confused on which boiler to choose

[gasafengineer]

And the way they render the output non-linear with temperature difference?

Water flow rate is non-linear , water flow temperature is near linear.

 

[plantroom]

Hey gasafengineer,you're going the same way as commercialman went ,he got banned because he disagreed with some on here who also happen to be moderators,seems these members-mods don't like any new member rockin the boat,funny how commercialman got banned soon after the run-in with Bengasman,to which if you read the thread bengasman was made to look a fool,just like the way this thread is looking.
I would guarantee this post along with yours will dissappear within a short space of time and your membership terminated.
Bengasman why do you dis-credit good people on here when you have no clue on what qualifications they may or may not hold? carry on arguing looks like it's going be fun.
All you gas engineers should get along without the bitterness displayed on here.

 

[CharteredEngineer]

Viessmann quote 15%, if you can understand German and read test.de, they also quote more than 15% for WC.

15-20% of the difference between band d and a; not 15% of the total. If you're so good at German, how come you didn't pick that up?

In reality, the saving is not even that. Provided the installation was designed and installed properly, the return temp is about 20 degrees lower than the flow. Therefore, wc only makes a noticeable difference when the flow temperature is above 75, and virtually nothing below 70. That in turn means, that the wc will not do anything for about 55 minutes out of the hour that the heating is on, unless the boilerstat is screwed up to max. If the boiler stat is set below 75, the wc will do virtually nothing to save money at any time because the cycle will only bring the return temperature near the 55 for a few moments before the boiler clicks off.
If you are such a clever engineer, how come you did not pick that bit up?

There is no point talking to you because you don't understand. Get yourself back to College.

 

[DP]

The way I see WC. When it is cold outside boiler stat needs to be set high. Return needs to be lower than 55 degree C for efficiency/ condensing sake. Lower the return temperature, more efficient the boiler.

Installing WC will surely be a bonus as sensor will be tracing external temperature, so setting boiler to lower flow temperature which will give lower return temperature ( as said before, cooler the better) as opposed to leaving the boiler stat at theoretical 75 with F/R differential of 20.

By the way, my missus was threatening to call in a heating engineer to 'fix' the system after I fitted 2 programmable roomstats to Ecotec 831. I still see some homeowner who use the programmers as manual devices, they hit the switch to start the heating and hit it again to switch off. I can visualize such people being out of harmony with things that are digital

I would love to fit an external sensor to fine tune my system

 

[bengasman]

....Just for clarity , room temperature values of around 20k are recomended by CIBSE ...

I really doubt that. Suppose you can't tell us which document exactly, could you?

 

[johnsville]

Interesting thread apart from the sniping on here. Just for the original question. A neighbor took out an 8 year old economical conventional boiler with a copper heat exchanger and fitted a new condensing boiler and put in WC as well. He was doing an extension and a new boiler location was needed, so a new condensing boiler had to be fitted. His gas bills dropped like a stone. The difference in economy on paper between the new and old boiler is not that great. He reckons the WC made all the difference. His radiators always seem to be just warmish not hot. He said the house is always just right in temperature. It always seems right to me when I am in there having the odd beer. His WC is also influenced by the room temperature as well as the outside temperature which I am sure gives improved economy and comfort as well. When the room starts to get too warm the boiler burner throttles down.

WC has been normal in commercial systems for about 60 or 70 years. As some have mentioned here, it is normal in domestic systems on the Continent and has been for decades, integrated with the boiler. It works. Go with the flow and move on.

 

[bengasman]

A neighbor took out an 8 year old economical conventional boiler with a copper heat exchanger and fitted a new condensing boiler and put in WC as well. He was doing an extension .... His gas bills dropped like a stone...

So he added an extension, changed his boiler from band d to a or b, and whilst the gasprices rose by about 20%, his bills plummeted despite the fact there was more house to heat.

