Radiators stopped getting hot - everything appears to be working.

[Johntheo5]

Thanks, so, UPS3 is P1, Wilo is P2, which of the other UPSs is P3?.
You mentioned a flow meter reading of 0.1 to 0.3M3/hr, is this a stand alone meter?, the Wilo also I think now shows a flowrate as well as the power? what are these readings both with by pass open and circulating normally through the system and its mode and setting?
if a separate flowmeter what is this reading?

 

[PolkadotFish]

Thanks, so, UPS3 is P1, Wilo is P2, which of the other UPSs is P3?.

UPS3 25-55 180

You mentioned a flow meter reading of 0.1 to 0.3M3/hr, is this a stand alone meter?

Yes, originally the system required metering for RHI payments. It has an ultrasonic measurement system that is accurate to several decimal places.

, the Wilo also I think now shows a flowrate as well as the power? what are these readings both with by pass open and circulating normally through the system and its mode and setting?
if a separate flowmeter what is this reading?

The Wilo and the ultrasonic flow meter largely, but not perfectly, agree. E.g. the ultrasonic might display 0.1273 but the Wilo will display 0.0

Obviously the flow rate and power usage are affected by the mode. I don't currently know which is the best mode, as none of them have fixed the problem.

Which mode would you like me to test on?

 

[Johntheo5]

You said above that P3 is a UPS3 25 55 180, do you mean a UPS 25 55 180?
If so can you run on bypass mode with P1 off?, run P3 on full speed. The Wilo, if like my 6M yonos pico can also be run in PP and CP modes and the head can be incrementally changed in 0.1M steps, if yours is the same, change to CP mode and set it to whatever gives the greatest flow and power, note these.

 

[PolkadotFish]

You said above that P3 is a UPS3 25 55 180, do you mean a UPS 25 55 180?

Yup, sorry.

If so can you run on bypass mode with P1 off?, run P3 on full speed. The Wilo, if like my 6M yonos pico can also be run in PP and CP modes and the head can be incrementally changed in 0.1M steps, if yours is the same, change to CP mode and set it to whatever gives the greatest flow and power, note these.

The pump doesn't call them PP or CP. I presume C(1 - 3) are the CP modes. But there's no head adjustment. The other two modes offer head adjustment. I set it at the maximum: 7.5 m

C3 mode: 43 - 44w 0.0 - 0.1m³/h
Ultrasonic: 0.168329 - 0.176668 m³/h

Underfloor heating mode (fully clockwise): 41 - 44w 0.0 - 0.1m³/h
Ultrasonic: 0.168328 - 0.176661 m³/h

Radiator mode (fully anti-clockwise): 17 - 21w 0.0 - 0.1m³/h
Ultrasonic: 0.135485 - 0.168308 m³/h

NB. Once it had been running for a while, changing modes suddenly sounded bubbly. I'm guessing I'm getting cavitation?

 

[Johntheo5]

Yes. The CP/UFH mode is clockwise to the right of C3, so very slowly turn it clockwise past C3, it will start at a very low setting with the selected head flashing for a few seconds each time you stop, so try this, it will probably start at 0.5M, you are trying to match the two pumps different characterestics withot cavitation.
C1,C2&C3 are the CC modes on the Wilo.

 

[PolkadotFish]

Ok. I see what you're trying to do.
How will I know when they mesh?

Any cavitation is quiet enough that it's not obvious until I suddenly change speed or modes.

Can I work out a ball park head to aim for from the curves?

I'm confused because the P3 curves show a maximum head of 4.5m, which is less than the actual head, let alone friction losses over 70/140m.
But there's the second pump, however, I don't understand how to calculate pumps in series.

 

[Johntheo5]

If you look at cc3 on the UPS 25 55 it has a no flow head of 4.5M and and 3.5M at say 1.5m3/hr so you are looking at that sort of range on the WILO, if the flowrate doesnt increase when you are slowly increasing this wilo head then you either have a blockage somewhere or one of the pumps, probably the UPS, is knackered IMO.

If both pumps are Developing 4.5M each then the total head is 9.0M, pumps in series.

 

[PolkadotFish]

If I were to replace the UPS 25 55, would it make sense to make P2 & P3 the same model of pump?

 

[Johntheo5]

Theoreticall, yes, but because you can incrementally increase the WILO head IN CP mode then I cant really see why that wouldnt work reasonably well.
What was the maxumum flowrate you got on bypass mode when doing this?.

