Heating Controls

TKK

The attached diagram is a representation of my hot water & central heating system.

The problem at the moment is that the two room thermostats are not working correctly. One is well out - at 15 degrees the zone is roasting - whereas the other is intermittently hot/cool on different days when left on the same setting. I had also posted before about adding a different timeswitch to give me 5/2 day control and boost functionality but I never got round to it so that's in the mix too.

So I basically need to change the timeswitch/programmer and the room thermostats. Seeing as I'm going to this trouble I'd like to end up with some decent level of control so as to use the heating as efficiently as possible.

I was thinking of getting the following:

2 * programmable thermostats
1 * 2 channel programmer

The idea being that I can set up the hot water channel just to switch the boiler on/off when necessary and that either room thermostat will turn on the relevant motorised valve and switch the boiler on/off through the central heating channel which will be left on constant. I'm aware that, because of the system design, I will get the hot water on when the heating is on but I'm not certain if the extra work involved in adding a three way motorised valve is worth it.

Is this a good way of doing this? Anyone have any suggestions/opinions?

TKK

In case it's relevant the boiler is a Vokera mynute 14e and the existing motorised valves are Myson MPE222's.

JamesM

I'm not too well up on programers etc.
My only contribution is: Remember that thermostats react to the temp in the immediate area. Make sure that the stats are not near rads, or in an area that the sun shines into - they will give false readings. I have seen a thermostat on a wall directly above a rad :eek: Or if a downstairs stat is in a cold draughty hall, the sitting room may get very hot before the hall finally reaches the temp, and the stat turns off.
Jim.

TKK

The stats are not above radiators. They are in rooms (sitting room downstairs & master bedroom upstairs) at the front of the house which only gets the sun in the evenings so, during winter when the heat is needed, passive heating of the rooms with the stats doesn't really seem to be a problem.

landydef

would thermostatic rad valves help???

TKK

They could be a good idea once I get the main control sorted out. They would allow me to turn down the temperature in a couple of rooms that aren't used that much. However, like I said, I need to sort out the main controls first. The current room thermostats are borked and the timer is completely useless for our needs.

davidoco

TKK wrote: »

that either room thermostat will turn on the relevant motorised valve and switch the boiler on/off through the central heating channel which will be left on constant.

You only need a single channel programmer for the hot water if that your plan. Using the prog stats you do the times and temperature on them for each zone. Feed the switched live off the stat to the zone valve and use the end switch on the valve to turn on the boiler and pump.

Look for a prog stat with optimum start, a boost or similar hold facility.

see here http://www.rvr.ie/default.aspx?subj=catalog/ProductsList&catIdPath=0_47_53_160

download the Honeywell CM901 spec document and you'll see how far stats have moved on.

maniac101

Check that your thermostats are actually working, you should hear them click when you pass the setpoint. Check if the corresponding valves open/close. Check also, if they're wired through a junction box, that they're not mixed up, i.e. stat controlling the wrong space. I've had this problem in the past.
I don't know if you have UFH, but you can have that hot and cold effect on alternate days due to the time lag in heating up the space. I find the best way around this is to set the heating to come on permanently for a couple of hours each night.

TKK

The thermostats do click and are causing the valves to open consistently. However they are borked because the temperature they are set at has no relation to the temperature in the room anymore.

I was intending to get programmable stats with the optimum start and boost/temporary override functionality. For some reason I had a mindblock with regard to the valve to boiler directly and assumed I'd need to run it through a channel on the programmer. I blame tiredness.