digital thermostatic timer

[Jim_Mercer]

The fan heater in my greenhouse cost less than any mentioned so far as I managed to be in Doggies when they had some old stock on clearance - I think I paid £7.99 for a 2kw greenhouse heater. They currently stock the green heater from China available elsewhere for less with different branding. As a backup I have soil/air warming cables running around the staging with its own thermostat which I think is still available.

[Cactusgirl]

Hi Jim, what size is your greenhouse and do you insulate it too in winter?

[Jim_Mercer]

Greenhouse is 8x6 with almost no insulation - a few twinwall sheets but mostly plain glass. I try and maintain 5°C and have a simple temperature loggerhttps://www.amazon.co.uk/Elitech-Accura ... gger&psc=1 to check temperature rather than max/min thermometer. This is the third heater I have had, the first was a Parwin? which was a nice solid British heater but no longer in production. hen the bearing in that failed I got one of the cheaper plastic greenhouse heaters which lasted a few years the Dobbies bargain was a recent purchase so durability untested.

[ragamala]

Jim, I have one of those data loggers too, and (costing only a tad more than a normal digital max/min thermometer) has been very useful for me. I recommend it.

I am assuming that your heater didn't cut in over the period your pic shows. In comparison here below is one record of temperature over two nights last year. This was when I was using a (PRC but not cheap - they go for £50-£80 on greenhouse supplier web site) heater without external thermostat control.

This told me two things. Firstly my heater cut in frequently - every 5 or 10 minutes, and when heating was triggered it raised the temperature about 2 degrees before cutting out.

But more importantly - the temperature at which the analogue thermostat cut in was unreliable. On the first night (and I didn't touch the control at all) the minimum temperature went just under 3 degrees. On the second night heating cut in at anything up to 8 degrees. A waste of energy, apart from anything else.

Having seen this I switched straight away to using a digital external thermostat to control the heater. This maintains an accurate minimum temperature for me. Some results showed even more erratic behaviour, which is why I can't myself recommend anyone to use a simple heater with no digital control. Maybe I was unlucky with this particular heater. It certainly packed up on me less than a year later.

I actually have two thermostats, a Biogreen and an Inkbird, for my two separate heaters. With a 2KW heater the Inkbird also gives ME the choice as to not only the minimum temperature but the temperature lift (and all in tenths of a degree) before cutting off the heat.

[Jim_Mercer]

I am assuming that your heater didn't cut in over the period your pic shows.

This was after installing new heater as a check that the temperature was not too high at night, might have to reduce heater setting and see if temp gets down to 5C. I keep looking at digital external thermostats, the saving I made on the heater would cover the cost of an Inkbird

[Cidermanrolls]

With noisy data like that, I would always look first for an interference causing data error. The up and down slopes are too similar for my liking and the frequency too similar across the time period.
What does the chart look like with the heater turned off?

[ragamala]

With noisy data like that, I would always look first for an interference causing data error. The up and down slopes are too similar for my liking and the frequency too similar across the time period.
What does the chart look like with the heater turned off?

Possibly it looks worse on the chart than it is in reality, given that this was over a two-day period. Counting the spikes and matching against the times, I see that the heater was cutting in on this occasion not every 5 or ten minutes, as I said before, but here probably about once a half hour, which to my mind gives no concern about interference.

I wouldn't have been surprised if it were more frequently , as this test was in an 8x4 cold frame with a limited amount of air to heat/cool compared with a large or (larger at least) greenhouse. It was a very cold couple of days last winter and I ran this after I became unhappy with the heater performance and no longer trusted its thermostat, which had allowed temperatures a day or two previously to go below zero, even with thermostat turned up way beyond minimum.

I have since used the logger sufficiently to be confident in its results. With no heater kicking in the results look more gentle, like Jim's, and now with digital control of heaters I am getting consistent min/rise temperatures during cold
periods.

[Jim_Mercer]

Just downloaded data from logger and found lowest temperature were on the 13th going down to 5.6 so I might have the thermostat on my heater set correctly, next few days might test it further! I have set the logger to record at 10 minute intervals so can get a few months data without having to reset.