Radiators stopped getting hot - everything appears to be working.

[PolkadotFish]

Presume its installed the right way round!,

Yup.
Points the right way. System worked for 10+ years.

It may be required to stop the LPG boiler (when on) pumping water into the top of the store

The system didn't have the LPG boiler when they commissioned the biomass boiler.

and back through the biomass boiler and even though unlikely up through the biomass boiler vent, so have a good look before (if) removing it.

The main vent is the F&E in the house. There's a bottle valve on the heat store tank.

My guess is that it relies on the spring pressure to be strong enough to counter thermal/gravity cycling of the hot water between the heat store and house? The pumped pressure (should) easily open it.

But I'm not sure how much of a gravity effect there would be given that both the flow and return go underground below the level of the heat store?

if its a swing check valve then I would be inclined to just renew it as these have little or no head loss.

I don't think it's that.
But it sounds interesting. I wonder if I should put one of those in instead?

 

[Johntheo5]

A swing check isn't designed to be a antigravity valve but I suppose if they were inclined a bit they would work, how far opened is the spring loaded one in the photo,?

 

[PolkadotFish]

A swing check isn't designed to be a antigravity valve but I suppose if they were inclined a bit they would work, how far opened is the spring loaded one in the photo,?

There's some "gritty" play, but it jams easily.
I don't know if it was open, closed or somewhere in between in either of the pictures, sorry.

Should I make a new post to ask people with gravity experience if I need to replace it?

 

[Johntheo5]

Your system worked for 10 years with that installed NRV so why not just replace it?, there might be something in the spec sheets re the dP required to open. Of course you could decide not to install it as the flow and return are downwards from the heat store, I have a heatpac oil fired boiler where the flow pipe turns downwards before going upwards and it certainly doesn't gravity circulate after the boiler cuts out.

 

[Johntheo5]

I seem to remember that it took 2.5M to open a new NRV that I tested years ago with a head of water, except you can get one with a very weak spring/low dP then you might be better off with just a swing check or none?.

 

[PolkadotFish]

My local plumbers merchant didn't have a 28mm NRV. So that decided it for me - I'll skip it for now and monitor for any issues.

Just got everything back together and tested the flow:

1.0 m³/h with both pumps running (83w & 46w).
0.8 m³/h with just the Wilo running (57w).

The NRV was definitely the issue!

This has been a slow, expensive and frustrating repair. I wish there were clear lessons learned to help me (or anyone else) in a similar situation, but I'm not sure what they are.

Thanks again @Johntheo5 for your help and everyone else who made suggestions.

 

[Johntheo5]

Where did you get/derive the 83W and for which pump is this?
What mode were you running the Wilo on?.

There is probably a fairly high dP through the stopped Grundfos, you could leave it in place and consider installing a bypass around it with a gate valve, you may end up with the same 1.0m3/hr then with the Wilo alone.

What is the ~ cost of the biomass per kwh?.

 

[PolkadotFish]

Where did you get/derive the 83W and for which pump is this?
What mode were you running the Wilo on?.

P3 UPS 25-55

It's on speed III - It says that's 85 (oops, not 83) on the data plate.

I'm sure that's not the actual value, but it's indicative of how much more efficient the Wilo is.

There is probably a fairly high dP through the stopped Grundfos, you could leave it in place and consider installing a bypass around it with a gate valve, you may end up with the same 1.0m3/hr then with the Wilo alone.

I'm surprised it would make such a difference.
The original heating system in the house was a solid fuel stove in the kitchen with an S plan.
But everything was in 28mm because we used to have so many power cuts, the system was designed to work as a gravity system as well.
I'd have thought that if a stationary pump had a fairly high dp, it would significantly restrict the thermal flow?

What is the ~ cost of the biomass per kwh?.

Blimey! That's a question and 7 Half's.

We are extremely lucky to have access to free/cheap timber.
Ignoring the thousands of pounds spent on kit (chainsaw, safety clothes, fuel etc) it costs us about 150 people hours preparing the wood for a year and about an hour a day for the half a year the system is running.

We burn significantly more wood than should be needed. But the system was undersized by the dodgy installers.

