Advice on plumbing a new house

[ReJect]

Combi boilers have limited flow rates, so fine for single bathroom homes or one or two people occupancy most likely.
So depends on your requirements, which you haven’t said.

Unvented cylinders can give as good a flow rates as the mains and pipework allows, - so substantial, especially for several outlets, mains supply permitting obviously. Filling a bath from an unvented cylinder mains system is where you notice the speed of fill up.
Combi though a simple solution if it suits you.

Note that microbore pipes for to radiators can only have very short runs. Plastic pipes have heavier walls and therefore much smaller internal bores, so will be even worse at flow performance to rads.

 

[JohnD]

every time you turn a tap on and start running water, they fire up, heat the heat exchanger (slab of metal), heat the water inside it, continue heating until you turn the tap off. You then have a slab of metal and a volume of water that are both hot for no purpose. This heat will then leak away. Next time you turn a hot tap on, it will do it again. You did not use this heat.

 

[gwebstech]

Combi boilers have limited flow rates, so fine for single bathroom homes or one or two people occupancy most likely.
So depends on your requirements, which you haven’t said.

Unvented cylinders can give as good a flow rates as the mains and pipework allows, - so substantial, especially for several outlets, mains supply permitting obviously. Filling a bath from an unvented cylinder mains system is where you notice the speed of fill up.
Combi though a simple solution if it suits you.

Note that microbore pipes for to radiators can only have very short runs. Plastic pipes have heavier walls and therefore much smaller internal bores, so will be even worse at flow performance to rads.

thanks for that mate, thats what i was saying - as someone said earlier, it depends on how its used which for a family isnt ideal

 

[gwebstech]

every time you turn a tap on and start running water, they fire up, heat the heat exchanger (slab of metal), heat the water inside it, continue heating until you turn the tap off. You then have a slab of metal and a volume of water that are both hot for no purpose. This heat will then leak away. Next time you turn a hot tap on, it will do it again. You did not use this heat.

thanks, so what are you saying is the best option than a combi?

 

[JohnD]

hot water cylinder that has adequate capacity so you only need to heat it once or twice a day. Timer/programmer so the boiler heats it before/during bathtime. The boiler will then fire and run for one or two continuous periods, which is much more efficient than on/off/on/off/on/off/on/off

 

[gwebstech]

Ive just been reading the boiler manual and it says to have 600mm from the flue to any opening, the wall in this room is only around 600mm wide so obv that means a flue wont be far enough away. Are flues only allowed to exit a wall in a straight horizontal line or can you add angles so that i could pipe it so the vapour is at least 600mm from the door (ie add a vertical 90 to the flue and make it go further up the external wall)

if the flue can only go out horizontally then this sorts the fan issue out as the boiler will need to fitted elsewhere

 

[oldbutnotdead]

Depends on your boiler. Intergas and Worcester permit horizontal out the wall then vertical up, no idea if others do but well worth checking before you buy.
EDIT THE boiler manual? One you've already bought or one that has been included as part of an install package

 

[gwebstech]

EDIT THE boiler manual? One you've already bought or one that has been included as part of an install package

id picked a combi and was looking through the manual, i havent bought one yet and after everyones advice i might just get a system boiler instead seeing as its a family house

 

[oldbutnotdead]

Fair enough. You really need the heat loss calcs and the water pressure numbers before selecting your heat source and system design.

 

[gwebstech]

Fair enough. You really need the heat loss calcs and the water pressure numbers before selecting your heat source and system design.

by heat loss cals you mean the BTUs needed for each room? or is it something else?

 

[oldbutnotdead]

As you said the BTU or kw for each room and add on 3kw for a standard cylinder

 

[gwebstech]

As you said the BTU or kw for each room and add on 3kw for a standard cylinder

hi mate

the total BTU is anout 30k plus 3k for cylinder so 33k total. The water pressure will be on a 32mm pipe so they say they aim for 1.5 bar pressure and 1 litre per second flow

so what do you think will suit the design best? im tempted to go for combi to run 1 shower and have a cylinder for the main bathroom. I think thats the best of both worlds. Will the cylinder need a separate programmer to say a Hive or nest? would it be treated as a zone or something on one of those 2 controllers?

thanks

 

[oldbutnotdead]

30kw. Hope its a mansion....
Pressure may be a bit low for simultaneous combi and unvented cylinder option but that would be my favourite (combi for shower, cylinder for the rest).
Yes ideally you'd have an individual zone for the cylinder. For a house your size you might want 2 heating zones so for control you'd need a 2 channel Hive for heating and another single channel Hive for hot water. Or Nest or whatever

 

[gwebstech]

30kw. Hope its a mansion....
Pressure may be a bit low for simultaneous combi and unvented cylinder option but that would be my favourite (combi for shower, cylinder for the rest).
Yes ideally you'd have an individual zone for the cylinder. For a house your size you might want 2 heating zones so for control you'd need a 2 channel Hive for heating and another single channel Hive for hot water. Or Nest or whatever

Mansion lol?? does that sound a lot in BTU?

pressure wise - id only see that as an issue with the combi powering the en suite shower wouldnt i?

i was wondering - with it being a new house with 100mm insulation in the cavity, should i go for 2 rads in the kitchen or 1? its quite a big space and i know how much of a pain a cold kitchen can be in the winter. What do you think?

thanks for the help

 

[oldbutnotdead]

Combi and unvented cylinder both rely on mains pressure to push water through to the taps. Your pressure sounds a bit low but if the flow (60 ltr/min) is as advertised you'll be fine, the combi will self-limit to 12 ltr/min leaving plenty of flow on the unvented.

2 rads would give a more even heat distribution at the cost of losing wall space. You can get underplinth heaters....