Conventional boiler.... comeback Combi all is forgiven!

[TellMeWhy]

Because weather comp seeks to match heat loss to heat load, by varying the flow temp.

Obviously it's dependent on emitter type, but an UFH install I have has three-4 hour burn time in winter, coming on 4 timed a day

We know how it works, my ATAG has one. Using the house as a thermal store? That is very misguided. Thermal mass can assist in any heating system. A boiler even with weather compensation will cycle if the heat demand is less that the lowest boiler modulating output. It is that simple.

Read SimonH2s posts on thermal stores. Dry the spit from your finger, take off the blinkers and learn something about heating.

 

[TellMeWhy]

Simon, a thermal store, which has to run at and kept a very hot temperature, should not be confused with a buffer vessel that allows all sorts of heating and hot water permutations

Are you confusing the two?

One poster on this forum has his thermal store set to 60C, which is against your wet finger in the air notions. A thermal store is also a buffer.

 

[ALEC1]

I know, mr all to well...

cycling is inevitable, and all boiler cope well with it...what is striking though is that boilers cycle much less if the are correctly sized, and installed with compensation controls...and of course with compensated flow temperatures when cycling occurs is much lower than for a thermal store.

Thermal stores again can be correctly matched with a boiler to minimise cycling but in reality they are not...and any way without being able to match flow to burner output on a thermal store you are stuck with the wrong flow rate!

Atag q series and some other boilers do have such pumps, but the vast majority of boilers do not. Thats one reason why thermal stores are a poor choice..

then there is the higher than necessary standing losses of the store, which are always greater at 80C than 55c for hot a hot water cylinder..

 

[TellMeWhy]

I live in this universe.

It is not the one we all know. In yours boilers and cylinders do not fail at all in 15 years.

A quality Combi has far less weak points than a system boiler, external controls and an unvented cylinder. Do not take my word for it, look at the controls. I doubt you have seen a quality combi in operation.

It's not down to personal choice. Some system are just plain better than others in requirements. Proper analysis and assessment is needed, not wet fingers in the air, or doing what the big mouths say at the trade counter.

As been mentioned, boiler makers have an interest in maintaining quality and reliability, rather than external controls makers. If all is well designed and in one box the reliability will be higher, than a system spread all over the house.

 

[TellMeWhy]

I know, mr all to well...

cycling is inevitable, and all boiler cope well with it...what is striking though is that boilers cycle much less if the are correctly sized, and installed with compensation controls...and of course with compensated flow temperatures when cycling occurs is much lower than for a thermal store.

This is uninformed drivel Thermal stores can 100% eliminate boiler cycling.

You haven't a clue about thermal storage and scant knowledge of heating overall. You only know a boiler with a weather compensator. I await SimonH2 to take you apart. This will be fun

 

[ALEC1]

it depends on the system boiler...if its one with an internal diverter valve and no plate heat exchanger feeding a cylinder you get a lot of advantages.. I agree though that boiler manufactures have a bigger interest in reliability than controls manufacturers...

but a combi will fire 20-30 times a day for hot water, a properly sized system boiler will fire 4-6 times a day for hot water

draw your own conclusions about reliability

 

[TellMeWhy]

but a combi will fire 20-30 times a day for hot water

More misinformation. Some have small water vessels and preheat heat exchangers to prevent this. Quality models do not cycle. My ATAG has a pre-heat heat exchanger and does not cycle when a tap is on for a second or so.

I find it amazing how misinformed so-called professionals are. Many can't handle figures for sure.

 

[Dan Robinson]

My mistake earlier there isn't a q60c. However, the q51c modulates from 9.8 to 48.7kw and doesn't diminish in any way the daftness of fitting one in a 4 bed house.

I have a thermal store running at 60 but I have it for other reasons. It is not the best solution for my house.

15kw system boiler and 150 litre twin coil unvented cylinder is.


, and before you get all high and mighty about Atag. Corgigrouch and I have far more experience of them than you.

Here is a Q60s we fitted and commissioned last week:

Untitled

• Dan Robinson
• 25 May 2013
• 5

 

[ALEC1]

but a combi will fire 20-30 times a day for hot water

More misinformation. Some has small water vessels and preheat heat exchangers to prevent this. Quality models do not cycle. My ATAG has a pre-heat heat exchanger and does not cycle when a the tap is on for a second or so.

I find it amazing how misinformed so-called professionals are. Many can't handle figures for sure.

combis fire every time a hot water tap is opened even your combi, system boilers do not...they fire when a fixed amount of hot water is used..

combis rarely cycle in hot water mode..unless the flow is lower than the min output...it rarely will be!

 

[Tom1981]

Lucky I don't deal with trade conter know it alls. I'm quiet independent on my thoughts even tho I work for the largest utility and service company in the gas industry going.

I have seen lots of good combi's, tho I do remember the old ones. I'm impressed with the quality of the new Ultracom2.

I'm a Service and Repair 'Engineer' it's my job to maintain and fix things, I can see upto 10 different beasties in a day, 5 days a week in the winter time. I don't install appliances or systems, but I sure do adapt them, and learn about them. I really do like Unvented Cylinders with a good boiler attached to it. A simple set of Zone valves connected to a basic wiring centre with neat wiring and a good quality programmable room thermostat, maybe even a wireless. I hate Y-plan valves, their not complicated, just a big weak point.

I am fully aware that systems can fail, boilers can fail, but most of that is down to poor design, or just a plain faulty part. It happens.

I've never seen ATAG here in Norfolk so can't comment, this is county of Limescale, I've worked all over it, and Mid Norfolk between Derheham, Watton and Swafham has got to be the worst in the country, a Combi can scale solid within 4 months without protection, even a appliance on a softener can scale up in 6 months. We've got lots of Worcester CDIs in Norwich, along with many many cheap bits of junk, maybe one day I'll see one of these super duper Combi's. Saying that my Grant is pretty nifty, but it is the size of a washing machine, could last a bomb blast lol.

 

[TellMeWhy]

Here is a Q60s we fitted and commissioned last week:

Untitled

• Dan Robinson
• 25 May 2013
• 5

That looks like 6 heating zones. I see no super large cylinder which is encouraging. An extra expansion vessel looks like it is fitted in a large CH zoned house system.

 

[TellMeWhy]

I'm a Service and Repair 'Engineer' it's my job to maintain and fix things,
...
...
...
I really do like Unvented Cylinders with a good boiler attached to it.

You would do as it keeps you in work constantly fixing the things.

Saying that my Grant is pretty nifty, but it is the size of a washing machine, could last a bomb blast lol.

I have seen plate heat exchangers on the sides of large water content oil boilers and do the DHW. The boiler itself acts as a thermal store.

 

[Dan Robinson]

There is a 330 litre unvented cylinder in the basement. If you think a house that needs 60kw of heating is going to be satisfied with a combination boiler then you truly are an idiot.

Oh wait. ..you don't know the difference between a pump and a zone valve

There is only 1 zone valve there and only to satisfy the local building inspector.

So tell us wet fingered plumbers how a house that only needs say a maximum of 12kw of heat for 3 or 4 weeks a year is best served by a monster boiler that can only go down to 9.8kw?

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FANTASTIC system design that!

 

[Dan Robinson]

What figures do you want?

 

[hazetimesfive]

*watches with interest*