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Smilin

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Hello,

I'm not a plumber, and may get some of the terminology wrong in this post, please don't shoot me down for it.

Since moving in to our home several years ago, we've had issues with the performance of our central heating. In winter, the living room can take up to two hours to get upto 18C from 15C in the morning.

History:
When we moved in, we had a heating engineer upgrade the system to S-Plan, and replace all TRV's in all rooms, remove the TRV's from the living room, and replace the heating controls.
a year later we noticed water flowing to the tank in the loft, the plumber extended the expansion vent pipe up higher in the loft space so the water had further to travel
Two years ago we had a new boiler installed as it was condemned by Cadent
Last year we noticed the issue where turning the pump up caused the water to flow up the expansion vent pipe again.
Since moving in, we've been gradually replacing the radiators, We now only have 1 radiator in the kitchen, and 1 in the spare bedroom to replace.

Observations:
If we put the pump on the highest setting the living room heats up quicker, but this causes water to flow up the expansion into the tank in the loft, and it ends up like sauna up there.
The tank in the loft doesn't overflow, suggesting the cold water feed if feeding into the system.
Looking at the pipework, it looks like the expansion vent is within 150mm of the cold water feed, and both are on the suction side of the pump.
I've attached photos of the pipework in the airing cupboard. A lot is hidden, but will hopefully give some insight

I have a suspicion about what's wrong, but wanted to see what the experts on here thought first.

Any suggestions?
James
 

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What’s the bypass set at?
 
A faulty or wrongly set bypass could cause slow increase in room temperature. I think however you have another problem as well as in a partial blockage causing the venting over. This is likely to be where the cold feed enters the system. The vent pipe should extend a minimum of 450mm above the header tank to prevent pumping over from pump surge, however under normal working conditions this should never happen.
Every time water discharges into the header tank you draw fresh water entrained with air into the system. This is most likely the cause of corrosion and sludge build up. I bet when you drained the water down it was dirty?
 
Smilin said:
Hello,

I'm not a plumber, and may get some of the terminology wrong in this post, please don't shoot me down for it.

Since moving in to our home several years ago, we've had issues with the performance of our central heating. In winter, the living room can take up to two hours to get upto 18C from 15C in the morning.

History:
When we moved in, we had a heating engineer upgrade the system to S-Plan, and replace all TRV's in all rooms, remove the TRV's from the living room, and replace the heating controls.
a year later we noticed water flowing to the tank in the loft, the plumber extended the expansion vent pipe up higher in the loft space so the water had further to travel
Two years ago we had a new boiler installed as it was condemned by Cadent
Last year we noticed the issue where turning the pump up caused the water to flow up the expansion vent pipe again.
Since moving in, we've been gradually replacing the radiators, We now only have 1 radiator in the kitchen, and 1 in the spare bedroom to replace.

Observations:
If we put the pump on the highest setting the living room heats up quicker, but this causes water to flow up the expansion into the tank in the loft, and it ends up like sauna up there.
The tank in the loft doesn't overflow, suggesting the cold water feed if feeding into the system.
Looking at the pipework, it looks like the expansion vent is within 150mm of the cold water feed, and both are on the suction side of the pump.
I've attached photos of the pipework in the airing cupboard. A lot is hidden, but will hopefully give some insight

I have a suspicion about what's wrong, but wanted to see what the experts on here thought first.

Any suggestions?
James
Click to expand...
This a bit long winded but would be surprised if it didn't solve your problem.
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SJB060685 said:
A faulty or wrongly set bypass could cause slow increase in room temperature. I think however you have another problem as well as in a partial blockage causing the venting over. This is likely to be where the cold feed enters the system. The vent pipe should extend a minimum of 450mm above the header tank to prevent pumping over from pump surge, however under normal working conditions this should never happen.
Every time water discharges into the header tank you draw fresh water entrained with air into the system. This is most likely the cause of corrosion and sludge build up. I bet when you drained the water down it was dirty?
Click to expand...
I think the vent pipe is about 600mm above the header tank.

I suspected a blockage between the vent pipe and cold feed. However, when I last replaced a rad, the water was pretty clear. I've got the engineer who fitted the boiler doing a service this weekend and I'll ask if he can remember how dirty it was when he replaced the boiler. I'll also ask him to check the magnaclean to see how it looks, as it hasn't been inspected since it was installed 2 years ago.

I wonder about air in the system, as I frequently need to bleed the heated towel rail in the bathroom, sometimes the water that comes out with the bleed has the odd black particle in it. The towel rail is the highest rad connected to the heating system, and last year the pump was fairly noisy, so much so that we're considering replacing, however if its due to air in the system, this may not be necessary.
 
