Upstairs radiators get hot WITHOUT heating being on?

[brookie]

When I select heating on, all rads get hot which is nice. But with heating OFF and hot water ON the upstairs rads get hot. Which component/valve is suspect? It's a gravity fed system with a baxi back boiler downstairs and a hot water tank upstairs in airing cupboard.
By the tank is a Honeywell electronic divertor valve - is this the culprit?
On this valve is a switch which can be set to Auto or Manual. Mine is in the middle Which way should it be set, what do they mean?
Any help would be great. Thanks.

 

[namsag]

If it has only just started doing this the valve is passing and needs changing

 

[gas4you]

I would say you have a 28mm Honeywell 2 port valve, not a diverter valve. As you say this is fitted next to the hw cylinder I cannot understand how, if this failed, it would let the rads heat up.

As you have a gravity BBU system I am going to plump for the fact that it has always done it. This is normal gravity circulation as the hw rises to the upstairs rads.

There is a slight chance that you have an anti gravity valve fitted to the ch flow and this has stuck open. Unusual though as these normally stick shut.

 

[brookie]

One rad upstairs always got hot but we've lived with that. We've just noticed that the other 3 rads upstairs are doing it as well which is why I want to get it sorted.
The valve in question in airing cupboard has written on it the following;
Honeywell Sundial Y Plan 3 Position Diverter Valve, Differential Pressure 1"/28mm body 8psi and 3/4"/22mm body 10psi.
If this was suspect could it give the symptoms I'm getting? Is there away of testing/checking it?
Where usually is the CH gravity valve? In the airing cupboard near the tank or downstairs near the Baxi boiler?

 

[gas4you]

Are you sure you have a gravity primary system?

Never known one of these to have a mid position valve fitted, even if it is a 28mm valve

 

[brookie]

Dave,
I rather naievely think/thought I had a gravity fed system as I have an expansion /top-up tank in the loft above so assume it's gravity fed?
If it's not, does that help you with diagnosis for me!?
Brookie

 

[D_Hailsham]

What does the Honeywell valve look like?

A.

B.

Do you have a pump? It looks similar to this and may be near the boiler or the Honeywell valve. This is a Grundfos but there are other makes, e.g. Wilo

 

[gas4you]

Sounds like a fully pumped system with mid position valve. I suspect the valve is stuck mid position.

Replace it.

 

[namsag]

If it was stuck mid position dave it would heat all the rads...

 

[gas4you]

Agree but from op's first post lever is in mid position.

I think it is one of those we won't know unless we see it ourselves.

I'm a bit stumped at present

 

[brookie]

Apologies for late get back. Looking at the pictures I have the Diverter valve "B" and I have exactly that Grundfoss pump which as you very wisely say is positioned right by the diverter by the hot water pump.
This morning with central heating OFF I put the switch on Diverter to AUTO and the upstairs rads get warm but not downstairs.
Is this the correct position or should it be set to MANUAL? Later I'll switch it over to MANUAL to see if there's any difference.
What function does this diverter valve perform?
Thanks for responses (and piccies) so far!

 

[D_Hailsham]

I have the Diverter valve "B" and I have exactly that Grundfoss pump which as you very wisely say is positioned right by the diverter by the hot water pump.

How many pumps do you have? You say you have a Grundfos and then you talk about a "hot water pump".

Any chance you can post a photo showing the Honeywell valves and the pump(s)? If not, a diagram would do; you can create one on Word or Paint. I need to see how the valve, pump(s) and HW cylinder are plumbed together

This morning with central heating OFF I put the switch on Diverter to AUTO and the upstairs rads get warm but not downstairs.
Is this the correct position or should it be set to MANUAL? Later I'll switch it over to MANUAL to see if there's any difference.

Leave it on Auto. The Manual position is only used when refilling the central heating!

What function does this diverter valve perform?

In the standard installation the water enters the diverter at the bottom of the T and the diverter then sends it through either the left or right branch, depending on the signal sent to the valve.

It would help if you could post the Model No of the Valve it should start with a V.

 

[brookie]

Sorry,typo - I meant hot water TANK not pump! I only have the 1 pump.
The model number of the diverter is V4073A1039.
I'll keep the lever on auto. Thanks for that.
I take it the inlet on the bottom of the "T" is hot central heating water from boiler? Where do the 2 outlets wander off to? The rads and what?
What I'm still unsure about is what this valve is doing or supposed to be doing. I think if I knew that it might shine some light on why upstairs rads get hot when I don't want them to!

 

[undercover]

If it has only just started doing this the valve is passing and needs changing

i think this is the problem

 

[D_Hailsham]

The model number of the diverter is V4073A1039.
I take it the inlet on the bottom of the "T" is hot central heating water from boiler?

Correct

Where do the 2 outlets wander off to? The rads and what?
What I'm still unsure about is what this valve is doing or supposed to be doing. I think if I knew that it might shine some light on why upstairs rads get hot when I don't want them to!

One outlet feeds the radiators; the other goes to the hot water cylinder. If the valve is next to the HW cylinder you should see the pipe from the valve going into the side of the cylinder

Here is a pic of the way it all goes together:

The idea of the diverter is to direct the hot water from the boiler to either the radiators or the HW cylinder or both, depending on what needs heating up.