Setting Condensing Boiler Flow Temperature

[onlyfitidealboilers]

think of a small rad as small pipe. (come back slower)

an a big rad as big pipe ( come back faster)

that is why when installing a new central heating system it is important to size the bypass rad as if its to small the greater the temp diffs, the flow could end up at 82 and the return at 52 causing the heat ex to be cooked to death.

common sense..

 

[Agile]

How do you know the target drop if it is not specified by the boiler manufacturer? As you know, the drop is dictated directly by the design of the heat exchanger. Many condensing boilers are simly rehashes of old non-condensing designs hence they have not been engineered for a 20C drop but must (should) remain at 11C.

Mathew

Whilst that may hyave been the case withg the Band B boilers they are no longer allowed.

However, I would disagree that they should therefore be operated at just 11 degrees.

The reality is that most boilers will operate at widely different conditions and its up to the installer to use whatever skill he has to set it up to be efficient. But when the education of installers is so widely variable that can be rather hit and miss. At least when you go to a solicitor or accountant they usually have at least "A" levels. You dont even need any GCSEs to get gas registered.

Tony

 

[MJN]

These discussions do highlight that when push comes to shove our efforts are at best often only squeezing the last drops of efficiency out of the system. There's certainly a law of diminishing returns at play.

That said, whilst efficicency savings per install can be slight there are still some very real overall benefits aggregated across everyone's installations albeit not quite as much as what many people might otherwise believe.

Mathew

 

[MJN]

Whilst that may hyave been the case withg the Band B boilers they are no longer allowed.

However, I would disagree that they should therefore be operated at just 11 degrees.

I wasn't referring to Band B boilers. Take the Ideal Icos for example, whilst it is a condensing boiler (Band A) it is designed for a drop of only 11C. It is therefore something of a compromise between adequate system performance and condensing efficiency. Of course, it's a cr@p boiler but that's exactly my point - it's a rehash of an old boiler design using an 'old-fashioned' (low serface area) heat exchanger.

But when the education of installers is so widely variable that can be rather hit and miss. At least when you go to a solicitor or accountant they usually have at least "A" levels. You dont even need any GCSEs to get gas registered.

Understood, and it's nice to hear it mentioned from someone with no opposing bias. To be fair, some of the criticism (including that from me) probably ought not to be aimed at the installers but rather the system (or lack of) that is there to support/educate them.

Mathew

 

[ajrobb]

that is why when installing a new central heating system it is important to size the bypass rad as if its to small the greater the temp diffs, the flow could end up at 82 and the return at 52 causing the heat ex to be cooked to death.

The Vokera Compact 29A has an automatic by-pass.

 

[onlyfitidealboilers]

and.............

 

[ajrobb]

and.............

Why do you need a by-pass radiator if the boiler has an automatic by-pass? The automatic by-pass ought to ensure sufficient flow through the heat exchanger even with all the radiators turned off.

 

[onlyfitidealboilers]

 

[MJN]

think of a small rad as small pipe. (come back slower)

an a big rad as big pipe ( come back faster)

No. Your premise is wrong.

A smaller radiator restricts the flow no more than a big one. The restrictions are due to pipe bore/length, fitting and valves.

that is why when installing a new central heating system it is important to size the bypass rad as if its to small the greater the temp diffs

Yes, but you are sizing it to disipate sufficient heat.

common sense..

Call it what you like - you're still wrong.

Mathew

 

[Agile]

that is why when installing a new central heating system it is important to size the bypass rad as if its to small the greater the temp diffs, the flow could end up at 82 and the return at 52 causing the heat ex to be cooked to death.

common sense..

If you had done the energy efficiency course, as you should have done, then you should have remembered that now all radiators should have TRVs and the system should have an auto bypass fitted.

As you specifically were refering to "when installing new systems" then clearly you are not installing them to the current requirements.

Quad erat demonstrandum that the education of installers is widely variable. Many have not even studied latin for example.

Tony

 

[onlyfitidealboilers]

think of a small rad as small pipe. (come back slower)

an a big rad as big pipe ( come back faster)

No. Your premise is wrong.

A smaller radiator restricts the flow no more than a big one. The restrictions are due to pipe bore/length, fitting and valves.

that is why when installing a new central heating system it is important to size the bypass rad as if its to small the greater the temp diffs

Yes, but you are sizing it to disipate sufficient heat.

common sense..

Call it what you like - you're still wrong.

Mathew

no am not mate. go am do a test on your house, iv worked for manufactures for many a year am test this daily. thats how we can tell a ****e rgi to a good one.. sorry but it is you who is wrong

 

[onlyfitidealboilers]

that is why when installing a new central heating system it is important to size the bypass rad as if its to small the greater the temp diffs, the flow could end up at 82 and the return at 52 causing the heat ex to be cooked to death.

common sense..

If you had done the energy efficiency course, as you should have done, then you should have remembered that now all radiators should have TRVs and the system should have an auto bypass fitted.

As you specifically were refering to "when installing new systems" then clearly you are not installing them to the current requirements.

Quad erat demonstrandum that the education of installers is widely variable. Many have not even studied latin for example.

Tony

your talking bull **** again tony.. if you have no bypass rad an just use a auto bypass what do you think the boiler will do every 5 mins, thats right tony it will short cycle. well done your boilers will last no more than 5 years if you adopt that.

 

[MJN]

With the greatest respect Onlyfitidealboilers, your ignorance of the subject is astounding given you apparently work in this area.

Mathew

 

[onlyfitidealboilers]

mjn am sorry but i feel the same about you..

 

[MJN]

Here's a hint for you: Boilers with internal auto bypass valves are not twice the size of others in order to accomodate a full-sized radiator inside of them... You should ask yourself why this is?

The reason for a bypass is to ensure there is always adequate flow through the boiler. Without any flow, because either all TRVs have closed or the pump has failed, there is a risk that the boiler could overheat. In the case of TRVs closing the purpose of the automatic bypass is not to disipate unnecessary excess heat into a radiator but to allow heated water back into to the boiler such that the boiler can detect the lack of demand (due to the high return temperature) and turn off.

This strategy is preferable to simply leaving the boiler chugging away heating nothing more than a bypass radiator in a place which doesn't necessarilly need the excess heat. It is a simple case of energy conservation.

I've got to ask: It sounds like you fit a radiator inline with the ABV, yes? Where is this radiator sited?

Mathew