From what I understand, on a central heating system the fill and expansion pipe and the vent pipe should be taken off the the main flow pipe before the pump, and also be taken off within 150 mm of each other. (I have seen indications from posts on here that there may be other suitable arrangements but I don't really understand the parameters). In addition, the minimum the top of the vent pipe can be above the level of the top of the boiler and/or pump (presume of whichever is highest) is about 2 metres. (Not really sure if the level above the boiler matters so much as the level above the pump, nor am I sure about what height difference is allowable between the boiler and pump).
Also, from a boiler manufacturer's installation instructions I understand that "the vent must rise continuously and be unrestricted". I take this to mean that the vent pipe needs to go straight up at 90 degrees to the flow pipe without any horizontal component. Now this is just one manufacturer and I am wondering about this in general but it makes sense to me that in all cases it would at least be better if it does go straight up.
The background situation is basically I have a flat roofed garage about 2.4 m high with the boiler in (probably not enough height for f+e tank and/or vent pipe - understand vent pipe could in theory go to alternate place than over f+e tank as long as it wouldn't freeze and went into a drain), and would like to keep boiler there. Currently system is Primatic, and current gravity hot water pipes have about a total of 12m horizontal run on them (with some vertical component too of course) to get to the cylinder in an upstairs bedroom cupboard (through these pipes as I understand the system has been successfully filling - after leaks -, allowing expansion and venting itself for many years). Minimum horizontal run for any pipes coming from the boiler and into the house is about 5m. I am thinking about trying to change away from a Primatic system to a system with a f+e tank.
Question - what kind of problems would be caused if the vent pipe and f+e pipe were taken off near the boiler (at ground level) and ultimately run upwards to the loft but with a large section of those pipes (say 10m) running horizontally or gently sloping upwards? To me it seems a bad idea to have such a long run for those kind of pipes which perform a regulation function anyway, but could it in theory work?
As for other options:
One - would there possibly be enough height in 2.4 m to install f+e tank in garage, particulalry if height over the pump was the more important as opposed to height over the boiler?
Two, currently the pump for the central heating is near the floor in the garage - the flow and return for upstairs and downstairs rads all come into that general area of the garage. I presume there would be an option to change all the radiator plumbing and just run a main flow and return from the boiler into the house then make all the other connections inside the house, thus allowing for the vertical rise of vent pipe and f+e pipe straight into the loft taken off the flow pipe somewhere in the house and just before the pump. (Downside is pump is in house and even the quietest must introduce some noise, plus replumbing). With this option, could I have the main flow and returns from the boiler taking the same route as the current gravity hot water flow and returns (i.e. about 2m vertically and 12m horizontally), then put the pump and f+e and vent pipes in the cupboard with the new cylinder? Or should the flow pipe not run so much up or so much across before introducing the pump? (Have to admit also with this latter route for feeding the downstairs radiators it would seem to be working against gravity - maybe this doesn't matter at all in the new fangled world of pumps!, also being in the middle of the house a bit messy and inelegant feeding all the radiators from there).
Also, from a boiler manufacturer's installation instructions I understand that "the vent must rise continuously and be unrestricted". I take this to mean that the vent pipe needs to go straight up at 90 degrees to the flow pipe without any horizontal component. Now this is just one manufacturer and I am wondering about this in general but it makes sense to me that in all cases it would at least be better if it does go straight up.
The background situation is basically I have a flat roofed garage about 2.4 m high with the boiler in (probably not enough height for f+e tank and/or vent pipe - understand vent pipe could in theory go to alternate place than over f+e tank as long as it wouldn't freeze and went into a drain), and would like to keep boiler there. Currently system is Primatic, and current gravity hot water pipes have about a total of 12m horizontal run on them (with some vertical component too of course) to get to the cylinder in an upstairs bedroom cupboard (through these pipes as I understand the system has been successfully filling - after leaks -, allowing expansion and venting itself for many years). Minimum horizontal run for any pipes coming from the boiler and into the house is about 5m. I am thinking about trying to change away from a Primatic system to a system with a f+e tank.
Question - what kind of problems would be caused if the vent pipe and f+e pipe were taken off near the boiler (at ground level) and ultimately run upwards to the loft but with a large section of those pipes (say 10m) running horizontally or gently sloping upwards? To me it seems a bad idea to have such a long run for those kind of pipes which perform a regulation function anyway, but could it in theory work?
As for other options:
One - would there possibly be enough height in 2.4 m to install f+e tank in garage, particulalry if height over the pump was the more important as opposed to height over the boiler?
Two, currently the pump for the central heating is near the floor in the garage - the flow and return for upstairs and downstairs rads all come into that general area of the garage. I presume there would be an option to change all the radiator plumbing and just run a main flow and return from the boiler into the house then make all the other connections inside the house, thus allowing for the vertical rise of vent pipe and f+e pipe straight into the loft taken off the flow pipe somewhere in the house and just before the pump. (Downside is pump is in house and even the quietest must introduce some noise, plus replumbing). With this option, could I have the main flow and returns from the boiler taking the same route as the current gravity hot water flow and returns (i.e. about 2m vertically and 12m horizontally), then put the pump and f+e and vent pipes in the cupboard with the new cylinder? Or should the flow pipe not run so much up or so much across before introducing the pump? (Have to admit also with this latter route for feeding the downstairs radiators it would seem to be working against gravity - maybe this doesn't matter at all in the new fangled world of pumps!, also being in the middle of the house a bit messy and inelegant feeding all the radiators from there).
