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Deleted member 123817
1 LPM or 9LPM for 9 loops
Discuss Viessmann Vitodens 100-w trouble maintaining central heating temp in the USA area at PlumbersForums.net
1 LPM or 9LPM for 9 loops
No way to increase flow really as pump speed is controlled by boiler and all loops are fully open. Viessmann tech suspects calcified main heat exchanger due to limescale buildup but theory doesn't explain boiler noise nor still fluctuating tap temp with brand new plate heat exchanger.That "upper operational limit is only the pump end of curve conditions so as the pump is new it does point to a restriction in the Hx or else the loops are full of sludge. You may have to prove both clear .
If you are handy yourself, maybe connect mains hose to UFH manifold with return disconnected, you will then get a feel for head required to give a flow rate of 1LPM/Loop by cracking open the mains.
You said originally no problems with DHW on old Hx but now some problems with new HX?
Maybe try and figure something out from the DHW (combi?) side, set the boiler HW setting to 3 or4? then open a hot tap fully or even two, measure these flow rate(s) and measure the DHW temp, see if you can can read off the boiler flow&return temps or just the flow temp if only one available, may be able to figure/confirm something from these readings.
Totally agreeI can't answer that but what I can say is if you look at my first ever post answering you there a picture of how it should be done ? , a small low loss header with a separate pump fitted would also do the job on your existing set up look at the Viessmann installation guide it may give you a better understanding . Kop
I can't answer that but what I can say is if you look at my first ever post answering you there a picture of how it should be done ? , a small low loss header with a separate pump fitted would also do the job on your existing set up look at the Viessmann installation guide it may give you a better understanding . Kop
Is that the system with the manifold circ pump and where you run the boiler at say 60/65C and UFH at 35/35C which reduces the primary flow rate substantially?. Your post #23.
If the pump speed is limited to 72% then the 7.5M pump becomes < 4M which probably isn't enough for 12mm piping but strange that the system worked OK apparently for years.
Well, I would be quite surprised if one pump couldn't give adequate flow through 16mm piping, my daughter has a mixture of rads/UFH serviced with a 16 year old Grundfos selectric 6M (one) pump, all heating working perfectly.
Don't know what length the loops are but assuming 100M then the pressure drop through each loop is 0.152M @ 1LPM, 0.54M @ 2LPM and 0.82M at 2.5LPM, these numbers become 0.18M, 0.66M & 1.0M for 120M loops.
I know you are in a dilemma after spending all that money but if I were you (and should have suggested this previously) I would go away and buy a 0 to 10M pressure gauge, install it in the UFH flow side of the manifold and run your system, that will tell a lot and may save you a pile of money at the end of the day. Also find out if that circ pump is restricted to 72% speed.
Yes, I was referring to KOPs post/photo.
If that's a question for me, then afraid the answer is no, but it would be very useful information if someone here has it.Have you ever noticed/noted the manifold pressure (if PG installed) on a UFH system without a manifold pump.
Closed system. Annual top-ups. No previous flush of heating water. Unknown what original installer put in the water if anything. The UFH is 120m2 so with an average of 5m of pipe per m2 and 0.15-0.17L per m of piping I'm estimating around 90-100L of water in the UFH. Is that enough to calcify a main HX? It's the original one. Boiler was new and installed 5 years ago.Why should the main Hx be calcified, its a closed system and except there is a constant leak somewhere and the system is being topped up with a auto fill PRV. If the system is manually topped once/twice/annum and the filling valve(s) are then shut then calcified Hx should not be a problem. Was this Hx ever changed?. Can understand if it was the DHW Hx was getting calcified due to constant mains water through one side of it.
dr might inform of the output of his boiler, if not already done so.
it needs a low loss header
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