marshian

Thank you for clarifying that - was not aware that 9kW ASHP had potential to modulate down to 3 KW - thought it was 50% at best

@JohnMo Of course I'm plucking numbers out of the air - my intro even said so "What would an MCS calculation come up with" So a 9kW ASHP can get down to 6kW - so a 6kW min input with a 3.5 kW heat loss at -2 That is designing a system to bloody cycle - No? How bad is it going to be at 10 deg C OAT?

100% this esp in bold I'm running a gas boiler at a WC flow temp of 34 deg C at -2 Return temp at 34 flow is 27 Deg C Boiler after a restart is modulating down to 3.2 kWh and running between 60 and 80 % of the time What would an MCS calculation come up with - a design flow temp of 45 deg and mandate a 9kW heat pump - the room temps would be bouncing of the TRV's acting as overheat limiters. I'd turn the flow temp down to 32 and the ASHP would cycle like a twat and give a COP of 2.5 or less That's just stupid or mad!!! (I've not decided which yet)

Agreed it's a great idea - however I'm sorry to say that my view is it would be as effective as below

Might be worth a separate thread on the two items pictured - perhaps someone more knowledgeable will be able to identify what they are??

In other news When on scheduled heating last year with higher slope 1.4 and higher level 4.0 I was bouncing the room temps off the target and using TRV's to control so needed a level of bypass to allow the circuit to still have flow when a significant number of the rads were closed by TRV's. Note - I always had one rad with elevated target (above what was achievable) and that was the Hallway rad Reasons - biggest heat loss (quite a large area across two floors 31.7 m3 or ~12% of total house volume - it's not a box shaped house) - ceilings are also landings above so effectively low heat transfer - Stairwell is double height "room" - only served by one radiator (it's big but I deliberately didn't over size it because of both space and I didn't want it over heated as the roomstat which turns off the CH is also in the hallway) Anyway that one hallway rad was not enough to supply the flow required to keep the boiler happy so by pass cut in when circuit got down to 2 or 3 rads in play. Tuesday evening I shut the bypass fully (well set it so that pressure required to open would be only achieved if all rads were closed) not sure why I had left it at the previous setting but I guess it was just something I didn't think about I am suspecting now that there has been some flow thro the bypass even with all rads in circuit because the number of cycles per day has dropped significantly - OK it's been colder but previous days have been just as cold and number of cycles is definitely reduced in a 24 hr period - will be interesting to see if that improvement continues as outside temps rise!!!!

Be interested on how much the boilers cycled - my bet would be not much more than they would with a flow temp of 50 and a room temp target of 20. It must be a fairly decent boiler to get down to 40 flow temp setting - My old Glow worm gas boiler had a minimum of 39 - that was the lowest temp it could be set too but damn thing wouldn't stop cycling constantly unless you put the flow temp up to 45 then it could just about cope with restarts.

I think it's a brilliant idea - accountability for the taxpayers coinage being rinsed thro the MCS scheme Trouble is EPC isn't much better for giving stupid results - now I haven't had an EPC survey done on my house because we have lived here 34 years - they didn't exist when we bought it and I don't need to do one unless we sell it - However it is needed for the BUS grant so I looked into it when I was making the decision to either go for replacement gas boiler or ASHP. Had a bat and ball email chain with a local EPC "inspector" in detail about the process and to be honest I was totally unimpressed with the responses to questions I asked - got the feeling it was a box ticking exercise and at £70 was an expensive box ticking exercise with very little value Examples of why I think this I have 75 mm of PIR under my suspended wooden ground floor it made a massive difference to heat loss in the property but it's not easily accessible to inspect - I said would photo's taken from when I was doing it help to prove that it was insulated This was the response The survey itself is a 'non-intrusive', it is purely a visual survey, meaning an Assessor can only enter information into the software that creates the EPC if they can see and photograph it, for instance if a loft cannot be accessed for any reason (may be the hatch is sealed because it has been painted over) an Assessor would record the loft insulation as unknown, the software would then assume the insulation levels to be 'as built' dependant on the age of the property, where as in reality there may well be 300mm in place. So in summary my suspended floor would be assumed to be un-insulated because Building regs at the time did not require it and because the openings have been covered by a solid oak floor it's not viewable All my rads are sized for flow temps in mid 30's to maximise condensing efficiency and the work I've done to improve the house has driven gas usage for CH and HW down from 25,000 kWh per year to under 9,000 I asked if this had a bearing on EPC results This was the response To answer the question about Kwh usage stated on the EPCs of the properties around you, these figures are all estimated from assumptions of occupancy based on the things such as the size of property, for instance for a four bed house it would be assumed that there will be five occupants and with a two bed house three occupants and therefore more usage in the four bed property. Now this of course is not always the case and the occupancy levels could be very different in reality! Now I can get that HW demand changes with occupancy and 20% of my gas usage is HW generation that's fair enough but CH usage reduces with insulation and to my mind doesn't change with occupancy!!!! Same size house as mine that does have EPC similar double glazed windows and doors is 18,000 kWh for Ch and 3,000 for HW EPC is 49 - E So that and a provisional guide from Octopus of £13,500 for ASHP install (less the 7500 BUS grant) I didn't bother and bought a new gas boiler I'm convinced the whole world is quite mad!!!!

