Multifuel CH pipe questions

[CliveS]

Hi All. New to the forum and would appreciate some help.
I’m in Spain, Costa Blanca doing odd jobs etc including afair bit of basic plumbing (new mains water pipes, PRV’s, toilets, gardenirrigation etc.) So not an expert by any means but fairly comfortable with thebasics.
At home I have wood burner at moment which I am about tochange for multi-fuel stove with a back boiler, a simple flow and return 2 portmodel. Electricity and gas prices here are getting crazy and I have access tolots of good seasoned wood so seems a no brainer.
I intend to install a simple vented CH system to supply 6rads in the villa. No HW
Header tank in the loft with 22mm flow to circuit returnbefore boiler, after pump. 22mm ventpipe on flow after boiler, to headertank. Pipe thermostat on flow line to switch pump. Small heat bleed off rad on separatethermal circuit.
Q1: What stops thepump forcing water back up the 22mm supply pipe from the header tank, ratherthan around the flow circuit of the rads? Is it just head pressure from the tank. Do Ineed a non return valve on this supply? From what I’ve read no but pleaseadvise.
Q2: Same with question with the vent pipe? No valve!
Q3: There is space under the floor, as always tight inplaces. When installing the tails to the rads, is it better to have them atsimilar lengths to each of the rads or is it not that important as the systemcan be balanced at the rads? The reason I ask is it will be easier to runlonger tails to some rads than others, rather than run flow and return to allcorners of the under-floor space.
Not an expert by any means so please excuse any obviouserrors in the above. All help appreciated. Indeed anyone fancy a long weekendin the sun / under my floor with free accomodation and lots of beer? Just buythe flights! Lol
Clive

 

[Best]

You are working with a potential bomb tbh.
Check with local regs in Spain before you think of attempting anything. Uk rules will be different.
What happens if your pump fails? The heat leak rad won't lose the heat a blazing fire creates.
I personally wouldn't want most plumbers doing that job as it needs properly done.

 

[Ermintrude]

Just build in a blast wall! Easy . 1000m concrete with t38 reinforcing bar with few layers of A393. Be fine . Backboiler will last longer than his pants when it starts to boil .

 

[WHPES]

You're way out of your depth and some of what you suggest is potentially very dangerous.

Local regulations apply on heating systems. Check what is allowed and if you are fluent in the lingo there will almost certainly be documentation avialable and design standards for such systems just the same as what we have here, which you need to carefullly follow. It could also require a local building inspector to sign off depending on regulations in your country.

Alterntively sometimes you just have to let more experienced and qualified do the actual boiler and primary installs and you can complete the radiator circuits etc.

 

[CliveS]

Well many thanks for the quick responses .............and shots across the bow! It was always my intention to plumb the rad circuit myself and get assistance with the boiler side of the install. I should have made this clear in the original post so many apologies for the omission. There are a number of ex pat plumbers in the area who I will speak with in due course. At the risk of having my 'throat jumped down': from the research that I have done when looking to buy a new fire, it would appear the system I am looking to have installed is the simplest one possible (not saying it is without problems or that skill to install is not required). On any project like this I have a genuine interest in how it works / functions and want to know the potential issues that can occur. Whilst considering my stove purchase / install my original 3 questions in the post came to mind.

 

[Best]

Hi again Clive!
It is not the simplest system possible, as you suggest! Solid fuel boilers of any type can just keep heating & even if there's some form of thermostatic air control on them. So heat loss to somewhere maintaining circulation is vital. Pipework needs not only to be very well installed, but also to manufactors instructions. 28mm pipework is needed on gravity circuits normally & vents & feeds 22mm minimum. Also the chimney/flue needs to be the proper diameter & type & with no chance of fumes escaping.
Remember also that not all plumbers are heating engineers & not all heating engineers know much about solid fuel systems! Many will just fit gas or oil fully pumped systems.

 

[AWheating]

you will need a good gravity circulation as suggested for the heat to go to which is why most systems will have a hot water cylinder. I would find the qualified person first and decide on the system design with this person. Then do what work you can yourself and allow the qualified person to check it and connect up the important bits. pointless putting in a dangerous system to save money, get it done properly.

 

[CliveS]

Well it would not be difficult to install a HW cylinder in the loft space (in Spanish villas it is very unusual to have access to the loft / roof slope void as they are normally completely contained during construction, however I have been able to 'break' into mine) if the additional heat drain of a HW cylinder would add safety to the system. To be honest my original reason for going down the CH route only was I was concerned whether the 8kw rated capacity of the back boiler stove I am looking at was sufficient to power my rads. If I could have HW that would be a bonus.

 

[AWheating]

best option would be a thermal store if you have the room, you would then have mains hot water and heating. most themal stores can stay warm for days after they have been heated so you would still have hot water a day or two after the last fire was lit. stick a solar pannel on it and your wont pay for much or need to have much of a fire to keep it warm.

 

[CliveS]

I wonder if someone could answer Q3 of my original post, the part I am happy to do on my own. Q3: There is space under the floor, as always tight in places. When installing the tails to the rads, is it better to have them at similar lengths to each of the rads or is it not that important as the system can be balanced at the rads? The reason I ask is it will be easier to run longer tails to some rads than others, rather than run flow and return to all corners of the under-floor space. It

 

[AWheating]

what do you mean by tails? leg of pipework from the main flow and return pipework?

 

[CliveS]

Yes, exactly that. The space is very limited and it would be easier to run longer 15mm supplies to 2 of the rads rather than trying to get and return into all corners of the under floor space.

 

[CliveS]

That should have read: Yes, exactly that. The space is very limited and it would be easier to run longer 15mm supplies to 2 of the rads rather than trying to get flow and return into all corners of the under floor space.

 

[CliveS]

That should have read : Yes, exactly that. The space is very limited and it would be easier to run longer 15mm supplies to 2 of the rads rather than trying to get flow and return into all corners of the under floor space.

 

[AWheating]

aslong as the run length is not too long and the rads are not massive then a 15mm flow and return to two rads would be fine at a guess.As a guide 15mm will do about 6kw max with a flow and return temp diff of 11degree. about 9kw max with a temp diff of 20 degree.