[Engineer-Ben]

Hi
I am currently very confused with my central heating system. I have noticed that when I switch on the "Hot Water" only, on the control unit, the actuator switches over correctly to heat the cylinder hot water tank. When I switch on "Central Heating" only, on the control unit, the actuator switches over correctly to heat the radiators. How ever when they are both on, in either order the radiators stay heated by there is no heat going to the hot water cylinder. From what I can see and work out is everything seems correct and working, but could it be a wrong actuator, or faulty actuator.

I have drawn up the wiring diagram we had installed and from what I can work out it seems all OK (not being an electrical bod!), and it has worked perfectly well up until I noticed the problem. Now the Actuator was replaced 2 1/2 years ago, and may possibly be the wrong one, and we had not noticed any problems because the imersion heater could have been supplying all the hot water! Which is what originally led me to finding this fault, and hence I have replaced the imersion heater and theromstat - Confussed!

Actuator : Danfoss Randall HSA3D
Valve : Has on it "Valve type EDT 2702
605-5-702
Use with Actuator type SD

Thanks
Ben

[hvac1000]

On many systems the domestic hot water takes a override position in the system. (that means it will run first until satisfied and then switch over to heat the house). If you feel the actuator was replaced by the incorrect one I suggest you compare the original plans/drawings with the model number of the new one to see if it is different. Also if your system has a system wide controller you may need to address setting issues with it. Go to the Danfoss site and check for there proper actuator for your system. The part numbers or sub list should have been compared before it was installed. Different actuators are used for different purposes depending upon system requirements/plans.

There is no one on this board that can tell you that info since you are at the location with all the plans/drawings/equipment. Many if not all of these systems are complex in nature and usually relay on a field diagnosis with various test equipment to accurately find the problem. I can say that I believe you will be looking at the auto switch over control for your system. What that control is I have no idea. If you provide a complete list of controlling equipment I will try to look up the install/service manual for that controller. I will need model and serial numbers since they make running changes and keep the same model number.

The system in my home is a very complex system with all the electronic valves and with computer controlled three system heat zones plus a domestic storage tank with a priority control module all its own. I can understand your statement of being (confused). Unless you actually work on this kind of stuff every day it is hard to keep up with.

[Engineer-Ben]

hvac1000
Many thanks for your help and advice.

I have since posting question done a lot of investigation and have found the Actuator body was incorrect for the valve I had. I have since checked over the wiring layout and traced all feeds etc and gained a good understanding of the system etc. I have since replaced the actuator after long talks with our local plumbing shop (who has been absolutley fantastic with his knowledge and free advice), and upon taking the actuator apart found that it was incorrect and the emersion heater was doing all the work. I now have a good knowledge of my system and the detailed workings of the actuators. Many thanks for help

[therinnaiguy]

Reenigne's don't you just love their money!