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

[Mr.B]

You do have a point but I try to offer advice and answer a direct question and not simply name a boiler.

The advocates of other brands can answer your questions about their suggestions as they have the figures to hand otherwise it's just a model and brand that you have to research yourself in the dark.

How low is minimum modulation for heating?
What's the residual head of the pump at the boiler, can adjustment be made.
Can they post a pump graph from their manuals?
Is the anti-cycle delay adjustable?
What control options, modulating stat, single or dual temp weather comp?
Can it be range-rated in heating and does the boiler fire from max heating output or from range rated.
PDHW a possibility?
Is is a heavy heat exchanger with mass (why heat up a big lump of metal in addition to running a kitchen tap for a couple of minutes).
If they've had good service from the brand or is the unit easy to work on?
Large bore or small bore exchanger?

Things like that for each suggestion.

As you can imagine, Vulcan, I'm extremely grateful you took the trouble to come back after, what might have been thought, a bit of a negative reply to your post (#18) some way back now.

You've listed ten points.

1. That's an easy onr to answer. I can see the figure given for each boiler.
2. Still haven't got that one cracked. Not familiar with the term or where to find it.
3. Nope, lost me there. A pump graph means nothing to me.
4. I've never seen the term 'anti-cycle delay' shown in any of the manu's literature I've looked at.
5. As I've probably said more than once the various controls offered by numerous third parties as well as manu's own controls are not exactly straightforward. If I showed them to my wife and told her she would have to master them if I dropped dead (not impossible I'm no youngster) she quite simply wouldn't have a clue ... and they confuse me almost as much.
6. That I have grasped. I can see Viessmann do and, apparently, Ideal either don't, or don't do it as comprehensively ... but I'm confident it's not as simple as what I said.
7. I've seen Urban Plumber's videos in which he describes his work with PDHW and I've read some comprehensive articles online - it might have been Heatgeek. Now even you, Vulcan, have got to admit is not exactly 'plug and play', is it?
8. I'm guessing this is aimed squarely at Intergas. Muggles and Razor used to rave about them. Much less so now. Muggles has offered a word outlining his reduced enthusiasm which I listened to and have no reason not to accept. Plus there are no local installers and their website hasn't shown any additions to the list of installers in Devon in the last five years. I'm inclined to think they're no more recognized than Johnson and Starley.
9. Ah! This is the one that really causes divisions of opinion. The universal recommendation of Vaillant and Worcester by most of the UK's population is famed - as you well know - far better than I in fact. Personally I'm fed up with hearing over and over again that Which recommend those two as well as Viessmann. Maybe they are the two or three best manufacturer? Who am I to say? But I also see, time and time again, the same criticisms ... I don't need to recite the pros and cons of those two/three makes. I also see the same old comments about Ideal and, again, I don't need to repeat them here. I read WB isn't easy to work on when compared to Ideal or Baxi ... but for every fan of a make or model there's the polar opposite on the next page .... you MUST know what I'm saying. You must have read a million more threads and articles than I have - and I've read a few in order to try familiarise myself and get a handle of what is and isn't a sensible route to go down. There's rubber hoses and plastic blocks in boilers, composite units in Baxis that contain most of the innards of the boiler and they all come as one part (or so I'm often told online or on forums) ... that might not be the case though, I'm not an installer or repairer. I could go on all night trying to explain how conflicting the advice that members of the public are subject to is - and whilst some of it is correct, even I can see that some of it is just stuff and nonsense and either mistakeny wrong or just plain lies ... but how is the man on the Clapham Omnibus supposed to tell right from wrong.
10. Apart from the obvious example of Intergas I honestly don't know which HEXs are categorised as one or the other. The available literatue gives little or no clue in my experience ... so how am I supposed to know that one?

Ringing manufacturer's helplines or technical lines is a lottery. No more no less. You, Vulcan, have insight into these things and if you rang Ideal, Baxi or Worcester you might be able to immediately discern that the voice at the other ensd of the line is a trainee with virtually no knowledge apart from the script he/she has in front of them but the likes of me is stuck with them and their automated telephone systems which may, or may not, grant you access to a human being. I can remember when you could ring someone like Pegler and speak to an ex engineer who knew exactly what he was talking about ... but too often we ring, and get 6 options to choose from and get absolutely nowhere. Have you tried ringing BT or TalkTalk lately? We are currently experiencing high volume of calls and you are in a queue, your call is important to us so please sit down and listen to Vivaldi's Four Seasons for the next hour and a half.

