Hello,
Long time lurker on this forum and I have been very thankful for the variety of information that I have been able to pick up.
I apologise in advance for the length of this post, please persevere.
We have recently moved house and have decided to replace the current boiler and vented system set up. We made the decision as the boiler is quite old (Glow worm Spacesaver 40-50F), the tanks are in the loft to clear the space and the header tank should just not be mounted where it is, we are also planning other renovations that would include new floors so we would like to get any plumbing changes out of the way.
I have had a number of people out for quotes mainly WB and Valliant accredited and some well recommended local people I have been quite open to the possibility of combi or unvented but have been disappointed by the number willing to talk about unvented (although looking at the £ difference I can understand why).
The house is a 4 bedroom 1 bathroom with 2 sections having flat roofs.
The plan is to redo the bathroom so it will have a bath and separate thermostatic shower, in the longer term we plan to add an on suite on the first floor and extend into the loft adding another on suite.
Currently there is about 9-10 KWH worth of rads which are insufficient especially in some sections, I have already worked out the replacements for these totalling 20KWH.
The main options I am looking through at the moment are:
Combi:
WB: 37CDI, 42CDI, Highflow 550
Valliant: 837, 937
Unvented
WB Boiler + Range 210L
Baxi Boiler + MegaFlow 210L
The installation of the 37 KWH combis starts at about 2.7kdepending on options rising to almost 4.4k for the big WB and then up to the 5k mark and beyond for the unvented options.
Right now I am trying to work out the justifications for spending the extra £££ on the 'better' options.
The boiler (and cylinder) would go in place of the current boiler in the utility this is just the other side of the wall to where the mains comes in in what looks like 22-25 mdpe this goes straight down to 15mm and then through the stopcock.
All of the companies tested the flowrate at the kitchen tap (4m from incoming) and all reported about 20L/m none felt the need to check pressure.
As 20L is marginal on the higher options I armed myself with a pressure gauge, 10l bucket and stopwatch and found the following:
Static Pressure: 3.5 bar
Garden tap fully open: 0.75 bar and 21.4 l/m
Garden tap: 1.5 bar and 17.1 l/m
Garden tap: 2 bar and 15 l/m
Garden tap: 2.5 bar and 11.7 l/m
Garden tap: 3 bar and 7.4 l/m
Kitchen tap fully open: 19 l/m
Bath tap fully open: 18 l/m
Kitchen and Bath tap fully open: 21.5 l/m combined
This is where I am trying to draw on the experience of the forum to help give an indication of what my possible results might be with the boilers\options I am looking at.
I have gone through the datasheets for the combis and tried to use the manufacturer specified min pressure for max DWH and this has given some interesting results as the WB seem to be more restrictive then the Valliant.
It seems with the 837 (0.75bar) I should get the full 15l@35 and with the 937 (1.3bar) I should get at least 18L.
However the 550CDI (1.7bar) which I liked to look of may only return just over 16 and the 42CDI (1.9bar) even less.
If the above is true (can anyone advise from experience?) then that would be a shame as I liked the fact that the WB modulate lower.
And then comes the issue of unvented, if I go by the datasheets I should get around 20l, and of course this would potentially be at a higher temperature rise, but of course £££, more spent on this means less elsewhere.
Which ever way I go the plan is to change the incoming so it goes straight to 22mm through to the boiler, hopefully this might release a little more flow.
If anyone could share there experiences in relation to the above I would be most grateful.
Long time lurker on this forum and I have been very thankful for the variety of information that I have been able to pick up.
I apologise in advance for the length of this post, please persevere.
We have recently moved house and have decided to replace the current boiler and vented system set up. We made the decision as the boiler is quite old (Glow worm Spacesaver 40-50F), the tanks are in the loft to clear the space and the header tank should just not be mounted where it is, we are also planning other renovations that would include new floors so we would like to get any plumbing changes out of the way.
I have had a number of people out for quotes mainly WB and Valliant accredited and some well recommended local people I have been quite open to the possibility of combi or unvented but have been disappointed by the number willing to talk about unvented (although looking at the £ difference I can understand why).
The house is a 4 bedroom 1 bathroom with 2 sections having flat roofs.
The plan is to redo the bathroom so it will have a bath and separate thermostatic shower, in the longer term we plan to add an on suite on the first floor and extend into the loft adding another on suite.
Currently there is about 9-10 KWH worth of rads which are insufficient especially in some sections, I have already worked out the replacements for these totalling 20KWH.
The main options I am looking through at the moment are:
Combi:
WB: 37CDI, 42CDI, Highflow 550
Valliant: 837, 937
Unvented
WB Boiler + Range 210L
Baxi Boiler + MegaFlow 210L
The installation of the 37 KWH combis starts at about 2.7kdepending on options rising to almost 4.4k for the big WB and then up to the 5k mark and beyond for the unvented options.
Right now I am trying to work out the justifications for spending the extra £££ on the 'better' options.
The boiler (and cylinder) would go in place of the current boiler in the utility this is just the other side of the wall to where the mains comes in in what looks like 22-25 mdpe this goes straight down to 15mm and then through the stopcock.
All of the companies tested the flowrate at the kitchen tap (4m from incoming) and all reported about 20L/m none felt the need to check pressure.
As 20L is marginal on the higher options I armed myself with a pressure gauge, 10l bucket and stopwatch and found the following:
Static Pressure: 3.5 bar
Garden tap fully open: 0.75 bar and 21.4 l/m
Garden tap: 1.5 bar and 17.1 l/m
Garden tap: 2 bar and 15 l/m
Garden tap: 2.5 bar and 11.7 l/m
Garden tap: 3 bar and 7.4 l/m
Kitchen tap fully open: 19 l/m
Bath tap fully open: 18 l/m
Kitchen and Bath tap fully open: 21.5 l/m combined
This is where I am trying to draw on the experience of the forum to help give an indication of what my possible results might be with the boilers\options I am looking at.
I have gone through the datasheets for the combis and tried to use the manufacturer specified min pressure for max DWH and this has given some interesting results as the WB seem to be more restrictive then the Valliant.
It seems with the 837 (0.75bar) I should get the full 15l@35 and with the 937 (1.3bar) I should get at least 18L.
However the 550CDI (1.7bar) which I liked to look of may only return just over 16 and the 42CDI (1.9bar) even less.
If the above is true (can anyone advise from experience?) then that would be a shame as I liked the fact that the WB modulate lower.
And then comes the issue of unvented, if I go by the datasheets I should get around 20l, and of course this would potentially be at a higher temperature rise, but of course £££, more spent on this means less elsewhere.
Which ever way I go the plan is to change the incoming so it goes straight to 22mm through to the boiler, hopefully this might release a little more flow.
If anyone could share there experiences in relation to the above I would be most grateful.