So one might be a pressure relief valve (the black one) but the other looks like a std ABV valve just one I haven't found on google images

I have two sonof temp and humidity meters and following some helpful advice from @Sparrowhawk on how to calibrate the sensors I trust them much more than I did All you need is a bit of salt

Between 55 and 60 in all areas except the loft - thats crazy high

Just to explain what an ABV does - it’s a circuit pressure activated bypass It should be set to open only when the circuit is too small for the boiler to be happy with flow thro it. my old glow worm boiler needed 10 litres per min (absolute min it would run with) when the CH circuit got down to less than 3 rads the flow was below 10 lpm so it would fault out - introducing an ABV into the circuit allowed a small amount of recirculation back to the boiler maintaining a min flow of 10 lpm - it did however mean the boiler cycled a lot but a cycling boiler was preferable to a fault code that stopped the boiler and required resetting manually

Having two ABV’s would be a bit odd - unless you have two heating zones?? If that was the case then you’d be balancing rads in each zone not trying to balance the whole circuit as one……. any chance of some context - ie what pipes are they on and what pipes do they link too?? oh and a really simple check if they are ABV valves and they are allowing flow is when the boiler is on a burn see what the temperature of the pipes above and below those two pictured is. If temps are same or similar it would indicate that they are allowing flow back to the boiler This would reduce the pressure in the CH circuit leading to rads not getting warm (or hot) and raise the return temp to the boiler and lead to increased cycling when the circuit gets smaller as TRV’s start to close or close completely

They both look like ABV’s to me - yikes

Love that second one - brilliant!!!

Thanks for sharing @SteamyTea That was a good read

lol Ours is always "Norfolk n Good" or if someone has nabbed it "Quiz team Aguilera"

I think the suggestion was for just one pub Oh and you aren't going to be crawling drinking guinness zero - peeing yes crawling no

Well it's pretty clear that that's the smoking gun found I've not seen a valve that choked before but I have seen a pump that was pretty similar Have you had a magnaclean or similar installed in the system yet - If you've put Fernox F3 in the system it's probably going to free up other deposits I'd want something in the circuit to collect them rather than letting them build up And yes you can look at it as £5 K saved (for now) Now do you still have the old Grundfos pump

https://www.facebook.com/norfolkmountainrescue/?locale=en_GB

I meet with a group of "Car Guys" under the umbrella of Norfolk Mountain Rescue Club I think that sometimes people think we actually do mountain rescues - I have to explain that Norfolk is well flat (unless you are on a push bike) It's just an opportunity to share tools, knowledge and occasionally we have been known to hold a spanner party

Baxi 400 Heat Only according to another thread - what kW rating is it?

ABV can look like this What boiler do you have?

For following rads - close the lock shield 1/8 turn - recheck flow and return after 20 mins if no improvement (ie bigger gap between flow and return another 1/8 of turn on lock shield and recheck after 20 mins Loo Bed 2 Dining 1 Dining 2 When you've got the DT's better check the rads where you had an issue and especially those towel rails because they are too good 8 and 12 deg on a towel rail means they are either massive towel rails or they aren't getiing that much flow - closing the lockshields on the other rads could increase the flow and drive down the DT - they you will need to do the same with those TR's ABV normally near the pump or could be in the boiler

Suggestion "Crown" at Stowupland (Just outside Stowmarket) Close to A14 been a while since I've been there but it still seems to get good reviews (Dog Friendly too)