Ideal Vogue combi. Range rating, or the lack of ......

[Mr.B]

I put my hand up to at least two failings. In fact there any many more than two.
An obvious weaknes is over-thinking things and digging too deep. I have some experience gained over many year with plumbing tools never far away, but things have got quite complicated now compared to my earlier years and I don't understand much of what I read about curves, graphs and set-backs.

If you combine that with a helping of indecisiveness and add the fact that a little knowledge is dangerous then you'll have sympathy and hasten to sort me out.

I WAS going to replace my 28 year old heat-only Ideal Classic (despite the fact it works OK) .... with a new replacement heat only.
But there's just us two and don't generally generally need to use more than one outlet together and am coming round to the idea of something like an Ideal Vogue Gen 2 32kw combi, or a Viessmann 30kw 100-W combi.

I have the benefit of good pressure and flow (4.5 static and 38 litres per min flow). Very soft water.
I have a dedicated 22mm mains cold water supply solely for a new boiler and a new 28mm gas supply solely for the boiler.
Drop Tight Presure reducing valves will be in place on (a) the house cold water system and (b) the exclusive 22mm feed to the boiler.
I realise I could keep the existing boiler. I know combi boilers are the spawn of the Devil. I'm very aware that (with a few exceptions) Worcester and Vaillant are the universal default recommendation.

Some respected contributors here say the 100 Viessmann is complicated, inferor to the 200-W (which is even more complicated) and that spares and installers aren't as ubiquitous as WB or Vaillant, plus are overpriced, insistant on crystal clear system water .... etc etc ....

I gather that Muggles has a few reservations about Intergas nowadays and I'm still not sure about Alpha, Navien or Vokera.

Some respected contributors here say Ideal is just plain shyte and list a dozen reasons not to waste your money on one, although the Vogue seems to get a bit more respect than the Logic.

The Viessmann turns down to 3.2kw
The Vogue turns down to either 4.6 @ 70 degress (or 4.9 @ 40 degrees.)

A stainless steel HEX is high on my preferences.Rightly or wrongly.

If you use a Mears calculator it says I neeed 13kw but my house is warm and although I have 14 rads, half of them are not used.
So essentially I shouild go for the Viessmann 100 given it's lower modulation. In fact I should really go for the 200-W coz that goes down even lower - but I'm a bit concerned that Viessmann might be a tiny bit left field and might be a be complex and I might not be able to be sure of always having someone who's very familar with Viessmann and who has mastery over its controls. Furthermore I read that their technicians are a mixed bunch. And what's their call-out times like in case of warranty calls?

Conversely, The Vogue has a higher turn down rate plus it, apparently, can't be range rated. Presumably there's a way of stopping it from cycling though?

I don't know what controls I would use but simplicity of operation for the Mrs and I is of the essence. I'm not gonna sit drawing graphs and doing advanced calculus in order to turn the temperature up a bit.

A local and respected Ideal MAX accredited installer is booked for later this week so I guess I'll know more then, but me being me I'd like to be fore-armed with a bit of insight ahead of his visit.

Ta.

 

[Notch7]

Conversely, The Vogue has a higher turn down rate plus it, apparently, can't be range rated. Presumably there's a way of stopping it from cycling though

It has a modulation ratio of 7:1 so it can modulate down a fair bit.

Presumably there's a way of stopping it from cycling though?

There is something important to consider.

The limiting factor is the minimum flow temperature at which your combined radiators can emit heat to maintain your target house temperature based on say lowest expected outside temperature.

If your radiators are too small the amount of heat released by them is not enough to maintain target room temperature at low flow temperatures.

If your boiler won’t modulate down enough + your radiators aren’t big enough, there won’t be sufficient difference between flow and return temps and the boiler will short cycle.

I have this compromise with my system, if I set the weather compensation curve too low, then the flow and return temps end up being just a few degrees apart, the boiler when it fires up the temp rises, it starts to ramp down but the flow sensor goes up beyond what the electronics says it needs, then it stops firing.


The other complication is TRVs, if you zone your radiators then as soon as the TRVs start to shut in the rooms set at cooler temps, the heat transfer capacity of the system reduces and the return temp goes up, then the boiler cycles.



So short cycling and ability to run at low flow temps is determined by a bunch of factors:

Boiler size compared to house needs
Heat loss
Size of radiators
modulation ratio
Zoning - more zoning means less heat transfer

Currently my boiler shows weather comp external temp 8 deg, flow 38 deg, return 36 deg, room temp is 21. The room stat is calling for heat so the boiler pump is running but boiler isn’t heating , it will fire up when the return temp drops a bit. It’s cycling but it’s more than a few minutes.

