Having just installed the monitoring kit, I’m noticing that the flow rate is lower that all the other systems I’ve looked at and the delta t is higher, 7l/min and r 4 degree respectively. So twice the delta t and half the flow rate. The pump is set to auto and seems to run at 100%.
All the systems I looked at are running at flow rate of 14l/min and higher with a delta t of closer to 2.
Everything is working ok and the cop is ok if not great.
Is this indicating any trouble or sub optimal flow in the system?
It’s an Aerotherm+ 5 with radiators on 22 to 15mm pipes.
In DHW mode and with the bypass valve set to 0 bar it the flow rate doesn’t change.
What’s your max.rem.head set to? This needs to be at its maximum value to give you maximum flow rate.
Just checked. It’s set to 900, which seems to be the maximum.
Looking at the system, following components are on the dhw path:
- anti freeze valves
- Altecnic 28mm Y strainer
- Magnetic filter
- Oem heat and flow meter
- ball valves
- Honeywell motorised 3-way valve
- Mix of 28 and 22mm pipes
Apart from a fault in the Vaillant, I think it can only be the y-strain filter or the 3-way valve. I’ll have a look at the valve later today and then give the installer a call (so much less fun than doing some plumbing work).
I assume there is no valve or pump setting in the heatpump itself that could be set wrongly?
You can manually set the pump to 100% instead of auto, after that you have exhausted all the options on the software side.
Thanks, did that and no change. Setting it to 80% reduced the flowrate to 5.8l/min.
Check and clean the Y Strainer and Magnetic filter.
Thanks I’ve done that now. It was a black mess. Only problem was that I had left the pump setting at 100%, so got a flow rate of 70l/min! All good now, 14l/min and 2C delta t.
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2°C is quite low. Are you sure you need that high a flow rate? Maybe there’s some potential for optimization left. Optimizing flow rate for ideal COP
I was just going on what the flow rate and delta t of vaillant arotherm 5kw without underfloor heating on heatpumpmonitor is. All if them had 12-14 l/min and 2-3 delta t. That’s just what vaillant does when the pump is set to auto. So far it looks like the cop has improved, but more than two hours data would probably be good before I declare success.
That is for todays data, about 5C outside temperature.
If your system can do higher flow rates than 14l/min you could go for a manual pump speed setting to reach for example 20l/min. That will narrow your delta t, and you will be able to lower the flow temp because of the higher mean temperature in the radiators. This will improve efficiency.
I would not go higher than 75-80% on the pump speed though, for the reliability of the pump. And I would also keep an eye on the flowrates, as it seems the system is quite dirty and blocks the filters.
There is an optimum there, an it’s not necessarily at the maximum possible flow rate. There really is a balance to be struck, depending on power requirements of the pump. I have investgated that extensively here: Optimizing flow rate for ideal COP
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Interesting. Definitely monitoring it. Another advantage of setting the pump % is that I will see if the filter is getting blocked before the system reaches 100%. Woke up this morning searching for power flushing machines to rent. Looks resonably affordable at my local hire base.
At the moment at 100% it reaches 28l/min (not 70 as I misread), so a bit high.
Set it to 60% which gives me 15l/min and will see if it goes down.
Interesting. My system seems identical to yours, vaillant 5 with 2.5 to 3kw heat loss. I suspect the vaillant 3.5 isn’t a wildly different machine so probably not lost much or anything by having the bigger model.
I’ve also got the AroTherm Plus 5kW. It’s pretty much bang on 860l/hr flow rate. I think the 3.5kW is possibly just a software limited 5kW
Hey guys, I’m gonna setup my DHW as per Mick’s latest blog post.
Does anyone know what the default noise reduction should be at outside of the DHW time as per Mick’s post?
Mine is currently set to 40% but should this be lower than this and also even in normal DHW heating mode does this 40% setting affect how quick the DHW heats up?
Hello,
For starters, anyone looking for in depth performance information, this technical document from the Czech Vaillant site is gold.
I’ve converted these tables into a set of kW vs COP graphs:
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You only get to set one, global noise reduction value.
So whenever you set a noise reduction time (via the schedule), this single value will kick in and limit the compressor for the time period chosen
There is no way to have different NR values at different times of the day.
Other than NR being enabled or not.
Note: remember that NR reduction mode is a limiter. So when heating in milder weather, you may not hit the compressor limit, so the unit will heat and perform exactly the same, regardless of NR. If that makes sense?
Finally yes, the amount of NR you choose does affect how quickly hot water will take during your NR scheduled time.
More NR = lower compressor = less heat output = longer run times
Less NR (or none) = higher compressor = more heat output = quicker run times
Note: unless you’re already in Eco mode so your compressor will be limited to 50rps (on a 5kW)
Hopefully that’s clear in here:
Has anybody played around with the central heating hysteresis setting. Looks to me like it makes the maximum temperature the it reaches when cycling lower (by reducing the allowed overshoot over the target temp), hence increases efficiency. … but increases cycling which reduces efficiency. Will be interesting to see where the balance is. Mine was set to 7 Kelvin, trying 4 kelvin now.
Hysteresis is only a secondary mechanism, cycling is primarily controlled via the EnergyIntegral setting. The hysteresis should ideally never engage. There’s plenty of details on the EnergyIntegral here on the forums.