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Electronic Thermostat - Can it be justified? |
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| message from Peter Hemmings on 11 May 2004 |
Hi,
I have just had trouble justifying the buying of the above to my
neighbour and wondered if, with new boilers they can still be
justified.
Background: I have a Baxi Barcelona fully pumped with two zone valves
(DHW and Htg) with a CM67 in the hall and TRV's on most radiators but
not in the hall. I leave the Heating controller on 24 hours with the
DHW on once a day. I am very happy with the convenience of the
thermostat and its operation in keeping the hall and downstairs at
constant temperatures.
My next door neighbour has had a large extension built with 3 extra
rooms and has ditched his old oil boiler and is fitting a new Valiant
Combi non-condensing boiler. I told him of the benefits and he said
that he was told by the Corgi installer that, as the has TRV's fitted
(maybe to all radiators) and the boiler sensed temperature and was self
regulating (sorry forgot the correct terminology) it would be of no
benefit to him except the convenience of temporary overriding settings
when on holiday etc!!
Unfortunately my argument that it was more efficient in maintaining
temperature went on "deaf ears" as he insisted that TRV's would do the
same on each radiator! Unfortunately I could not think of a reasoned
case for my system and I am now not sure that there is one.
So, (at long last) can someone let me know if they are still
worthwhile in these days of self-regulating high efficiency boilers or
are the now redundant?
Thanks
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| Dave Gibson replied to Peter Hemmings on 11 May 2004 |
I have TRV's on all my rads and must confess that the only thing I use my
electronic timer/thermostat for is for the timer function (except at the
beginning and end of the heating season). Normally I set the temperature to
26 deg and let the TRV's sort all the room temps out. Even though this way
round the circulation pump is on throughout my chosen heating periods I
still find it gives a higher overall efficiency.
I will add that the 'stat is in the hall, normally our coldest room. At the
beginning/end of the heating season (like around now, April/May time and
Sept/Oct) I turn the hall rads off and reset the target temp to a around 22
deg. That way if we get a warm day the circulation pump stays off.
So in answer to your question, yes they still can be justified (IMHO).
Dave
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| IMM replied to Dave Gibson on 13 May 2004 |
In your case it acts as a high limit and an optimiser, if it has one.
having the pump continuously on is better than switching it off and on. If
a the last closed TRV opens heat is readily available and no warm up period
fro the boier. Make for a more even temperature.
If only TRVs are used on all rads then an auto by-pass valve needs to be
fitted.
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| Dave Gibson replied to IMM on 13 May 2004 |
Its a solid fuel boiler with indirect cylinder + heat dump on gravity
circuit, so heating circuit does not require bypass.
Dave
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| IMM replied to Dave Gibson on 13 May 2004 |
My comments were directed more to the OP who has a Barcelona.
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| Peter Hemmings replied to Peter Hemmings on 16 May 2004 |
Christian,
Yep, agreed but my point was that originally the upstairs rads had
TRV's which also did not call for heat.
OK, I accept electronic thermostats are more efficient but the overall
cost (in my case) would probably take have taken considerably more than
2 years to recoup.
Yep I completely agree with the above but my case was somewhat
different.
Thanks for the information
All the Best
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| Christian McArdle replied to Peter Hemmings on 12 May 2004 |
It would only comply with the letter of approved document Part L1 if there
is a boiler interlock that turns off the boiler totally when there is no
call for heat. This normally requires either a room thermostat or a flow
switch to detect that all the TRVs have closed.
Christian.
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| Peter Hemmings replied to Peter Hemmings on 13 May 2004 |
Just a quick thanks to all who replied and FWIW my observations on
subzoning.
Also in respect to savings (on my system) I can confirm it saved its
cost in just over 2 years.
In message <40a376b2$0$20509$ed9e5944@reading.news.pipex.net>, Christian
McArdle <cmcardle75@nospam.yahooxxxx.co.uk> writes
A word of caution here, it really is "horses for courses". I had a
well insulated double glazed 70's semi and plumbed downstairs and
upstairs zones on separate thermostats/timers.
The system worked OK but as I left most doors open, the upstairs
bedroom heated up during the day and only in the extremes of winter
would it call for heat!!
So (in my particular case) the extra expense/time fitting was not
justified.
I agree with the subzoning principle for your layout. but I think cost
benefits of plumbing four zones might well be marginal particularly if
you had to pay for all the work!
Thanks
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| martin.shaw11 replied to Peter Hemmings on 17 May 2004 |
"electronic thermostats are more efficient but the overall
cost (in my case) would probably take have taken considerably more than
2 years to recoup."
A study was carried out using similar houses and families to find out
what the energy saving was for an electronic thermostat. There turned
out to be none. This was because the ordinary thermostat had such a
large hysteresis that it was used purely as an on off switch and was off
for significantly long times, particularly at night.
Obviously the electronic version is superior (I know I recently
upgraded to one) but don't expect any running cost savings necessarily.
