Choice of thermostat advice please

[diselsamm]

Hi

I'm having issues with my wireless Honeywell thermostat. It's sat in the living room, set at 18C currently. It makes my Worcester Greenstar 18Ri to short cycle. So, the moment it gets cold outside my boiler works for about a minute, then stops, and starts again in about 5 minutes, then repeat. Obviously the temp in my living room does not fluctuate so much. I've got a total of 8 radiators at home up and downstairs, and happy to agree the boiler is oversized for my property. But I can clearly see the thermostat is the one calling for heat (know this from the led light on the receiver).

I've been thinking of having the thermostat and receiver replaced with maybe a Drayton Wiser or Greenstar Comfort I. Any suggestions on the choice of thermostat?

I've a Honeywell Y6630D1007 wireless thermostat and a Honeywell ST699 programmer and want to rip them off.

 

[diselsamm]

To be fair I am not sure what better a boiler is there on the market compared to mine. Mine is a detuned 12 kW greenstar RI. 45dB noise, modulating in the 4-12kW range. Simple and simple to fix. I have a one zone Y system.

 

[John.g]

Your heat demand will rarely be much lower than 4kw but if your existing stat has TPI control then it will cycle it on/off, you should be able to buy a relatively fairly basic digital stat, if you do purchase one ensure that its one with a low differential of 0.2C/0.3C and where the TPI control can be disabled or one without TPI, like mine.

 

[diselsamm]

I am thinking about Honeywell Y87RF2024, which will be a direct replacement for my current setup, keeping the old programmer. Unfortunately I can't find much info on how that thermostat operates. This and I am not sure of the benefits of this replacement thermostat over the analogue one I currently have and which seems to be working fine.

 

[gmartine]

Smarter stat systems uses geolocation to get local temperature if weather comp not used, my very old mother (92) has your boiler (9kw) bolted on to tado in a 3 bed semi. Seems to work ok, target temp is 22.2 deg C.

 

[diselsamm]

I am not sure I am comfortable with my skills to replace my Honeywell controls with Tado. I think I also have to take down the programmer which will cause cosmetic issues (I know!). I am comfortable to replace myself my receiver and thermostat with the Y87RF2024, and keep my programmer, which works fine. The question is, is it worth it?

 

[gmartine]

I was answering your query about a stat being able to monitor the outside temperature #23. It needn't be Tado but most smart systems connect to an outside weather service via the internet and adapt your heating in an anticpatory manner, that amongst some other features will save you something.

 

[diselsamm]

thank you gmartline. By the way I am very happy how well the key plug worked out. I can't recognise my own boiler now.

 

[gmartine]

Good to hear, when I get a chance I'll take a pic of my mother's boiler as I've noted the temperatures on the flow temp dial. From memory one oclock is about 60 deg C which hers is set to. Worth playing around with that of you haven't already, obviously it'll take longer for the room to get up to temp so allow for that if you experiment.

 

[diselsamm]

Now that you reminded me, I will dial it down as mine is set near to max atm. It's a long story but previously the boiler was not able to go over 68C and we had to keep the dial at near max. Basically the boiler was overheating and cutting out. This happened due to an extremely problematic conversation of the system to sealed one, resulting in circulation problems both in the pipework and in the main heat exchanger.

 

[gmartine]

Running the system at 80 or so degrees is far from ideal and will exacerbate the symptoms of your original enquiry. Never mind the return flow temp being excessive and above dew point or out of condensing mode it sounds like you have more fundamental issues than simply replacing the room stat will resolve.

 

[diselsamm]

Here is the long story. I inherited a system with a F&E tank, which was noisy. We converted the system to a sealed one. But it was not properly cleaned. In the mean time the HWC failed as well. My trusted heating engineer (not involved in any of this previously) cleaned the system chemically and flushed (both chemically and with a pump) the boiler heat exchanger as was very sludged due to previous owner neglect and following sealing of the system. We discovered that the boiler was overheating and was not going over 68C (locking out). The location of the magna clean filter was initially wrong and that was rectified. Currently the system is clean, the boiler finally dropped gas consumption, the plug you suggested had a further positive impact. It is nice and warm at home now. The system is properly balanced with temp clamps. The boiler is properly condensing. In fact the radiators are not hot to touch. Which is different to how they used to be, and still it is much warmer and nicer temperature wise at home.

 

[diselsamm]

I wanted to bring this one to conclusion. My cycling issue is completely eradicated. What solved it was: 1) plug key, kindly suggested by gmartline (thank you!) and 2) replacement of the wireless thermostat and receiver with a new (digital) one. I chose
Honeywell Home Single Zone Thermostat (Y87RF2024). The replacement was super easy and took less than 5 min.
I will make a new post asking for advise on how to decommission the wired programmer.