Hi,

Our house is arranged over 3 floors and the current system has a zone
valve for each floor, all 22 radiators have manual TRVs. For various
reasons the old control system must be replaced (long story). The boiler
is a large traditional open flue boiler (not condensing), hot water is an
unvented cylinder on a separate time clock.

Right now some rooms remain cold even when the thermostat thinks the house
is up to temperature (it's an old stone house with little scope for extra
insulation and we're not going to replace any radiators). I think it's due
to poor placement of the thermostats rather than an unbalanced system or
undersized rads.

The honeywell HR80 wireless radiator TRVs with their CM-Zone http://
www.cm-zone.com/ or EvoHome http://www.evohome.info/ controllers looked
interesting as an option but fitting one to each radiator in the house
would be very expensive, cheapest I found the HR80 is £75 so £1650 for the
whole house!

Would extra zoning/room scheduling really save that much extra (enough to
justify all the HR80s) over the 3 zone control we currently have?
Particularly for the first and second floor which just have bedrooms &
bathrooms - individual rooms (eg spare room) that are not in use can
already be turned down via their TRV. Whilst it would be nice to have
separate control of the the bathroom temperatures, I can't justify nearly
that much expenditure to achieve it.

Instead I'm considering using either the evotouch:
http://products.ecc.emea.honeywell.com/europe/ecatdata/pg_evohome.html
or three cm927 programmable stat units:
http://products.ecc.emea.honeywell.com/europe/ecatdata/pg_cm920.html
to control the 3 heating zones via the existing zone valves. If necessary
I could still add a couple of HR80s to act as remote sensors in the rooms
that don't get hot enough under the current system or just move the
wireless stats from the hallway into those rooms.

The price breakdown (without HR80s) is as follows:

With EvoHome -
[*] evotouch controller with one relay: £251
[*] Two DT92 sensors/setpoint adjusters - £65 each
[*] extra relay for boiler control - £60

Total cost £441.

With CM927 -
[*] 3 x CM927 stat & relay packs: £102 each
[*]One extra relay for boiler control £60

Total cost £366.

The CM927 option is cheaper but I won't get the snazzy touch screen
central control, or the flexibility to later add extra zones by filling
the house with HR80 TRVs (evotouch supports up to 8 zones). Right now I'm
leaning towards the evotouch.

I believe that when a boiler relay is fitted both stats performs load
compensation by cycling the boiler, dependant on how close to the set
point it is and how fast the house is loosing heat. Can anyone verify this?

Is a direct load compensation like this right for a conventional open flue
boiler? The Honeywell pages say the CM927 & evotouch are for any boiler
but I read some worrying things about direct load compensation resulting
in condensate corroding the heat transfer matrix when used with non
condensing boilers.

I'd get a gas safe man in to do the install (unfortunately all the
domestic installers I've contacted so far have been rubbish at giving
advice) but once it's in adding extra wireless TRVS should be a DIY job.

Any comments or suggestions would be much appreciated. Should I be
considering any other systems? I've also looked at heatmiser:
http://www.heatmiser.co.uk/
but to me it didn't to seen as good as the honeywell options.

kind regards,

drbob

On Mar 11, 7:49*pm, drbob wrote:
Hi,

Our house is arranged over 3 floors and the current system has a zone
valve for each floor, all 22 radiators have manual TRVs. For various
reasons the old control system must be replaced (long story). The boiler
is a large traditional open flue boiler (not condensing), hot water is an
unvented cylinder on a separate time clock.

Right now some rooms remain cold even when the thermostat thinks the house
is up to temperature (it's an old stone house with little scope for extra
insulation and we're not going to replace any radiators). I think it's due
to poor placement of the thermostats rather than an unbalanced system or
undersized rads.

The honeywell HR80 wireless radiator TRVs with their CM-Zone http://www.cm-zone.com/ or EvoHome http://www.evohome.info/ controllers looked
interesting as an option but fitting one to each radiator in the house
would be very expensive, cheapest I found the HR80 is £75 so £1650 for the
whole house!

Would extra zoning/room scheduling really save that much extra (enough to
justify all the HR80s) over the 3 zone control we currently have?
Particularly for the first and second floor which just have bedrooms &
bathrooms - individual rooms (eg spare room) that are not in use can
already be turned down via their TRV. Whilst it would be nice to have
separate control of the the bathroom temperatures, I can't justify nearly
that much expenditure to achieve it.

Instead I'm considering using either the evotouch:
http://products.ecc.emea.honeywell.com/europe/ecatdata/pg_evohome.html
or three cm927 programmable stat units:
http://products.ecc.emea.honeywell.com/europe/ecatdata/pg_cm920.html *
to control the 3 heating zones via the existing zone valves. If necessary
I could still add a couple of HR80s to act as remote sensors in the rooms
that don't get hot enough under the current system or just move the
wireless stats from the hallway into those rooms.

The price breakdown (without HR80s) is as follows:

With EvoHome -
* * * *[*] evotouch controller with one relay: £251
* * * *[*] Two DT92 sensors/setpoint adjusters - £65 each
* * * *[*] extra relay for boiler control - £60

Total cost £441.

With CM927 -
* * * *[*] 3 x CM927 stat & relay packs: £102 each
* * * *[*]One extra relay for boiler control £60

Total cost £366.

The CM927 option is cheaper but I won't get the snazzy touch screen
central control, or the flexibility to later add extra zones by filling
the house with HR80 TRVs (evotouch supports up to 8 zones). Right now I'm
leaning towards the evotouch.

I believe that when a boiler relay is fitted both stats performs load
compensation by cycling the boiler, dependant on how close to the set
point it is and how fast the house is loosing heat. Can anyone verify this?

Is a direct load compensation like this right for a conventional open flue
boiler? The Honeywell pages say the CM927 & evotouch are for any boiler
but I read some worrying things about direct load compensation resulting
in condensate corroding the heat transfer matrix when used with non
condensing boilers.

I'd get a gas safe man in to do the install (unfortunately all the
domestic installers I've contacted so far have been rubbish at giving
advice) but once it's in adding extra wireless TRVS should be a DIY job.

Any comments or suggestions would be much appreciated. Should I be
considering any other systems? I've also looked at heatmiser:
http://www.heatmiser.co.uk/
but to me it didn't to seen as good as the honeywell options.

kind regards,

drbob

As I understand it the problem is that some rooms fail to reach target
temp. If they're only a few degrees down, a tiny very quiet fan
bosting unit that sits under the radiator (or on it) could be all
that's needed.


NT

On Fri, 11 Mar 2011 20:56:03 -0800, Tabby wrote:

As I understand it the problem is that some rooms fail to reach target
temp. If they're only a few degrees down, a tiny very quiet fan bosting
unit that sits under the radiator (or on it) could be all that's needed.


The rooms failing to reach target temp is part of the problem, however
even if it wasn't an issue the control system would need replacing as it
is totally unsuitable for a domestic setting (It's a commercial energy
management system more suited to a factory, the only way to change
anything is to enter a password on a central panel and go though a dozen
menus. How it ended up in a house is the long story I alluded to before).

So any comments about the system I proposed in my original post or
suggestions for other options would be much appreciated.