HI Folks
As per the subject - does such a thing exist?
(Tried Googling - massive amount of hits .....)

Situation is - ground-source heat-pump to conventional radiators, which
all works well.
Programmable wall-stat in sitting-room - calls for heat, starts
heat-pump, temperature then rises slightly, turn off stat.

The heat-pump is just a big fridge-in-reverse - and takes a serious
amount of surge current to get the compressor spinning. It's said that
short-cycling (stop/start) isn't good for these units.... - and
common-sense suggests that, once started, it'd be wise to let the thing
run for half an hour or so each time..?

In an attempt to minimise this short-cycling, the engineers installed a
din-mount time-on-delay relay (8 mins or so), between the 'stat and the
heat-pump - idea being to sort of 'debounce' the call-for-heat from the
stat.
The pump itself is installed in the workshop.
When I'm working out there, I frequently hear the circulation pump start
up, then, after the short delay, the lighting dips & the compressor
starts - only to cut out again after no more then 30 seconds... This
can't be a Good Thing?

I did call the engineers back, who said 'oh no Sir, it can't possibly be
doing that' - and went away, promising to return.... that was some
months ago.

So - wondering whether fitting a programmer that's more capable would
make sense, or if the 'delay-on' timer should be changed to a 'run-on'
configuration....?

Any ideas, please?
Thanks, Adrian

Danfoss 40704

On 17/05/2017 08:00, Adrian Brentnall wrote:
HI Folks
As per the subject - does such a thing exist?
(Tried Googling - massive amount of hits .....)

Situation is - ground-source heat-pump to conventional radiators, which
all works well.
Programmable wall-stat in sitting-room - calls for heat, starts
heat-pump, temperature then rises slightly, turn off stat.

The heat-pump is just a big fridge-in-reverse - and takes a serious
amount of surge current to get the compressor spinning. It's said that
short-cycling (stop/start) isn't good for these units.... - and
common-sense suggests that, once started, it'd be wise to let the thing
run for half an hour or so each time..?

In an attempt to minimise this short-cycling, the engineers installed a
din-mount time-on-delay relay (8 mins or so), between the 'stat and the
heat-pump - idea being to sort of 'debounce' the call-for-heat from the
stat.
The pump itself is installed in the workshop.
When I'm working out there, I frequently hear the circulation pump start
up, then, after the short delay, the lighting dips & the compressor
starts - only to cut out again after no more then 30 seconds... This
can't be a Good Thing?

How often?
It may be that it only needs 30 seconds to reheat the water if only one
radiator is actually on and the rest are off due to thermostatic valves.

Compressors normally have a protection mechanism to prevent them being
restarted too soon. My dehumidifiers, AC, fridge and freezer all have
them built in.

My wireless stat has a built in anti cycling system, by default it will
only operate six times an hour but I have set it to 12 as I have little
water in the system.


I did call the engineers back, who said 'oh no Sir, it can't possibly be
doing that' - and went away, promising to return.... that was some
months ago.


Find the manual for the timer and see if its set correctly.

So - wondering whether fitting a programmer that's more capable would
make sense, or if the 'delay-on' timer should be changed to a 'run-on'
configuration....?

Any ideas, please?
Thanks, Adrian

Danfoss 40704

On 17/05/2017 13:16, dennis@home wrote:
On 17/05/2017 08:00, Adrian Brentnall wrote:
HI Folks
As per the subject - does such a thing exist?
(Tried Googling - massive amount of hits .....)

Situation is - ground-source heat-pump to conventional radiators,
which all works well.
Programmable wall-stat in sitting-room - calls for heat, starts
heat-pump, temperature then rises slightly, turn off stat.

The heat-pump is just a big fridge-in-reverse - and takes a serious
amount of surge current to get the compressor spinning. It's said that
short-cycling (stop/start) isn't good for these units.... - and
common-sense suggests that, once started, it'd be wise to let the
thing run for half an hour or so each time..?

In an attempt to minimise this short-cycling, the engineers installed
a din-mount time-on-delay relay (8 mins or so), between the 'stat and
the heat-pump - idea being to sort of 'debounce' the call-for-heat
from the stat.
The pump itself is installed in the workshop.
When I'm working out there, I frequently hear the circulation pump
start up, then, after the short delay, the lighting dips & the
compressor starts - only to cut out again after no more then 30
seconds... This can't be a Good Thing?

How often?

