Splitting radiators into 2 zones

[Gaz the Sparky]

I am having the heating system upgraded in my house and currently have all the floorboards up.

I have found all the manifold points for all the radiators in the house. At the moment they are all on one zone.

I am wanting to split these into 2 zones upstairs and downstairs.

My question is do I need to move both the flow and returns of the radiators?

Or can I leave the returns as they are and just move the flows to a new manifold controlled by a new zone valve ?

How best is it to pipe the 3 zone valves from the 1 22mm flow from the boiler?

 

[Madrab]

Yes, all the returns can feed into a single pipe back to the boiler.

Pipe size really depends on length of pipe runs, bends, pump(s), valves etc. is it a combi or System/HO? If your putting in 3 2 port valves then it would suggest you have a HW cylinder too? At a min I'd keep the main flows and primaries at 22mm and then branch 15mm feeds to the rads to keep resistance to a min.

 

[Gaz the Sparky]

Yes, all the returns can feed into a single pipe back to the boiler.

Pipe size really depends on length of pipe runs, bends, pump(s), valves etc. is it a combi or System/HO? If your putting in 3 2 port valves then it would suggest you have a HW cylinder too? At a min I'd keep the main flows and primaries at 22mm and then branch 15mm feeds to the rads to keep resistance to a min.

Thanks for the reply

At the moment there is a 22mm flow from the boiler to 2 zone valves one for the radiators and one for the presurised hot water tank

the radiator return 22mm and 22mm from the hot water coil then tee into the 22mm return back to the boiler.

I am looking at lifting the 5 upstairs radiators off of the existing pipework and creating a new zone adding another 22mm zone valve.

So questions as above I guess I can leave the returns of the upstairs radiators and just move the flows onto a new manifold and valve.

Next there is 1 radiator in the hall which has no trv so there is always a flow but as I’m splitting the 2 zones should I install another non trv radiator on the upstairs new zone? Or should I install a bypass valve

I also have 1 radiator downstairs that goes cold when the hot water valve opens. When the hot water is off valve closed it heats up but when the water is on the downstairs radiator doesn’t heat up.

I have read online that you can fit a balancing valve on the return of the hot water cylinder to drop down the flow rate of the hot water. Or would balancing the radiators solve this problem ?

Thanks for your advice

 

[Madrab]

So questions as above I guess I can leave the returns of the upstairs radiators and just move the flows onto a new manifold and valve.

All returns can feed back into the single return to the boiler.

Next there is 1 radiator in the hall which has no trv so there is always a flow but as I’m splitting the 2 zones should I install another non trv radiator on the upstairs new zone? Or should I install a bypass valve

You'll be better off getting an automatic bypass fitted to the system

I also have 1 radiator downstairs that goes cold when the hot water valve opens. When the hot water is off valve closed it heats up but when the water is on the downstairs radiator doesn’t heat up.

Balance the system properly and fully once the alterations are complete. You'll want to check where on the flow that radiator is fed from as it may not be on the correct branch.

 

[stem]

Next there is 1 radiator in the hall which has no trv so there is always a flow but as I’m splitting the 2 zones should I install another non trv radiator on the upstairs new zone? Or should I install a bypass valve

This is not only done to maintain flow through the system, and these days many boilers have an integral by-pass anyway so no external by-pass is needed. A TRV should not be fitted to a radiator in the same room that a room thermostat is located. Otherwise the TRV could interfere with the operation of the room thermostat and stop it working.

 

[Gaz the Sparky]

This is not only done to maintain flow through the system, and these days many boilers have an integral by-pass anyway so no external by-pass is needed. A TRV should not be fitted to a radiator in the same room that a room thermostat is located. Otherwise the TRV could interfere with the operation of the room thermostat and stop it working.

So it would be better to have another non Trv valve on the new upstairs zone. The new thermostat is to be fitted on the landing to control the new zone so will leave the landing radiator without a trv

So to make the new upstairs zone all I have to do is lift the flows of all the upstairs radiators and install a new zone valve and connect the flows to that. It won’t effect the heating in a bad way if I leave the returns as they are?

Or Should the flow and return of each radiator go back to the same point to keep the flow balanced ?

 

[Madrab]

You do need to check your boiler MI's, many boilers do need a external bypass and should be fitted before the valves

 

[stem]

So it would be better to have another non Trv valve on the new upstairs zone.

Yes, in the same room that the room thermostat is located.

