I currently have a system with pumped heating, gravity HW. Heating has TRV on all rads except bathroom (bypass). There are no room therms or cylinder therms.
I intend to add a tank therm and zone valve to give the ability to heat CH only and avoid overheating the tank.
Should the 2 port valve be fitted near the tank or the boiler - and should it be on the flow or return?
Is there such a thing as a RF tank thermostat to prevent the need for a long wiring run?
thanks
It doesn't matter that much - whichever is the easier. You need to make sure that the boiler will accept not having the gravity circuit and will need to arrange that the boiler switched live is turned off when neither the HW cylinder or the CH demand heat. THis depends on the wiring and control scheme, but look at Honeywell's site for the different wiring plans, S, Y and W. You may also need a bypass for the boiler.
Yes. Danfoss Randall make one that matches their room thermostat range.
.andy
To email, substitute .nospam with .gl
The problem is getting the wiring from the downstair utility loft - to the main house loft. Using a RF tank therm would be easier to fit the valve downstairs near the boiler if thats ok.
The boiler (potterton netaheat) has a switch inside for gravity or pumped - even with the valve the system will still be gravity.
The manual show the curent layout (gravity hw) and shows an "optional valve" so the boiler should accept it ok.
Will have a look on the honeywell site for the diagrams.
You may also need a bypass for the boiler.
Currently the bathroom rad is always on - acting as a bypass. To sort this out if I add a TRV to this, and then plumb in a hydralic bypass across the flow and return pipes to the boiler have I done the right thing?
Will check it out. Thanks
Thanks for the help
On the few C plans I have done (if this is a C plan), I can remember that you need to be careful that the valve does not cut off the overflow to the header tank and so is usually on the return side of the hot water tank.
Adam
Sorry I misread the detail of your post. Are you planning to only fit a zone valve and thermostat and not convert to fully pumped?
If so, this is a C-plan arrangement, and as Adam says, you must be careful not to position the zone valve such that it would interrupt the path to the vent.
Notwithstanding siting to avoid blocking the vent path, it shouldn't matter.
Yes it should so scrub the comment about Y,S and W plan and look at C which is much easier anyway.
It depends on what the boiler manufacturer's manual says on that - i.e. whether a bypass is needed if you convert to C plan.
.andy
To email, substitute .nospam with .gl
The intention was just to add a 2 zone valve and NOT convert to fully pumped on the basis that water heat up is not a problem - and fitting is simplified.
Right - So need to fit value on pipe that does not have vent fitted!!! Should be ok.
Beware that the valve and any pipework changes could affect the natural convection, requiring you to add a pump anyway.
Also, it shouldn't block the supply of fresh water to the boiler. Safety requires the vent to be clear to allow steam to escape and the supply to be clear to allow water to quench the boiler. Although this only applies if there is no automatic overheat cutout, this is very likely to be the case on an old gravity circulated boiler).
Christian.
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