marshian

Boiler is on a burn - pump is circulating - my question is where is the heat going if it's not going to the rads??

Those heat losses seem really high unless they are massive rooms I used the Heat engineer software (before I was aware of the spreadsheet on here) and it didn't seem like a steep learning curve to me I'm using flow temps of between 28 and 35 with T22 Rads and bedroom temps are set 2 deg higher than the std 18 for bedrooms I think I'd be trying to run the house with a single boiler temp for both UFH and Rads

it’s not hit and miss at all - 4 butts all fill to within 5mm of the lid before they just internally flow back to the soakaway, they normally come with pretty clear and easy to understand instructions Having said that I’ve mostly got flap diverters - so I can switch off the flow to the butts in winter

I think he was refering to the Smart Thermostats as Holy Grail - They aren't and it's very easy to over zone and screw the boiler efficiency Absolutely ^ this ^ - Running the lowest flow temp possible to maximise condensing efficiency improvements Do Baxi not have their own controls to enable PDHW because if they do I'd be using that - in fact I'd always favour manufacturers controls over 3rd party ones. The only reason I have a Wiser system is previous boiler manufacturers controls were archaic because the boiler design was 18 years old - when I change the boiler I stayed with the 3rd Party controls because I'd learnt a lot about what not to do!!!! "Experience is what you get when you don't want it"

Well I don't like having rooms unheated - it makes other adjacent rooms have to work harder but I think part of your house must have a one pipe circuit (maybe house extended or poorly executed circuit extension) but I was in this situation and I really wanted to do this I would do below Turn of the CH and Pump. Isolate both flow and return valves on the rads you want to stop having on - Drain down the rads and temporarily remove to make life easier. Make a simple link pipe up to fit between flow and return on those rads - Open up both ends fully All my rad tails come up from suspended wooden floors so I have enough room to push the pipes down and then hang the empty rad back on the wall It (the bypass) will provide a very small amount of heat input to those unused rooms but should stop the issues you have with turning them off impacting rads later in the circuit. (if you want to minimise that heating input then lag the pipework but I'd say a little heat wouldn't hurt)

I agree longest length of beading first then shortest - reverse for assembly but I’ve always put a wallpaper scrapper blade in the middle of the longest length - never tried one side as your picture shows??

no you need to replace the sealed unit - with same size and thickness sealed unit The frame is normally unchanged

I really regret not ducting my roof rainwater drains to a couple of IBC's under the patio - instead of filling the big hole up with brick rubble and old broken patio slabs (soakaway) I have 800 Litres of rainwater storage (mix of butts and tanks for spring summer autumn watering) and I always run out in the summer - mainly because I have to empty them all in the winter because of freezing issues and I'm reluctant to switch them to collection before April. They fill up real fast when it rains to a point that the excess often goes to the soakaway because they are full. The IBC's being underground would have been highly unlikely to reach freezing point and I could use them to top up any above ground storage in the summer. When we run out in summer I end up filling them with a hose from mains water. Should have done that IBC thing I really should!!!

I know this is probably a daft suggestion but I've always wondered in a house with UFH and Rads why you can't run the flow thro the rads first - then the return from the rads feeds the floor (with whatever flow it needs) the return from the floor combining with the return from the rads that didn't go thro the floor. So in my house (all rads) if my upstairs rads were the only rads and I had UFH downstairs the boiler flow would be between 30 and 35 dependent on OAT - the return would be 25 to 29 at same OAT The UFH could have as much flow as it could take - the return from UFH mixing with unused return from the rads? Like I said daft idea................

Funny I had a little play before we went away for a long weekend normally I turn everything down to frost protection if away for a few weeks but wanted to see the impact of a set back setting - posted elsewhere The plan Away for a few days - in my book that’s a good time to experiment with “setback” temps Turns out that the “room temp” adjustment of the weather comp curve is remarkably close to the actual room temps for the majority of rooms (like having a roomstat that works for nearly all the rooms) 20 gets 20 19 gets 19 18 gets 18 17 gets 17 So now I have a quick and easy setback process that reduces (I hope) heatloss if away but still keeps a level of heating in the house. Interesting will be how quickly will restoring the normal result in room recovery The results Scores on the doors after a long weekend in Venice (which was equally cold as here and a tad moist some days) For the days in Jan before we left house kWh/HDD was an average of 4.5 and pretty rock solid For the three days were were away house kWh/HDD was 3.13, 3.18 & 3.82 The saving over the normal usage was 45 kWh over the 3 days For the 24 hrs coming back from setback house kWh/HDD was 6.32 The cost of getting the house back to temp over the normal usage was 24 kWh So overall a 21 kWh saving in CH or in money terms £1.07 I'll not bother in future This did not include the saving from not heating HW which was 12 kWh so essentially 50p I'll continue to do that because it makes no sense to heat water that isn't going to be used Gas boiler - all rads - running WC and DHWP

In the interest of discussion I'm going to disagree UK has always lagged behind other countries - The mandating of condensing boilers was done without also mandating how to ensure they condense for all of their operating time - for many replacements they were left on virtually the same settings as the previous non condensing boilers - huge opportunity missed IMO Had I been informed that lowering flow temps would have gained me 7 % efficiency gain the rad changes I have made in the last 3 years would have been done 13 years ago As a result we also missed on getting houses ready for ASHP with lower flow temps which is why you state that ASHP with 55 - 60 deg flow temps and a cop of 3.5 to 4.0 would result in far more conversions but those flow temps and COP is not possible with the current ASHP hardware. I upgraded all my T11 rads to T22 of the same overall dimensions - in terms of output at same temp that's 1.4 times bigger (@T50) - you don't even notice they are bigger - That enabled me to go from a ~60 deg flow to a ~30 deg flow - I am on 22mm circuit with 15mm from circuit to rad but even microbore would would flow enough l/min to ensure the rads were warm enough to heat the house Total spend on rad upgrades was far less than the cost of a boiler change On this point I agree but I don't trust the government to run a bath let alone set a framework for reducing the use of FF

