Help understanding system

barry181091

Hi all,

Trying to help a relative with their heating system. Its a two storey dormer with 14 radiators. Two zones, downstairs and upstairs (Downstairs includes hot cylinder as upstairs zone valve is after cylinder). Old internal firebird broke down last year and a new external Grant Vortex 50/90 was put in.

The issue is the upstairs radiators don't really get hot while downstairs gets red hot. Apparently it has been like this since the house was built in 2004, so old boiler and new.

A) I have bled all the radiators and there was no air really.

B) I turned off the downstairs zone and increased Grundfoss pump to 3 and the radiators heated in ten minutes. I did not have time to figure out which had the effect here.

All I can think is either a severe balancing issue or simply that the pump is turned down too low. Does anything look amiss in the photos below?

From what I gather, its an unvented system. The hot pressure around the house isn't particularly great so I don't understand the point of this instead of a standard vented system? I believe there is a tank in the attic.

This is directly in the house from the boiler. Flow/return, Grundfoss pump (On 2) and zone valve to downstairs zone.

This is the hotpress system. Flow/return (I think!), pressure gauge (At 0.7/8 bar), expansion vessel and pump that doesn't work.

What does the tap beside the pressure gauge do?

10-10-20

What does the tap beside the pressure gauge do?

That's your refilling valve. You look to be at 1bar, so that might be ok but depends on the system, but the red arrow is set at 2bar, so perhaps there's low pressure. Open that tap and let it come to equilibrium - you might hear a flow initially and the black needle will rise, and if you do it's a good indication that there was a slight under-pressure.

B) I turned off the downstairs zone and increased Grundfoss pump to 3 and the radiators heated in ten minutes. I did not have time to figure out which had the effect here.

I'd be interested to know what happened if you turned off the DS and then left the US rads on without adjusting the pump - I presume they still fail to get up to temperature quickly?

I think from looking at the photos that the cylinder is in the loop whether DS or US is on, could that be correct? Then I'd suggest that the balance issue could then be at the cylinder itself, and maybe the DS rads are also too open.

I'd close off that red valve at the bottom of the cylinder and count the turns to closure. Then open it and count again. Then close it off so that it's about 20% to 25% open. Then fire-up the boiler and see what happens upstairs & report back.

barry181091

https://www.boards.ie/discussion/comment/119990233#Comment_119990233

I will try not adjusting the pump and just turning off the downstairs zone.

The cylinder is indeed in the loops whether DS or US is enabled. I will try that about the closing of the valve! I'm still stumped as to the benefit of this unvented system if not connected to the mains 😕

Another oddity of the system I have noticed is that there is a standard time clock "Constant on/off/timed" to turn on the boiler and then a thermostat downstairs and upstairs. From my testing, all the thermostats control is the zone valves and NOT the boiler. This seems crazy to me so the boiler can be happily running away, zones up to temp and closed but all the while still burning oil. Is this normal?

wiz569

The zone valves in turn should control the boiler.

10-10-20

Another oddity of the system I have noticed is that there is a standard time clock "Constant on/off/timed" to turn on the boiler and then a thermostat downstairs and upstairs. From my testing, all the thermostats control is the zone valves and NOT the boiler. This seems crazy to me so the boiler can be happily running away, zones up to temp and closed but all the while still burning oil. Is this normal?

No, that's normal. The valves actually call for heat from the boiler when the thermostats close (low temperature) - there should be two wires running back to the boiler from each valve which make contact when the valve is fully open.

https://flameport.com/electric/central_heating/heating_wiring_S_plan.cs4

Look at the orange wire coming off the valves in this diagram above, it goes back to SL (switched live) on the boiler.

barry181091

https://www.boards.ie/discussion/comment/119991108#Comment_119991108

Thanks, that looks like I great site. I will have to look at the wiring to confirm this. I know I did turn off both thermostats, so down to 10c, and the boiler kept running. Presuming correct wiring, would there ever be a large delay from thermostats turning off to boiler turning off? One other thing I was thinking that could be affecting things is the frost stat in the boiler itself.

EDIT: Perhaps a stat on the cylinder is calling for heat from the boiler if not up to temp?

For reference here is one of the two thermostats.

This is the timeclock controlling the boiler. They both appear pretty standard.

10-10-20

So basically, those Myson valves have an LED on them and that goes out when the valve is closed (not calling for heat). The respective valve should close as the stat is turned off.

Just be careful - the wiring through the valves and out to the the stats is 230v.

barry181091

https://www.boards.ie/discussion/comment/119991785#Comment_119991785

Yep, when the thermostat turns on the respective valve lights up. What I am unsure about is the wiring from that valve to the boiler, if any. Many thanks, I will update later!

barry181091

Ok so a quick update. I turned down the hot cylinder return as above and that seems to really have improved the radiator heating upstairs. So that is a positive.

Next I examined the wiring of the boiler, main timer and zone valve junction box. From what I can see, I think the only thing connected and switching to the boiler is the main timer. When I turn the timer off it immediately turns the boiler off, but you can see the light on the boiler so its obviously switching it and not just cutting power.

This is the switch for the DS zone valve, controlled by the downstairs thermostat via grey wire I think. The orange and grey wires are just tied together I think. According to the data sheet this is connected to an aux switch in the walve.

Finally the mess of wires behind the timer.

Looking at the grant vortex manual, perhaps there is a wiring center somewhere in the house but I doubt it.

10-10-20

Yeah, that's a bit of a half-job. Good news is: you found the wiring "center". ;)

If it was me, I'd remove the zone switches and fit a two zone timer and correct the wiring from the valves so that it follows the S-plan diagram. That way you get a boost and timer function for both zones.

barry181091

https://www.boards.ie/discussion/comment/119994061#Comment_119994061

It's just a bit ridiculous. 3k for the new boiler 12 months ago along with the new stats and controls and then they end up not being wired in correctly. I think you are right about the upgrade. Ideally another zone valve would be added for the hot water too. No need really for the hot water when there is an electric shower in the house but the lack of control over it is just a bit silly.

I wonder how much extra oil this currently "system" uses if both room stats are off and reached temp but the boiler just keeps going.