Over the last month the boiler typically has been running at a flow temp of between 35 and 45 deg dependent on external temp which has been in the range of -1deg to 10 deg.

 

[Mr.B]

I'm obliged. Thank you.

I shall sit and inwardly digest your post but in the meantime would just add a couple of things I omitted earlier.

I DO have TRV's (Pegler Terrier2) on all the rads except one (smallish) one on the landing, quite close to the cylinder and pump - it's permanently reasonably hot. It's pinched down a bit.... the other rads with TRVs on are generally warm to the touch but never very hot.

The rads were sized when the house was built in 1996. It's fairly standard construction with 4 beds and a bathroom (with a shower over it that we both use (not togethet) plus an en-suite with just a shower that rarely gets used.

The current boiler (Ideal Classic 250 cast iron HEX 50,000 btu) is, as mentioned, 28 yrs old
The pipework is 10mm microbore using (I believe) a manifold on the landing under chipboard 8x4 sheets ..... which feeds the downstairs rads via drops sited behind dot and dab plasterboard on the walls.

I'm not going to replace the rads.
The walls and loft are insulated.
It has PVC double glazing.
When you say zoning .... the rads are all on the same circuit. It's Y plan.

The installer will, I hope, speak about Weather Comp. Physically it's easy enough to run.
The Vogue has Opentherm and Ideal do an RF thermostatic controller which apparently works in conjunction with it.
The Viessmann apparently doesn't have Opentherm.

As mentioned, the 32kw Vogue turns down to either 4.6 @ 70 degress (or 4.9 @ 40 degrees.)
I realise the vast oversizing in terms of 32kw but would go for 30 or 32 kw for obvious hot water related reasons. .... furthermore I'm hoping that giving the boiler its own supplies of copious water and gas the issue of the shower dropping down if a WC was flushed might be eased.

You've dropped the phrase "weather compensation curve" into your reply. I was afraid of that

Thanks again

 

[Mr.B]

Reading your reply over and over .... I'm guessing an ideal system for an average well insulated 3 bed house would have a boiler of something like 12 or 15kw with a modulation rate of 10 to one plus an unvented cylinder thus doing away with the need for 30 kilowatts from a combi that's only rated thus to instantaneously heat water for hot taps. I can get my head around that basic principle but it gets much much deeper than that does it not? I've scanned lots of forum threads and, frankly, given up trying to understand most of it.

Regarding my selected two boilers, I suppose there's not a huge difference in the modulation rate between the two. If i went for the Vogue it would mainly be due to the greater likelihood of an RGI being available who was familiar with it. And I can't help think Viessmann is a bit too clever and complicated .... but, I could very easily be very wrong.

Having said that from what I can see the only one with a significantly lower modulation rate is the Viessmann 200 with a figure of something like 1.2kw.

 

[DP]

If your boiler won’t modulate down enough + your radiators aren’t big enough, there won’t be sufficient difference between flow and return temps and the boiler will short cycle.

Boiler will not short cycle as ant cycling function will kick in,

Currently my boiler shows weather comp external temp 8 deg, flow 38 deg, return 36 deg, room temp is 21. The room stat is calling for heat so the boiler pump is running but boiler isn’t heating , it will fire up when the return temp drops a bit. It’s cycling but it’s more than a few minutes.

I would be happy with those figures as boiler will be condensing very well so efficiency will be maximum

I put my hand up to at least two failings. In fact there any many more than two.
An obvious weaknes is over-thinking things and digging too deep. I have some experience gained over many year with plumbing tools never far away, but things have got quite complicated now compared to my earlier years and I don't understand much of what I read about curves, graphs and set-backs.

If you combine that with a helping of indecisiveness and add the fact that a little knowledge is dangerous then you'll have sympathy and hasten to sort me out.

I WAS going to replace my 28 year old heat-only Ideal Classic (despite the fact it works OK) .... with a new replacement heat only.
But there's just us two and don't generally generally need to use more than one outlet together and am coming round to the idea of something like an Ideal Vogue Gen 2 32kw combi, or a Viessmann 30kw 100-W combi.

I have the benefit of good pressure and flow (4.5 static and 38 litres per min flow). Very soft water.
I have a dedicated 22mm mains cold water supply solely for a new boiler and a new 28mm gas supply solely for the boiler.
Drop Tight Presure reducing valves will be in place on (a) the house cold water system and (b) the exclusive 22mm feed to the boiler.
I realise I could keep the existing boiler. I know combi boilers are the spawn of the Devil. I'm very aware that (with a few exceptions) Worcester and Vaillant are the universal default recommendation.

