Manifold versus TRV's

pomiwi

Hello, we are based in NZ and are looking at getting gas powered radiator heating (water), using a Bosch Worcester 37 cdi boiler. We are sold on having 2 x zones, living and bedrooms, and potentially the NEST thermostats to control both zones. NZ houses are easy, all one level, complete under floor access, so I am potentially going to run a flow and return pipe from each RAD to a central point. Question now is what to do next. The intent is to have 1 x nest controlling each zone, so the night time NEST needs to control the bedrooms. Our children are likely to need say 18 degrees at night in their rooms, where-as in the master bedroom we may want it colder say 15. My plumber recommends that we fit a manifold and no TRV's to the RADs and we restrict the flow to the radiator in the master bedroom, and place the NEST in the master bedroom. Set the nest to be 15, which in effect should be sending more flow through the kids bedrooms and they will be hotter? A guy I work with says something about flow speed has no direct relationship to heat and we should not bother with manifold and just do TRV's. Put the NEST in the hallway and ensure the RAD in the hallway is on full heat (no TRV) away from the NEST, and set NEST to temp you want bedrooms. You want your room colder turn your TRV down. Which way sounds the best option?

Gordy

Per the topic heading use both. Manifold distribution controlled with trvs.

SWEI

I would suggest a bit of research before you install a NEST on a radiant system. No need for zone thermostats if you have TRVs -- and they work better anyway.

Gordy

In rereading your post. Agree with others. Skip the nest thermostats.

Pipe everything home run to a manifold as you want , and use trvs. This gives total, and precise control to each radiator, and each room.

While it is quite possible to slave an entire system off one thermostat. It requires precise heatloss calculations room by room, and precise emitter sizing to achieve desired different set points in different rooms. Provided these rooms remain isolated.

How ever this confines you to the restrictions of that type of design. In the future desired room temps can change, and the next owner of your home will be bound to your design desires.

Using the home run trv system allows temperature setpoint flexibility to meet future changing needs.

pomiwi

Thanks for your comments. So you are suggesting TRV's on each radiator and no NEST - So I would use the standards FW120 controller that comes with the Bosch, set it to desired temp and timings etc then turn radiators up and down during the times using TRV? I was hoping for some more automation i.e. I didnt want to have to go to each TRV in the bedrooms in the morning and turn down or off etc, that was what i was hoping the zones would do ie bedrooms off AM and living on, then swap at night, any ideas how i would achieve that without zones? i was also liking the nest geo fencing ie turn heating off when we went out of town, thanks 4 helping

Gordy

Well more details on what your habits are is helpful when giving advice.

Will you be running outdoor reset? This will give the best efficiency potential of the boiler.
If so it is best not to set back as you describe.

The trvs are manual yes. But they do make ones that can be programmed as you stated. More dollars.

SWEI

I'm not intimate with the FW120, but the FW200 has some fairly sophisticated control options, including a vacation mode. I would investigate the options available in the controller before I decided on a thermostat. Many mod/con boilers have the ability to use one or more of their "thermostat" terminals as a trigger for internal functions (think boost, setback, vacation, etc.) The so-called smart thermostat (which is still just a switch as far as the boiler is concerned) then becomes more of an occupied/unoccupied sensor/timer and not a temperature control per se.

pomiwi

Thanks for your comments. I am not sure what outdoor reset is. OK here are our requirements and habits. We are a young family of 5 with quite predictable habits in terms of being away from home etc. At night our bedroom doors remain open. We wish to heat the living areas of the house to say 21 during the day, and keep bedrooms at say 16. The during the night we wish to turn living off (or drop down to say 10) and bedrooms up to 19. We want individual control in each bedroom i.e. TRV so we can turn the master down if too host and kids bedrooms up. On top of all this I also want some way of controlling the heating when on occasion we break habit and go away for a weekend and forget to turn it off, and also some way of monitoring the usage to drive more efficient behavior. Geo-fencing is a nice to have. We wish to avoid constantly messing with TRV's whether that be manually or through an APP. We have not run pipes, or installed boiler yet, it is all up for grabs. We havent even chosen the thermostat, FW120 was mentioned but what ever we get must work with a Worcester 37 cdi. I am confused as to what is best to do, single thermostat with TRV's, Heatmiser, NEST, Ecobee 3 - Manifold Argh!!! P.S. Its a heating system only no hot water.. hopefully that is enough information for you guys to help...Appreciate your help.

