18 May 2018
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United Kingdom
tl;dr: Why install RF36 instead of HRE36 or Ideal Logic+ 35? How does weather comp/new thermostat differ to boiler's internal modulation? Is a non-pumped gravity shower acceptable (better than an 8kw electric) upstairs even with very old slow recovery HWC, or just go combi at 13lpm in small property? Why do people install RF with UV and not a system boiler if combis are less reliable? Why does my quote say condensate going outside to soakway and not under floorboards to nearby waste?

Any now for the long version!

I've moved in to a small terrace house and want to replace the broken (fully pumped) open vent boiler. Although I prefer OV, I am considering the Intergas Combi Compact RF 36 or the Combi Compact HRE 36/30 or an Ideal Logic+ 35kw so I can install a shower upstairs.

I'm confused by the RF module and how it all integrates with weather compensation, etc. and whether combi is the right approach.

I've had a couple of reputable people in to quote, but some have had "interesting" ideas such as plumbing condensate in to the water butt or quoting a 25kw (far too borderline spec for showers IMO). I guess "20 years experience" means they've hired 20 people with 1 year experience each!:)

The property is a small two storey house and will have three/four people during the expected boiler lifetime.

So I believe the 13lpm combi will give a better mixer shower upstairs than either an electric or gravity fed shower. There is no shower there at the moment.

My copper HWC is small and probably old since it only has inches not mm on a sticker on it at 36"x18" which I believe is 27 gallons/120 litres. So I think a gravity/pumped shower would empty it with consecutive showers (minimum 10lpm @ 10 minute shower at 60:40 hot:cold), and I gather it would be slow to reheat since a thread on here said effectively 4kw recovery rate for old cylinders even when fed from an 18/24kw boiler.

So I think the cost to install a new HWC and a potentially noisy shower pump to get enough shower flow upstairs means a combi may be adequate. Or are those 0.1 bar shower heads really usable and HWC recovery ok on old tanks? (Water coffin tank is in loft).

I currently have an old programmer with separate DHW and CH controls, and a rotary dial wired thermostat.

So these Honeywell RF controllers replace the timer and the thermostat? Are they part of evohome? Or is that something different and incompatible with the Intergas RF thermostats?

Do these RF controllers go in the same place as my existing wired thermostat, or need new wiring? (I don't know what wires are in my thermostat).

What benefit do these RF thermostats have over some thermostat like Nest or the T6?
What is weather comp/new thermostats doing that the boiler's self-modulating isn't already doing since I thought these new boilers drop down the heat automatically if the radiators don't take any more heat.

Are there any modern controllers that don't require complicated controls and apps and phone gps? And where the thermostat programmer doesn't tell burglars "this person is on holiday for another week/phone gps is nowhere near the property, so take your time."

I guess if I'm going "smart home" then eventually I'd quite like the bedroom radiators to be low during the day and only on before bed, but I'm not convinced I'd ever make back the cost of a smart radiator TRV. I can see they'd be good in large houses.

If I'm not using the RF module, is there any benefit to the RF boiler compared to the Compact? The only difference in the user specs is that the RF says high efficiency motor, but I don't understand if that makes any difference.

I also don't understand why people buy the combi but then use it as a system boiler instead of installing the system boiler? Is it because of the RF module?

The prices I've seen online suggests the RF is actually cheaper than the Intergas 36. But, I've read in the forum that the Vogue is (something like) "finally a decent Ideal boiler". Given that seems similar cost but higher DHW flow, is that a better idea than Intergas? Or stick with OV?

And, is there any complication with condensate going in to kitchen waste (6' away under floorboards) since my quotes want to take it outside to a soakaway (no drain there), whereas I thought it would go to the sink or downstairs toilet (maybe 9' away).

Far too many questions! So thanks in advance.
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In a post you mentioned the Intergas Canetis Superflow. I can't seem to find any reviews anywhere or detailed specs/dimensions, just press releases that make bold comparisons to 200l unvented cylinders. What's your impression of it?

I assume it's floor-mounted and if it's fitted and warmed up (seemingly via Central Heating flow or via flue recovery) then does that mean the RF boiler could pass (say) 20lpm of 40C blended water instead of 13lpm of 40C water warmed from cold water mains, or does the system have some hard limit on flow?
The Combi Superflow setup should achieve about 18l/min at 55°C I believe. The unit isn't actually an Intergas product - it's offered uniquely by The Intergas Shop under license from the original designers. Richard Borrows, the owner of The Intergas Shop, is very knowledgeable on all things Intergas. He also runs The EvoHome Shop, where he has a similarly high level of knowledge should you be interested in that.

