marshian

Well that was sub optimal!!!

Then it must be because that’s what your house needs to keep it warm 😉

Just to explain why you don’t see the same thing on initial heat up On initial heat up you have a cold circuit even if the flow is a little low (and I think it is) the water has a lot more capacity to take the heat from the boiler so it doesn’t overshoot in the same way - once the circuit has some temperature in it the capacity of the circuit and flow to take the initial purge and hi level burn before the boiler modulates down is much reduced

Nice - very nice indeed My retirement project is to restore this To as it was in the COI back in the late 80's But it has a bit of a troubled history

Regardless of the regs if there are any - both my ground floor flow and returns have drains out side if the house (actually under the decking in the rear garden) - conventional drain points - just foam lagged in case of freezing temps

Diagrams are handy - I'm pretty sure I have FInk style Trusses I took note - just had other things going on As far as drama and real life examples go - be careful using examples like cutting holes in aeroplane windows with a multitool - you might think it's humor/fun but it may not be received in the same way - that's the problem with text on the internet - you don't get to see the facial expression as the humor/fun is delivered the storage up there is pretty minimal (xmas decorations, empty suitcases, my stock of foam pipe insulation and the odd tote bin of things I don't want to throw away) and items are well spread out I'm not using it as another room but I do want to be able to get access to all areas of the loft easily - I'm not happy with 400 mm of loft insulation over the top of trusses so I don't have a clue where I can stand safely without putting a foot thro the ceiling below (that's why it was boarded originally) You raise a valid point but 30 years my loft has been boarded out and I've seen no evidence that it was in any way excessive loading - no sags or cracks in the ceilings They (trusses) are actualy marked up with manufacturer (swedish I think) and a BS std - I think from memory BS 5268 because the cold water storage tank is in the loft framed off the trusses - I need to check and note down the details One thing I would say they aren't the spiders web of skinny timber I looked at in a friends new build house - they looked like match sticks holding the roof up!!! Appreciate that it's my neck on the line and I do have a habit of "over engineering" stuff so the advice is appreciated

so you need to increase the flow rate thro the boiler to stop this overshoot - open all the lockshields 1/2 a turn (except the towel rails) see if that stops it - if it does wind them back a 1/4 and see how it reacts - if it doesn’t add another 1/4 turn and see if that helps if you get to a point where the boiler isn’t overshooting then you can drop the flow temp and you’ll get longer burns at lower flow temps but you’ve got to get the boiler happy on initial purge and burn

Mine (wiser hub) doesn’t any more - I set it to oil boiler and that halved the number of cycles -then set it on open therm boiler settings (even though it’s not wired for open therm) - that fixed it when I was running scheduled heating slots. Noe it doesn’t do it at all but I’ve set the majority of TRV’s to 0.5 deg above actual room temps and that can’t be achieved with WC flow temps But that isn’t @seanblee‘s issue I’m sure of it and it’s a bit off topic

9 cycles an hour between 12 and 1? And in the afternoon way more - I’d not be happy with that at all

I’d be doing something very different - I’d be sizing my rads for the lowest flow temp my boiler can run at but I’d be looking to do that for the whole house in order to get the boiler efficiency to high 90 % efficiency (ie 97-98%) that would make me heat pump ready for when the boiler needs replacement with just the addition of a HW tank (cos you currently have a combi so no HW tank) However I appreciate that everyone has a budget and sizing for 60 deg might be what your budget accommodates. I wouldn’t mix and match and have part of the house with oversized rads and the rest of the house sized for 60 deg C flows.

It's a different approach if you are using online calculators based on room volume then please be aware they will probably oversize the requirement. As others have said you really need to do a whole house heat loss - but if you are already running 60 deg flow for the rest of the house then I guess you need to size the rads for the new area with the same temp regime and just do a heat loss of that area. With your current rad positions you should get a good even spread of heat and as you say you can turn the rads down if they are a little over size whereas if you undersize a rad you can't really turn it up (all you can do is up the flow temp) or replace it for a larger one

Sorry fat fingers - same questions still apply

Anyway back to topic - what's the reason for using T11's @tommyleestaples Space constraint? Already fitted? Asthetics?

Same age but I cross over between metric and imperial depending on factors Really small stuff - Thou (I have a automotive habit so spark plug gaps and tappet clearances) Small stuff - CM and MM and to a push M Bigger stuff - Inches and Feet (Boats are still x footers and I'm 5 foot 13 inches 😉 ) Really big stuff - Miles (although knots and fathoms if I am boating) I don't do lbs and ounces - I do Kgs but weight in stone is much easier for me to translate in my head Still work out miles per gallon (the proper sized one not the poxy little one the USA use) even thou I buy fuel in litres It's all a little weird really!!!

Funny that - customers* are strange!!! * it's why I don't have any I have every sympathy for those that do!!!