Gordy

outdoor reset modulates the boilers supply temperature to match the load the structure sees at a given outdoor temperature.

Example:

It's 40* F outside the system may only need 120* F supply water temp.

If it's 20*F outside the water temp may be 135*F

This is program is setup at installation, and comes with the boiler. This control also makes the boiler operate efficiently by only producing just warm enough water to offset the load.

Doing daily setbacks does not work well with this type of control.

jumper

TRVs should work very well with individual circuits. When retrofitted to old monoflows (diverters) distribution,not always. It's not a matter of messing with them. Once set where you like it you can leave it alone. You can always set back HHW supply temperature. It's not done often,but a common return is somewhat less messy than individual returns. And nobody will be confused which is supply and which is return.

SWEI

A thermostat, no matter how "smart" is really just a switch. It can only say one of two things to your heating system: either "it's too hot" or "it's too cold." That level of communication is simply not enough to deliver reliable comfort and efficiency.

Modern boilers modulate in order to change the temperature of the water they supply to the system. ODR is simple but very effective. It pairs beautifully with TRVs, because they are a proportional flow control device. Conventional zone valves and pumps are on/off devices and so suffer from the same limitations as a conventional thermostat.

Gordy

Can you get these in New Zealand?

Gordy

pomiwi

Hey, outdoor reset is called weather compensation - yes we will be getting that with the boiler, has an outdoor temperature sensor. I will check on Honeywell, I think my plumber said they interfer with a radio frequency that NZ ambulances use, but will check. thanks

Gordy

Well Unless someone else knows of a similar programable TRV set up like the honey well all ears. Pretty sweet I think. Will do everything you want too.

Unhippy

Try the these ones if the honeywell ones are going to give you issue's
http://www.conrad.com/ce/en/overview/0812043/MAX-Wireless-Heating-Control

i intend to use them on my rads when i get it all done.

i had an older style programmable remote TRV setup in my previous house.....it was great....trv's where underfloor so well out of harms way in case of kids, dogs...or just people shoving furniture against the wall without looking first.

I'm guessing your somewhere in the North Island if your looking at a gas boiler install.....i'm in Dunedin

Unhippy

Try the these ones if the honeywell ones are going to give you issue's
http://www.conrad.com/ce/en/overview/0812043/MAX-Wireless-Heating-Control

i intend to use them on my rads when i get it all done.

i had an older style programmable remote TRV setup in my previous house.....it was great....trv's where underfloor so well out of harms way in case of kids, dogs...or just people shoving furniture against the wall without looking first.

I'm guessing your somewhere in the North Island if your looking at a gas boiler install.....i'm in Dunedin

pomiwi

Thanks for your recommendation. Yeah we are in new Plymouth. Do you know what frequency they run on? Have you tested them yet?

Unhippy

They run 868Mhz which is also the upper end of the NZ cordless phone spectrum.....it also is used for half the wireless stuff around the place, gate openers, wireless alarm's etc

The ambulances in the 'naki area run 141.3875 and 141.4625

I haven't tried the TRV's yet.....haven't even got my radiators in at the moment

pomiwi

Thanks for your information on them. The cost comes in around $750 NZD, for 10 x rad TRV's, the cube, the thermostat etc. I am really confused about what to do, any help would be appreciated. What I have so far is:

1. 10 x rads on the wall
2. Each rad has flow and return individually run back to a central point in the house

The plan was to connect them all to a manifold.

The minimum I want is two zones i.e. one zone for day with bedrooms on low and living on full, and one for night with the opposite affect. I also wouldnt mind some sort of remote APP control, but to be honest we are a young family with pretty static routines.

I have a Bosch Worcester 37cdi boiler with weather compensation and a FW120 controller.

What should I do? If it bought these MAX bits, how would that work? Would the boiler be on 24/7 and the TRV's would open and shut based on their configuration which would tell the boiler to pump water? Would the CUBE talk to the Worcester FW120 controller? I am confused

Big Ed_4

For what you want lowering and raising temperatures in different sections of the house at different times you will need to have use programable thermostats like the Nest per zone.The Bosch control comes with the outdoor reset .An outdoor reset to me is an no brainer and is an must for efficiency and even heat comfort ..Programing the Bosch room setback control will drop the temperature through out the house which you may not want to do. You can bypass the boilers control set back settings and rely on the Nest.

