I have a pumped CH/Gravity Domestic HW utilising a Primatic cylinder .
I replaced the gaskets on the Boiler heat exchanger and also replaced
the cylinder connnectors as they were the wrong type and prone to
leaking .
Previously the DHW used to get very hot so I have a Danfoss-Randall
cylinder stat which is a valve with a sensor,similar looking to a TRV
the valve sitting in the flow or return domestic pipe and the sensor
is strapped to the cylinder .
I've never been able to get my head round how this sytem works .How
does the water in the CH part get topped up as it must need due to the
water dissipating away . I presume there must be some mechanism in the
coil part that allows this while not allowing the CH and DHW to mix .
If this cylinder stat closes when the water reaches the set
temperature does the flow within the gravity part just stop
completely until the temperature reduces and the valve opens again
....I don't know how long this would be ?
Stuart

"Stuart" wrote in message
news
I have a pumped CH/Gravity Domestic HW utilising a Primatic cylinder .
I replaced the gaskets on the Boiler heat exchanger and also replaced
the cylinder connnectors as they were the wrong type and prone to
leaking .
Previously the DHW used to get very hot so I have a Danfoss-Randall
cylinder stat which is a valve with a sensor,similar looking to a TRV
the valve sitting in the flow or return domestic pipe and the sensor
is strapped to the cylinder .
I've never been able to get my head round how this sytem works .How
does the water in the CH part get topped up as it must need due to the
water dissipating away . I presume there must be some mechanism in the
coil part that allows this while not allowing the CH and DHW to mix .
If this cylinder stat closes when the water reaches the set
temperature does the flow within the gravity part just stop
completely until the temperature reduces and the valve opens again
...I don't know how long this would be ?
Stuart

The flow and return pipes to the primatic cylinder must have "no" valves on
them of any sort. "Take the valve off ASAP". The cylinder is also the F&E
tank and must have a clear way to the boiler in both flow and return.

Have a normal electric cylinder stat to keep the boiler from cycling when
DHW only is on. A boiler interlock. When the CH is on you get DHW whether
you like it or not and the cylinder temp is determined by the boiler stat
which may be too hot for DHW. To have a set DHW temp also have a blending
valve on the DHW draw-off.

So, you need a low pressure DHW blending valve and a normal cylinder stat.



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On Sun, 20 Mar 2005 17:56:36 -0000, "Doctor Evil"
wrote:


"Stuart" wrote in message
news
I have a pumped CH/Gravity Domestic HW utilising a Primatic cylinder .
I replaced the gaskets on the Boiler heat exchanger and also replaced
the cylinder connnectors as they were the wrong type and prone to
leaking .
Previously the DHW used to get very hot so I have a Danfoss-Randall
cylinder stat which is a valve with a sensor,similar looking to a TRV
the valve sitting in the flow or return domestic pipe and the sensor
is strapped to the cylinder .
I've never been able to get my head round how this sytem works .How
does the water in the CH part get topped up as it must need due to the
water dissipating away . I presume there must be some mechanism in the
coil part that allows this while not allowing the CH and DHW to mix .
If this cylinder stat closes when the water reaches the set
temperature does the flow within the gravity part just stop
completely until the temperature reduces and the valve opens again
...I don't know how long this would be ?
Stuart

The flow and return pipes to the primatic cylinder must have "no" valves on
them of any sort. "Take the valve off ASAP". The cylinder is also the F&E
tank and must have a clear way to the boiler in both flow and return.

Have a normal electric cylinder stat to keep the boiler from cycling when
DHW only is on. A boiler interlock. When the CH is on you get DHW whether
you like it or not and the cylinder temp is determined by the boiler stat
which may be too hot for DHW. To have a set DHW temp also have a blending
valve on the DHW draw-off.

So, you need a low pressure DHW blending valve and a normal cylinder stat.



So what sort of set up is displayed here then ?.
http://www.invensyscontrolseurope.co...%20leaflet.pdf
The gravity valve with the two connections for gravity systems not the
three port one ..
Stuart
ps..The valve isnt fitted yet anyway so no need to worry on that score
...



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"Stuart" wrote in message
...
On Sun, 20 Mar 2005 17:56:36 -0000, "Doctor Evil"
wrote:


"Stuart" wrote in message
news
I have a pumped CH/Gravity Domestic HW utilising a Primatic cylinder .
I replaced the gaskets on the Boiler heat exchanger and also replaced
the cylinder connnectors as they were the wrong type and prone to
leaking .
Previously the DHW used to get very hot so I have a Danfoss-Randall
cylinder stat which is a valve with a sensor,similar looking to a TRV
the valve sitting in the flow or return domestic pipe and the sensor
is strapped to the cylinder .
I've never been able to get my head round how this sytem works .How
does the water in the CH part get topped up as it must need due to the
water dissipating away . I presume there must be some mechanism in the
coil part that allows this while not allowing the CH and DHW to mix .
If this cylinder stat closes when the water reaches the set
temperature does the flow within the gravity part just stop
completely until the temperature reduces and the valve opens again
...I don't know how long this would be ?
Stuart

The flow and return pipes to the primatic cylinder must have "no" valves
on
them of any sort. "Take the valve off ASAP". The cylinder is also the
F&E
tank and must have a clear way to the boiler in both flow and return.

Have a normal electric cylinder stat to keep the boiler from cycling when
DHW only is on. A boiler interlock. When the CH is on you get DHW
whether
you like it or not and the cylinder temp is determined by the boiler stat
which may be too hot for DHW. To have a set DHW temp also have a
blending
valve on the DHW draw-off.

So, you need a low pressure DHW blending valve and a normal cylinder
stat.

So what sort of set up is displayed here then ?.

http://www.invensyscontrolseurope.co...bdb024142f72/D
20_6%20Tapstat%20leaflet.pdf

This is not a primatic setup. NO VALVE, of any sort should be on the
primary flow and return of a primatic cylinder. Take the valve back, and
get a normal cylinder stat and DHW blending valve.



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