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New Vaillant Ecotec Plus 832 DHW flow rate much lower than old 24kw combi it replaced
- Thread starter smallfry
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They don't work off a DT of 35. And yes I'm sure.
They work off approx 42 DT
They work off approx 42 DT
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Deffo a possibility. I recon the electronics in the new model would pick that up and give some sort of fault indication.
Old models just wouldn't activate on crossed pipes. New flow sensor same as ecoFIT will detect partial flow if crossed.
However it monitors dhw outlet temperature & compares to flow/return to detect if plate is blocking or scaling, so don't think this will be the case. But always no 1 check on a new install!
Good to hear, Vaillant do include the flowrate (13.0LPM) at a dT of 35C which I allways took to be the standard for all gas boilers.
They do though, also state that this boiler has a flow restrictor of 10.4LPM, which gives a dT of 43.8C but they don't quote this dT, presumably because it isn't the standard.
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They legally have to quote it at DT35 (and I'm sure DT30 also) as a testing standard. Causes lots of confusion, but its not up to them its a requirement.
Running at DT35 means in summer, if you have a cold inlet temp of say 10 degrees, you have 45 at outlet, average showering temp is about 38-39 so all is well. In winter when the cold inlet is 1 degree, your outlet is then only 36, so too cold for most people to shower in even before you mix any cold into it.
Restricting it to a flow rate to give 42, means worst case 43 at the outlet. Stops an awful lot of winter call out issues. But on paper looks like a poorer flow rate.
As you correctly point out the Power/Flow/DT are all related, so no 30kW boiler can give any more than any other 30kW boiler, its just a case of more flow at lower temp, or lower flow at higher temp.
Something still seems off though as if the op is getting 18 l/min on cold then I'd expect them to hit the 10 l/min or very close at the hot, assuming there's not unusual runs/filters/restrictive valve work on the mains to and from the boiler.
Yes its a bit confusing for the layman like me to decode the boiler specs
The install guide (linked below) mentions the following for the ecotec plus 832 (model in the tables is VUW 25/32):
- Flow rate (ΔT = 35 K) = 13.0 l/min
- Flow rate limiter = 10.4 l/min
I didnt intially spot the flow rate limiter. Would you know why they quote a flow rate for delta 35c that is not ever obtainable?
Also good point re crud in filter. will ask engineer to check it.
Thanks
Nvm - @ScottishGasMan you already answered in reply to @Johntheo5Yes its a bit confusing for the layman like me to decode the boiler specs
The install guide (linked below) mentions the following for the ecotec plus 832 (model in the tables is VUW 25/32):
- Flow rate (ΔT = 35 K) = 13.0 l/min
- Flow rate limiter = 10.4 l/min
I didnt intially spot the flow rate limiter. Would you know why they quote a flow rate for delta 35c that is not ever obtainable?
Also good point re crud in filter. will ask engineer to check it.
Thanks
These posts didnt show until refresh after my post above.
Cheers
As said above by @ScottishGasMan,
The boiler can do 13lpm "adding" 35°c to the temp of the cold main.
In summer this would be fine as cold main is already at @10°C
In winter, with cold main at @1°C, adding 35°C to it would not be enough for a comfortable shower temp, so slowing the flow rate down via a flow restrictor, allows more heat added by the boiler to reach a comfortable temp.
If that makes it easier for others to understand.
The boiler can do 13lpm "adding" 35°c to the temp of the cold main.
In summer this would be fine as cold main is already at @10°C
In winter, with cold main at @1°C, adding 35°C to it would not be enough for a comfortable shower temp, so slowing the flow rate down via a flow restrictor, allows more heat added by the boiler to reach a comfortable temp.
If that makes it easier for others to understand.
I've allways thought a 40C dT standard would be better but on the other hand how often does the mains fall to 1.0C, the lowest I've seen around here is 5C so a dT of 35C will still give a acceptable 40C washing/showering temperature. I'm farly sure I have seen some manufacturers using this 40C dT?.
Manufacturers will do what they want to do, whether we think it's right or not.
Sometimes they take numerous comments on board.
Sometimes they take numerous comments on board.
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Up here it's pretty common to see 1-3⁰C on cold mains inlet in winter. Seen it over 20⁰C in summer. Depends on the area and how deep they decided to bury the pipe.
For the moment anyway if @smallfry sets the DHW temp to say 55C (to avoid scalding) then, a boiler flowrate assumed at only 7.0LPM will still give a equivalent flowrate of, 7.0*1.5, 10.5LPM at 40C, with a boiler output of 21.98kw or, 7.0*1.67, 11.67LPM at 40C if the DHW is set to 60C, with a boiler output of 24.42kw. (from mains at 10C).
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