Upstairs rads getting hot, downstairs not at all.

[justanotherguy]

I probably need a professional for this, but can anyone help me narrow it down, so I don't get completely fleeced please!

From what I can gather from searching, it looks like it could be sludge and/or pump failure.

With the combi set to 65C rad flow temp, I see it cycle from about 50C to 75C in 60 seconds, and then the flame symbol turns off while the rad symbol flashes. I believe this means the heat isn't being distributed properly, hence the frequent cycling of the boiler?

I've tried turning off all the upstairs rads, but it doesn't seem to have helped downstairs.

 

[gas112]

what make and model of combi .
Also if your topping up taps are under the boiler check that you havent accidentally partially turned off the boiler isolating valves

 

[Harry Bloomfield]

From what I can gather from searching, it looks like it could be sludge and/or pump failure.

It does help you much, but your diagnosis is likely correct!

 

[justanotherguy]

what make and model of combi .
Also if your topping up taps are under the boiler check that you havent accidentally partially turned off the boiler isolating valves

Thanks.

It’s a Vaillant ecoTec plus 837

The valves underneath have grey tabs facing the front of the boiler saying “closed”.

The CH flow out is hot to the touch.

 

[CountryFan]

Thanks.

It’s a Vaillant ecoTec plus 837

The valves underneath have grey tabs facing the front of the boiler saying “closed”.

The CH flow out is hot to the touch.

Can you post a photo of these? Also, could be a failing diverter valve.

 

[justanotherguy]

Thanks.

Bit hard to capture as clearance underneath is limited. I've take a photo of the five pipes, and additionally one of the label showing what's what.

 

[CountryFan]

Thanks.

Bit hard to capture as clearance underneath is limited. I've take a photo of the five pipes, and additionally one of the label showing what's what.

View attachment 403058


View attachment 403059

Ok, so those grey taps should remain closed as that's the integral filling loop. So it's either a pump issue, sludge or possibly failing diverter valve

 

[Razor900]

What are D.0 and D.2 set to in the parameters?
How many rads do you have
And which exact model 837 is it? There have been at least 3 variations depending on age

 

[dilalio]

Drain some water from a rad and see what the consistency /colour is like.

 

[justanotherguy]

What are D.0 and D.2 set to in the parameters?
How many rads do you have
And which exact model 837 is it? There have been at least 3 variations depending on age

Thanks for your help.

I had to look up how to check d codes - I press "i", then scroll through the d codes with +/-, then "I" again to show the value.

Here's what I get, if that's right:

D.0 is 27

D.2 is 20

There're 3 rads + towel rail upstairs, and 3 rads + tiny bathroom rad downstairs (so 6 to 8 depending how you count)
Label says ecoTEC plus 837 R1 and "GB 376/3-5" if that means anything

I have been able to get the downstairs going temporarily by completely turning off all upstairs rads, including the towel rail (which I'd forgotten), and all except one of the downstairs rads. Then it finally gets hot.

I then gradually turned on the other two downstairs, and they also got hot.

But the moment upstairs rads come on, the downstairs stops again - so I guess that points to a pump issue?

I do still see the the boiler cycling from burner on, going from 50 to 80C, then burner off, then radiator flashing symbol for 30 seconds (which I believe means burner off, pump on), then back to the start every 60 to 80 seconds.

I've tried fiddling with the heating flow temp, and have wacked it up to max of 75C for now (even though I know that's not efficient)

 

[justanotherguy]

Drain some water from a rad and see what the consistency /colour is like.

Not sure how to do that. I bled them from the top and the water was clear there, but I guess I need to undo something at the bottom to test water there. I'm slightly concerned about going from partly working to a completely broken / leak emergency during cold weather if I muck something up!

 

[dilalio]

Not sure how to do that. I bled them from the top and the water was clear there, but I guess I need to undo something at the bottom to test water there. I'm slightly concerned about going from partly working to a completely broken / leak emergency during cold weather if I muck something up!

No drain valve?
Magnetic filter on the system?

 

[terryplumb]

Did the system heat all radiators previously,and at some point the downstairs rads stopped heating up ?

 

[justanotherguy]

Did the system heat all radiators previously,and at some point the downstairs rads stopped heating up ?

Hmm, actually that's a good question. I assumed that, but now I'm remembering a few months ago I changed my Tado system to heat to a minimum of 16C in all the bedrooms 24/7, as I realised belatedly that was a cause of damp and probably didn't save that much money on heating (it's a 1950s house with solid walls)

So it's possible this never worked in colder weather before and I didn't notice, because I had the bedrooms off during the day, and downstairs off during the night.

Just to add, to remove Tado from the equation I removed them from the downstairs rads to ensure they weren't blocking flow - they weren't)

 

[terryplumb]

I suggest you call in a heating engineer.