I think we found ourselves another troll.
//www.diynot.com/forums/viewtopic.php?p=1969455#1969455

 

[johnsville]

No. He fitted a top efficient boiler which would be band A. His extension was a small kitchen utility room in which the new boiler went in. Most of it was the old garden toilet which was a part of the house. It was heavily insulated and added little to heating demand. His bills dropped like a stone and not because of price hypes.

A troll? Anyone who is proven wrong here gets accused of being a troll. Laughable.

BTW, good work CharteredEngineer. Nice intelligent posts.

 

[sequencedancers]

All I want is a reliable boiler but still confused.

I was firstly recommended by the repairer to my Alpha combination boiler that is was uneconomical to repair, and that the Baxi duo tec 33 was a good boiler to replace it with, but I have read that they break down quite regularly, so this as put doubt in my mind. on this site I have been recomended viessman vitodens 200, and also have read that vaillant is a reliable boiler and also worcester greenstar

I may not have explained my requirements correctly I live in a detached house whith just my husband and I living there. I said with 2 bathrooms but one has a bath the other only has a shower that is electrically heated, then there is kitchen, utility room, liiving room, dining room, study, conservatory and 3 bedrooms, most rooms have one radiator except living room 2, conservatory 2, and kitchen 2

I want a reliable boiler that is not going to break down every winter as my alpha has done, are any of the above boilers ok or any other suggestions

 

[BGEngineer]

The Baxi Duo Tec does not break down very regulary, where did you read this? As I say the early ones had a problem with the electrodes but that is now fixed. Personally I only install Worcester, but Vailliant and Viessman are both good as well.

 

[silverback]

All I want is a reliable boiler but still confused.

I was firstly recommended by the repairer to my Alpha combination boiler that is was uneconomical to repair, and that the Baxi duo tec 33 was a good boiler to replace it with, but I have read that they break down quite regularly, so this as put doubt in my mind. on this site I have been recomended viessman vitodens 200, and also have read that vaillant is a reliable boiler and also worcester greenstar

I may not have explained my requirements correctly I live in a detached house whith just my husband and I living there. I said with 2 bathrooms but one has a bath the other only has a shower that is electrically heated, then there is kitchen, utility room, liiving room, dining room, study, conservatory and 3 bedrooms, most rooms have one radiator except living room 2, conservatory 2, and kitchen 2

I want a reliable boiler that is not going to break down every winter as my alpha has done,

This is a pointless question to ask on here, as each installer will recommend his preferred manufacture, who the next installer will criticise, so you will never get a definitive answer, my own personal preference would be either ATAG or Viessmann boilers, but they are my personal preferred boilers and if you really want to push the boat out, try Rotex (lets wait and see that name get used alot once the Google warriors on here have Googled it.)

 

[bengasman]

I want a reliable boiler that is not going to break down every winter as my alpha has done, are any of the above boilers ok or any other suggestions

Bar a few really bad ones ( personally I would never install an Ideal unless I really hated the customer ) it does't make that much of a difference compared to how good the guy is that will install it.
Three quarters of the boilers I repair are not broken down to poor quality of the machine but poor quality workmanship of the installer/service people.

Even Alpahas which are not topnotch can do fairly well when installed and maintained properly.
It's like cars: you can buy a £100,000 Merc, if you don't brake it in at all, diy the service and stick the wrong oil in, you're bound to get problems.

 

[gasafengineer]

. Suppose you can't tell us which document exactly, could you?

Sure , CIBSE part B (HVAC) , shame you won't be able to google the document.

 

[hansthebear]

some people seem to place the blame for any unreliable boilers on the original installer, giving the impression that anything is reliable as long as its installed correctly.

this is bad advice in my opinion

if it were me i would fit a vaillant.

 

[gasafengineer]

I design my systems to the requiements of the client.

To what figures are you basing MRT? & which correction factor are you using regards heat load output?

Return water temperature needs to be less than 55k to enable the boiler to condense & between 30 & 40k to operate most efficiently , ideal flow temperatures for weather compensation should be 70k flow @ -3 celcius outdoor temps & 40k @ 15 celcius outdoor temps , obviously these figures will be based on a 50k deltaT.