchen boost, speed 3 is not used, and speed 4 is the normal trickle rate. That’s odd @ProDave, I have the same unit as yours but 1 is the slowest???.? Link to comment Share on other sites More sharing options...
ProDave Posted January 12, 2020 Share Posted January 12, 2020 5 minutes ago, joe90 said: That’s odd @ProDave, I have the same unit as yours but 1 is the slowest???.? It's quite possible I have remembered it wrong. 1 Link to comment Share on other sites More sharing options...
phatboy Posted January 15, 2020 Share Posted January 15, 2020 For my bathroom i just rely on the MHRV units built in humidistat. For the kitchen, I got a clever relay with a wide input voltage and a timer, and connected it into the wiring for the extractor fan motor. So the system boosts when the extractor comes on, and remains boosting for 30 minutes after. Link to comment Share on other sites More sharing options...
Oz07 Posted January 16, 2020 Author Share Posted January 16, 2020 That's what I wanted. Although wouldnt work in cloakroom. It's done now. Im just going to have a switch above the worktop to boost. No biggie. Separate switches for wetrooms Link to comment Share on other sites More sharing options...
PeterW Posted January 16, 2020 Share Posted January 16, 2020 I’ve just wired a normally open relay to the MVHR and put the humidity sensor across the NC terminals and the no volt boost on the control board. Then taken the power to the relay via a switch in the kitchen for fan boost, this connects the NO terminals direct to the board. That way the kitchen switch overrides the humidity sensor Out of interest, @Jeremy Harris what do you have your humidity sensor set to ..? I’m seeing a background of 60 or so at the moment. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 16, 2020 Share Posted January 16, 2020 3 hours ago, PeterW said: Out of interest, @Jeremy Harris what do you have your humidity sensor set to ..? I’m seeing a background of 60 or so at the moment. I have to change the threshold around twice a year, because of the seasonal change in RH. Right now ours is set to 52% RH, with a 2% hysteresis, and that seems to work OK. The house is currently sitting at 38% RH downstairs, but the extract plenum is at 48%, probably just because the air in the extract plenum is a couple of degrees or so warmer than the house. Ideally I'd like the humidity switch to just work on rate of change, rather than an absolute threshold, as that would, I think, make it adjustment free. If it just worked so that boost was triggered if the RH rose by a few percent over the space of a minute, then I think that should work a bit better. A sudden change in RH is likely to be a more reliable indicator of the need for boost ventilation than the RH hitting a set threshold. Link to comment Share on other sites More sharing options...
PeterW Posted January 16, 2020 Share Posted January 16, 2020 2 minutes ago, Jeremy Harris said: If it just worked so that boost was triggered if the RH rose by a few percent over the space of a minute, then I think that should work a bit better. A sudden change in RH is likely to be a more reliable indicator of the need for boost ventilation than the RH hitting a set threshold. Thanks @Jeremy Harris Sounds like a very simple PIC/Arduino sketch to manage that ..? May have a look and a play... Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 16, 2020 Share Posted January 16, 2020 16 minutes ago, PeterW said: Thanks @Jeremy Harris Sounds like a very simple PIC/Arduino sketch to manage that ..? May have a look and a play... It's something I keep meaning to do, but haven't got around to it. Something really simple, that just detects a rise of a few percent RH over a few minutes, and then switches on boost until the RH comes back down to close to whatever the pre-boost RH was would probably work well. Doesn't need to be very complex, and just having a fixed boost timer triggered by the sudden increase might work well enough. Link to comment Share on other sites More sharing options...
Oz07 Posted January 16, 2020 Author Share Posted January 16, 2020 My god you two are speaking another language 1 Link to comment Share on other sites More sharing options...
joe90 Posted January 16, 2020 Share Posted January 16, 2020 2 hours ago, Jeremy Harris said: Doesn't need to be very complex that’s easy fir you two to say ? 1 Link to comment Share on other sites More sharing options...
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