I rest my case M'lud and shall take my seat whilst the Honourable Gentleman for the Defence is called.

 

[MNW67]

2. Still haven't got that one cracked. Not familiar with the term or where to find it.
3. Nope, lost me there. A pump graph means nothing to me.

The "head" of a central heating pump is a measure of its power to force water through your central heating system i.e. the boiler, pipes and radiators. These days it is measured in mbar, bar, or metres of water. It used to be measured in inches or feet of water.

When you have a combi or system boiler, where the pump is built in to the boiler, they usually use the term "residual head". This is the amount of power the pump has left over, after it has forced the water through the boiler itself, to circulate the system water through the pipes and radiators.

So say you have a pump which can give 4m of head at a flow rate of 20 litres per minute. And say that at a flow rate of 20 litres per minute it takes 1.5m of head just to push that water through the boiler. This would mean that at a flow rate of 20 litres per minute, there would be 2.5m of "residual head" left over to push the water through the pipes and radiators.

Below is a graph which I think is from a Vokera. It shows the residual head vs flow rate for various pump output percentages.

 

[Mr.B]

That's genuinely helpful.

I wasn't familiar with the term 'residual head' but can see it's meaning from what you've kindly said.

Having said that I still say I don't see it openly displayed by manufacturers in their literature. Furthermore I'm unsure how, in practical terms, I should use the information if it was.

I remember in my training, in 1974, amongst many other topics we had to learn we had classes entitled Hydraulics. We seemed to work in feet, inches and gallons in those times and I can assure you that we were given to understand that a gallon of water weighs ten pounds.

 

[vulcancontinental]

Using that graph from a boiler with an unusually powerful pump for Vokera on the Y axis you see the available head.
Below you see flow rate on the X.

To get the flow rate for a condensing boiler installation multiply the specific heat capacity of water by the temperature difference across the flow and return then divide the result into the kW you need so, 4.2x20= 84 divided into 8kW = 0.09l/s x 3600= 342l/hr.

If the system has a resistance of 2m strike a line across to see what flow rate it will actually provide against the resistance if left unaltered and it's nearly 4 times that which is required therefore the water comes back to the boiler too quickly and the delta T narrows from the desired 20 to 5 or 6 degrees.

Nobody cares, rads are hot, gas is cheap, pumps are cheap to run and a little bit of efficiency is lost but nobody complains.

Apply similar small losses to each of the points above and it adds up but in the real world it is still small.

We went metric in 1971 supposedly.

Any of the boilers mentioned will keep you warm and clean.

 

[Johntheo5]

The "head" of a central heating pump is a measure of its power to force water through your central heating system i.e. the boiler, pipes and radiators. These days it is measured in mbar, bar, or metres of water. It used to be measured in inches or feet of water.

When you have a combi or system boiler, where the pump is built in to the boiler, they usually use the term "residual head". This is the amount of power the pump has left over, after it has forced the water through the boiler itself, to circulate the system water through the pipes and radiators.

So say you have a pump which can give 4m of head at a flow rate of 20 litres per minute. And say that at a flow rate of 20 litres per minute it takes 1.5m of head just to push that water through the boiler. This would mean that at a flow rate of 20 litres per minute, there would be 2.5m of "residual head" left over to push the water through the pipes and radiators.

Below is a graph which I think is from a Vokera. It shows the residual head vs flow rate for various pump output percentages.

View attachment 336438

Yes, residual head, one would think, is the head available after the boiler HEX, I have seen remaining head stated as well on some boiler MIs,
Looking at a typical "7M" head pump like a Dab Evosta 4-7 which has a closed valve head of 6.8M, its pump curves show a flowrate of 20LPM (1.2m3/hr) at a head of 4.7M, now IF this is typical then a residual head of 3.4M at 20LPM (above) means that the boiler HEX loss is only, 4.7-3.4, 1.3M, this seems extraordinarily low IMO, Vokera, though, do state, quite clearly.......

 

[Mr.B]

To get the flow rate for a condensing boiler installation multiply the specific heat capacity of water by the temperature difference across the flow and return then divide the result into the kW you need so, 4.2x20= 84 divided into 8kW = 0.09l/s x 3600= 342l/hr.
If the system has a resistance of 2m strike a line across to see what flow rate it will actually provide against the resistance if left unaltered and it's nearly 4 times that which is required therefore the water comes back to the boiler too quickly and the delta T narrows from the desired 20 to 5 or 6 degrees.