If a system is designed and executed properly then after initial filling it takes something like roughly 90 days if I remember correctly to expel free air and dissolved gases within the system to a point where the chances of corrosion are minimal. However, open vented systems are notorious for being problematic, beit venting over, or a leak etc. As I said, every time water vents over into the tank you are drawing fresh air in, this would restart the average 90 days, probably less as the amount of free air and dissolved gases would be less but all the same start a cycle over again. You say you're having to vent the towel rail upstairs. Naturally these in those locations are at a high point in the system where the less dense air likes to accumulate, so this comes as no surprise.
The filter on the system should be serviced and cleaned yearly along with the boiler, a lot of these filters have a dial on them with numbers from 1-12, indicating which month it was installed and thereby which month to check
I do think this is a corrosion problem, I would have your plumber check the filter to give you an indication of the level of magnetite within the system.
 
I havn't come across any post here where combining the cold feed and vent, preferably just under the F&E tank hasn't solved the above type problems.
If you have a vent and cold feed 100 mm apart, then even a flowrate of 10LPM in a 22mm pipe can create a imbalance of 870mm due to (even clean) pipe friction losses and the surface area of the F&E tank being (in my case anyhow) ~ 364 times times that of the 22mm pipe. If 150mm apart, can cause a imbalance of over 1000mm, in practice, probably far less as this is I think deemed a neutral point, however whatever the reason(s) the above works. I can set my circ pump to 6M (test only) and even with just 2 rads on will never see a problem in the F&E tank.
 
The problem I think I foresee is though is that the vent and cold fill are piped into the system behind the cylinder. Accessing the pipes there would be a problem. The adjustment to combined feed and vent would have to be done in the loft, alternatively seal the system.
If there's evidence of large scale corrosion though this would still need to be addressed.
 
It looks very close coupled so shouldn't be a problem, from that point of view, wonder if being on the pump suction has any effect.
 
The images above suggest the pump is on the flow after vent and feed. The problem is most open vented systems are decades old and even if the orientation of vent fill and pump is correct from the start that is an awful long time for corrosion to occur. The management of system water quality and thorough expelling of air and dissolved gases is something that is really only been taken seriously in recent years.
 
V, C, P is what it's usually abreviated as. There are other possible locations for the cold feed and pump but you would be creating a negative pressure throughout most of the system, this of course pulls dissolved gases out of solution and can accelerate a corrosion process..
 
And yet, some open vented systems like my own, almost 1/2 a century old have never given the slightest trouble, with some of the original rads, and only the odd drop of inhibitor thrown in.
 
John.g said:
And yet, some open vented systems like my own, almost 1/2 a century old have never given the slightest trouble, with some of the original rads, and only the odd drop of inhibitor thrown in.
Click to expand...

All comes down to the installer, their understanding and the quality of the installation I suppose.
Once up and running most systems are pretty capable of looking after themselves but not always, there's a lot of variables to consider.
 
I reckon it helps a lot if its a combined vent and cold feed installed like mine right up at the F&E tank as there is no or little sludge up there.
 

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SJB060685 said:
The images above suggest the pump is on the flow after vent and feed. The problem is most open vented systems are decades old and even if the orientation of vent fill and pump is correct from the start that is an awful long time for corrosion to occur. The management of system water quality and thorough expelling of air and dissolved gases is something that is really only been taken seriously in recent years.
Click to expand...
I take it the upgrade to s-plan, the heating engineer wouldn't have changed the orientation or the pipework around the vent, feed, pump area? Just trying to get an idea of how long that pipework has been there. I think it has been replaced at some point as it no longer lines up with the pipe clips attached to the wall.

I may ask the plumber tomorrow to change it to a combined vent/feed arrangement.
 
No no changes would have been made.
You could ask the attending engineer to convert a combined feed and vent but if you have a blockage and it's where I suspect this would need to be cleared as well.
 
After the boiler service, and a quick look in the loft, the magnaclean was in a state, and the header tank is not much better. Unfortunately the guy who services the boiler is booked up for 3 months now, so I'm having to find someone else.
 

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Based on the above I recommend finding a decent engineer who could do a thorough powerflush and possibly redo the pipework as mentioned previously. A flush might be all that's needed.
 
Smilin said:
After the boiler service, and a quick look in the loft, the magnaclean was in a state, and the header tank is not much better. Unfortunately the guy who services the boiler is booked up for 3 months now, so I'm having to find someone else.
Click to expand...
Cut a bit off that vent pipe as well, it shouldn' be dipping in the water.
 

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