Discuss COMBI 2 ZONE + UF + EXPANSION VESSEL ADVICE in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Hello i'm new to the forum, I've done a little searching on here and still have questions.
Some history...
I had 11 double rads in my house then i extended the house and added underfloor heating and 4 more double rads, the extension was all plumbed in and has been running for a year now.
My central heating was/is working but some rads are not as warm as others and the boiler never really shuts off even though none of the 3 stats are calling for heat, sometimes the heat rises rapidly and sometimes it drops rapidly, this doesn't seem to happen as often as it used to before i had the boiler serviced, nothing major was wrong with it just something clogged nothing broken, i think it's struggling with the what to do when the 2 other zones go on and off plus it needs another expansion vessel.
I had the original 11 rads power flushed a month before adding the new ones and the UF.
I had my boiler serviced a few months a go and was advised to add an extra expansion vessel. I used an app to calculate what size and 26.5l is the total size needed so i'm gonna go for a 18l to add on to the 10l inside the boiler.
I'm in the middle of re-decorating the room that the boiler is in and framing a wardrobe around the boiler area so I've got the floor up where all the pipes are to and from the boiler to 2 zone valves and the UF system. One zone valve is for the 4 rads in extension and the other is for the 11 rads in the older part of the house. They are getting moved into the wardrobe.
The UF unit only has 1 loop and a blending valve, the blending valve is impossible to set because when the other zones call for heat the temp increases or decreases, the clip on shut off thermostat inside is set to shut off at 55 degrees but it can't be wired to a zone valve because the 11 rad thermostat controls one zone valve and the 4 rad thermostat controls the other zone valve so i might have a problem there and the underfloor thermostat switches the UF pump on or off at the same time as calling the boiler for heat and CH pump which isn't what it should do from what I've read. The UF pump should always be on.
I have the chance right now to re-plumb everything and re-wire everything so any advice would be really good. I won't be doing the plumbing or re-wiring but in my experience unless i know what should be done it ends up being sub-par or poorly performing because it was done the easy way for example when i first got the UFH fitted i specifically told the plumber i needed a zone valve put in and when the sparky came to wire it up when i was a way i got a phone call to tell me i should have a zone valve fitted!!!

Does the expansion vessel have to go before any zone valves?
Do i need a bypass valve installed to maintain a circulating circuit with all the TRV's and zone valves on the system?
Would the system benefit from flow control valves to balance between the zones, if so where do they go?
The wiring is already a nest so should i get a wiring centre installed?
Would it be a good idea to get an outdoor weather compensator installed because where i live i get four seasons in a day so it sounds like ill save money on my heating. If so where does that get wired to?
I'm going to get a magnetic filter installed close to the return to the boiler after the last rad, is that the best place?
When teeing off to a zone valve and said zone is closed does the dead end in that part of the pipework effect the system in any way?
When a zone's return is teed into another zone's return going back to the boiler should non return valves be fitted or does that not matter? i.e when the return from one zone is coming from the South and the other zone is coming from North and the return to the boiler is going to the West.
My boiler is a Worcester Bosch 42CDi Greenstar and somewhere in the manual it says that 28mm pipe for the gas feed might be required, my pipe is 22mm, is this something that i should get changed? What would be the reason to change it?
 
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Many of those questions are very much heating engineer related.
You really need to ask your heating installer and gas service engineers to provide proper advice and do the work.
Just state the basics to them, - i.e, How the system is performing, or not.
The gas pipe size is for the gas boiler installer and subsequent gas service people to make sure it is correct. (Length of gas run is one deciding factor.)
Your thoughts about zones are wrong and I think you are overthinking it.
 
Wow thats alot of information to shift through this early in the morning worcester bosch 42cdi combi or system ? if it is then your internal pump is to small you should have had a worcester low loss header fitted and worked you various heating circuits off there , probly need a bigger expansion vessel also , Gas supply will most certainly need to be 28mm , sorry but off to work will check in later do some investigation into a low loss header install give worcester a call tell them your system layout make it sound like its new layout they will advise you also. Cheers kop
 
Wow thats alot of information to shift through this early in the morning worcester bosch 42cdi combi or system ? if it is then your internal pump is to small you should have had a worcester low loss header fitted and worked you various heating circuits off there , probly need a bigger expansion vessel also , Gas supply will most certainly need to be 28mm , sorry but off to work will check in later do some investigation into a low loss header install give worcester a call tell them your system layout make it sound like its new layout they will advise you also. Cheers kop
It's a Combi boiler. I'm getting a 18l expansion vessel added to the system.
I'll have a look into the low loss header, thanks. Looking forward to more advice. I'm going on Nightshift tonight tho :(
(Edit) looked into it on the WB website, its like a manifold for two boilers but I assume that's not what your suggesting and it would be a benefit to use with just one boiler?
 
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Here's the pipework, the pipes from the boiler cross over because the first boiler I had was the opposite away around, I'm going to ask to get it all tidied up. All of them used to be under a worktop and sink in the corner of the old utility room so plastic pipe was used, I'll ask to change that to copper. I'll have to drill a new hole for the gas in the middle.

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No plumber would use that many compression fittings. Proper diy.
 
It's a Combi boiler. I'm getting a 18l expansion vessel added to the system.
I'll have a look into the low loss header, thanks. Looking forward to more advice. I'm going on Nightshift tonight tho :(
(Edit) looked into it on the WB website, its like a manifold for two boilers but I assume that's not what your suggesting and it would be a benefit to use with just one boiler?
You can do the same with one boiler it just makes it easy to connect the 3 circuit flow and returns ,all needs coming out and repiping really sorry . kop
 
That's ok kop, I am more than happy to do what needs to be done correctly this time so I don't have more headaches down the road.
 
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