----------------------------------------------------------------------------------------------------------------------------------------------------

Looking at a typical "7M" head pump like a Dab Evosta 4-7 which has a closed valve head of 6.8M its pump curves show a flowrate of 20LPM (1.2m3/hr) at a head of 4.7M, now IF this is typical then a residual head of 3.4M at 20LPM (above) means that the boiler HEX loss is only, 4.7-3.4, 1.3M, this seems extraordinarily low IMO, Vokera, though, do state, quite clearly.......

----------------------------------------------------------------------------------------------------------------------------------------------------

OK, I started this particular thread so hopefully have a little bit of say in keeping it vaguely on track.

I've quoted the two extracts from recent replies and have to ask the question ..... are those two extracts intended to be seen as appropriate to any of the points I have gone to considerable lengths to make? Are they even slightly relevant to the title of the thread regarding whether or not the boiler I'm considering is range rateable?

I ask because, quite honestly, I barely understand a word (or mathmatical calculation) that they include.

Have I not made it plain that the numerous formulae, calculations and advanced technical theorising that I see are sailing over my head?

What I WILL say, though, is that everyone has been really polite and cooperative and for that I'm very grateful. Sometimes threads get a bit ugly and there's no hint of that here .... thanks muchly.

Just look at those two examples and tell me if they're likely to answer the question I asked or are in any way sympathetic to my clearly saying that graphs and charts and calculus are not something I find easy to grasp.

Unless we return to, what is for me, the real world, then maybe we should draw a line under it.

 

[gas112]

its not that big a deal

Not a big deal really , here is you being an expert on something that you know nothing about 2 and a half boilers my ar5e.
People in the trade have seen loads of pictures of these melting inside and various videos of these going on fire and melted so that`s the ones circulating in media there will be loads more out there ideal are telling their staff to down play it .

 

[MNW67]

Unless we return to, what is for me, the real world, then maybe we should draw a line under it.

I think maybe posters are struggling to establish the level of detail you are requiring. At times you have asked some quite in depth questions.

It seems to me that Ideal boilers do not have some of the features which might be helpful in some situations for fine tuning a problematic installation. I have read experienced installers on here complain that, on the Logic, even after balancing the radiators, sometimes it simply hasn't been possible to get the dT any larger than about 5C, when it is supposed to be around 20C. Presumably in this situation the ability to slow down the pump would be useful. Others have complained of too much cycling. In this case, the ability to increase the anti-cycle time (i.e. the time between the boiler turning off and coming back on) might be helpful. Several other boiler manufacturers offer these features on some if not all their models. Vaillant/Glowworm, Vokera, Viessmann, Intergas, Worcester Bosch, Alpha all offer these features on some models definitely. I don't know if Baxi/Main do.

 

[vulcancontinental]

To get the flow rate for a condensing boiler installation multiply the specific heat capacity of water by the temperature difference across the flow and return then divide the result into the kW you need so, 4.2x20= 84 divided into 8kW = 0.09l/s x 3600= 342l/hr.
If the system has a resistance of 2m strike a line across to see what flow rate it will actually provide against the resistance if left unaltered and it's nearly 4 times that which is required therefore the water comes back to the boiler too quickly and the delta T narrows from the desired 20 to 5 or 6 degrees.

----------------------------------------------------------------------------------------------------------------------------------------------------

Looking at a typical "7M" head pump like a Dab Evosta 4-7 which has a closed valve head of 6.8M its pump curves show a flowrate of 20LPM (1.2m3/hr) at a head of 4.7M, now IF this is typical then a residual head of 3.4M at 20LPM (above) means that the boiler HEX loss is only, 4.7-3.4, 1.3M, this seems extraordinarily low IMO, Vokera, though, do state, quite clearly.......

----------------------------------------------------------------------------------------------------------------------------------------------------

OK, I started this particular thread so hopefully have a little bit of say in keeping it vaguely on track.

I've quoted the two extracts from recent replies and have to ask the question ..... are those two extracts intended to be seen as appropriate to any of the points I have gone to considerable lengths to make? Are they even slightly relevant to the title of the thread regarding whether or not the boiler I'm considering is range rateable?

I ask because, quite honestly, I barely understand a word (or mathmatical calculation) that they include.

Have I not made it plain that the numerous formulae, calculations and advanced technical theorising that I see are sailing over my head?