I was a bit surprised at what I saw - quality control clearly not the best Sounds like they are functioning relatively well - verticals really do seem to need a bit more flow and a slightly higher flow temp than an equivalent T11 or T22 to get the same heat output Worth a look - I have a very large vertical (Millano) with a built in diverter and after my experiences above I had a good look in that one and it's 100% diverted

So first section completed Yes I know the edge closest to the roof tiles and felt isn't supported - it's just acting as a dust/condensation cover for the insulation

Up to about 2 years ago that's all I used.................... Mainly because I had a dos based programme for calculating rad sizing for rooms and that's the only unit of measure it used

Verticals are a pain - you have to sacrifice some delta T at the rad - they aren't as good as heat emitters and need a good bit of flow - restricting them doesn't work very well Ladder type towel rails are the work of the devil - they don't balance very well - they are rubbish as heat emitters and generally they live to short circuit!!! My bypass rad is a 1400 x 500 T22 in the hallway - it has a flow rate of 7% of the total - keeps the hall at 18 deg and allows the boiler to fire if the circuit shrinks to just a few rads

Depends on the rads - running 60 deg flow on my old glow worm I was struggling to better 8 deg on a T11 and 14 on a T22 rad I gave up worrying about getting rads to the highest possible delta T and just concentrated on getting the right mean water temps to heat the rooms So in responding to your last question a higher than 10 deg delta is going to make life worse for your boiler so no don't aim for more aim for less The rads get noisy because you are restricting the flow so generating system noise Open the lockshields a little and lower the pump speed and keep it on a fixed speed - proportional will do the opposite of what you want Just for an example I'm running a ~30 deg flow temp at around zero deg outside air temp - I get a delta at the boiler of 7 deg Pump speed is 2 (fixed) and is around 0.5 m3/hr - there are 13 rads in the circuit My biggest rad 700 x 1400 K33 has a flow in of 30 deg and a return of 24 deg and it's getting nearly 20% of the total circuit flow but it's a big room and one rad has to heat that room

the passing of @joe90 reminded me I hadn't come back to this topic So taking on board the sensible part of @Gus Potter's post and finding no local SE remotely interested in doing any calcs - the majority didn't even respond to an email and those that did said it wasn't worth their while or advised me it would be prohibitively expensive - I guess expensive is a relative thing the few that did respond wouldn't even give me a ball park so I'll take that as a brush off. So in the interests of getting my head round it I did some myself - unfortunately I do them the practical way A section of the loft I stripped of the existing boarding that has been down for 30 years I was surprised at the weight of the boards removed - it was all double boarded with 10mm OSB and 12mm chipboard (pretty sure I laid the OSB and then found it a bit flexible underfoot so double boarded it with 12mm Chipboard to stiffen it up So area covered was 13.8 m2 Weight of the boarding removed 197 kgs So loading was 14.2 kgs per m2 for the old boarding So new boards 18mm OSB work out at 10.3 kg / m2 so 142 kgs To raise the floor area in this section I need to use 7 I-Beams and at 3 kg per m length that's 50kgs Total weight 192kgs for new raised loft flooring (or 13.91 kg/m2) Oh but I hear you say what about the insulation - so lets cover that 150mm superglass loft insulation is 10.76 kgs per pack - each pack covers an area of 7.71 m2 That's 1.38 kg /m2 100mm superglass loft insulation is 11.28 kgs per pack - each pack covers an area of 12.12 m2 That's 0.9 kg /m2 So based on doubling up 150 with 100 a 13.8 m2 area will need 32 kgs of loft insulation or 2.28 kg/m2 So the total load, I-joists, boarding and loft insulation is 16.2 kg/m2 I'm quite comfortable with that.........

As a Vauxhall/Opel Fruit I demand pics OK please share some pics - quite partial to a well sorted shovit

Well I defer to your "Boiler Knowledge" cos I only have good knowledge about Glow Worm boilers (although that crosses over to Valliants) but if a 38CDi Classic can run 40/30 then I'd say the system is too restrictive right now to allow it to do that with a 10kW min

Made me chuckle because I'd just written a post about just that situation - rads with inbuilt diverters which don't

I'm not sure if it helps but I put vertical rads in two bath rooms (the towel rail ladder type rads just weren't cutting it) They were heating the rooms fine at higher flow temps (~55 plus) but one was bloody awful at lower flow temps {~40 deg C) They were both had equally poor delta T between the flow and return at either higher flow temps or lower flow temps but one definately wasn't much of an improvement on the old ladder type towel rail. I took the worst one off the wall removed the lockshield and trv and shone a torch down it whilst taking a picture from the other end That light you can see is the clearance around the inbuilt diverter I knocked it out and fitted one of these (trimmed it to size) Difference was like night and day you could feel the first 3 columns getting warm the flow rising to the top and the the cooler water leaving the rad down the columns on the other side. It was so effective I did the same to the other identical rad - and that one was better too and now they heat the bathrooms to 22 deg C fine even at ~30 deg flow temp