Gravity based back boiler CH system - Advice needed.

[ftahumour]

@Hugh Jaleak - thanks for the feedback. I'm getting schooled in a hurry, appreciated.

At present, apart from the pump failing for the second time in my ownership, and the rads and pump hitting 80C+, there isn't any functional issue with any part of the system.

With that said, I have replaced 3 radiators (+2 of the new ones again within 12 months, another story), the thermostat, the controller, the pump electronics (pump speed selector black box) and most recently the Boiler thermocouple during my ownership of 5 years. So one could argue, it's like trigger's Broom now but overall it has been relatively inexpensive to keep going until 2025.

When I replaced 2 radiators last year it showed me that the system needs to be flushed properly and that I should install a Magna clean or equivalent metal catcher sooner than later. With this in mind, I'm tyring to work out what else makes sense to change while the system in fully drained, make a list and prepare for it.

I can do some electrics and have a multimeter, I can and have done basic plumbing, but don't have the tools to handle more complicated stuff like solder piping and cutting and bending the bigger bore pipes. I have other reasons to hand over to a pro at certain times to satisfy the Mrs too, as jobs need to be done quickly and efficiently or I get the stress. Not ideal for my wallet, but I often get reminded "do you want to be right, or do you want to be happy" lol

The air separator part of the system is news to me, as was the CH stat temp, so I'm learning during this process. I will research what I need to replace the aerjec with and add this to the plumber's list of works.

I do appreciate the knowledge and advice.

 

[ftahumour]

Duplicate

 

[ftahumour]

Hi again guys,

further to my previous queries, I'm trying to work out the Boiler return on my system with the aim of checking if I have space to fit a Magnaclean Atom.

In the attached picture, Blue is Cold pipes (main feed to loft tank + main feed to electric shower, I think), Teal is a pipe that heats up first when CH and HW are both turned on by the programmer. Orange are the pipes that heat up second (after Teal), however they overtake Teal in temperature after the first 5 minutes of the system being on.

I can't look at the boiler directly as its in the chimney stack and the pipes feed into a cavity wall in the back of the kitchen as they go to the HWT cupboard.

First: - Which of these pipes is likely the Boiler return?
Second: - Is it safe to fit a Magnaclean Atom on the pipe feeding the pump before the Aerjec?

Thanks in advance.

 

[gas112]

its perfectly ok to fit it on the flow

 

[Harry Bloomfield]

I'm rather embarrassed to report that the HW Tank stat was set to 50c!

Those stats are never really accurate, but you should be measuring the temperature, at the hot tap, immediately after the boiler has finished heating the water, and after the water temperature has settled at the hot tap. >55C is what you should be aiming for.

To achieve the temperature of >55C, your boilers stat, will have to obviously be set a little higher, usually it needs to be +10C of the hot water temperature. That is to avoid your boiler constantly cycling on and off, trying to achieve an hot water temperature, which it cannot ever manage.

With that said, I have replaced 3 radiators (+2 of the new ones again within 12 months, another story), the thermostat, the controller, the pump electronics (pump speed selector black box) and most recently the Boiler thermocouple during my ownership of 5 years. So one could argue, it's like trigger's Broom now but overall it has been relatively inexpensive to keep going until 2025.

Don't forget to add some inhibitor, to protect the system.

 

[ChrisJP]

It sounds like the system has been drained and re-filled several times whilst you have owned it. Did you always replace the corrosion inhibitor each time? If not, that could be the source of the black sludge you're encountering and the fact that several radiators have had to be replaced.
As for converting to a combi - I really wouldn't bother. Because they operate at higher pressure than header tank fed vented systems you'd probably need to replace most if not all the old piping and radiators to prevent the possibility of leaks. You also normally have no store of hot water and it can take a long time for the HW to get to the taps, because first the boiler has to fire up to heat it. My personal view is that combi systems are much over-rated.

 

[dilalio]

I wouldn't worry too much about the cylinder not getting to 60°c.

 

[ftahumour]

its perfectly ok to fit it on the flow

Thanks that's good to know. Only, the pipe gets hot, like 80-85C hot. Im concerned about the plastics in the Magna clean not handling the heat over time.

