Hi all,
Just had a Navien NCB 40kw combi installed by an approved fitter. The DHW rates of the boiler seemed promising on paper - 16.4lpm at a 35 temp rise and 22.9lpm at a 25degree rise. More than adequate for what we need. The only issue now its installed is that I'm not getting any more than 9 or 10lpm using the boilers display. I knew it would be a compromise fitting a combi as I had an Ideal Istor previously (cylinder & system boiler all in one), but the reduction in DHW is quite noticeable.
I've a new 25mm mains - fitted years ago mind, the Istors 22mm pipe feed now goes to the Navien (although reduced to a 15mm connection). I have 25lpm at the outside tap off the kitchen wall and 3bar pressure (not sure if this is static or dynamic but it was a gauge screwed to the outside tap???). Gas pipe is 22mm probably 20 feet to boiler). There is a tee off at the stop tap where it enters the property leading off to the cold supplies for the house - the other leading to the Navien. The hot water supply pipes to a bathroom and ensuite and kitchen from the boiler are 22mm (again from the old Istor) which tee off in 15mm to the fittings, the cold water pipes seem to be in 15mm to the various outlets. I've a bathroom and an ensuite. Boiler is in the basement, the bathroom 2 floors up and ensuite in the loft conversion.
The fitter assures me he's seen much higher readings on 40kw Naviens. He just doesn't know why it only reads between 9-10lpm.
I just wondered whether the quoted figures related to the flow rate when hot water is mixed with cold? I guess then it probably would be a much higher flow rate which is why the showers seem ok. Apparently the incoming temperature is 9 degrees, so setting the boiler hot water temp to 45degrees should give approx 16lpm...but it's a mile off based on the display.
Just wondered if I was missing something as my fitter couldn't shine any light on it and said he would speak to Navien? I never expected it to match the Istor with multiple outlets on at the same time, but I did expect a slightly better flow rate with one outlet...particularly to my bath tub which we used to fill in no time, which now takes noticeably quite a bit longer to fill.
Is the reality that what I'm getting currently is actually normal for a 40kw combi? Thanks for any comments.
Just had a Navien NCB 40kw combi installed by an approved fitter. The DHW rates of the boiler seemed promising on paper - 16.4lpm at a 35 temp rise and 22.9lpm at a 25degree rise. More than adequate for what we need. The only issue now its installed is that I'm not getting any more than 9 or 10lpm using the boilers display. I knew it would be a compromise fitting a combi as I had an Ideal Istor previously (cylinder & system boiler all in one), but the reduction in DHW is quite noticeable.
I've a new 25mm mains - fitted years ago mind, the Istors 22mm pipe feed now goes to the Navien (although reduced to a 15mm connection). I have 25lpm at the outside tap off the kitchen wall and 3bar pressure (not sure if this is static or dynamic but it was a gauge screwed to the outside tap???). Gas pipe is 22mm probably 20 feet to boiler). There is a tee off at the stop tap where it enters the property leading off to the cold supplies for the house - the other leading to the Navien. The hot water supply pipes to a bathroom and ensuite and kitchen from the boiler are 22mm (again from the old Istor) which tee off in 15mm to the fittings, the cold water pipes seem to be in 15mm to the various outlets. I've a bathroom and an ensuite. Boiler is in the basement, the bathroom 2 floors up and ensuite in the loft conversion.
The fitter assures me he's seen much higher readings on 40kw Naviens. He just doesn't know why it only reads between 9-10lpm.
I just wondered whether the quoted figures related to the flow rate when hot water is mixed with cold? I guess then it probably would be a much higher flow rate which is why the showers seem ok. Apparently the incoming temperature is 9 degrees, so setting the boiler hot water temp to 45degrees should give approx 16lpm...but it's a mile off based on the display.
Just wondered if I was missing something as my fitter couldn't shine any light on it and said he would speak to Navien? I never expected it to match the Istor with multiple outlets on at the same time, but I did expect a slightly better flow rate with one outlet...particularly to my bath tub which we used to fill in no time, which now takes noticeably quite a bit longer to fill.
Is the reality that what I'm getting currently is actually normal for a 40kw combi? Thanks for any comments.