 

[Johntheo5]

That's OK, I grew up a stones throw from the sea and every March a continuous East wind used expose a vein of turf that ran the full lenght of the beach which we used cut with shovels and save + dry out for months on end. It kept our Stanley N07 stove & a open fire running throughout the winter, hundreds of "man" hours but great fun.

We are extremely lucky to have access to free/cheap timber.
Ignoring the thousands of pounds spent on kit (chainsaw, safety clothes, fuel etc) it costs us about 150 people hours preparing the wood for a year and about an hour a day for the half a year the system is running.

We burn significantly more wood than should be needed. But the system was undersized by the dodgy installers.

Something not adding up here re the Wilo.
The Wilo IF running on CC3 will only flow 0.3m3/hr at a head of 7.4M and 46W
Can you confirm that 46W number.

Just got everything back together and tested the flow:

1.0 m³/h with both pumps running (83w & 46w).

That adds up with the Wilo on CC3.

0.8 m³/h with just the Wilo running (57w).

 

[PolkadotFish]

That's OK, I grew up a stones throw from the sea and every March a continuous East wind used expose a vein of turf that ran the full lenght of the beach which we used cut with shovels and save + dry out for months on end. It kept our Stanley N07 stove & a open fire running throughout the winter, hundreds of "man" hours but great fun.

Our old system was a Stanley. I kind of miss it. The kitchen is a lot less dusty though.

Doing the wood processing used to be fun.
It's become increasingly frustrating as we've realised the inefficiencies in our system.

Spending an hour a day keeping the furnace topped up is 7 hours a week - a working day!

Something not adding up here re the Wilo.
The Wilo IF running on CC3 will only flow 0.3m3/hr at a head of 7.4M and 46W
Can you confirm that 46W number.


That adds up with the Wilo on CC3.

I was adjusting the Wilo on "radiator" mode to find the maximum flow (trying to sync it with P3?).
I didn't spend very long - it was just a quick test at midnight when I'd got everything back together.

The heat store is hot now - I'm about to get it running and will try to find the best setting for the Wilo.

Any advice welcome!

 

[PolkadotFish]

The heat store is up to 92°c

The sonic flow meter is reading 0.000000 m³/h

That meter is on the return run. Those pipes feel cold.
The flow side pipes feel warm, even in the house. So there is some movement but not circulation. I presume this is the hot water expanding.

So far I think the NRV was superfluous.

Now to call for heat and see what happens...

 

[Johntheo5]

I was adjusting the Wilo on "radiator" mode to find the maximum flow (trying to sync it with P3?).
I didn't spend very long - it was just a quick test at midnight when I'd got everything back together.

The heat store is hot now - I'm about to get it running and will try to find the best setting for the Wilo.

Any advice welcome!

Radiator (PP) mode is useless with this set up, change to CP (UFH) constant pressure mode and start at a low setting and keep increasing it to get max flow/watts, you will probably find that it goes right up maybe as far as 7/7.5M.

 

[PolkadotFish]

Radiator (PP) mode is useless with this set up, change to CP (UFH) constant pressure mode and start at a low setting and keep increasing it to get max flow/watts, you will probably find that it goes right up maybe as far as 7/7.5M.

Both the radiator and underfloor heating modes go up to 7.5m

Yesterday the radiator mode seemed to give a faster flow.
I'll experiment with both.

 

[Johntheo5]

Assuming both pumps on and if the Grundfos stops while in PP mode then the pump will ramp down IMO whereas in CP or CC mode the pump will still try and deliver its max setting.
Up to 7.5M head (with both pump running) I wouldn't expect to see any great difference between CP & PP modes, it would be interesting to see what would happen if you set it to say 7.5M in PP mode and then stop the Grundfos and see if the flow falls lower than stopping it while on CP mode with the same 7.5M setting.
If you find in CP (or PP) mode (both pumps running) that you are getting ~ 1.0m3/hr at 7.5M then CC3 might be the most appropriate setting.

 

[Johntheo5]

Looking at both pump curves again, I think CC3 would probably be the best setting, the Wilo alone was flowing 0.8m3/hr at 7.5M (CC3), it will flow 1.0m3/hr at 7.4M, the Grundfos will flow 1.0m3/hr at 4.4M to give a combined head of (4.4+7.4), 11.8M. Expected flow rate, 0.8*sqroot(11.8/7.5), 1.0m3/hr, exactly the same as the actual flow.