TimCx

This balancing is getting very complex in my house ! I have 2 small rooms which are essentially plant rooms, one has the indoor part of the ASHP and underfloor heating manifold and the other some plumbing related to solar thermal and a second underfloor manifold, however both of these rooms have extract valves in them. I am also struggling to get the extracts rates right for the kitchen and the system remains unbalanced as the total extract rates are higher than I can achieve for the inlets. As the 2 plant rooms are not really utility rooms and are small (approx. 2.5 m2 each) and normally don't have people in them can I close both of these valves and not include them in the calculations?

Excellent thanks you mentioned lock nuts made me realise I wasn't sure how they are meant to lock, my vents have nuts but they were not locked, most only had 1 but I have now put 2 on each, how should they be locked? Are they to just stop the vent being wound in too far or should they be locked either side of the threaded bit?

Thanks Jack, mine is not that clever, I wish it was it would be a lot easier.

Regarding terminals being 'fully open' mine are round screw in things with no markings, I have removed all the screw-in bits to clean them. Am I better off starting with the covers off or should I just connect them as far out as they will go, I am not sure if this would make any difference . I hope to complete the balancing by Sunday., wish me luck ;-) I thought I had read somewhere that the required flows for each room e.g. 13ls (45m3) for kitchen could be done on boost and that the normal running could be at a lower rate but I can't find where I read that. From your info I think I need to ensure that the required rates are available on the normal setting and that boost should be higher? Thanks

Does anyone have any ideas on this, I have been searching elsewhere but I haven't found anything useful especially about the Kitchen situation. Thanks

I am working through balancing my system now that my replacement MVHR is installed, it replaced a failed system from an defunct manufacturer so I was not able to change the ducting other than near the new unit. I have done some initial tests before doing the proper balancing but I hit a couple of issues and hopefully someone can offer some advice: 1) The default setting on the new MVHR (Vent Axia Kinetic Advance S) gave very poor rates, I have now increased these and I am getting better rates without trying to properly balance it yet. The unit it correctly sized for my house but the ducting may be less than ideal. In order to get the flow rates required I may need to run the boost setting at somewhere near 75%. Is the normal or does it indicate a problem? 2) We have a cooker hood in the kitchen, I am not sure how to take that into account with extraction from the kitchen, there is also a vent in the kitchen. Can I keep the vent at a lowish rate and rely on the cooker hood to meet the required kitchen extract figure? Thanks

Thanks again Andy, yes I noticed that in the circuit but on the old unit the boost switches were connected to the unit live and the black wire so if any was switched then the black wire was live. There are 7 boost switches and they were wired in parallel to a common point near the unit. I think I will leave the boost wiring for the electrician as I wont be using it initially. The isolation switch will be next to the unit and visible

Hi Andy Thanks for your reply its very helpful, the other means relates to energising the boost line when not using the MVHS supply to power it. I have added a scan of that page to this comment Yes they do state 3amp fuse is required and I will ensure thats done. Thinking about it a bit more as the boost line is energised from the MVHR supply then a 2 pole isolator to isolate the supply from the CU will also isolate the boost line anyway so I should not need a separate isolator for the boost line? I also found a statement in the 'Warnings and Safety Information section' of the manual that says 'The unit should be provided with a local double pole fused spur fitted with a 3A fuse having contact separation of at least 3mm....'

I am about to wire my new MVHR, the attached lead is 4 core with L, N and Earth and an additional black cable that if energised (at 240v) will switch on the boast function. The boost wiring is connected to switches outside the wet rooms, these were (in the old system) connected to the live from the unit and if any switch was closed then the black wire with be at 240v and will initiate boost, I wont be using this boost initially want to be able to add it later. What is the correct way of wiring the unit for isolation, the unit wiring diagram looks as though it should be connected to a 3 pole fuse spur but I have not been able to find one (see attached) All wiring will be checked and signed of by a qualified electrician.

Wow thanks again, can I ask what you mean by 'insulating tape' is that the electrical type tape or something else?

Excellent thanks and yes it is the wired type, I was going to add a Jubilee or worm drive clip to keep it in place and possibly some aluminium foil tape as well, but are they needed as it will be pretty tight?

I am nearly ready to install my new MVHR unit and I think I have everything ready to go. My pipework is nominally 125mm. I have just tried a test fit of some Flexi Duct to the spigots on the MVHR unit, it seems hard to get it onto the spigot. Is there a trick to using this stuff? Any tips appreciated. Thanks

Just in case its of use to anyone in the future, I checked with Soudal about using Soudalduct with plastic ventilation pipe, I said I wanted to check because it only mentions metal ducting, the technical advisor said that was its primary use but its fine for plastic as well.

Thanks all, I have done a but more research and managed to speak to someone who has fitted this stuff before, his preference was Soudaduct. As the Soudal state that is for metal duct I phoned their technical help line to ask if its OK for plastic and they said yes its fine, so I think I will use that.

Am I right in thinking that RH is Relative Humidity in this context?