Some respected contributors here say the 100 Viessmann is complicated, inferor to the 200-W (which is even more complicated) and that spares and installers aren't as ubiquitous as WB or Vaillant, plus are overpriced, insistant on crystal clear system water .... etc etc ....

I gather that Muggles has a few reservations about Intergas nowadays and I'm still not sure about Alpha, Navien or Vokera.

Some respected contributors here say Ideal is just plain shyte and list a dozen reasons not to waste your money on one, although the Vogue seems to get a bit more respect than the Logic.

The Viessmann turns down to 3.2kw
The Vogue turns down to either 4.6 @ 70 degress (or 4.9 @ 40 degrees.)

A stainless steel HEX is high on my preferences.Rightly or wrongly.

If you use a Mears calculator it says I neeed 13kw but my house is warm and although I have 14 rads, half of them are not used.
So essentially I shouild go for the Viessmann 100 given it's lower modulation. In fact I should really go for the 200-W coz that goes down even lower - but I'm a bit concerned that Viessmann might be a tiny bit left field and might be a be complex and I might not be able to be sure of always having someone who's very familar with Viessmann and who has mastery over its controls. Furthermore I read that their technicians are a mixed bunch. And what's their call-out times like in case of warranty calls?

Conversely, The Vogue has a higher turn down rate plus it, apparently, can't be range rated. Presumably there's a way of stopping it from cycling though?

I don't know what controls I would use but simplicity of operation for the Mrs and I is of the essence. I'm not gonna sit drawing graphs and doing advanced calculus in order to turn the temperature up a bit.

A local and respected Ideal MAX accredited installer is booked for later this week so I guess I'll know more then, but me being me I'd like to be fore-armed with a bit of insight ahead of his visit.

Ta.

For me it would be a Vogue any day of the week
Cracking software and features on this boiler- even draws a graph of parameters and boiler can be operated right up to the moment it is to be stripped down for service.

At present you have got a heat only boiler with water heated in a cylinder and you are going down the combination route and most likely have got a cold water cistern as well as a F&E cistern. My concern would be is the present system as is, will it be tight enough to withstand sealed system operation.

Furthermore, combination route you are taking is a compromise between heating and hot water. In fact I woukd say you are picking a boiler to give you adequate hot water delivery and heating the radiators is a bonus

Your present boiler consumes 18.3 Kw to deliver 14.7 Kw of useful output. To make the system work, all you need is a 15 Kw heat only boiler, so for radiators the combi is way overpowered. Instead of changing the boiler, I would fit Honeywell Evohome to present system and source a fan, pcb and gas valve for the present boiler. It will outlast almost any current boiler

 

[Notch7]

I'm guessing an ideal system for an average well insulated 3 bed house would have a boiler of something like 12 or 15kw with a modulation rate of 10 to one plus an unvented cylinder thus doing away with the need for 30 kilowatts from a combi that's only rated thus to instantaneously heat water for hot taps

Yes if you choose a combi, the size is determined by hot water capacity, in which case modulation ratio becomes important.

I would say a typical 3 bed semi probably does only need a 12kw or 15kw system boiler. Mine is 18kw, it possible should’ve been 15kw although I’m doing a garage conversion which will add 2 rads so maybe it will be about right.



Your system is 10mm microbore, I don’t know if that means anything in terms of a new boiler. Maybe that will limit the ability to have low flow temps, I’m not sure

By zoning I meant the zoning effect caused by TRVs, they choke the system and will cause more cycling….the theoretical best scenario is to choose the correct radiator sizes to create the desired temp for each room and have TRVs fully open. The most efficient heating is very low flow temps, boiler on for most of the day so the system heats the house up and the boiler just trickle feeds heat to maintain heat loss.


Personally I think you might be over thinking the modulation rates, tge difference between say an Ideal,at 7:1 and a Viesseman at 10:1 won’t make a massive difference in efficiency, other parts of the system will have more influence.


Choosing a boiler brand is hard, In my case I asked the heating engineer if I could have weather compensation and hot water priority and he suggested the Ideal as it has 2 switched lives for heating / hot water and it’s electronics is designed to that out of the box. He also said he liked working on Ideal boilers: easy to service / repair and there’s loads of them about so merchants carry most of the parts. I’ve certainly been extremely happy with it since it’s been fitted, but I’m no expert and no doubt anybody swapping from a 45 year old boiler with vented system to a new fully pumped and pressurised would be chuffed. I’m sure you would happy with any of the brands you’ve talked about.

DIYnot is certainly one of best forums for plumbing and heating, so you will get some great advice on here I believe the private Combustion Chamber section is used a lot by heating engineers and there are quite a few that visit the plumbing and heating section, so you are in a place with lots of extremely experienced any knowledgable professionals (Im just a total amateur who happened to have his boiler changed, so am none of those things).