As Dan has said, the difference between the ECO RF and the HRE is that the ECO RF has a 10 year warranty, whereas the HRE has a 7 year warranty. Oh, and it has that RF chip on the board which is compatible with some of the older Honeywell controls such as the CM927. It'll also run Intergas InTouch, which gives you app control of the boiler.

You need to know your incoming mains flow rate & pressure before a decision can be made on whether a combi is right for you. You can't get out more than you put in.

I wouldn't touch a Logic with a barge pole - they've had too many issues. The Vogue used to be good, then they updated it to the Gen2, which seems to have reduced the build quality. Neither are as good as Intergas
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Thanks for the info on Logic. I hadn't realized they'd updated the design.

It makes sense now about the RF chip now, so for evohome I'd ignore the internal RF (since it's older spec so incompatible) and need the OpenTherm/Modulation pack (RF bridge + controller) instead; or use one of the other older thermostats for RF, or some other thermostat. I'll have to read up more.

Would you need weather comp with evohome/opentherm thermostats, or are they basically competing controls?

I bought a pressure gauge and from the back garden tap I get around 20lpm at 2bar, drops to 1.5bar when kitchen cold tap is on full (from which I normally get 9lpm when full on). Back garden tap pressure drops to around 1 bar when kitchen tap off and front garden tap is also on full.

From the front garden tap I get around the same at 2bar which also drops to 1bar when other tap on full.

My mains is probably around 20mm to the front of the 1930s property and the other side of the stop tap it is 15mm and tees.

So I guess I'd get maximum 15lpm @ 40C @ (just under) 2 bar from boiler, then pump 4.5m to upstairs shower so come out at around 1.5 bar, but if a tap is on downstairs then I might a shower at 1bar, so still higher than a gravity shower from loft.

And if kitchen tap is on full then if it gets 9lpm I'd still get 6lpm upstairs which is better than a 10.5kw electric shower.

At 60C, the spec says 9lpm so 10 minutes for a bath.
And if the water board drops us to minimum spec 9lpm at 1 bar then I'd still just about be ok since it would still be stronger than a gravity fed shower from the loft, but I would have no spare capacity for other taps.

Or are my assumptions wrong? I'm happy to run the RF with the OV HWC if it has a benefit over combi mode.
If you have OT, the weather sensor is ignored - although the temperature outside is then reported to the screen of Evo for general information.
When my installer came around to check pipe runs and firm up the estimate, we encountered a few problems that none of the quoters expected. Nothing that can't be resolved, but it requires more work than we expected.

So, we're thinking to install it in the bedroom since it's tricky to get all necessary pipework, drainage and wall space elsewhere.

I'm guessing the 45/50db noise is when the boiler is on full, so it would be less noisy if it's just doing central heating for a few degrees, or is that wishful thinking? Next door's combi sounds like a jet engine.
The boiler will be near a non-opening window. Does the flue need a plume kit to go up above the gutter to reduce it blowing on to and rotting the wooden window frames/guttering boards/external insulation? Or is that just myth? Or will that mean that in the future people will refuse to service/fix the boiler since they need a ladder on the rear extension to verify the flue on every callout?

We have a 1930s roof where the (clay?) tiles are not nailed and just have grooves to hang on to the wood and overlap. They have no lining/felt/insulation inside to stop rain. Will that cause a problem with plume entering the building since we only notice holes when we get rain inside, but tiles could get cracked in summer. I guess risk is minimal since the wind would blow it every which way.

We're now thinking to keep the open-vent since combi might be too loud in the bedroom with odd working hours and it firing on full for a shower when other people asleep. I'm thinking a low 24kw Eco RF so all the pipework enters at the bottom and looks neater.

The Evohome looks nice, but the online demo page seemed a little too complicated for our daily use. We only have something similar to the sundial controllers and simply hit "boost" on days/nights that we are in and want the heating on since sometimes 18C feels cold and sometimes it feels hot depending on sunshine/mood. Unfortunately modern controllers seem to want launch, scroll, scroll, click, override, scroll, scroll, confirm, confirm again, back, back, click, exit.

For anyone interested, I noticed that there are now a couple of brief youtube videos on the Superflow so water enters the boiler at 30C so RF24 gives 12lpm at 55C with 25C rise, with the smaller one tipped to be the bigger seller.

I also found a matrix of which thermostats/boilers support which OpenTherm commands which might interest some people, but the table only works in some browsers:

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