Biasi/Savio 428S - Roomstat or not ?

[steviebobs]

Hi

I have had several great replies to my questions re this boiler and its past issues, but I have probably the simplest general question to ask now.

This system was not installed with a roomstat, (pump always running) and for years I have adjusted house temp via boilers stat.ie quarter on if not too cool and up to threequarters when chillier. (It is a fairly large detached bungalow)

Now that I have finally put some thought into it, it seems logical that I should have the boiler stat turned up and fit a room stat in the lounge controlling the pump, set at about 22/23 degs.

Views please? Apologies for overlooking what maybe the obvious for years...

Regards and Thanks.

SB

 

[D_Hailsham]

Now that I have finally put some thought into it, it seems logical that I should have the boiler stat turned up and fit a room stat in the lounge controlling the pump, set at about 22/23 degs.

Not only logical, it is now a requirement, under building regulations, to have a "boiler interlock", which is a means of turning the boiler off when the house has reached the required temperature. The usual way of doing this is the room thermostat. This will shut down the boiler and stop the pump at the set temperature, say 21C, and turn it back on when the temperature has dropped to, say, 20C. The boiler's temperature control is normally set to max.

You need a "volt free" thermostat.

If you do not have a programmer, you should consider installing a programmable thermostat.

 

[steviebobs]

Thanks for that reply D_H

I have a Danfoss 102 doing the programming, but my backround in electronics/electrics means I would have no probs complying as you say. so the next Q is which roomstat ? - is the Honeywell DT200 ok - seems simple enough to incorporate.

Regards and Thanks again.

SB

 

[D_Hailsham]

is the Honeywell DT200 ok

It's suitable, but the DT200 is now obsolete and has been replaced by the DT90E (wired) or DT92E (wireless)

 

[steviebobs]

Thanks again DH

did some web reseach last night and discovered that the 200 had been superceded.

I have decided to go 'wireless' and am just wondering now about whether to get just a roomstat or go for a programmable roomstat (CMT921).

The clock on the boiler went faulty many years ago so I wired a danfoss 102 that I already had to replace the original clock and it has worked fine.

Leave well alone perhaps and just go for the DT92E....

Regards and thanks again

SB

 

[Happyplumber]

a progammable wireless room stat will be an ideal solution for you.

Honeywell are excellent products and highly recommended

 

[steviebobs]

Thanks HappyPlumber

It is probably just me thinking that the Danfoss works (but may not tomorrow...) and also getting used to progging the timer remotely from the boiler !

SB

 

[D_Hailsham]

I have decided to go 'wireless' and am just wondering now about whether to get just a roomstat or go for a programmable roomstat (CMT921).

Go for the 7 day version CM927 aka CMT927. It will give better control than the DT92E plus Danfoss timer; and you will find the seven day feature very useful as you can change just one day of the week without upsetting the others.

 

[steviebobs]

Thank You all for your advice and guidance - the 927 gets ordered this pm !

SB

 

[steviebobs]

Well, I have installed the new Honeywell today and have to admit it is doing a few unexpected things, but believe I may be trying to use human logic versus algorithm.

It seemed to take a while to settle down,

1. I had to re-bind it when I installed it and again an hour later - seems to be staying 'bound' now.

2. Room temp display seems slow to respond to change - I am using two digi thermos as reference and they appear to be ahead of it when room temp increases.

3. I have got it on Manual to test its radio links and response, and have a situation where the room temp and target temp are both 21 but 'call for heat' symbol is on and BDR91 green light/boiler still on.

4. Call for heat symbol on roomstat on when boiler has turned off ( In fairness it does refer to this in the book, so have accepted it can happen).

So, am I trying to apply logic to a device that is smarter than me - ie using a smart algorythm etc. or is it misbehaving !!

Have to admit on 'unpackaging' the batteries were loose in the box and not 'cling wrapped' which makes me wary about this perhaps being 'used' before despite being a 'new' unit...

Any comment welcome.

SB

 

[D_Hailsham]

Room temp display seems slow to respond to change - I am using two digi thermos as reference and they appear to be ahead of it when room temp increases.

The CM927 moves in 0.5 degree steps, .i.e 20, 20.5, 21 etc.

What type of digital thermometers are you using? I have an IR thermometer. My CM927 currently reads 21. If I point the IR at the stat it reads 21.1C

I have got it on Manual to test its radio links and response, and have a situation where the room temp and target temp are both 21 but 'call for heat' symbol is on and BDR91 green light/boiler still on.

Is it on continuously or does it turn on for a few minutes and the go off for a few. If so, this is the PI algorithm working to maintain a constant temperature.

Call for heat symbol on roomstat on when boiler has turned off ( In fairness it does refer to this in the book, so have accepted it can happen).

This is normal. Mine is doing this at the moment: Set temp 21C, Room temp 21C. Don't forget that the boiler will cycle on and off to maintain the set temperature. I think the temperature is measured to a closer tolerance than the display, so a Room Temperature of 21C may mean anything between anything between 20.75C and 21.25C. So if it is just below set temperature, the flame will be on, even if the boiler is in the "off" part of its cycle.

 

[steviebobs]

THanks D_H

Answers probably as expected.

I didnt want to believe the unit was fault, moreso that I was 'under-estimating' the power of the algorithm.

I will give it 24 hours play and report back - nice and warm though...

Steve

 

[Agile]

Better to fit and forget!

Now does anybody understand E61s?

Tony

 

[D_Hailsham]

Now does anybody understand E61s?

Might do, if you said what it is.

 

[steviebobs]

HI

Dont want to get paranoid, but have set the auto settings now with a view to using 'Manual' when I want to over-ride. I have it Manual today as we are at home all day.

Just a couple of things: (Tony Glazier's point taken, but I just cant leave 'new' alone..until I trust it's ok)

1. I have set Target Temp at 18 degs and the room temp got there, boiler switched off, fine, but the room temp dropped to 16.5 before boiler came back on.

2. I have a couple of digi thermos near the roomstat and both read about 2 degs above roomstat reading for room temp. I have used these digi thermos for my tropical fishtanks and have found them quite accurate, is it poss that the roomstat readout is inaccurate for some reason?

S

ps - think the e61 is a Nokia (or a BMW...)