The new thermostat is to be fitted on the landing to control the new zone

Putting the upstairs thermostat on the landing is a bad idea. Not only is the upstairs thermostat located in an area it has no control over, and that is actually controlled controlled by the downstairs thermostat. It will also will be receiving heat rising up from the downstairs zone. Usually upstairs landings are one of the warmest places in the home, and if so the worst place to locate a room thermostat. Heat rising up from downstairs could cause the upstairs thermostat to switch off all the bedroom radiators even if the bedrooms are cold. Most new builds where the building regulations require they be built with two zones, locate the thermostat in the master bedroom, and slightly downsize the radiator to ensure it's the last upstairs room to warm up.

It should be in a cool bedroom, ideally the last to warm up. That way the other rooms will be warm enough, (but not overheated because of their TRV’s) before the room thermostat switches the entire zone off.

 

[Gaz the Sparky]

Yes, in the same room that the room thermostat is located.


Putting the upstairs thermostat on the landing is a bad idea. Not only is the upstairs thermostat located in an area it has no control over, and that is actually controlled controlled by the downstairs thermostat. It will also will be receiving heat rising up from the downstairs zone. Usually upstairs landings are one of the warmest places in the home, and if so the worst place to locate a room thermostat. Heat rising up from downstairs could cause the upstairs thermostat to switch off all the bedroom radiators even if the bedrooms are cold. Most new builds where the building regulations require they be built with two zones, locate the thermostat in the master bedroom, and slightly downsize the radiator to ensure it's the last upstairs room to warm up.

It should be in a cool bedroom, ideally the last to warm up. That way the other rooms will be warm enough, (but not overheated because of their TRV’s) before the room thermostat switches the entire zone off.

Thank you Stem for your explanation of the correct thermostat location. I will fit the thermostat in the master bedroom instead.

With regards to my other questions

Am I ok just to lift the flows of the upstairs radiators ? Or should the returns be lifted and run back to the same location as the flows to keep the system flowing equally or does it in fact not matter ?

Other question is the one radiator that goes cold when the hot water valve opens. Should I fit a valve ofsome discripton to the return of the heating coil to restrain the flow through TVs how water coil or not ?

 

[Gaz the Sparky]

Bumping this thread again as I'm still altering the pipework and have a couple more questions if you don't mind me asking.

I am installing the upstairs thermostat in the master bedroom, but can I still have a TRV on this radiator and do i need to have a smaller radiator in the bedroom or can I leave the existing one ? does one of the radiators on the upstairs zone need to have standard valve on so there is a flow or can this be left out if i install a bypass valve by the zone valves.

Again the downstairs hallway has existing valves on to allow the flow but can these be removed and a TRV installed as there is a bypass valve by the zone valves.

the downstairs thermostat is in the hallway so again do I need to downsize the radiator or can i keep the existing radiator I guess i could turn the TRVs down in the rooms with the thermostats ?

cheers for the replys

 

[endecotp]

I am installing the upstairs thermostat in the master bedroom, but can I still have a TRV on this radiator

You shouln't have a TRV on this radiator. Instead, the new thermostat will turn the boiler (and/or zone valve) off when this room is warm enough.

Regarding the bypass - as Madrab said above, you need to check the instructions for your boiler as many incude an internal bypass.

 

[Gaz the Sparky]

right I'm going to fit a bypass valve anyway but each zone will have one radiator which has normal valves one in the downstairs hallway as the downstairs thermostat is in the hallway and the upstairs zone will have a normal valve on the master bedroom radiator as that is where the upstairs thermostat is

 

[oldbuffer]

Just a small point. Make sure the Tee from the hot water cylinder remains the last junction into the return before the boiler. Otherwise, you can get reverse circulation through the central heating with some radiators getting hot when the hot water is being heated.

 

[Gaz the Sparky]

Just a small point. Make sure the Tee from the hot water cylinder remains the last junction into the return before the boiler. Otherwise, you can get reverse circulation through the central heating with some radiators getting hot when the hot water is being heated.

With regards to the returns all the radiators in the house are currently plumbed in on one zone could I remove just the flows to the upstairs radiators and leave the returns as they are and put just the upstairs flows onto a new zone valve or will this mess the system up.

 

[oldbuffer]

What you want to do is fine. My point only applies if you were to change the returns so that the hot water return joins the other returns other than as the last junction before the boiler.