What I WILL say, though, is that everyone has been really polite and cooperative and for that I'm very grateful. Sometimes threads get a bit ugly and there's no hint of that here .... thanks muchly.

Just look at those two examples and tell me if they're likely to answer the question I asked or are in any way sympathetic to my clearly saying that graphs and charts and calculus are not something I find easy to grasp.

Unless we return to, what is for me, the real world, then maybe we should draw a line under it.

What I WILL say, though, is everyone here has been really polite and cooperative ... that doesn't always happen, so thanks very much.

Any of the boilers you mentioned originally or have been named subsequently will ensure your wife is comfortable. All you have to do is get a good installer that likes the boiler he's fitting and the rest will be plain sailing. As always however, the devil is in the detail.

 

[Mr.B]

Any of the boilers you mentioned originally or have been named subsequently will ensure your wife is comfortable. All you have to do is get a good installer that likes the boiler he's fitting and the rest will be plain sailing. As always however, the devil is in the detail.

My Mrs. will be pleased to hear that, thanks.
And thanks, too, for all the replies here, I'm grateful for the timen taken.

 

[Notch7]

Not a big deal really , here is you being an expert on something that you know nothing about 2 and a half boilers my ar5e.
People in the trade have seen loads of pictures of these melting inside and various videos of these going on fire and melted so that`s the ones circulating in media there will be loads more out there ideal are telling their staff to down play it .

I note you’ve not helped the OP by stating the problem has been corrected and a new boiler won’t suffer that problem.

Please can you quantify “loads” That could mean half a dozen.

How do you know Ideal are telling their staff to,”down play it”


Perhaps you should try sticking to facts

 

[Notch7]

have read experienced installers on here complain that, on the Logic, even after balancing the radiators, sometimes it simply hasn't been possible to get the dT any larger than about 5C, when it is supposed to be around 20C. Presumably in this situation the ability to slow down the pump would be useful. Others have complained of too much cycling. In this case, the ability to increase the anti-cycle time (i.e. the time between the boiler turning off and coming back on) might be helpful.

I would say those apply to the Ideal vogue which I have.

I certainly get a dt of 5 deg or less quite a bit and the result is short cycling.

I notice the boiler often has the pump running but not firing, I’m guessing it does that whilst the room stat is calling for heat but return temp is too high for boiler to fire up.

Overall though the boiler has run over the last month with a flow temp of between 38 and 46 deg with outside temps ranging from about 3 to 10. Return temp is pretty much always below 40, so I believe the boiler is always doing a reasonable percentage of condensing.

 

[vulcancontinental]

I would say those apply to the Ideal vogue which I have.

I certainly get a dt of 5 deg or less quite a bit and the result is short cycling.

I notice the boiler often has the pump running but not firing, I’m guessing it does that whilst the room stat is calling for heat but return temp is too high for boiler to fire up.

Overall though the boiler has run over the last month with a flow temp of between 38 and 46 deg with outside temps ranging from about 3 to 10. Return temp is pretty much always below 40, so I believe the boiler is always doing a reasonable percentage of condensing.

Yes, pump runs during anti-cycle to stop overheating in the heat exchanger. Wider delta T is more difficult to acheive as the boiler modulates flow temperature as the 'headroom' reduces. A slower pump would help but it wouldn't be much difference to fuel costs.

 

[vulcancontinental]

My Mrs. will be pleased to hear that, thanks.
And thanks, too, for all the replies here, I'm grateful for the timen taken.

No problem but I always work on the principle the OP is not the only reader.

 

[Johntheo5]

I would say those apply to the Ideal vogue which I have.

I certainly get a dt of 5 deg or less quite a bit and the result is short cycling.

I notice the boiler often has the pump running but not firing, I’m guessing it does that whilst the room stat is calling for heat but return temp is too high for boiler to fire up.

Overall though the boiler has run over the last month with a flow temp of between 38 and 46 deg with outside temps ranging from about 3 to 10. Return temp is pretty much always below 40, so I believe the boiler is always doing a reasonable percentage of condensing.

Assuming dT at almost full output is 15C then you just can't avoid running at a dT of 5C or less with WC once the flow temperature is less than ~ 40C, it goes down to 3.7C with a flow temperature of 37C don't know what the minimum output of your boiler is but just assuming 6kw then the rated outout of your rads must be ~ 6/0.23, 26kw to avoid the boiler cycling and its going to be very difficult for it to fire up without repeated cycling at a flow temperature of 36C.