Does This Microbore & Manifold Layout Sound OK?

[2point8ghiax]

I have bought a wreck to live in, and need to put a heating system in myself as cheaply as possible. The small 3 bed house has a recently fitted Glow Worm 30 CXi combi, but nothing that you could call an effective heating circuit/system. Does my proposed Microbore (yes, I know its not ideal ) layout sound OK? -

Run 22mm copper flow and return pipes 2 metres from the boiler (situated ground floor), then split the flow pipe into two 22mm Speedfit plastic pipes. One of these pipes will go to a 4 outlet flow manifold on the ground floor, and the other to a 4 outlet flow manifold upstairs. Then split the return pipe in the same way, with a return manifold downstairs and one upstairs. (N.B. Each manifold has 4 X 10mm outlets)

The downstairs manifolds will feed 4 small to medium rads. The upstairs manifolds will feed 3 medium rads and a towel rail.

Hope this makes sense. Will it all work? Is there anything else to consider, and do I need a bypass? Many thanks.

 

[kirkgas]

as you say microbore is not ideal but what you suggest will work fine, try to fit the manifold centrally to the 4 rads if possible, an automatic bypass is a better option than fitting 2 open lockshield valves to one of the rads

 

[2point8ghiax]

Thanks for the quick reply Kirkgas. I mentioned that the first 2 metres of the flow and return pipes will be 22mm copper. Is it ok to have the bypass near the end of these pipes (i.e. 2 metres away from the boiler) or does it need to be further from the boiler?

 

[kirkgas]

the instructions for the valve will tell you, (i THINK you need 6m of pipe in the circuit so that is 3m out then valve then 3m back on return will give you 6m), remember it needs to be accessible for maintenance, so you might need to pipe the 22mm to one side of the room and even if it is still left under the floor you can still get to it (if a carpet is fitted) if laminate flooring or tiles you should really pipe it to somewhere above the floor then back down again to the rads

 

[2point8ghiax]

Thanks again. Presumably the 6 metres is a minimum. So if I put the bypass near the upstairs flow and return manifolds, which will be under the carpeted landing, this will be OK?

 

[bengasman]

You will need considerably more than 6 metres if the pipe is run in plastic. You can avoid the whole bypass issue if you use a y-plan rather than a s-plan. Do not use microbore, it is pointless, keep it in 15mm

 

[Nige F]

You will need considerably more than 6 metres if the pipe is run in plastic. You can avoid the whole bypass issue if you use a y-plan rather than a s-plan. Do not use microbore, it is pointless, keep it in 15mm

Very true... Microbore copper was invented to save time/effort and maximise profit before plastic was capable of being used on c/heating. Invest in a Makita 90degree drill (240v)and a stubby auger- drill through your joists and cable in some 15mm barrier pipe. Then when you no longer need the drill- stick it on eBay -seriously .

 

[2point8ghiax]

You will need considerably more than 6 metres if the pipe is run in plastic. You can avoid the whole bypass issue if you use a y-plan rather than a s-plan. Do not use microbore, it is pointless, keep it in 15mm

Err, its a combi.

Alternatively, can I get 4 branch manifolds with 15mm outlets?

The reasons I'm using microbore/manifolds are;

A) I'm skint

B) Its a small house

C) The ceilings have been pulled down for replastering/boarding which means I can easily run manifolds and pipes for the upstairs rads from under the floor

D) Its a lot quicker and easier

E) I will only be living here for 5 years max.

Thanks for your advice.

 

[kirkgas]

You will need considerably more than 6 metres if the pipe is run in plastic. You can avoid the whole bypass issue if you use a y-plan rather than a s-plan. Do not use microbore, it is pointless, keep it in 15mm

why would OP need more than 6m of pipe if it was plastic, the idea of a bypass is to give the pumped water a route in case all trv's are shut, so why would pipe material matter? unless you have heat loss in mind, ie plastic will lose heat slower than copper, but pipes under floors should be insulated to minimise heat loss anyway, from memory (which isnt always a good thing!) i dont recall different minimum bypass circuit lenghts for different materials,
i do agree that microbore isnt the best as i posted, but OP asked if their plan for microbore was ok which it is

 

[D_Hailsham]

You will need considerably more than 6 metres if the pipe is run in plastic. You can avoid the whole bypass issue if you use a y-plan rather than a s-plan. Do not use microbore, it is pointless, keep it in 15mm

why would OP need more than 6m of pipe if it was plastic, the idea of a bypass is to give the pumped water a route in case all trv's are shut, so why would pipe material matter?

