Honeywell Evohome or just a "normal" wireless stat

[wizbongre]

Hi all,

Alongside some other more mundane tasks on the lists of things to do for our heating system, I want/need to get some sort of control system in place, over and above the digital time programmer on the boiler itself and the TRV's on all radiators.

I'm torn between going for a traditional 5 + 2 day digital wireless room stat, or something more complicated like the Evohome... We've got quite a big old semi that has solid walls and is a bugger to keep warm - our GlowWorm 30cxi is doing its best but I think more refined controls will help with efficiency and maintaining comfort.

Given the Evohome is relatively expensive, once you've bought the thermostat kit and then enough radiator valves for the house (we'd need 12) I was wondering if I could do it in stages? So just buy ther thermostat kit at first and use that as a normal (if expensive) room stat?

Any other thoughts or suggestions about the Evohome, or suggestions for something else similar?

 

[Dan Robinson]

Evo is great (I have it).

But also look at the Gloworm Climapro 2

 

[wizbongre]

Thanks Dan. I've not really found too much bad press about the Evohome generally, other than the costs. The big draw is being able to control different rooms at different temp/time crossovers throughout the day, such as bathroom & kitchen first thing for breakfast and three S's, then living room of an evening for example.

However, I'm conscious this kind zoning is only really successful if doors are kept shut, else hot and cold spreads from room to room, whereas a plain old room stat in the hall works across the whole house. As I said, it's a biggish house to heat in this way though!

I looked at the Climapro first but from what I could understand, it's only compatible with the newer Flexicom and Ultracom boilers - I have one of the older 30cxi models. Or am I missing something?

 

[Dan Robinson]

I have been informed it is compatible with all boilers - but the really clever bits won't work.

Happy to be corrected though.

 

[wizbongre]

That's interesting - I'll have to look into it a bit more again then.

Might even try phoning GlowWorm themselves!

 

[Dan Robinson]

You might get a little more help from those that know here. We have some real Glow-worm/Vaillant experts on hand.

 

[bell824]

climbapro wont work with CXI, the software isn't compatible.

 

[ALEC1]

However, I'm conscious this kind zoning is only really successful if doors are kept shut, else hot and cold spreads from room to room, whereas a plain old room stat in the hall works across the whole house. As I said, it's a biggish house to heat in this way though!

You also need thermal insulation between the rooms....ask any one who lives in a flat...if there is no insulation you can tell who whether the heating is on in the neighbours flat or not just by their boiler activity!


The problen as ever is the minimum flow rate through the (usually oversized) boiler....rads need much less flow than boilers...so on a big house you would need a low loss header...

 

[wizbongre]

Thanks for the follow-ups all.

Room to room insulation is a good point. I noticed the other day I could feel heat coming through the wall from one living room rad to our integral garage - no doubt this effect is happening all over the house. Ok if it is transmitting through internal rooms but not good if going externally, or into the garage.

So, few things for me to think about:
• Evohome probably not worth the expense so may as well go for a normal wireless room stat in the hall and heat the house as a whole (any recommendations? Contemplating the Honeywell CM927.)
• To help the above, carry on with insulating/draught proofing as much as possible (loft just done, other little draughts done and integral garage next on list as doors currently let a decent breeze through.)
• Research radiator backings, such as foil, Radflek, etc. Won’t help with efficiency or economy but may help with overall comfort. Could be cheap enough to try on external walls to see if it helps too.
• Current boiler sizing versus house requirements – not heard of a low loss header so need to research that. I should also probably do some proper calc’s of the house’s heat loss versus the boiler’s output. I’ve seen mention of range limiting or something for a boiler – can this be done after it has been installed and commissioned or is it an install only activity? As I understand it, this allows full heat for DHW but reduces the CH output to be as efficient as possible – is that right?

Certainly got lots to think about and most of it is free/inexpensive which is good. Any more advice and suggestions very welcome.

 

[wizbongre]

Just done a bit of measuring and calculating...

Using http://www.idhee.org.uk/calculator.html and a lot of messing around due to the shape/layout of the house, I get a requirement ~18kW. Using http://www.theradiatorcompany.co.uk/heatoutput/ I get a radiator requirement of ~14kW.

So, given our GlowWorm 30cxi is rated at 24kW for CH (I think) I assume that means it is over-sized?

Can it be range limited (assuming it wasn't at install of course - is it possible for an engineer to test/check if this is the case?)

 

[ALEC1]

I'd look at the climapro controls, which can be retrofitted to GW's. the allow a compensated flow to the heating on indoor modulation only or with an outdoor sensor...

 

[wizbongre]

I'd look at the climapro controls, which can be retrofitted to GW's. the allow a compensated flow to the heating on indoor modulation only or with an outdoor sensor...

All the stuff I've found so far has suggested Climapro isn't compatible with our older 30cxi (none Flexi/Ultracom) - I've read it only works with post 2007 boilers.

I've read about too many problems with weather compensation so far so that's off the table at the moment - thanks for the suggestion though.

 

[bell824]

I'd look at the climapro controls, which can be retrofitted to GW's. the allow a compensated flow to the heating on indoor modulation only or with an outdoor sensor...

some people refuse to read the whole post Alec guilty as usuall look above

FOR YOU ALEC THE CLIMBAPRO IS NOT COMPATIBLE WITH THE XI RANGE!!!!

 

[bell824]

Can it be range limited (assuming it wasn't at install of course - is it possible for an engineer to test/check if this is the case?)

cxi's came out the factory pre rated at 15kw so unless it was adjusted at install (probably not) then that is probably were it is.

 

[wizbongre]

@Bell824 - That's the sort of information that really helps - thanks very much. So if I take the kW requirements based on the radiator calc's I did its probably bang on, or at least pretty close.

Beginning to think I'm over complicating things and looking for issues that aren't really there!

Taking a step back, will order a room stat tomorrow (toss up between the Honeywell CM927 and the Myson MRPT RF - hedging towards the Myson for the increased setting points) and some radiator pipe thermometers to get the whole system properly balanced.

I've now got a long list of heating work to do - shame the weather isn't letting me get on!