Central Heating comes on when only Hot water is on

P1Fanatic

QrizB said:

OK, I think I know of a way to stop the radiators getting warm but it's going to require a little bit of DIY work. (I had a similar problem with my 3-way valve a few years ago, but mine's a different model - I'm hoping they all work in a similar way.)

• The actuator housing is attached to the valve body by two screws. Remove them.
• Underneath the actuator you'll see the valve spindle. It has a flat on it. Place a small spanner on that flat (or, if you're very careful, a pair of pliers) and gently turn the valve to shut off flow to the radiators.

Don't do any of this if you aren't comfortable.

Thanks for that but not something I am comfortable messing around with. Currently trying to get BG to come out earlier as have a Homecare policy with them.

molerat

Moving the lever left and right a few times sometimes gets it going again

P1Fanatic

oldagetraveller1 said:

This is exactly what was happening to my system in September.

Same Danfoss three way valve and actuator.

It was the actuator that was stuck and not quite at the end of it's travel for hot water only. The manual lever position indicated that.

BG changed it after determining the actual valve wasn't sticking/stuck.

That particular motor unit had only lasted 4 years.

Where was the lever positioned in your case? Mine is at the top (Auto) position where it has always been.

I went back through my paperwork and it was March 2020 it was replaced (so the new one is 2.5 yrs old) before by SSE (had a boiler / heating policy with them back then). What I hadn't remembered is that also in that case they had done a Boiler Service a week prior to us noticing the issue. Very strange.

nadsat

These valves have two parts - the motorised head and the actual value. If the value can be turned OK with the head off then that's OK and it's a fairly simple matter to change the motorised head as long as you match the wiring. 

molerat

When I had those horrible things I kept a spare motor head in the cupboard, classed as consumables !

Mister_G

At least the Honeywell ones last 10 years!

jimjames

oldagetraveller1 said:

BG changed it after determining the actual valve wasn't sticking/stuck.

That particular motor unit had only lasted 4 years.

My Danfoss has failed at a similar age, they really don't seem to be very robust. I suppose it depends if it's cheaper to replace or to keep heating running all through the summer at some point in the day so the motor is less likely to fail. Fortunately the motor can be replace separately and isn't massively expensive.

Mister_G

The problem with the Honeywell one is that the motor is continuously in the stalled condition.  It only uses a few watts but is powered all of the time.

nadsat

Mister_G said:

The problem with the Honeywell one is that the motor is continuously in the stalled condition.  It only uses a few watts but is powered all of the time.

Surely the power is off when it returns to closed by its spring. It only uses 6W under power. I've just had a second Honeywell motor fail after just 2 years -  the first lasted 15 years.  It's a 2 port valve on the heating circuit. Also on the system is a Danfoss 2-port for the hot water, which also failed but the second one is fine. I have also replaced the valve bodies for both as they can seize up. 

Nebulous2

We bought our previous house new in the early 90s. Our heating had two motorised valves, one in the airing cupboard and one under the floor.

Unfortunately the only access under the floor was a hatch at the front door and the valve was close to the rear wall. To replace it required crawling from the front of the house to the rear with a very limited gap between the joists and the ground. 

The valve was replaced 3 times in nearly 30 years, twice a plumber sent an apprentice down, and the third time BG called a small thin guy to come and do it for them.