2 Zone Heating System

[asadm]

Hi All,

Let me start by stating that I am not a plumber. I should add that I have laid the piping and installed the radiators on a combi system previously...

With that in place, I am looking to have a new modern and efficient heating and hot water system in my house. The house is a shell at the moment as I am having ceiling boards removed and the house re-plastered. It seems an opportune time to re-plumb and install the most appropriate system. I have a combi system at present.

I have 3 bathrooms and two young kids, so water consumtion will be well contended! For this reason, I have discounted a combi and started to lean towards a system boiler with an unvented cylinder. Additionally, I plan to have a heating zone for upstairs and a seperate one for downstairs. Finally, I plan to lay a "trunk" with 22mm for the flow and return which goes as close as possible to the rads and then tees off into 15mm to feed the rads.

First question - is this an efficient, modern and suitable system? Should I be considering anything else?

Second question - assuming you agree on the above, do my two zones need their own flow and returns? i.e. a separate flow and return set for upstairs rads and a separate set for downstairs or can both upstairs and downstairs share the same return pipe but need a separate flow pipe which will have a zone fitted to it?

I look forward to your responses. Thanks in advance!

 

[ShaunCorbs]

normally if new build zone up and down stairs separate (with there own room stats)and unvented cylinder with a combi

you have two options

1: heat only boiler with unveted cylinder

2: combi for tap's eg kitchen sinks etc and cylinder for baths showers etc

 

[Simon F]

at some point all return pipes are connected, only 1 going into the boiler.
but run seperate return pipes back to the boiler for up and down and the cylinder or you can end up with heat going where you dont want it to.

 

[stevetheplumber]

you dont need to run seperate flow and return pipes but if you dont you will have to find space,preferably easily acessable for the motorised valves that will control each floor and run wiring to them back to the boiler if you go this way ensure the f and r pipework is large enough
shauns suggestion of using a combi and a cylinder is quite a good system as combis are cheaper than systems and youll always have some hot water

 

[GasmanxxxR1]

Maybe look at honeywell evo home, each rad is its own zone

 

[asadm]

Thanks for all the responses. I concluded that the unvented cylinder with 2 zones is the way to go. I have noted the suggestion on evohome. Any further considerations in terms of combi v system boiler in conjunction with an unvented cylinder?

I also appreciate that when the flow and return leave the boiler, there is a single set and I have concluded from your suggestions, that I should have a separate set teeeing off this for upstairs and downstairs (as opposed to sharing the return across both zones). A further question on this please - my instincts are telling me to bring the F & R out of the boiler into the ceiling void for a few metres (the chosen route) and then tee off for the two zones. However, this will mean that my two zone valves will be in the ceiling void i.e. plasterboard would need to be cut if they ever need replacing. Advice please?

Alternatively, I could tee pretty much as soon as I come out of the boiler and have my zone valves there, attached to the wall, near the boiler. Instinctively, a tee so early on doesn't feel optimal...

Once again, thanks for your advice

 

[Riley]

If you're piping from scratch why not put the valves in the airing cupboard near the unvented and tie all your pipes in there for f&r and the dhw cylinder

 

[asadm]

Hi Riley, A slight wrinkle perhaps...my boiler will be situated in the kitchen downstairs and the tank will be upstairs. Will your suggestion require a F&R to head to the tank and then tee off at that point? If yes, this will probably incur an extra 12 metres of pipe but also will it be inefficient to pump the water up there and then back down again?

 

[Riley]

Where will the pump be?

 

[Riley]

It's swings and roundabouts really. I would never put a valve somewhere where it can't be accessed as at some point they will need replacing. Airing cupboard is logical as I'd say I find 95% of zone valves in there. That's not to say that they have to be though. I've seen them in kitchen cupboards, behind removable panels, all sorts bit of creativity required perhaps but MAKE THEM ACCESSIBLE!!

 

[asadm]

Open to advice on that. I am meeting with the plumber this weekend and would appreciate any recommendations you can offer based on the above.

