We have a Tempest Solar cylinder which has two coils and has 250l volume. Solar thermal array on the roof.
The Grundfos circulation pumps were replaced when we had a low loss header removed.
We now have just a single loop circulation pump which does DHW and space heating.
What were your drivers for replacing the pumps and removing the LLH, other than the 'usual' better design + increased efficiencies?
Optimum flow rate is 15 lpm (set manually on the dial and operates at 48 to 50 watts) but as stated above this rises to 17 lpm on the DHW cycle but we don’t see any problem with this small rise in flow as we get our target 48c temperature in 30 minutes.
That's pretty good recovery (assuming it starts 10+C below setpoint) - assume the dual-coil is helping here. Was the main driver for two coils the quicker recovery?
the pump is the Yonos-Pico 25/1-8 article 4215517/23w26/180.
Thanks. I see it's a Wilo - were you aiming for very quiet ones? What other pumps did you consider and what made the Wilo your preferred?
Let me know if you get any further with using the grundfos pump you mentioned.(Grundfos UPM3L 25-75 130AZA)
The Grundfos UPM3 manual intimates the speed is infinitely-controllable between a signal of 11% and 84% (<= 10% and it'll run at maximum, 85% - 91% it's minimum, etc - see the manual for more detail), should the signal 'strength' sent be suitable. On that basis I assume the FTC sends five signals raning from 11 to 84 (speed 1 = 11, speed 2 = 29, 3 = 47, 4 = 65, 5 = 83/4)...
it sounds plausible as a solution if it can provide enough head pressure for you’re pipe runs.
That was going to be my next question - I know pressure immediately refers to vertical lift but I've seen mention of its consideration with smaller-diameter pipe; do you / does anyone have an idiots guide to calculating suitable pump pressure?!
1. What were your drivers for replacing the pumps and removing the LLH, other than the 'usual' better design + increased efficiencies?
Main reason: We surveyed our pipes after installation and discovered a very balanced load down 2 main branches of 22mm pipe spines. It also occurred to me that the 10mm microbore was all copper and short runs at that. We were chasing improved efficiency. We had reached 3.4 CoP but could see the LLH was still getting mixing which was a loss of efficiency. So we presented our findings to our installer as a sketch:-
We stated the unknown pipework was now known and should cope as a single loop. And they agreed and did the amendment FOC.
DHW increased flow rate
we don’t see any problem with this small rise in flow as we get our target 48c temperature in 30 minutes.
2.
That's pretty good recovery (assuming it starts 10+C below setpoint) - assume the dual-coil is helping here. Was the main driver for two coils the quicker recovery?
Reply: I’ve heard about double looping the DHW coils for greater efficiency but that’s not what we have done sorry. The second coil is for our Solar system to preheat the water at the bottom of the tank and fully provide DHW during summer months.
we noticed a longer hpDHW cycle meant that the hp spent a long time heating at the end of the cycle with not much HW gain. So we removed the back end by shortening the heating period to see what temperature we got.
we are happy with 48c so we have left it at 30 min cycle. And that also means no immersion backup is required either.
the pump is the Wilo- Yonos Pico 25/1-8 article 4215517/23w26/180.
3.
Thanks. I see it's a Wilo - were you aiming for very quiet ones? What other pumps did you consider and what made the Wilo your preferred?
We now have just one circulating pump instead of 2. I chose the Wilo because it has a vario dial so I can precisely dial up 15 LPM which sets at around 48 to 52 watts and it’s tiny illuminated display tells me what the flow rate is live.
Let me know if you get any further with using the grundfos pump you mentioned.
it sounds plausible as a solution if it can provide enough head pressure for you’re pipe runs.
4.
That was going to be my next question - I know pressure immediately refers to vertical lift but I've seen mention of its consideration with smaller-diameter pipe; do you / does anyone have an idiots guide to calculating suitable pump pressure?!
The Wilo we now have has a max head of 9mtrs but as it’s dialled back from its top output it has reduced noise and reduced kw consumption. Circulating pumps are operating continuously and so by reducing the number of them is an immediate efficiency gain.
Im no hydraulics expert but multiple bends, linear pipe runs of microbore (and other pipe sizes) all contribute to resistance ergo increased head. Also the dozens of inserts for push fit piping all have an impact. Perhaps someone reading this might have a calc or guide for this….
So we presented our findings to our installer as a sketch:-
...We stated the unknown pipework was now known and should cope as a single loop. And they agreed and did the amendment FOC.
Nice*
We now have just one circulating pump instead of 2 ...
The Wilo we now have has a max head of 9mtrs but as it’s dialled back from its top output it has reduced noise and reduced kw consumption. ...
Im no hydraulics expert but multiple bends, linear pipe runs of microbore (and other pipe sizes) all contribute to resistance ergo increased head. Also the dozens of inserts for push fit piping all have an impact.
* Were you / your installer able to calculate a head figure from your diagram, then? Assume that you then chose a pump based on other criteria (like live readout) with some, ahem, head room just in case?
* Were you / your installer able to calculate a head figure from your diagram, then? Assume that you then chose a pump based on other criteria (like live readout) with some, ahem, head room just in case?
I presented several pieces of data to try to convince that I’d done a fare bit of reading and testing. I think my install designer was as much swayed by my apatite as my findings. Info Included:
Total water volume calcs,
Total rad volume,
Min. Water volume required,
lengths of 10mm runs,
Existing secondary flow rates
Existing deltaTs
Climate zone of our home etc.
We just discussed the pump size of the existing and what options there were for convenient manual adjustment, approx flow rate display and quiet operation….. But also for the long term the possibility of potential increased flow resistance as a circuit gets older. our installer proposed the Wilo which has been ideal. It doesn’t have FTC6 adjustment but we didn’t have that anyway with the original setup because we had a third party cylinder (not the Mitsubishi pre-plumbed hydrobox)
In use however, I think the hand dial adjustment of the Wilo is perhaps more exacting at targeting a given flow rate.
NEW PUMP in situ.
Also showing the bypass of the secondary pump location.
This post was modified 5 months ago 3 times by SUNandAIR
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