If you are handy, I would just remove the UPS, P3 and install a spool piece, a bit of pipe in its place and just run the WILO on bypass, you should still then get maybe 0.6/0.7m3/hr, at least this should prove something, if the flow is still only 0.1/0.3m3/hr then definitely a restriction somewhere IMO.

 

[PolkadotFish]

I can't get the Wilo to do anything other than fluctuate between 0.0 and 0.1, wherever I set it.

If it's a blockage somewhere, how would I identify that?

If the UPS 25 55 is knackered, why didn't it work when I put the new Wilo in the P3 position?
Maybe the P2 pump is also knackered? Or should the more powerful Wilo work anyway?

In terms of getting the pumps to match flow rates, assuming we can fix the current problem, shouldn't P2 & P3 also match flow rates with P1, because they're all in series (once the bypass has closed).

Before the system failed, I've been looking into getting smart TRVs to try to improve efficiency in the house, but won't all the pumps will need to be able to simultaneously adjust their flow to match demand?

 

[Johntheo5]

Again, yes, but should still work in a fashion, they did, didn't they, but try and establish if you have a restriction first, I would definitely try that piece of pipe first, if a 7.5M pump cant pump more than 0.1/0.2m3/hr through 140M of 28mm pipe then something else amiss??

Its a open vented system?, is the F&E cistern full of water and no blockage in the cold feed?

 

[PolkadotFish]

Yup, I'll try the pipe.
.
Will it make any difference if the Wilo is at the top of bottom? I'd rather put it at the bottom, P3 position, and "remove" P2.

I could, as a temporary experiment, try putting P1 in the P2 position?

I'll try it over the weekend and report back.

Thanks for your help and suggestions so far.

 

[Johntheo5]

I would just try that spool piece first, you can allways change the position of the Wilo later if required.
What is the elevation of the F&E cistern above where its teed into the system and is the vent just next to it or is the store just vented?
Are you happy that the cold feed is unrestricted and finally!,
What was the flow rate when the system was working properly?

 

[PolkadotFish]

I would just try that spool piece first, you can allways change the position of the Wilo later if required.

Good plan.

What is the elevation of the F&E cistern above where its teed into the system and is the vent just next to it or is the store just vented?

Approx 2m above. There's a vent on the return just before P1 and on the hot water tank.
The heat store is not vented.

Are you happy that the cold feed is unrestricted

The property as a whole has low water pressure. But the supply from the F&E tank is unrestricted.

What was the flow rate when the system was working properly?

I don't know.
The system has always been under-powered for the house - we have to keep the thermostat low and top up the biomass boiler every 1½ hours during cold weather. But it worked - The hot water and radiators would get hot; I had no need to query the flow rate.
The installers went bust, so I can't go back to them for info or help.

I'll update when I've tried your idea with the pump.
In the meantime, any suggestions on how to identify/locate a restriction in the system?

 

[Johntheo5]

Good plan.

Approx 2m above. There's a vent on the return just before P1 and on the hot water tank.
The heat store is not vented.

Assuming the heat store is "vented" then its a bit surprising that there isnt a vent of some sort (even manual) from the top of the store, you could fit a vent ( AAV but with a isolating valve to enable cleaning) on the flow pipe where it exits the store because any trapped air can cause little or no circulation.
Do you get any air from the rads when you vent them even with LPG boiler on?.
Can you post a photo of the details on the heat store labels.

The property as a whole has low water pressure. But the supply from the F&E tank is unrestricted.

By unrestricted I mean that there is no blockage in this pipe, this can be quite common where its teed into the system, you could drain off say 5L or so and see if the F&E cistern starts refilling rapidly which will prove it clear.
Is it teed into the flow or the return piping?.

I don't know.
The system has always been under-powered for the house - we have to keep the thermostat low and top up the biomass boiler every 1½ hours during cold weather. But it worked - The hot water and radiators would get hot; I had no need to query the flow rate.
The installers went bust, so I can't go back to them for info or help.

I'll update when I've tried your idea with the pump.
In the meantime, any suggestions on how to identify/locate a restriction in the system?

If the Wilo set to C3 at 7.9M still only results in very poor circulation on bypass then it logicall has to be a restriction somewhere or air somewhere, the condition of the F&E cistern if you look into it will give a good indication of a clean/dirty system.