Normally it's best to instal the thermostat in the coldest heated room . But will always end up in the Master bed room

Sizing panel radiators , You will first need to know the min amount output needed by a room to room heat loss calculation and know your designed temperature for your area. Now you know the min needed .Then choose the size radiator based on the listed supply water x BTU output chart . Condensing boilers are designed to run on low temperatures so you want to look on the lower end of the supply water BTU scale .. max 160* and below .. Larger the radiator the lower the supply water needed to heat the space . Lower the supply temperature the better with condensing boilers . Those high efficiency ratings on condensing boilers are based on low temperature supply . Will an larger size look better on the wall , if increasing try to increase on the same percentage per room when using an thermostat . Some panel radiators have built in throttle valves where you can adjust water flow either by it's cap and valve adjustments like on an Buderus so you can fine tune or pop on an TRV if needed.. Cool weather rooms Like North West rooms I would like to see an increase of size .. Easier to decrease output then increase . Remember the outdoor reset is controlling the supply water temperature as outdoor temperatures changes .. As the outside temperature drops the buildings increases BTS loss per hour , supply temperature increases to replenish and maintain inside temperature. You can make changes by adjusting it's curve ..

I would install them on an manifold and home run them rather then diverter tees ,It would give you the option of shutting off the radiator , using TRV's and most of the time all you need to run is 3/8" Heat PEX to supply enough BTU's (if ok with your plumbing inspector). I should add on this note , I only use "A" PEX . Its a expandable PEX which it's fitting are much closer to the supply tubing size B&C clamp type 1/2"... If using TRV's I would also use an automatic variable speed circulator,diverter valves or an pressure bypass in that order. You don't want to dead end a normal circulator ..


Note..When installing parallel piping like PEX manifolds it's an must to" reverse return" the radiators supply and return piping . Reverse Return.......On the supply manifold the tap nearest the boiler connect it's return on the tap furthest away from the boiler on the return manifold .First one to leave the last to return. .. This will equalize the pressure drops and even the flow to each loop or radiator .

All the adjustments should be set the coldest day of the year

pomiwi

Thanks for your help that's awesome! I am struggling between the MAX individual radiator control versus 2 x google nest's (1 zoned for bedrooms and one zoned for living). Usability is a big concern. Individual control of each radiator would be technically awesome, but the wireless comms, batteries in each TRV etc might be troublesome. And what would it save me in terms of energy use, 5% over nest and 2 x zones?

Gordy

How many bedrooms? In the future do you see all sleeping area individuals liking the same temperature? Using all bedrooms as 1 zone may seem fine now until children get older, and wifey has a change in life. Trvs give control to individual rooms.

gennady

You cannot do zoning with zone valves or zone pumps in the systems with outdoor reset, it will take hours for the zone to come to the setpoint after off period due to low temperature of the water. You will need the boost for this zone. Boost will overheat another zone or zones which were not off. For the same reason do not use setbacks.
If you want the zoning, you will need to move to modulating mixing valve zoning, with individual outdoor resets and boosts for each zone. While it will give you proper control, it will be considerable expense and it will create another problem.
Boiler has a minimum load for continious operation, and breaking load into smaller loads will bring boiler operation out of modulating. Boiler will switch to on/off operation and will become conventional non modulating non condensing boiler.

All saving and comfort you hope to get will not be achieved.
Do not listen to plumbers and engineers. Find good reputable heating professional.

Bottom line: go plain vanilla TRVs without any programmed setbacks.

That's my 2 cents.

pomiwi

Thanks for your replies. We have 4 x bedrooms. Just looking for simple solution to let us heat bedrooms at night without having to hear living areas and vice versa. I am thinking trvs on each bedroom is a must as like you say my wife might like the room cooler than the rest I am running all radiators flow and return back to central place, just because it's easier and in the future wouldn't rule out individual control of each radiator, but not now. So I am thinking two zones, two thermostat and controllers one for each zone and the fw120 that comes with Bosch just controlling the set back etc. I'm not sure what the last post means, but if I did this and didn't reduce flows on any manifold would that work? Sorry for the questions...