Hot water temp is 40 Degrees - Ideal Mexico 2 Boiler

[JackK]

Thank you - I will be asking someone else to do the task but not many people understand the system as its complicated

I had people suggest an unvented cylinder! And also a combi boiler so I want to make sure I know what to ask them to do

The 2 port valve was always there even before the cylinder was changed and worked fine. The cylinder was replaced and the pipework bent upwards and in 22mm rather than 28mm

If I follow the very helpful advice here I am told

1. Not worth trying to do the boiler flow in 28mm and rebend it so gravity will push water through coil - Absolutely no point in trying that?
2. Add a pump after the two port valve (Problem is what happens when 65 degrees thermostat on cylinder is met and how it can be turned off if I remove the port valve
3. I don’t completely understand your point on hot water rising in the radiator - Some of the radiators are cold at bottom but I put that down to sludge

For me its most important to get the cylinder working from gas again and it looks like the concensus is to put pump either after the two port valve or instead of it yes? Failling that a gravity coiled cylinder

 

[Hugh Jaleak]

Previous thread here. https://www.diynot.com/diy/threads/cutting-barrel-steel-pipework-for-new-cylinder.609542/

I suggested then you redo the flow pipework to the cylinder, so it drops from the original steel down to the top connection on the cylinder coil. (Needs to be 28mm pipework.) You may then have a chance, but I'm not sure you've got the right cylinder. 22mm Tappings suggest it's only suitable for Fully Pumped systems.

Regardless of that, asking gravity to push water round the convoluted setup you've managed to create there is never going to work.

 

[Harry Bloomfield]

Regardless of that, asking gravity to push water round the convoluted setup you've managed to create there is never going to work.

So, we all agree - he needs to add a pump?

 

[MNW67]

Thank you - I will be asking someone else to do the task but not many people understand the system as its complicated

So what is now your best understanding of the system? I don't think you have ever explained it all at once.

From what I have pieced together, you say there is a 3 inch flow pipe coming from the boiler. This goes straight up to the attic. It then drops down again through the house and feeds the radiators, one by one, before returning to the boiler. But on the way up to the attic, it tees off into a 2 inch pipe which feeds the cylinder. After leaving the cylinder, this pipe does not rejoin the 3 inch main circuit, but instead returns separately until it reaches (or gets very close to) the boiler. Did you also say that, before you changed the cylinder, the flow through the cylinder was so good that it actually took all/most of the flow away from the radiators? Which floor is the cylinder on?

 

[Hugh Jaleak]

So, we all agree - he needs to add a pump?

No guarantee that will work, could cause other issues, pumping over etc.

My personal opinion is, he needs to get a suitable cylinder, (Telford for one, still offer Indirect Cylinders suitable for Gravity primaries), and rejig the pipework to suit. My understanding from last May is, the original cylinder was replaced due to and this was supposedly a temporary solution until the OP could do a full system replacement.

Pretty sure Gravity requires the larger bore pipework to work, I was told over 30 years ago as an Apprentice, Gravity wont work on 22mm Primaries. The OP has proved it certainly wont work with the setup he's got!

 

[danfre]

Raise the cylinder and use 28mm pipe work

 

[DP]

Raise the cylinder and use 28mm pipe work

That is an option but not if the indirect coil is for pumped circulation. Water will heat up a little better I assume

15/50 pump on lowest setting is what would be my first port of call

Pumpover may already be an issue as water is brown in colour according to one of the earlier posts

 

[JackK]

That is an option but not if the indirect coil is for pumped circulation. Water will heat up a little better I assume

15/50 pump on lowest setting is what would be my first port of call

Pumpover may already be an issue as water is brown in colour according to one of the earlier posts

Hi - Is brown water from magnaclean not the result of sludge and dirt from old steel pipes in the house?

Raising the cylinder would achieve what exactly?

 

[DP]

Hi - Is brown water from magnaclean not the result of sludge and dirt from old steel pipes in the house?

Raising the cylinder would achieve what exactly?

Jack, read what I wrote to explain how a radiator functions in my previous post. Apply that explanation to a cylinder
Why does a hot air balloon go up and not down when burner is fired?

Megnatite is black. Rust can be any colour. Pumpover or oxygenating water will make the water brown.

