magnaclean filter and low loss header

Whatever you say. :rolleyes:

You keep say the circulation pump pushes water through the rads.

I've asked before, what motorized valves do you have,

The system pump is common to the hot water and heating.

Lets have a few pics showing the valves etc around the cylinder.
 
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other.

The two primary pipes go where. ??

Where does the how tee into them, there must be at least two motorized valves. :rolleyes:

Or are you saying the two boilers only do the heating.
 
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GT, I wasn't disagreeing about the buffer tank, just the bender valve, it isn't needed.

An AVDO in the by-pass would close the short circuit and ensure there's a full flow through both boilers, see drawing. and actually improve circulation with all 3 pumps doing the same job, instead of working against each other'

I agree with the short circuit you noticed.

You missed it on blending valve.

The blending valve does:

1. Ensures the delta T is within rage to prevent heat X cracks.
2. Ensures a good flow through the boilers
3. Eliminates the third pump.

Increasing the headers to 42mm raises the cost greatly to the point a superior buffer tank is more cost effective and a far superior solution.
 
Be aware that Gayton is merely a boiler user who likes to post among the professionals having read a few internet postings!
 
Sorry GT, still disagree, about the blender, or the cost comparison to the buffer tank.

The 3 port valve needs a by-pass on port B, or AB to the return depending how it's wired up.

Other than that the pipes still look undersized for the boilers.
 
The 3 port valve needs a by-pass on port B, or AB to the return depending how it's wired up.
I don't understand why there is a 3-port valve for a single zone CH and DHW when there is a 2-port valve on the DHW by the cylinder, unless it's left over from the previous installation (single 25kW non-condensing with vented indirect DHW).
Other than that the pipes still look undersized for the boilers.
Yes, I think it's crazy having two boilers pushing through a single 22mm circuit. However, as I can balance all the radiators to 11°C drop with the pump on max, I don't think its critical. Also, by winding up the feed temperature, I could heat the house to 20°C in the coldest snaps we had last year.

I must say I now don't like running largish CH and indirect DHW from 2-pipe 'heat-only' boilers. If I'd have known you guys 9 years ago, I think I might have asked for a single 4-pipe system boiler with separate CH and DHW flow temperatures, if they made them back then. My partner was accounts manager for a large local heating engineers (70 plumbers and apprentices) with Council an University contracts, so I trusted them. The plumber was time-served, one of their best and a lovely guy but the boilers have always been a problem. Unfortunately, his knees were shot, so the apprentice did most of the pipes in the roof voids (pipe insulation is sparse). We had Keston out several times during commissioning and they replaced the first heat exchanger and numerous circuit boards. I have come to distrust having electronics in the same casing air as the plumbing.
 
Be aware that Gayton is merely a boiler user who likes to post among the professionals having read a few internet postings!

Glad you didn't include me in that Tony :D

He thinks he is a professional. I suppose a cowboy fitter is a professional in that he takes money from people.

There is only two here who understand the problem here and have tried to get a solution. I am one of them.
 
Sorry GT, still disagree, about the blender, or the cost comparison to the buffer tank.

The 3 port valve needs a by-pass on port B, or AB to the return depending how it's wired up.

Other than that the pipes still look undersized for the boilers.

That is where the small buffer tank comes in. It separates the heat generation from the heating and DHW system. The two can operate without influence on each other.

As I say, avoid 42mm headers.

The blender is to protect the heat X's.
 
We had Keston out several times during commissioning and they replaced the first heat exchanger and numerous circuit boards. I have come to distrust having electronics in the same casing air as the plumbing.

Keston had every right to disown the boiler and charge for the Heat X. You are blaming the product not the poor installation.
 
Please can we avoid getting into a slanging match.

Notice many have come in offering no value to the thread at all, claiming they are professionals. If I was the MOD I would delete the posts and warn the posters.
 

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