 

[DP]

Your system is 10mm microbore, I don’t know if that means anything in terms of a new boiler. Maybe that will limit the ability to have low flow temps, I’m not sure

Will help setting up the 20 degree delta figure

 

[Mr.B]

Lots to consider above . Further thanks.

The possibility of leaks is a major concern. The local installer I spoke of has done work locally on the estate - I'll quiz him when he visits, and next door neighbour's swap to a combi has been OK, but, yes, very valid point. one that troubles me.

I shall spend more time re reading the replies.

 

[Mr.B]

Can you explain the 20 degree delta and why the constriction of 10mm helps. Presumably the degree of friction within the pipework? But all is not entirely clear.

 

[DP]

Maximum return temperature needs to 55 degrees so in theory flow can be 75 degrees.

Lower flow temperature means return will lower and boiler more efficient.

10mm will only have one radiator on each pipe run. Based on radiator size, pipe length is important. Fact that pipe is more resistive, will be easier to set the differential which is done with all the rads on line and trvs fully open

Look at Intergas eco combi boiler. This can be installed as open vented, is OT compatible too

 

[Ltnman]

I live in a 1990 built dob and dab 4 bedroom smallish detached house with a 32kW Ideal Vogue fitted in August 2022. The CH temp is set for 50C to boost boiler efficiency and runs through 10mm microbore pipework downstairs with standard pipework upstarted. Rather than using weather compensation I use the Ideal Halo Wi-Fi controller https://idealheating.com/installers/products/controls, which is iPhone controllable if required. Over the years the house had two rads swapped for towel rails, two bedroom rads changed to doubles and a large double rad put in a garage conversion. Also a tiny rad was installed in the airing cupboard.

It was impossible to set the drop across the rads to 20c so I make do with around 10c. By balancing the rads carefully my TVR’s never cut in so maintaining the balance. All in all I am happy with my setup. The boiler doesn’t cycle with the halo adjusting the temperature up to 5 times a day with different temperatures at the weekend. I was also worried about a lack of range rating but in reality it has never been a problem.

 

[Mr.B]

All received, ta muchly.

Understood re. significance of 10mm ... but, of course, I can't change the pipe runs, and won't change the rad sizes but understand the importance of balancing with the TRV's open.

I've looked long and hard at Intergas, at one time it was the Intergas heat only I considered seriously but now we've started to consider the combi option much more seriously (as you'll have gathered). The absence of Intergas installers locally isn't helping confidence and the same old question of spares availablity is alway in the background.

Regarding pressures I've just ordered a Caleffi/Altecnic 535015 Drop Tight Pressure reducing valve to replace the 18 year old 533 model under the kitchen sink. It's on the feed to thewhole house cold supply. I have incoming at 4 bar and flow at 38 lpm. I'll keep the pressure at, say, 3.5 bar. the present valve isn't Drop Tight and that seems to defeat half the purpose of having one in the first place. It arrives in a few days.

 

[Mr.B]

I live in a 1990 built dob and dab 4 bedroom smallish detached house with a 32kW Ideal Vogue fitted in August 2022. The CH temp is set for 50C to boost boiler efficiency and runs through 10mm microbore pipework downstairs with standard pipework upstarted. Rather than using weather compensation I use the Ideal Halo https://idealheating.com/installers/products/controls, which is iPhone controllable if required. Over the years the house had two rads swapped for towel rails, two bedroom rads changed to doubles and a large double rad put in a garage conversion. Also a tiny rad was installed in the airing cupboard.

It was impossible to set the drop across the rads to 20c so I make do with around 10c. By balancing the rads carefully my TVR’s never cut in so maintaining the balance. All in all I am happy with my setup. The boiler doesn’t cycle with the halo adjusting the temperature up to 5 times a day with different temperatures at the weekend. I was also worried about a lack of range rating but in reality it has never been a problem.

I'm most grateful for the above.

I shall sit quietly and re-read it.

As you know my house is 1996 built, has dot and dab, has 10mm up and down and I'm considering a 32kw Gen 2 Vogue combi.

I have just bought a 500 x 400 rad and TRV for the airing cupboard from Screwfix for £34. Obviously not fitted as we speak.

I shall need controls for the boiler too ...........

.......... So your post is somewhat pertinent.

 

[MNW67]

AFAIK with the Vogue, there is very little adjustment on the pump settings. So, if you need to run the pump slower to widen out the dT, there isn't much there to play with

 

[Mr.B]

There you have me.
I'm taking note of what you say, but haven't got a sensible reply. But thank you. Hopefully others will be able to comment, for better or worse.

I wish I knew a bit more than I do.