Alternative to TRVs?

[Hellcat]

Ok so I'm after advice on the mother of all central heating systems.

Rather than fiddling with TRVs and adjusting them weekly (daily even) as ambient temps raise and fall, I want to automate the system as much as possible.

Currently got an old Combi providing the 'umph', but the rest of the house is a blank canvas.

Within the constraints of currently available technology - please let your creative juices flow (and return?)

 

[htgeng]

Ok so I'm after advice on the mother of all central heating systems.
Within the constraints of currently available technology - please let your creative juices flow (and return?)

Sounds like the mother of all homework questions, but anyway....

You should probably ditch the old boiler and get a shiny new model, which is somewhat the opposite to what Mr Ramsay has done. Having said that the new one didn't have zero miles on the clock

Some people love to be constantly going around fiddling with TRV's but are you saying you don't want to do that?

 

[D_Hailsham]

Rather than fiddling with TRVs and adjusting them weekly (daily even) as ambient temps raise and fall,

Why do you think it is necessary to "fiddle with TRVs" as the ambient temperature alters?

The whole idea of the TRV is that it controls the flow of water through the radiator to maintain the room at a constant temperature - assuming the boiler is producing the necessary heat. Of course, if the outside temperature rises above that set on the TRV, the TRV will shut off the radiator completely and the room could rise to a higher temperature.

 

[Hellcat]

Yep, can't be hastled with constant adjusting of TRVs. Wanting to set it and go.

My initial rough idea was a digital room stat combined with zone valve for each room. ZV's mounted somewhere easy to get to like in the hallway since we know how much they like to stick. Base the whole system on a individual demand.

I've experience with multi-zone systems so this comes to me as a (too?)obvious extension on that principle.

As for the boiler. Think it will be staying for now, it's reliable and there and installed with the flow and return feeding from the extension into the main house.

 

[Hellcat]

Why do you think it is necessary to "fiddle with TRVs" as the ambient temperature alters?

The problem I find with TRVs is their proximity to the radiator means in a large room they're slowing the flow well before the rest of the room is getting upto temp.

Plus they don't give any feedback to the boiler... meaning until a bypass rad heats a hallway or similar upto temp for a roomstat to turn off demand the boiler is 'boiling' away. It all seems rather primative.

 

[Timmyturtle]

The whole point of TRVs is they dont need to be touched once set to the desired temperature

 

[tosh]

id get urself a room statt, less bother m8

 

[D_Hailsham]

The problem I find with TRVs is their proximity to the radiator means in a large room they're slowing the flow well before the rest of the room is getting up to temp.

I can see that problem happening if you have only one radiator in a large room as there will be air circulating round the room by convection, which may cause draughts. Mounting the TRV so the head is horizontal helps.

Plus they don't give any feedback to the boiler... meaning until a bypass rad heats a hallway or similar up to temp for a roomstat to turn off demand the boiler is 'boiling' away. It all seems rather primitive.

What feed back do you want? Until the coldest room, or the one which is slowest to heat up has reached temperature, you need the boiler running. Rooms which are not so cold or heat up faster will reach the set temperature sooner and the TRV will shut the rad down.

I made sure the hall heated up slower than the rest of the house by turning the hall rad down. It needed a bit of experimentation to get it right.

You could of course install a Honeywell CMzone system, with wireless thermostats or go the whole hog and put in a Hometronic system, but that will cost more than a new boiler!

 

[Hellcat]

All these sounds like work-arounds though - heating up some rooms slowly so they heat up last - I've one real chance as I'm re-furb'ing the house to do it right - do it once. Costs are spread over years.

Hometronic - is that total home automation like control4 systems? Don't quite need that.

Will look into the CMzone system though.

 

[Hellcat]

CMzone was close - but those valves on the rads are ugly!

 

[D_Hailsham]

I've one real chance as I'm re-furb'ing the house to do it right - do it once. Costs are spread over years.

The first thing to do is insulate the house - cavity walls, lofts, double glazing, draught proofing. You will then us less fuel and also find that there is a more consistent temperature throughout the house, which means fewer draughts and you will feel comfortable with a lower temperature.

You might be able to get a grant to help with insulation - try your gas and electricity suppliers.

Any control solution is going to be a compromise - unless you have each room as a separate zone with it's own motorized valve controlling the boiler.

Have you checked that your radiators are the correct size for the heat loss of the room?

 

[Hellcat]

I've one real chance as I'm re-furb'ing the house to do it right - do it once. Costs are spread over years.

The first thing to do is insulate the house - cavity walls, lofts, double glazing, draught proofing. You will then us less fuel and also find that there is a more consistent temperature throughout the house, which means fewer draughts and you will feel comfortable with a lower temperature.

You might be able to get a grant to help with insulation - try your gas and electricity suppliers.

Any control solution is going to be a compromise - unless you have each room as a separate zone with it's own motorized valve controlling the boiler.

An initial plan was to have a separate zone for each room with its own valve.

Insulation is difficult as the house is solid wall, single glazed sash - conservation area. Will be insulating under floors and in attic to the maximum possible thickness.

Are there any technical issues with using seperate zones for each room that I might have overlooked?

 

[D_Hailsham]

Insulation is difficult as the house is solid wall, single glazed sash - conservation area. Will be insulating under floors and in attic to the maximum possible thickness.

I had an Edwardian house with 13 inch solid walls - luckily not in a conservation area - so I know your problems.

Are there any technical issues with using separate zones for each room that I might have overlooked?

Complexity!

1. The pump will be working against a widely varying head as the valves open and closed. So you will need a variable pump, such as the Grundfos Alpha.
2. You may need to install balancing valves.
3. You will need wireless controls for each motorized valve with a method of synchronizing them. Read Honeywell Wiring Guide pages 24/25.

 

[simond]

The varying head problem can be addressed on older boilers with a bypass, such as the Danfoss AVDO.

By the time you've bought all those motorised valves, hidden them, bought all the separate zone controllers (and hidden them) Hometronic seems like the elephant in the room.

Did you just fancy trying to reinvent the wheel? I can tell you that the 20 or so Hometronics we've fitted in 2008 have a 100% customer satisfaction record. OK, it costs £3-4K, but compared to other supposed energy saving methods (solar springs to mind) it pays back and does what is promises.

 

[Hellcat]

The varying head problem can be addressed on older boilers with a bypass, such as the Danfoss AVDO.

Will certainly look into this varying head issue. I'm not sure how my dad's system gets around this - he has a 5 zone system (3 central heating zones and 2 hot water cylinders). Used to have a bypass with the old boiler but perhaps the new one has variable pump or internal bypass?


3. You will need wireless controls for each motorized valve with a method of synchronizing them. Read Honeywell Wiring Guide pages 24/25.

Wiring I've got a good scheme to work to. A developed version of the Honewell Guide. Excuse the light... was acting as my 'boiler' during my testing.

Untitled

• Hellcat
• 1 Dec 2008
• 1

Untitled

• Hellcat
• 1 Dec 2008
• 1