marshian

Can you increase the size of the rad (height or length) to save ripping the arse out of it? I guess the question is how many more watts are needed to get the temp to target.

Crickey That's a bloody hard hit!!!

Micro managing room temps with "Smart" TRV's done that - it's great fun developing really accurate schedules for every room Trouble is it kills boiler efficiency - stone dead Heat all rooms to a lower temp using lower flow temps - no TRV interventions - your boiler will thank you because it'll always have a decent circuit to work with Your wallet will like it because short cycling gas boilers will burn thro gas whilst providing little in the way of heat to the home.

Exactly ^ WHS Do a decent heat loss calculation yourself or pay someone to do one. I had a 24kW boiler in a house with a 4 kWh heat loss at -2.5 Deg C OAT - it couldn't modulate down below 10 kWh so cycled like crazy in the shoulder seasons and wasn't that great for cycling in the middle of the winter either. When it was replaced I dropped down to a 16 kW boiler that could modulate down to 4.0 kWh - I could have gone down to 11 kW but I think HW recharge time would be longer than 30 mins which wouldn't be acceptable to me and also the smallest boiler 11 kW couldn't be range rated down. Make sure if you do oversize the boiler that you at least get one that has a decent turndown (modulation) that at least mitigates the oversizing issue.

My feelings exactly - I was less than impressed........... Ahhh I had miss-understood you are proposing leaving vented for CH but unvented for HW/CW - that actually wouldn't be too bad as I've never found an issue with HW or CW pipework - it would leave just a F&E tank in the loft so just two pipes (CW Feed for top up and a combined 22mm Vent and circuit make up pipe). It gets cleaned out once a year - it's easily accessible, has a good fitting lid, reasonably well lagged, in a loft where 80% is boarded, access is excellent and it's well lit, All the pipes to and from are lagged (Plus I did the plumbing when I relocated the tank from a stupid place right by the loft hatch so I'm very confident in the std of joints)

First point is no plastic in the house - it's all copper and it's going to stay that way but the 22mm that are tee'd to 15mm to feed the rads circuits under the first floor I've already found 2 x 15mm joints that had no soldering from build in mid 1980's (On CH return rather than flow) - sealed up with limescale rather than solder. This makes me mistrust the plumbing - 4 beds and 2 baths and 3 rooms have had floor lifts over the last 34 years but to lift all the remaining 3 room's floors to check/replace is a nightmare. (it would be just three rooms but still not keen to do that) Second point that makes me lean away from unvented is we often get water interruptions with the water company fixes leaks elsewhere in the area - it's handy having a decent sized tank in the loft as we don't have an issue unless we run the tank out which will last a couple of days of "reduced" usage.

Just an update on the RAS-B2 TRV bodies I used the Danfoss installer app to get the base line settings but over the first week I tweaked them from the suggested to get the rooms to where I want then to be. Vertical rads need more flow than suggested (no convector fins I think is the main reason). I've not had to adjust them since and room temps are rock solid and the DT on the rads are all between 5 and 7 deg. Pump output is also rock solid at 0.6 m3/hr Absolute game changer I reckon - the Wiser EB4 bodies were good and I've been happy with then for a few years but the adjustment range was too coarse from 1-3 (I ended up using a setting along side a tweak on the lockshield to get the flow rate right and this caused a little system noise and I really dislike system noise - it's me I know but I want a quiet heating system) Next thing on the list is the HW side and options are 1. Replace the tank with another vented tank but with a 2m2 coil 2. Keep the current tank but use a PHEX and reconfigure the pipework to suit that 3. Replace the tank with ASHP compatible tank 3m2 coil (and stay vented) 4. Replace the tank with direct tank but use PHEX and reconfigure pipework to suit (Vented) 5. Replace the tank with ASHP compatible tank (3m2 coil) and convert to unvented (upside is I get to ditch 2 shower pumps - downside is risk of leaks in old circuit)

OK so they really are underspec'd for your heat loss

Are yours K1 or K2?

Link me up to an example of a similar rad to what you have on the net please - I'm assuming they have convector flutes on the back and they aren't just flat surfaces both sides and single panel?

Sounds like a recipe for harmony! Oh it isn't

I do get that but if you are fitting longer rads you can always raise the rads slightly and run the pipes from the original exit along the back of the rad hidden from view Issue for me with the K33 was wall space was at a premium - french doors at one end - fireplace in the middle on one side furniture on the other side - leave one wall with a doorway to fit a rad that just meets the requirement... It's thickness wasn't a problem as nothing else is there.

Ahh my error 800 wide 600 tall K3 Steelrad is 1911 w at T50 T50 to T30 = 1911 x 0.515 = 948 w so even two of them won't crack 2 kW heat loss although you could run them a little warmer 800 wide by 700 tall K3 Steelrad is 2170 at T50 so 1117 w at T30 OT My K33 1400 x 700 is rated at just over 4kW at T50 - it'll happily keep the room at 19 deg C running WC flow temps I'm running it at DT11................... I need 660 w in that room Add two squidgy people in the mix and the temp climbs to 20.5 (which is about the limit of my comfort and the bottom of Mrs Alien's accept zone)

Ouch if your heat loss in a room is well over 2kW and you current spec rads are 1100w at DT50 the the rad spec was bloody terrible for a condensing boiler - looks like the builders choose fancy over functionality and cheaped out on the size to minimise costs You'd need rads rated for 5500w in total at T50 to run them at around 50 deg flow temp I'm not even sure you can get K33's in 600 width that will hit that output.

I'd have to agree with that - boiler total kW oversized with a relatively high lowest modulation and rads that need higher flow temps to meet the heating needs of the property with a very low delta between flow and return https://www.heatgeek.com/do-we-really-need-dt20 I think you'd have a huge change in house/room comfort and system performance going to conventional T22 rads sized for a less than 50 deg flow temp Is it a possibility to swap the rads you have around to increase the sizes in some rooms and reduce the expense of purchasing more rads for all rooms? I'd be very concerned about a 50% increase in gas usage for moving from scheduled to 24/7 (ish) I reckon mine is a good deal less than 10% increase for a move from scheduled to 24/7 (and that's with a boiler that miss-behaves occasionally)