 

[ftahumour]

Those stats are never really accurate, but you should be measuring the temperature, at the hot tap, immediately after the boiler has finished heating the water, and after the water temperature has settled at the hot tap. >55C is what you should be aiming for.

To achieve the temperature of >55C, your boilers stat, will have to obviously be set a little higher, usually it needs to be +10C of the hot water temperature. That is to avoid your boiler constantly cycling on and off, trying to achieve an hot water temperature, which it cannot ever manage.



Don't forget to add some inhibitor, to protect the system.

Thanks. I will validate this, but I know the water is hot at the tap, it will burn you if you leave your hand under it, ask me how I know.

 

[ftahumour]

It sounds like the system has been drained and re-filled several times whilst you have owned it. Did you always replace the corrosion inhibitor each time? If not, that could be the source of the black sludge you're encountering and the fact that several radiators have had to be replaced.
As for converting to a combi - I really wouldn't bother. Because they operate at higher pressure than header tank fed vented systems you'd probably need to replace most if not all the old piping and radiators to prevent the possibility of leaks. You also normally have no store of hot water and it can take a long time for the HW to get to the taps, because first the boiler has to fire up to heat it. My personal view is that combi systems are much over-rated.

I've replaced radiators because they started leaking. I only had to drain upstairs once, the other times the valves held the water at bay.

You are correct in that no inhibitor is in the system and that the system is full of ****, likely causing rads to fail (although its the newer stuff that has failed shortly after being replaced rather than the older stuff), either way, my ignorance on this topic. Hence why trying to formulate a plan of action to fit a new pump and an iron catcher while the system is flushed and drained, all at the same time hopefully.

Looks like Im almost there with a plan of action now. Still unclear if I should plan to replace the aerjec at the same time or not (this will require someone who can desolder and resolder), its got lots of oxidisation build up on the bottom of the inlet, but isn't leaking as far as I can tell.

 

[Exedon]

I'd definitely be getting shut of the aejec and using a more conventional H section.
No reason you can't use something like tectite classic fittings if you don't fancy soldering.
Couple of pictures of a removed Airjec unfortunately fairly typical of how they get, causing pumping over problems.

 

[ftahumour]

I'd definitely be getting shut of the aejec and using a more conventional H section.
No reason you can't use something like tectite classic fittings if you don't fancy soldering.
Couple of pictures of a removed Airjec unfortunately fairly typical of how they get, causing pumping over problems.

Ok. Thanks for the feedback and the pictures, that doesn't look good for sure.

Can you give me an example of the kind of product I will need to replace it? All the products I can find in searching are in-line airators, but these are 1 inlet and 1 outlet, how do I accommodate the overflow pipe going into the loft in such a setup, or do I just replace the Aerjec with a simple T piece of 22mm pipe and fit an in-line airator just before or just after the Magna clean device? Sorry if this comes across as dumb, but Im struggling with the planning of the plumbing and the selection of the correct replacement parts.

 

[dilalio]

Ok. Thanks for the feedback and the pictures, that doesn't look good for sure.

Can you give me an example of the kind of product I will need to replace it? All the products I can find in searching are in-line airators, but these are 1 inlet and 1 outlet, how do I accommodate the overflow pipe going into the loft in such a setup, or do I just replace the Aerjec with a simple T piece of 22mm pipe and fit an in-line airator just before or just after the Magna clean device? Sorry if this comes across as dumb, but Im struggling with the planning of the plumbing and the selection of the correct replacement parts.

You don't need a product.

You just connect the feed and vent to the pipe in an "H" configuration, the correct way around and the correct distance apart.

2 tees is all you really need... Use compression then you can always take it apart for future attention!

 

[fixitflav]

You just connect the feed and vent to the pipe in an "H" configuration, the correct way around and the correct distance apart.

And make the cold feed up and under, to avoid convection warming the F/E tank, encouraging algae growth.

 

[dilalio]

And make the cold feed up and under, to avoid convection warming the F/E tank, encouraging algae growth.

Ideally, but rarely done.