 

[JackK]

Jack, read what I wrote to explain how a radiator functions in my previous post. Apply that explanation to a cylinder
Why does a hot air balloon go up and not down when burner is fired?

Megnatite is black. Rust can be any colour. Pumpover or oxygenating water will make the water brown.

Hi - I read your post a few times and I understand the principle of hot water rising - But I am not experienced as you

If the cylinder was gravity is it not the case that the hot water from boiler would flow around teh coild in cylinder and be pumped back through the white pipe? Therefore I dont understand why heat rising principle applies here?

If I fitted a pump or increase the flow pipe size more flow from boiler would go through the boiler

I am so sorry to ask basic questions but I try to understand it to check what can be done

 

[Johntheo5]

No guarantee that will work, could cause other issues, pumping over etc.

My personal opinion is, he needs to get a suitable cylinder, (Telford for one, still offer Indirect Cylinders suitable for Gravity primaries), and rejig the pipework to suit. My understanding from last May is, the original cylinder was replaced due to and this was supposedly a temporary solution until the OP could do a full system replacement.

Pretty sure Gravity requires the larger bore pipework to work, I was told over 30 years ago as an Apprentice, Gravity wont work on 22mm Primaries. The OP has proved it certainly wont work with the setup he's got!

If it is a gravity system then make sure that the cylinder coil is not corrugated.

 

[DP]

If it is a gravity system then make sure that the cylinder coil is not corrugated.

A cylinder, unless it is specific for gravity circulation, will always need pumped. These have high recovery coils and have seen some cylinders with bunched microbore pipes for high recovery. There was one offered by Wolseley- this cylinder was tiny but recovery rate was pronominal. An unvented cylinder coil is nominally rated at 24kW and can heat the cylinder in about 15 minutes to 75% capacity.

Try gravity circulation on these, cylinder will stay cold. This will be despite plumbing being correct

Many years ago replaced a leaking gravity fed cylinder on a back boiler. Did not work so converted circulation to pumped to make it work.

 

[Johntheo5]

I rarely if ever see any real data from the makers of cylinders with high recovey coils apart from the coil rating, the time taken to heat up the given volume and sometimes the coil area, I don't see the boiler flow temperature and circulation rate required to achieve this, also it would be very nice to see the continuous DHW flow at different flow temperatures from a given base mains temperature, I have seen these numbers for "tank in tank" type cylinders, like example below., the primary flowrates are enormous at 43 & 58 LPM respectively and flow temp looks like at least 85C.

Mains water Temp 10C
10	Deg.C
Water Capacity Litres		161		203
Heating surface M2		1.26		1.54
Primary FlowRate LPM		43		58
Litres in first 10 minutes	40°C	321		406
Litres in first 10 minutes	45°C	275		348
Litres in first 10 minutes	60°C	161		209
Litres in first hour	40°C	1063		1349
Litres in first hour	45°C	911	(161L cyl)	1156	(203L cyl)
Litres in first hour	60°C	549	LPM	689	LPM
Continuous flow 40°C	Ltrs/hr	890	14.83	1132	18.87
Continuous flow 45°C	Ltrs/hr	763	12.72	970	16.17
Continuous flow 60°C	Ltrs/hr	465	7.75	576	9.60
Initial heat up time 10°C to 85°C	min	22		20

 

[Notch7]

Pretty sure Gravity requires the larger bore pipework to work, I was told over 30 years ago as an Apprentice, Gravity wont work on 22mm Primaries. The OP has proved it certainly wont work with the setup he's got

I’m just getting really old system with gravity hot water, it’s 28mm going from boiler straight up into airing cupboard located directly above. There are no kinks or bends.

in fact I remember my parent system was exactly the same, 28mm and airing cupboard directly above.


The people who built the systems back then knew to keep the gravity side a simple loop.

 

[DP]

Guys, look at post 14
water coming out of the gate valve, will move along that horizontal pipe, will rise to where the AAV is fitted. Then the hot water will need to defy laws of physics for hot water to flow down the vertical 22mm ( guessing it will be at least 600 mm height) pipe side of the cylinder and set up circulation through another hurdle that is the high efficiency indirect coil that is designed for pumped circulation that is lacking here