Actually, we should have sent the boilers back before they were installed as at least one had been dropped and dented the casing from inside.
magnaclean filter and low loss header
- Thread starter ajrobb
- Start date
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Doitall, I think you have misunderstood how this system is intended to work, but I don't have time to read through the entire thread; apologies in advance if it is me that has misunderstood you.
I would say there is no short circuit; the gate valve is wrong only in that it is liable to be shut repeatedly by people who do not understand this system.
Have a look at this article, in particular figure 2;
http://www.esmagazine.com/Articles/Feature_Article/BNP_GUID_9-5-2006_A_10000000000000115181
Figure 2 shows an installation with 2 'mod/con' (modulating condensing) boilers. The boilers' F&R connections are joined with a 'hydraulic separator' (aka a LLH) which is, apparently, a huge short circuit. This is entirely intentional; there is no short circuit whilst any or all of the 3 secondary pumps are taking all the flow entering the hydraulic separator and shoving it out around the secondary systems.
Figure 2 is very similar to the OPs existing installation. Bear in mind that the author is probably the best known heating engineer in North America and this design DOES work.
The OP's system is an intelligent design but I think I would find problems in ensuring that it worked as intended without installing flow measuring devices and temperature sensors.
G
GaytonTonner
Replace the LLH for the cylinder buffer and that is roughly what I proposed. A buffer is a hydraulic separator in my proposal. The the buffer is superior to the LLH.
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With respect Onetap and GT.
I've been designing and installing Large Domestic and commercial heating heating sytems for 50 years, I know a little bit about it.
And all this rubbish in fig 2 is an expensive over the top bodge, that still won't solve the pipe issues around the cylinder.
If it was going to be ripped out and start again then yes, go for the buffer tank, it's a good system.
An LLH is a blender, if the size is calculated why the hell would you wany anything else.
The question, remains, what is the OP prepared to spend to get it working.
Increase the header.
Bring the heat and hot water pipes back to the header with 2 port valves.
Under a grand.
Fit a buffer and God knows what 5grand.
I've been designing and installing Large Domestic and commercial heating heating sytems for 50 years, I know a little bit about it.
And all this rubbish in fig 2 is an expensive over the top bodge, that still won't solve the pipe issues around the cylinder.
If it was going to be ripped out and start again then yes, go for the buffer tank, it's a good system.
An LLH is a blender, if the size is calculated why the hell would you wany anything else.
The question, remains, what is the OP prepared to spend to get it working.
Increase the header.
Bring the heat and hot water pipes back to the header with 2 port valves.
Under a grand.
Fit a buffer and God knows what 5grand.
Notice how fig 2 is remarkably like my pic, And a proper LLH
The one big difference is both boilers connect to the header independently, which prevents unwanted circulation through the lag boiler.
The design has been around for at least 50 years, and has never let us down yet, it works in every case.
View media item 29587
The one big difference is both boilers connect to the header independently, which prevents unwanted circulation through the lag boiler.
The design has been around for at least 50 years, and has never let us down yet, it works in every case.
View media item 29587
G
GaytonTonner
I outlined how it can be done using a cheap unvented ss cylinder. A very cheap way. No disrespect, however I find commercial systems tend to stick to old ways. The boilers move on but the pipes around stay the same config.
Take a very close look at my pic above, and tell me what has change, other than all the fancy bits.
G
GaytonTonner
How big are the boilers? They can't be that big as they appear to be using domestic pumps. All that ironwork is NOT cheap. A simple off-the-shelf SS buffer cylinder with a stat would be a better solution, which you agree on, totally isolating the boilers from the system. It would also be much cheaper as well.
The Germans use buffers with a domed bottom, the reverse of the top, to prevent sludge build up. A good filter will stop the build up.
LLH do blend but a very crude way of doing it and the Delta T of the boiler not guaranteed. So, Heat X cracks may re-occur.
The boiler are 60Kw each, the two pumps in the pic are shunt pumps and no difference to the inbuilt pumps in the Kestons, they only need to circulate the water through the low loss header. In the OP case it could be considerable smaller, and many manufacturers supply an off the shelf LL headers, I know Valliant, Viesmann, Broag, MHS etc do.
All the pipework is commercial the Op is looking at copper a fraction of the size, it's only a bleeding bungalow not a 10 room mansion.
If I was incorporating Solar, ground source heating etc, then the buffer tank is 100% the way to go, in a small 3-4 bed property that only need one boiler, if it was installed properly it is over the top and expansive.
Low loss header may be crude but let me assure you, simple works and works very well irrespective of size, you are trying to over complicate a small domestic system.
The HX are going down because of the poor circulation, what you need to do is read and understand what I have said then go away and think about it, especially the bit that say the larger pump can stall the smaller pumps when they are modulated down to the lower speed.
You can argue all you like, I don't know you or what you do for a living, and don't care for that matter, but at least listen to your betters.
And I don't give a monkey's what or how the Germans doitall, or care either, they are not the worlds authority on good design,
Please ignore GT's interjection. He proposed the buffer tank, I did not.
My point is that the OP's installation is nearly identical to both the primary/ left-hand side of Fig 2 above and the LLH picture you posted. If you were to stick a gate valve in the middle of the 'hydraulic separator', then you've got the OP's system.
This system could be made to work with minimal pipework amendments; that is what he wants, to get the Kestons working efficiently and reliably until new boiler time.
A LLH is NOT a blender, if working properly; I think you have misunderstood this. It will act as a blender if the secondary flow rate> primary flow rate, causing a reversal of flow in the common pipework.
GT is Water Systems/Dr. Drivel, a notorious troll.
G
GaytonTonner
It takes one silly poster to post something and they all follow on like sheep. The name is Gayton. I agree about the LLH and blender.
Doitall, you are not better, just old or doing old ways.
Precisely Onetap, the first pic I posted is virtually identical to the OP's setup, apart from the AVDO and the circuit pipes are taken individually from the header.
I agree it can be made to work with the minimum of alterations and cost.
Sorry a low loss header acts as a blender via the shunt pumps, and ensures perfect circulation through the boilers at all times even when they modulate down.
If GT is watersystem, bigburner, Drdrivel, I'm sorry GT you're an idiot, so please confirm or deny.
G
GaytonTonner
If GT is watersystem, bigburner, Drdrivel, I'm sorry GT you're an idiot, so please confirm or deny.
Do not call me an idiot, or refer to me as anyone else. You have proven on this thread quite lacking.
The LLH/blending proved that. The blending valve is just a back-end protection valve. Do you know what one is? The forum is full of regular posting oddballs. One had never heard of gas taps, another had never heard of insulated heating pipes underground, another did not know about AHU units being heated by combis and the beat goes on. When they are put right they get aggressive, because they think they know it all, instead of saying, "thanks I never knew that".They are hard work, so the ignore button is best for them.
G
GaytonTonner
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