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Discuss Danfoss HS3 3 Port Valve Question in the Central Heating Forum area at PlumbersForums.net

Tom163

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Hi guys,

Two questions I am hoping you can help me with.

1) My Danfoss HS3 motorised actuator has a rest position of B hot water as I found out is normal. Once I put the central heating on the valve winds fully to A again as expected but once the CH has been turned off the valve remains at A and it seems like something is still powering the actuator keeping it there. However it will return to B if it turn the hot water on and then rest there. I thought this was the actuator on its way out so replaced this part only (not the valve yet) but the new actuator does this too.

Is that normal behaviour, staying at position A even with the heating off until HW is called or should it return to B (rest) soon as the heating has gone off?


2) I have a strange problem where sometimes when I put the heating on it also heats the hot water tank up. I am 100% nothing is actually turning the hot water on at the programmer. After Googling there were lots of reports of radiators getting hot when the hot water was on but my problem is the opposite way around. Any advice? I was still thinking dodgy 3 port valve..

My system is a conventional boiler (oil fired Worcester) with water tanks in loft, hot water cylinder in airing cupboard upstairs.

Thanks in advance.
 
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CBW1982

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Hi Tom,

It seems to me your 3 port valve is getting stuck in mid position and then maybe stuck on the heating. Fortunately you can purchase just the actuator without the need for draining down. That is assuming it’s your motor and not sludge. However unless your competent I would enlist a heating engineer who can test and replace as necessary.
 
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Tom163

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Hi CBW,

Sorry I forgot to add to the original post in question 1 that I have changed the Actuator already for a brand new one (same Danfoss HS3) but getting the same behaviour with it staying at position A once the call for heat has finished. I am booked in to get the valve itself changed as I don't dare attempt that myself.
 

CBW1982

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Ah I see. Then I would suggest it’s sludge related or perhaps a wiring issue?
 

Harvest Fields

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Hold on. So let me get this straight? When you have the water on by itself, the motor is in B port. When the heating is on by itself, it is in A port. When they are on together it is in the middle?
 

CBW1982

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Hold on. So let me get this straight? When you have the water on by itself, the motor is in B port. When the heating is on by itself, it is in A port. When they are on together it is in the middle?
I think he’s saying that with the heating on, and no hot water demand, the hot water cylinder is heating up. After heating has been on is in the rest position of port A.
 

SJB060685

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Is this valve with hot water off function? If so then it holds its last position after demand is satisfied, that’s what it does. Correct me if I’m wrong please
 

garygvl

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Three port valves will stay powered up and in the heating position after a demand for heating has ended unless there is a demand for hot water. Most houses finish the day with a heating demand so this is why the valve actuator gets hot and eventually burns out the motor. Most danfoss actuators will show signs of browning on top of the body due to heat from the motor
 

SJB060685

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As above! It’s common for the valve to burn out as it’s commonly got a feed to it, if hot water it’s just spring return and ok but as Gary says if CH was last call then it’s motored over to CH and burns out over time. I always preferred an S plan
 

Harvest Fields

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The above is where I was heading to. So effectively the old one was probably fine. If you still have it, I would put the old one to one side so that you have a spare.
 
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Tom163

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Hi guys,

Thanks everyone for the responses, much appreciated. I still have the old actuator head so will keep that as a spare & my central heating guy is going to look at fitting the 3 port valve body itself in a few days hopefully this will cure the other problem I have.

All the best.
 

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