I have a Santon 210 litre unvented cylinder. I've had water running through the tundish for a while.
Initially, I had a very weak hot water flow to taps and showers. The gauge at the combination valve showed only about 1.2bar pressure. The santon system should be set at 3.5 bar according to the instructions and panel on the cylinder (See below)
TABLE 1: OPERATIONAL SUMMARY
I removed the Santon combo valve cartridge and it was gunged up inside, and the return pressure spring had corroded and was broken in two. So I fitted a new combo valve, and at 3.5 bar, the hot water pressure was now great.
I also had a leak through the tundish going back quite a while. This would be fairly continuous, and normally luke warm. However, when the boiler was fired up to heat the hot water zone, this drip would be more constant, and the water would be hot. It would continue like this until a shower was taken or the hot water taps used for a while. I also would notice when the boiler was running to heat the water, that the cold water pipe running into the bottom of the boiler would actually warm up right up to the combination valve?
Again, on checking, its the 6 bar cold water side PRV that is venting (hot water) , not the cylinder 10 bar TPRV. I replaced the 6 bar PRV.
I then run the hot taps, turned off the water supply and let the pressure fully release. With the taps still on (no water flow of course), I filled the Expansion vessel with air to 3.5 bar to match the cold pressure through the valves to the cylinder.
There is no tundish drip when the boiler is not fired up . However, there is a drip (albeit much reduced now) when the boiler is fired and heating the cylinder water. This again goes away mostly when a tap or shower is run but has not been fully eradicated.
What could the issue be? I have verified that the 10 bar cylinder TPRV is not venting when I get the drip through the tundish (it is functional ok, as Ive tested it). Ive a brand new 6 bar PRV on the cold inlet side, and the expansion vessel is only 3 years old, and not showing any signs of malfunction. Holds the air charge and no water is coming from the Schrader valve.
Could anyone shed any light on where the issue might lie given the info above? All of the equipment seems to be ok, I can't help but think it has something to do with the inlet pressure or Expansion vessel pressure.
The combo valve is set to 3.5 bar. The empty pressure of the expansion tank is at 3.5 bar.
How critical is it to have the two exactly the same? Does it matter if the expansion tank is at 3.6 bar or 3.4 bar? Is it better slightly over or under?
Should I reduce the combo valve to 3 bar, and the expansion tank pressure to 3 bar, even though the Santon instructions advise to charge the expansion vessel to 3.5 bar, and set the combo valve to 3.5 bar?
The thermostat on the cylinder is set to "5" which apparently reflects 70 degrees. Should I try reducing it to "4"?
Both Expansion vessels (the original that came with the cylinder) and the replacement from a few years ago are 19 litre.
I've read in a few places online to allow 10% of the cylinder capacity. In this case 210 litres (so 21 litre exp vessel?)
A few sites I check on recommended a 24 litre vessel for a 210 litre capacity cylinder. Should I look at replacing the vessel to a 24 litre version is it ok to do that and would it maybe give me some extra capacity for expansion when the water is heated?
Lastly, (and its a long shot), I have a leaking mixer tap on the bath. Its been leaking with a slow drip for years. I cannot change it out, because its at the side of the bath and encased in a tiled bath frame. I've tried several replacement ceramic cartridges to no avail, as I think its a manufacturing flaw in the tap. I've read something about back flow from a leaky mixer tap affecting some heating water cylinders. Now the drip from the tap is minimal, maybe a drip every 5 seconds, Could this be an issue here, and should I maybe fit a one way valve on the hot supply pipe?
Many thanks and sorry for the war and peace post!
Initially, I had a very weak hot water flow to taps and showers. The gauge at the combination valve showed only about 1.2bar pressure. The santon system should be set at 3.5 bar according to the instructions and panel on the cylinder (See below)
TABLE 1: OPERATIONAL SUMMARY
Maximum water supply pressure to PRV | 16.0 bar |
Operating pressure of unit | 3.5 bar |
Expansion vessel charge pressure | 3.5 bar |
Expansion valve setting | 6.0 bar |
Nom inal storage capacity of units | (see Section 2 Table 2) |
Max. primary working pressure (Auxillary Coil) | 3.0 bar (indirects only) |
Max. primary working pressure (Solar Coil) | 6 bar |
Opening temperature of T&P Relief Valve | 90degC |
Opening pressure of T&P Relief Valve | 1 bar |
I removed the Santon combo valve cartridge and it was gunged up inside, and the return pressure spring had corroded and was broken in two. So I fitted a new combo valve, and at 3.5 bar, the hot water pressure was now great.
I also had a leak through the tundish going back quite a while. This would be fairly continuous, and normally luke warm. However, when the boiler was fired up to heat the hot water zone, this drip would be more constant, and the water would be hot. It would continue like this until a shower was taken or the hot water taps used for a while. I also would notice when the boiler was running to heat the water, that the cold water pipe running into the bottom of the boiler would actually warm up right up to the combination valve?
Again, on checking, its the 6 bar cold water side PRV that is venting (hot water) , not the cylinder 10 bar TPRV. I replaced the 6 bar PRV.
I then run the hot taps, turned off the water supply and let the pressure fully release. With the taps still on (no water flow of course), I filled the Expansion vessel with air to 3.5 bar to match the cold pressure through the valves to the cylinder.
There is no tundish drip when the boiler is not fired up . However, there is a drip (albeit much reduced now) when the boiler is fired and heating the cylinder water. This again goes away mostly when a tap or shower is run but has not been fully eradicated.
What could the issue be? I have verified that the 10 bar cylinder TPRV is not venting when I get the drip through the tundish (it is functional ok, as Ive tested it). Ive a brand new 6 bar PRV on the cold inlet side, and the expansion vessel is only 3 years old, and not showing any signs of malfunction. Holds the air charge and no water is coming from the Schrader valve.
Could anyone shed any light on where the issue might lie given the info above? All of the equipment seems to be ok, I can't help but think it has something to do with the inlet pressure or Expansion vessel pressure.
The combo valve is set to 3.5 bar. The empty pressure of the expansion tank is at 3.5 bar.
How critical is it to have the two exactly the same? Does it matter if the expansion tank is at 3.6 bar or 3.4 bar? Is it better slightly over or under?
Should I reduce the combo valve to 3 bar, and the expansion tank pressure to 3 bar, even though the Santon instructions advise to charge the expansion vessel to 3.5 bar, and set the combo valve to 3.5 bar?
The thermostat on the cylinder is set to "5" which apparently reflects 70 degrees. Should I try reducing it to "4"?
Both Expansion vessels (the original that came with the cylinder) and the replacement from a few years ago are 19 litre.
I've read in a few places online to allow 10% of the cylinder capacity. In this case 210 litres (so 21 litre exp vessel?)
A few sites I check on recommended a 24 litre vessel for a 210 litre capacity cylinder. Should I look at replacing the vessel to a 24 litre version is it ok to do that and would it maybe give me some extra capacity for expansion when the water is heated?
Lastly, (and its a long shot), I have a leaking mixer tap on the bath. Its been leaking with a slow drip for years. I cannot change it out, because its at the side of the bath and encased in a tiled bath frame. I've tried several replacement ceramic cartridges to no avail, as I think its a manufacturing flaw in the tap. I've read something about back flow from a leaky mixer tap affecting some heating water cylinders. Now the drip from the tap is minimal, maybe a drip every 5 seconds, Could this be an issue here, and should I maybe fit a one way valve on the hot supply pipe?
Many thanks and sorry for the war and peace post!