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| N. Thornton replied to Peter Hemmings on 13 May 2004 |
electronic stats give much better heat regulation than TRVs, and thus
save needless energy use. They also allow different temps for
different times, again saving on energy. They typically pay back their
cost in a couple of years I worked out.
Regards, NT
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| Pete Cross replied to N. Thornton on 13 May 2004 |
So once the room with the thermostat is up to temp, the rest of the house
'loses' it's heating until the thermostat closes again ?
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| Martin Angove replied to Pete Cross on 18 May 2004 |
Define "off" though. Most programmables don't actually go off overnight,
just down to some lower-than-normal temperature. This winter, for
example, I fitted such a device in my parents' house. We happen to be
lodging there at the moment with two small children and there is also a
slightly wimpy lodger who can't stand the cold yet sleeps with his
window wide open (a crack I can understand).
In the "old days" before the programmable, the heating used to get
switched off overnight at the main switch (no timer) and so if the house
temperature dropped, it dropped and you cuddled deeper into your duvet.
When I was a child here in the 70s there were no radiators upstairs and
the single glazing would sometimes have beautiful fern-like patterns of
frozen condensation on them on a winter morning. Plenty of "me too"
replies to that one I suspect.
This winter, since the programmable, I have been woken several times by
the sound of the heating coming on at (say) 3 a.m. (the pump is the
other side of a plasterboard wall from the head end of my bed) in order
to keep the thermostat happy: it is set to an "off" temperature of 14C.
Below this certain people start complaining :-)
To return to the question though, I suspect that there is a *lot* of
complicated background to deal with before you can compare mechanical
with electronic, programmable or otherwise. For example, although the
"off" period of a mechanical may be longer, so too may the "on" period -
occupants only turning the thing down when it is too hot, and probably
opening a window as well!
To veer wildly off-topic, my mother-in-law has a thermostat which I am
pretty sure doesn't work. She regulates the house temperature (no TRVs
anywhere) by twiddling the flow temp. knob on the front of the boiler
:-)
Hwyl!
M.
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| IMM replied to Pete Cross on 13 May 2004 |
That is why you put it in the coldest room in the house that requires a
cooler temperature. The hall.
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| Christian McArdle replied to Pete Cross on 13 May 2004 |
Yes. Either put it in the coldest room so the rest of the house is already
up to temperature before it closes off, or put it in the room you are likely
to be using (i.e. lounge) so you don't care that the rest may not be as
accurately controlled.
Much better still, use subzoning and have different programmable thermostats
for each zone. I have zones for upstairs (bedrooms), downstairs
(receptions), kitchen and (soon) conservatory. This way each can have a
different temperature profile over time to reflect usage patterns and each
follow more accurately the desired temperature. The thermostats are placed
in the most used (or only) room in each zone.
Christian.
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| Christian McArdle replied to Christian McArdle on 14 May 2004 |
Ideal then. The subzoning would mean that there is no call for heat and the
upstairs radiators don't get hot, saving you money.
For me, it was just the cost of the thermostats and zone valves. Around 60
pounds per additional zone. There was no appreciable need for extra
pipework, certainly nothing in comparison to the extra length needed to
relocate the boiler to the loft.
The conservatory should always be on a separate zone, if at all possible.
This would save a fortune if you use the room infrequently (i.e. as a dining
room). I wanted a separate zone for the kitchen as has very different
construction to the reception rooms (much more external wall and window) and
runs a fan convector, which wouldn't share a zone particularly well with
radiators.
Christian.
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| Christian McArdle replied to Christian McArdle on 17 May 2004 |
That sounds like a comparison between an electronic (non-programmable) type
which is set to target temperature all the time to a manual type used as a
switch. How would it compare to a programmable one, which is also off for
long periods (i.e. overnight)?
Christian.
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| Christian McArdle replied to Christian McArdle on 18 May 2004 |
That's hardly the fault of the thermostat. Set it to 5C and tell them to
stop whinging!
Apart from the manually operated aspect, this is probably an efficient
method of modulation, as conventional boilers have greater thermodynamic
efficiency at low temperatures. However, you must be careful if there is any
sign of condensing operation if the knob is set too low. She should ensure
that no visible steam or water comes from the flue.
Christian.
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| martin.shaw11 replied to Christian McArdle on 19 May 2004 |
Good point. I think the comparison is still interesting though.
There was still a problem, because the poor response of the mechanical
thermostat meant that the system was switched off by the consumer until
they got cold and then they switched it back on only when they could be
bothered ie when it got really cold.
On the other hand the 'electronic' consumer tended to have their
house on the warm side because they comfortably could.
I can't remember where I saw the article (it was on a website) but the
article was pretty convincing.
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| IMM replied to N. Thornton on 13 May 2004 |
news:<SSMw0mBACToAFwJ6@phemings.demon.co.uk>...
The CM67, and others, has an optimiser. You punch in your occupancy time
and it delays the boilers firing until it needs too, keeping it off until
the last minute if need be. They also have inbuilt boiler anti-cycling.
Some boiler have this inside, but a belt and braces would do no harm.
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