As there's the on-delay timer, can be as often as 6 or 7 times per hour.

It may be that it only needs 30 seconds to reheat the water if only one
radiator is actually on and the rest are off due to thermostatic valves.

Don't think that's happening.
I think what's happening is that the room-stat triggers the on-delay
timer. The temperature then increases, and the stat drops out, but the
timer continues to run. I 'think' that the timer then tones out, and
causes a brief 'on' signal to the compressor, even though it's input
signal has already dropped.. Need to double-check this with the timer
manufacturer though..


Compressors normally have a protection mechanism to prevent them being
restarted too soon. My dehumidifiers, AC, fridge and freezer all have
them built in.

My wireless stat has a built in anti cycling system, by default it will
only operate six times an hour but I have set it to 12 as I have little
water in the system.

What make/model?


I did call the engineers back, who said 'oh no Sir, it can't possibly
be doing that' - and went away, promising to return.... that was some
months ago.


Find the manual for the timer and see if its set correctly.

The delay-on timer? - yes it is.
Thanks
Adrian

So - wondering whether fitting a programmer that's more capable would
make sense, or if the 'delay-on' timer should be changed to a 'run-on'
configuration....?

Any ideas, please?
Thanks, Adrian

Danfoss 40704

Adrian Brentnall wrote:

As per the subject - does such a thing exist?

The heatmiser prog stats allow setting a switching differential
from 0.5 to 3 degrees, in 0.5 degree steps.

On 17/05/2017 13:44, Adrian Brentnall wrote:

My wireless stat has a built in anti cycling system, by default it will
only operate six times an hour but I have set it to 12 as I have little
water in the system.

What make/model?

CMS927 honeywell IIRC.

On 17/05/2017 14:29, Andy Burns wrote:
Adrian Brentnall wrote:

As per the subject - does such a thing exist?

The heatmiser prog stats allow setting a switching differential
from 0.5 to 3 degrees, in 0.5 degree steps.

Ah thanks, Andy.
You mean the PRT-B - on the right-hand side of this page?
https://www.heatmiser.com/en/battery-thermostat-series/

Adrian Brentnall wrote:

Andy Burns wrote:

The heatmiser prog stats allow setting a switching differential
from 0.5 to 3 degrees, in 0.5 degree steps.

You mean the PRT-B - on the right-hand side of this page?
https://www.heatmiser.com/en/battery-thermostat-series/

That, or the similar slimline ones for 230V/12V power instead of
battery, also the touchscreen range, in fact I would suspect any of
their programmable range have similar configuration options.

On 17/05/2017 15:42, Andy Burns wrote:
Adrian Brentnall wrote:

Andy Burns wrote:

The heatmiser prog stats allow setting a switching differential
from 0.5 to 3 degrees, in 0.5 degree steps.

You mean the PRT-B - on the right-hand side of this page?
https://www.heatmiser.com/en/battery-thermostat-series/

That, or the similar slimline ones for 230V/12V power instead of
battery, also the touchscreen range, in fact I would suspect any of
their programmable range have similar configuration options.

Thanks!
The current 'stat is battery, so having a replacement that doesn't need
12 or 240v would be a good thing....

Adrian Brentnall wrote:

The current 'stat is battery, so having a replacement that doesn't need
12 or 240v would be a good thing....

They no longer seem to sell 230V models that also have a hot water
timer, unless I've not seen the right section of the website.

Don't be tempted by their older wifi based ones they were insecure as
hell, therefore I'd also be wary of their newer wifi ones too (though I
think they work by making outbound internet connections now, not inbound)

HI Andy

On 17/05/2017 19:48, Andy Burns wrote:
Adrian Brentnall wrote:

The current 'stat is battery, so having a replacement that doesn't need
12 or 240v would be a good thing....

They no longer seem to sell 230V models that also have a hot water
timer, unless I've not seen the right section of the website.

The hot water's on a separate timer (odd way of doing things - but
that's what they did, and it seems to work) - so straightforward c/h
controller is fine


Don't be tempted by their older wifi based ones they were insecure as
hell, therefore I'd also be wary of their newer wifi ones too (though I
think they work by making outbound internet connections now, not inbound)

I'm generally in favour of simpler rather than complicated..
and can't think of any good reason (for us) for a wi-fi-connected
thermostat (given that we're usually in the house 95% of the time).

Thanks for the warning, though!
Adrian