 

[asadm]

I could come along with the F&R out of the boiler horizontally in the ceiling void as described earlier and then drop vertically (behind a kitchen cupboard) put in place the tees and zone valves and then back up and away for downstairs and upstairs. This would be creative and accessible as you suggest but does the U arrangement of the piping present any challenges?

 

[Riley]

What issue do you envisage??? I feel this is leading somewhere?as long as the system is bypassed correctly if the boiler requires one then I think you should be fine

 

[asadm]

A birdie told me that I should avoid U's when laying out pipes. I would struggle to explain this any further. I think air locks and flow rate were mentioned...
If it gets your blessing, I'm happy to take that approach.

 

[Riley]

If it's a fully pumped system then it should work ok. Just be sensible with AAVs and sensible pipe runs

 

[asadm]

Can I go back to my initial disclaimer and confess that I don't entirely understand AAV, fully pumped, etc. and the implications it may have on what I am trying to do.
Fundamentally, am I best to create this U and make the Zone Valves accessible or alternatively do this as soon as I come out of the boiler?

 

[Norcs]

Hi Riley, A slight wrinkle perhaps...my boiler will be situated in the kitchen downstairs and the tank will be upstairs. Will your suggestion require a F&R to head to the tank and then tee off at that point? If yes, this will probably incur an extra 12 metres of pipe but also will it be inefficient to pump the water up there and then back down again?

No its not inefficient to pump up and back down again within a small domestic system.
You make up a three port flow and return manifold. You can buy them but they are expensive.
The boiler primary flow and return connects to the end of the manifold.
Zone valves on the flow. You keep everything compact but accessible and easy to work on. Main priority is to think of the guy doing the fixing.
Automatic air vent on the highest point (with an isolater to shut it down as they are notorious for leaking.) Usually on the cylinder top connection if the cylinder is on the first floor.

 

[asadm]

Thanks for the response. Can I clarify that you are suggesting that I use this approach near the boiler? One of the options under consideration was to tee off the two sets of flow and returns (2 zones) as soon as the flow and return comes out of the boiler. This would allow me to situate the zones in the same kitchen unit as the boiler. This would Lao not warrant any air vents. I was concerned that since this is so early on in the process, I may be losing pressure/circulation. Hence the later arrive was to form a U arrangement after a few metres of the flow and return away from the boiler.

 

[Norcs]

If the cylinder location is more central to the property then pipe the f&r to that location.

Then make up two manifolds with 3 ports each. Fit the manifold vertical with air vent valves on each.

 

[asadm]

Thanks Guys. Just a further thought. Is it more efficient to have the boiler and cylinder co-located? I am starting to wonder whether I should lose some bedroom space to put the boiler up there as well as the cylinder. This gives me more options in relation to what is being discussed here too

 

[asadm]

Hi,
I am preferring the option to co-locate the boiler and cylinder and will go with this unless you guys advise otherwise. The Gas and Water mains enters the garage and will be very easy to run across to the selected destination.
One further question for you pros if I may please: If I have all the rads connected up and flow and returns terminated where the boiler and cylinder will be situated, how much should I budget for the installation of the boiler and cylinder. I would estimate that a day would be ample to bring the gas and water provision to this location, especially as I am having all ceilings removed prior to the plastering. I am detached and the selected location is an external wall. I am hoping that this covers of the main variables.
I will pay for all materials and therefore only interested in labour costs.

 

[stevetheplumber]

to give a price even roughly we need to know where yopu are? usually best to run the gas external

 

[Scott_D]

What are you doing? What do you want the plumber to do?

 

[asadm]

Hi Steve, I am based in Aylesbury. I am hoping this along with the information I have provided gives a good basis for an estimation. I look forward to your response.

 

[asadm]

Hi ScottD,

I will provide two sets of flows and returns at the location where the cylinder and boiler will be installed. These will be connected to the appropriate radiators.
I will pay for all materials.
I need plumber to install boiler and cylinder at this location (and associated components). This backs to an external wall which can be used for flu. Gas supply and water mains are nearby and it's inconceivable that extending these to the required area would take the plumber more than a day.

I would appreciate your estimation on the labour cost.