12 Litres Per Minute - OK for a combi?
- Thread starter gerbils
- Start date
Sponsored Links
Depends on what make and size of boiler it is.
Vaillant ecoFIT pure 35kW
Sponsored Links
It's rather low for that size of combi really, probably wouldn't get the benefit of such a large input.
Ideally, dynamic flow pressure would be measured, not static, as it's not just HW output rather HW output with other outlets on the mains being used at the same time.
Ideally, dynamic flow pressure would be measured, not static, as it's not just HW output rather HW output with other outlets on the mains being used at the same time.
waste of many putting such a big combi in at 12.5 by time its passed through valves and plate that will have restricted the flow down quite a bit . You would get away with a 24kw combi which will give you 10l at the 35 degree temp rise
Waste of money in terms of upfront costs or running costs? We're only being offered 35 unfortunately. Advice is so conflicting - we've had quotes saying 30kw is right and others saying 40!
Some say our water is perfect others that we need to spend on increasing the flow and digging up our drive.
I think it would be easiest to go back to coal - lol.
Last edited:
in upfront costs . Anyone saying 12.5 is perfect is talking nonsense
I agree. What I can't understand is how good or bad it is in practice. Clearly the plumbers quoting only care if it makes water hot, but we obviously want to improve what we have and be trouble free. Happy to wait 15-20 mins to run a bath (better than waiting an hour to re-fill a cylinder).
For some perspective, our taps upstair run at 6litres per min and the shower is running at 3 litres a min, I would like to think if we can get that to 8 that would be a significant boost for us.
Our shower is directly above where our new boiler will sit - does this help?
It would be a pretty old cylinder that would take that long to recover a cylinder TBH - a modern cylinder with a high recovery coil could have it @ 70% , from anywhere around 20 odd mins if on DHWP @ ~18Kw (cylinder size dependent)
Where is the 12.5L/min figure coming from if the taps run @ 6L/min or is that when they are both running at the same time? Is the 3L/min from the shower an electric shower?
The cylinder is 35 years old, same as the current boiler.
static 12.5L/min and 1.8 Bar is from one of the very respected local plumbing firms who quoted us for a 40kw Combi.
The 6 L/min (tap) and 3L/min (shower) were measured by me basically filling up 1 Litre several times.These are upstairs and so come from our tanks/cylinder rather than mains.
Last edited:
.... and they didn't give you dynamic readings? That's a bit pointless as static readings are not that important when it comes to day to day use, real life usage would always be based around dynamic readings.
If they are well respected and then quoting any boiler, never mind a huge 40Kw combi, on those readings, then their reputation is not deserved IMO. How many bathrooms, showers etc does the property have?
No dynamic readings given.
We have 1 bath, 2 showers, 15 rads.
The whole experience of getting a boiler has been frustrating, mainly becasue every man and his dog seem to advise something diferent and it's hard for a layman to know what's best. We've had it all.
Re flow rates, we used heatable at first, $12 million turnover, endorsed by Which, and they don't even ask what your flow is like. I questioned this and they said they spec by number of radiators. BOXT who I believe are even bigger and backed by Worcester Bosch do ask the question, but it's based on how quickly you fill a pint and according to them 12L/min is "Fast" and the best of their 3 options which are Fast (under 5 seconds), Average (under 10) and. Slow (more than 10). Only on slow will they block the purchase.
9 seconds to fill a pint is 3.1L/min if my maths is correct.
Last edited:
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
