Valiant Ecotec Plus 637 radiators not heating up fully

[Marc118]

Last year we moved into a converted bungalow that has a Valiant Eco tec plus 637 boiler. Along with a unvented hot water cylinder. The property has been refurbed and both of these are only a few years old.


We have a circuit for downstairs and a circuit for upstairs heating, controlled by two actuators or zone valves. We have a stat in the hallway and one on the 1st floor landing.


When we first moved in, it was winter and all stats were at max. Our gas and electric bill for the first month was £500 so you could imagine our surprise.


I’m an air con engineer by trade so I know a little bit about heating circuits.


I turned the stats down to 21 but the living room, which is quite big struggled to get warm. There was also a back room where the radiator just didn’t get warm. I proceeded to balance the whole system which certainly made it better but still not great.


With that the summer came and the cold nights were soon forgotten but I’ve decided to get ahead of the game now before the cold nights draw in.


We’ve got a magna clean installed and I tool it out and cleaned it and it was totally blocked with about 20mm of black stuff. I cleaned this and put it back. I then checked the temps at each radiator and the most I was getting was 55’C on top of the radiators with some at 45 and 50’C even though the boiler flow was reading 75’C.

I checked the flow sensor and this seems to be reading slightly out. I took this out and cleaned the contact but it didn’t make much of a difference.

The temp of the flow pipework is 68.5 but the boiler is reading it as 75’C, is there a way to put an off set on this sensor?


Even still I suspect this wouldn’t make a huge difference if some of the radiators are only at 50’C but I’m looking for some advice and hopefully some pointers of things to check

 

[oldbuffer]

1. If the Magnaclean was full of magnetite, it suggests the system has a lot of magnetite in it. Either not cleaned at boiler install or has happened since.
2. If you have an infra-red thermometer, or an infra-red camera, try and work out the heat pattern in each radiator. If hot at top but cold at bottom it suggests radiator has some sludge blockage.
3. Take any affected radiators off, flush out with mains pressure cold water (in the garden!), tapping with a rubber hammer to dislodge sludge. Clean up side down and right way up.
4. Alternatively, (and to also clean pipework), get a power flush done, or hire the machine and do it yourself. (Kamco web site has good instructions).

If none of the above has the desired effect, do a heat loss calculation, preferably for each room, and work out if the radiators are big enough. It sounds as though the system has been set up to run in condensing mode (for economy). If so, expect a flow temperature of around 75 and a return temperature of around 55. This suggests for an average room temperature of 20 that the delta T value (difference between average of flow and return and required room temperature) will be 45. You will need to adjust (increase) expected radiator heat output for each room to allow for this. If this calculation suggests the radiators aren't big enough you have two choices, change the radiators or run the system at a higher (non-condensing, less economic) flow temperature.

I can't remember for sure, but I think the boiler flow temperature shown is the desired maximum flow temperature, rather than the actual one.

 

[Marc118]

Thanks for the reply.


I’d say on most of them it is hot at the top but cold at the bottom tbh. I’ll try taking the rads off and look at the colour of the water at the same time. Hopefully they’re not too sludged up but I guess I’ll see.

One tho g I am sure of is that each radiator doesn’t get a supply of anymore than 60’C and defiantly not 70’C.

What are the settings that I need to check to see how it’s been set up to run?


Also can I work out the size of the radiators? I have 4 of the black Art Deco radiators but there’s no info on them at all?


Finally, Is there anyway that I can work out the duty of each one or is it only by using the method you suggested?

 

[snb]

as you have the system 637 boiler the canoe filter in the boiler return pipework is most likely to be blocked with the amount of crud on the filter and it could have also caused the automatic bypass to be stucking open. A quick drain down of the system wouldn't do any harm and then clean the canoe filter and the internal bypass.

 

[Marc118]

Hi, bit of an update on this.

I removed 4 of the radiators downstairs and flushed them out. On a couple of them, black water did come out but not excessive amounts of sludge. I then checked the magnaclean last week and again found it slightly blocked so there must be some crap in the system.
I've now put some Sentinel X800 in the system and I'm going to let it circulate before having the system power flushed.

One thing that i wanted confirmation on was the below

On my boiler the hot water comes out of the boiler and goes to the top of my zone valves/actuators that feed the following
1) downstairs heating

2) Upstairs heating
3) Hotwater​

But there is also what I would say is a bypass line that goes back to the inlet of the magnaclean on the boiler return. So when the zone valves are closed the water has somewhere to go.

But is this in the correct place?

To me that pipe will always have 75 degrees water going back on to the return of the boiler. Only when the zone valves open up will the supply water go to the radiators and the tank and then come back up the return to the magnaclean and mix with the bypass line (that is already 75'C) but this doesn't seem correct to me because this pipework coming from the top of the zone valves is from the supply so will be giving it a false load/reading on the return

To me I can understand this bypass line being there when the zone valves are shut but when they are open, you would want the boiler to sense the water coming back from the radiators so that it can ramp up the pump or increase the flame but will the supply going directly into the return something just doesn't add up.

Can anyone advise?

 

[ScottishGasMan]

Get some photos and post them up. a bypass line would have a bypass valve on it which stops the water "bypassing" when the zone valves are open

 

[Marc118]

Ive attached 2 images.
So on the image that shows the zone valve, the 22mm going onto the top of the valves is the supply from the boiler.
On this photo you will also see the other pipe the 'bypass' (marked with a yellow arrow) this has a gate valve on it that is fully open and goes back to the inlet of the magnaclean on the return as per the second pic.

There will always be 75'C going onto the magnaclean return to the boiler as far as I can tell unless i'm missing something?

The other 2 pipes going onto the magnaclean return are the upstairs and downstairs radiator circuits.

 

[ScottishGasMan]

close that gate valve over fully

 

[ScottishGasMan]

it shouldnt be there in the first place. Might find that will help the circulation round the system a tad

 

[Marc118]

it shouldnt be there in the first place. Might find that will help the circulation round the system a tad

Yes that was my thinking but if I close the gate valve and the boiler is on. Where will the water go? Or would it trip on a high pressure fault?

 

[CBW]

This boiler has a built in bypass valve

 

[ScottishGasMan]

Yes that was my thinking but if I close the gate valve and the boiler is on. Where will the water go? Or would it trip on a high pressure fault?

Where its supposed to "the radiators"

Boilers got a built in bypass (and a good one on these boilers) it wont over heat or damage its self)

 

[ScottishGasMan]

Close the gate valve fully, that pipe is not supposed to be there in the first place if its linking the flow and return pipes

 

[Marc118]

Appreciate the help. I'll try closing it and see what effect it has on the radiators. The temps have never gotten above 48'C so far.

 

[Marc118]

So ive closed the valve on the 'bypass line' and just had zone valve 1 open - which is for the downstairs rads only.
The temps is about 10% better but the rads are still only about 51'C max, with a flow temp of 75'C.
I've gone through the disgnostics menu and noted a couple of things
D003 Outlet temp value 999 - I assume this sensor isn't connected
D004 Cylinder outlet temp -99 - again I assume this isn't connected
D014 pump speed target value - 0 Auto
D015 Pump speed actual value - 15%
D041 Return temp actual value 66'C - This is incorrect and is actually 55'C

Could this be the problem?