In my case it was 13 years but same reason - didn’t want it to be a distress purchase - knew what I wanted and how I wanted it set up and saw no point waiting any longer

still less than 6 cycles an hour if it’s 8 min burn 3 min coast any boiler is going to cycle more when house is up to temp as it’s only going to need to replace heat lost - good tine to do a few meter reads to give you a goid idea of your heat loss at whateve OAT it is now

If I am right about the kitchen then whichever rad is warmest the lockshield on that rad needs to be wide open - balance the circuit on the lockshield on the other rad. You will still get a drop in temps across each rad but there will always be one rad that has the higher temps If I'm wrong and it is plumbed in normally - ie two pipe than a bunch of your other rads will go cold quickly and your return temp at the boiler will go up

No the opposite - the more open you have a lockshield the more flow it allows - therefore the more likely the return flow temp is higher - the rad may emit more heat but it's only because the meant water temp has increased. It doesn't sound like you need more heat and your boiler doesn't need a higher return temp.

OK a constant flow temp at least means you can see differences in the flow and returns Good You don't want TRV's influencing the flows Ahhh - IMO Not the best time to balance - I know you have all the TRV's open but the rads will have already started to have hotter returns due to warmer room not sucking the heat out of the rads so your delta will be smaller You really want to do it 30 mins after a cold start - enough time to get flows thro all the rads but not enough time that the rooms are warm and are already not pulling the heat from the rads due to a smaller differential between room temp and mean rad temp Good you don't want the TRV's to start messing with the flows With "single panel single convector" T11 rads sized for an 80 deg flow temp it might be conventional wisdom but we really shouldn't be running condensing boilers like that.............. At 55 flow temps best I could get on T11 Rads was 7 to 8 deg On T22 Rads (Double panel double convector) was 12 to 14 Boiler flow temp 55 Boiler Return temp 39 (so overall delta across the boiler was 16 deg) And to do that I had to really slow the flow thro the rads to a point where I needed flow thro the ABV as soon as TRV's started intervening System was much happier with a bit more flow thro the rads lower differences between flow and return on each rad but no ABV until circuit got down to less than 5 rads and very similar delta at the boiler It was at this point I realised trying to achieve conventional wisdom on rad deltas was bloody stupid.....

A thought................ How old is the house - has it been knocked about or extended? I just wonder if part of the circuit has been piped up single pipe configuration (AKA the old way where the rads are daisy chained return from one rad going to flow of another and so on) Nah it couldn't be that surely Then again I look back at some of the temp logging and Kitchen 1 and Kitchen 2 and think ooh the return from 1 rad is the flow temp for the other................ Originally one rad and then another one added without taking the feed from flow and piping up a separate return

Fully open is fine unless the rooms are at 30 deg C they shouldn't intervene Removed just makes 100% sure they don't interfere

The boiler is set up to run on WC for CH with DHWP Only parameters that I have found and adjusted to suit the house and optimise the boiler are only applicable to CH (DHWP are max output (19kWh) and max flow temp (82 Deg C). Max Water Temp Limit 70 Deg C Max Output 40% (so 8 kWh because anything more is not needed - I may drop this further to around 6 kWh) No Anti-cycle parameters that I have found Pump Over run is non adjustable (set to a 3min max from factory) I'd attach the Installation and operation manual but it's too large but a google for Viessmann 100-W B1GA should get you to a copy The Valliant (Glow worm) Anti-cycle parameters took me for ever to get my head around but once I did it was very useful and getting a 24 kWh boiler with a 10 kWh min to work much better with less cycling! (mainly because I was also using pump overrun to manage the time between burns as well)

My flow temp last night at 6 deg C was 30 deg C The boiler over the course of 15 mins gradually went over target temp at min modulation 10.6% (3.2 kWh) by 4 deg in order to extend the run time so finally shut down at 34 Deg C I wasn't busy so watched my temp sensors for the 20 mins it coasted (pump running boiler not firing) and it re-fired shortly after this picture was taken. Left side display is flow temp Right hand side is return temp I'm pretty sure my boiler doesn't follow the flow temp - 5 deg rule My previous glow worm boiler didn't either

Yeah it may well be but the boiler is reacting to the temperature it gets from the internal sensor.........

Hmm OK I'll defer to your knowledge but I think 5 deg delta from flow temp is really bloody narrow at 60 deg flow temp - especially as on that flow setting the boiler is getting no benefit from the condensing process with a return of 55 The glow worm I had would only re-fire when return temp = flow temp (typically with a 50 deg flow temp return needed to get down to 31 (ish) before the boiler fired Same with the Viessmann I have now (trouble is I'm running much lower flow temps but a 30 deg C flow temp it re-fires when it sees no difference between flow and return temps which is around 24 deg C (I thought this was because most of the heat in the circuit had been extracted)

But you said you set it to 60 flow and at 56 return it fired up? I realise that 60 = 65 when boiler coasts but I would expect a 60 deg set point to relight at 50 deg not 56

That's not a lot of difference between flow and return for the boiler to re-fire??

Same here all the windows and doors replaced with PVC double glazed back in 1994 still got them 30 years later - glazed units might not be up to current regs but they all still seal perfectly no leaks or drafts - never had a single glazed unit fail and they haven't gone yellow either but they were the best quality units we could find. Neighbour is on his 3rd set of windows and doors and he's only been in that house 20 years - first set to replace aluminium framed originals, they went yellow in a few years and then one by one the glazing started failing - most recent set has already had glazing units replaced Buy cheap rubbish you need to buy it more often