Flow and return temperatures for LPG consening boiler

[shraheens]

I have gone through a lot of vokera valiant raven heat etc… websites and I maybe I have missed it but I just couldn’t find anything regarding flow and return temps for condensing LPG boilers

At the moment I'm sizing radiators up my new house, I just wanted to know the flow and return temperatures of these boilers. I'm have got conflicting temperatures of 60oC flow and 40oC and also 50oC and 39oC, so really I'm neither right or wrong on that subject so on the condensing side off things

what is to be considered the optimum temp since it is condensing its important to get this correct especially on the sizing of the boiler, so I hope anyone can give me help on that one!

Also the LPG connection is going to be copper so if ½ is fed from the LPG tank wouldn’t that be plenty for to feed a 9.0kw to 26.6kw boiler.

Finally what is the best condensing boiler out there I hear and know of a few vokera out there, my installer thinks that there bullet proof but I have heard of a lot of heat exchangers failing? (Maybe there bullet proof cheap for him!!!) so I have looked at the Valliant a lot I email every one of these companies in the last week and only a day passed keston replied,as of yet no one else has replied, maybe I should go with keston !??

Any how any one with better experiences let me know, because I certainly don’t know and that what this forum is for !!!

I would like to thank you for all your time and effort and a lot of patience for reading this,

Thanks again everyone

 

[doitall]

If your looking for a decent boiler then the Broag Avanta range is worth looking at. you should be looking at a temperature differencial of 15c across the flow and return.

Gas pipe size will depend on distance the same as any gas pipe. To an extent it will also depend where the second stage regulator is fitted, as this could reduce the low pressure pipe length considerably

 

[gas4you]

When I fit a combi I always leave the boiler stat set to 60C. If it is heat only with a HW cyl then I leave it at 65C.

Doesn't matter whether it's LPG or NG.

 

[shraheens]

Thanks lads for that!! The gas point isn’t that far away so I should get away with 1/2" pipe


I understand there should be like a 15c differential between the flow and return

But what flow temp should I go with especially since it’s a condensing boiler and I want to size it Farley tight to what it needs.

Would it be 80c flow 60c return to which keston gave me or is there a rule like should it be 55c flow 40c return, that’s is suppose is the question im
stuck on !!

Gas4you do you mean to go on say if I had HW go 65cflow and 50c return

That makes sense if I was sizing it but im not sure is that what you meant

Thanks again lads it’s appreciated

 

[gas4you]

Yes I hink thats what I said, but go for a 20C differential for a condenser.

 

[bengasman]

The MI will tell you exactly what the system should be set for.
In general the return temp should be max 54 C. this is why most condensers, if not all, require a 20 degree drop.

 

[shraheens]

Yes I think I will go for 65c flow to 45c return that should be plenty
I should be covered on that I don’t know a lot who’s the MI??

Im setting up the rads sizes and im just making sure that I haven’t gone or done anything wrong you know it’s like double check I don’t want someone to come and tell me ahhh you should have!!!,

lad’s gas4you thanks very much and also to doitall and bengasman, it handy to have you professionals for advice and fair play to you all for giving it straight !


Thank you again

 

[Agile]

Surely your installer should be advising you on these design objectives?

Tony Glazier

 

[bengasman]

MI = Manufacturer’s Instructions aka the service and installation manual.
It will tell you every relevant size, setting and value for that particular boiler.
Is valid at all times and overrides the general gas regulations.
If the one for your boiler says: 76 for flow and 57 return, than that is what you got to do.
Hence it is totally irrelevant what all the websites say; only your boiler counts.