Digital Room Stat

[Leelums]

Hello,
I have just recently replaced and old tired looking room stat which although was working correctly, it looked unsightly!

The new Room stat is a Sunvic digital stat, http://www.sunvic.co.uk/tlx7501rt.html , which is definately fitted correctly. However it is not performing as desired. If the stat is say adjusted to 19 degrees it will get quite warm and in some cases uncomfortable, the room will then drop to a cold uncomfortable temperature before it calls for heat again. So if I set it a 20 the temperature of the house gets unbearable but again it gets quite cold before it calls for heat, and setting it to 18 is just too cool.

The thermostat can only be set in 1 degree steps (5 - 35 degrees)
The system is an open vented fully pumped central hating system and all pumps and valves are oprating correctly.

So have any one have any ideas?

Thanks
Lee

 

[breezer]

sounds like your heating is too slow for the stat, or the stat is too fast for the heating

try a mechanical stat

 

[Leelums]

Is this usual, if so can the heating system be tweeked? I have already turned up the boiler stat to full (which was set quite low) due to the cylinder stat never reaching 60 degrees, and this seems to have made the response of the heating system better, but is still not perfect. I have recently turned the boiler stat down a little with no improvement.

Lee

 

[croydoncorgi]

Tweaking the temperature of the boiler will make no difference. The problem must be in the stat itself if the old one worked OK in the same position.

Evidently the 'temperature gap' in the thermostat's performance curve (technically, its hysteresis) is too great, so there are several degrees difference between switch-on and switch-off points.

WHY this should be so is tricky! 'Conventional' bi-metal strip mains-voltage thermostats (like the one you just slung!) have a special 'anticipator' heater which ensures that the gap is not too wide (which is why older 'stats need a neutral connection as well as live and call-for-heat).

It sounds like either this particular stat is faulty OR the whole design is suspect. either way, try contacting Sunvic techical and ask them what the difference between the two temperatures should be. They've been making stats for a long time. They should know the answer.

 

[bathjobby]

Agree with croydoncorgi; old one worked, this one doesn't = !
I did similar upgrade and used one of these; http://www.heatmisershop.co.uk/Heatmiser_PRT_Standard-p-16135.html
with no problems. Instructions do state a 1/2 degree C tolerance which can be verified in operation by observation od displayed temp and boiler calling.
Sounds like you have a duff one....

 

[Leelums]

That is a nice stat!
Yeah thanks for the advice guys. However something tells me that the stat is not faulty and is 'in the design' as croydoncorgi stated. Maybe if I buggered about moving it somewhere else it may respond better, but I can't be bothered so I will replace it with a new mechanical one (maybe with an LED so I have some novelty feature remaining!)

Meanwhile if anyone else can advise or has had similar problem and found a solution, I would love to hear from you!

Thanks
Lee
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