The 30cxi has a built in auto bypass!

 

[bengasman]

why would OP need more than 6m of pipe if it was plastic, the idea of a bypass is to give the pumped water a route in case all trv's are shut, so why would pipe material matter? unless you have heat loss in mind, ie plastic will lose heat slower than copper, but pipes under floors should be insulated to minimise heat loss anyway, from memory (which isnt always a good thing!) i dont recall different minimum bypass circuit lenghts for different materials...

Admittedly never checked with a manufacturer, but purely based on logic. If the manufacturer states a minimum length to be utilised with a bypass, I can think of no other reason than dissipating heat. If the bypass would be half a metre, it would dissipate virtually no heat, and a fair sized low content boiler could easily overheat before turning off the gas. Plastic dissipates considerably less than copper, hence should have more length. I install fewer than one heat-only boilers a year, and have never done one on a s-plan, so can hardly claim to be an expert on bypasses.
Not really relevant for this op, as it is a combi with integral bypass which I didn't realise.

 

[kirkgas]

why would OP need more than 6m of pipe if it was plastic, the idea of a bypass is to give the pumped water a route in case all trv's are shut, so why would pipe material matter? unless you have heat loss in mind, ie plastic will lose heat slower than copper, but pipes under floors should be insulated to minimise heat loss anyway, from memory (which isnt always a good thing!) i dont recall different minimum bypass circuit lenghts for different materials...

Admittedly never checked with a manufacturer, but purely based on logic. If the manufacturer states a minimum length to be utilised with a bypass, I can think of no other reason than dissipating heat. If the bypass would be half a metre, it would dissipate virtually no heat, and a fair sized low content boiler could easily overheat before turning off the gas. Plastic dissipates considerably less than copper, hence should have more length. I install fewer than one heat-only boilers a year, and have never done one on a s-plan, so can hardly claim to be an expert on bypasses.
Not really relevant for this op, as it is a combi with integral bypass which I didn't realise.

ben my dissipating heat comment was to get heat away from the boiler by circulating rather than heat loss through the pipe wall, which is why i said the material shouldnt matter, my thoughts on the bypass were to actually allow the water to flow round and cool down but primarily to pump round when the valves were shut so it wasnt noisy

 

[bengasman]

Just realised that I have never asked anybody in the know, like the manufacturer, WHY the bypass must be as given. Always assumed it was to get rid of excess heat, but as we know, assumption is the mother of all eff ups.

 

[kirkgas]

Just realised that I have never asked anybody in the know, like the manufacturer, WHY the bypass must be as given. Always assumed it was to get rid of excess heat, but as we know, assumption is the mother of all eff ups.

i have always thought (just waiting on the people queuing up to put me right ) but my thoughts on bypass were if boiler was on and all rads had trv's some would shut down as they should when hot and others would be manually shut by customer, this would leave water pumping out of boiler along circuit and hitting each shut valve, the water would then bounce (technical term) back to the boiler and be noisy and cause the boiler to possibly shut down on overheat as the burner is still on but the water cant leave the boiler, the bypass would allow the water to circulate round the (6m?) bypass circuit and alleviate the pump noise as the water had somewhere to go, internal bypass in boiler is to assist the boiler to not go to overheat but is not really designed to stop circuit noise as the internal bypass is minimal length, that is why it is now better to use auto bypass valves as they are spring loaded and when the system is cold and at lower pressure the valve is shut allowing all the water to go to the rads, as the system heats up the pressure increases, as the trv's close down the pressure increases even more forcing open the spring in the valve, this is better than having a fixed gatevalve as a bypass as the water goes round it all the time slowing rad heat up time

 

[bengasman]

I can see the logic. It does raise the question why a bypass is not required for a 3port valve where you could have the same situation as you described if the timer is set for ch only