Just a quickie; can someone with a Danfoss TP9 explain the switch that selects between 'gravity' and 'pumped' referred to here:
Cheers,
Rich.
That's precisely right.
If you look at the first diagram, CH ON is only connected to the pump. It clearly has to bring the boiler on as well - otherwise you'll be circulating a lot of cold water!
Good. I was worried that the controller would be like my current one, ie switching on the whole hot water system whenever the CH is timed to be 'on' (or alternatively not being able to switch on just CH, whichever way you want to look at it!)
Cheers,
Rich.
Well, I'm afraid that's what it does! What did I say which led you to suppose differently?
With a gravity hot water system, you get hot water whenever the boiler is on. Thus, when the boiler is on for CH you also get HW whether you want it or not.
If this is a problem, the solution is to convert it to fully pumped, OR to go for a C-Plan system (see
Then - and only then - can you have independent control over CH and HW.
Thanks. I think we need to differentiate between CH on, and the thermostat producing a signal that says 'switch on the CH pump/fire up the boiler'.
I have a house that I'm not living it full time yet, and I want to have the temperature set to 5 degrees C during the week using a programmable thermostat. So technically the CH will be 'on', but I have no need for the HW during the week.
If I use a standard programmable thermostat, the CH on the timer must be 'on' 24Hrs a day, and so the HW will be on 24hrs a day too - not ideal.
What I'm looking for, I suppose, is 'semi-independant' control of CH and HW. I want the boiler to come on if the thermostat switches on the CH pump - I realise that with a gravity system, this will also heat the HW, but with the 'stat set to 5 degrees, I don't envisage it happening much.
Ideally, I'd fit a C-plan system or even a fully pumped one, but we're due to convert an attached barn next spring, and I'm planning underfloor heating on a seperate zone and thermostat, as well as a new boiler then - so don't really want to cut into the wet bits twice!
Have I managed to be a little clearer this time? I have phases of being frankly a bit cinfused about all this, and then moments of inspiration when I see something like the cunning micro-switch valve used in C-Plan when I go 'Oooooh! NOW I get it!!!'
Cheers,
Rich.
*Please* don't top post!
OK, I can see what you are setting out to achieve.
If you don't want to change the plumbing, you can get somewhere close by using a relay.
Set the programmer for fully pumped even though it ain't, and leave CH permanently on. Wire the relay coil in parallel with the pump, so that it is energised when the room stat turns on. Connect one contact in the relay (common if it's a changeover type) to CH ON on the main programmer. Connect the other contact (NO, if changeover) to the boiler.
That way, whenever the heating comes on, the relay will switch the boiler on. But when HW alone is on, it won't turn the pump on, because the relay won't be energised.
Ok, I guess I'll have to do that. Any recommendations for a source for a nice easy to wire relay? (ie screw terminals, in a box to stop prying fingers).
You know, I never understood why people don;t like top-posting. Doesn't it mean you have to scroll down to read the new bit?
Cheers,
Rich.
Have a wander along to your nearest Maplins and see what they've got. You'll need a relay with a 240v coil which is capable of switching a load of (say)
5 amps. You may have to provide your own box for it, and solder some wires onto the pins, with the other ends connected to barrier strip.It means that the discussion follows on in a logical order. It's easy to scroll down to the new bit - because it doesn't have >'s at the start of each line. It's also good practice to snip bits out which are not relevant to your reply - thus reducing the amount of scrolling needed.
Hello again!
Michael Chare's intervention is making me have second thoughts about this whole thing. Seemingly the TP9 is both a two channel (i.e. CH + HW) timer
*and* programmable thermostat, combined in one unit. According to Michael, it does just what you want - straight out of the box. This isn't too obvious when reading the installation manual which you referenced earlier, but is certainly worth checking out.Do you have a sales brochure for it - because that might tell you more about what it actually *does* than the installation manual does?
I dont think that it is to obvious even from the instructions which you can download.
Look at it this way: It 'has' to work like I said because (in normal operation) there is no 'off' condition for the CH, just a lower temp. So if they provide timed HW what would be the point of this?
Unlike a separate programmer and thermostat, the TP9 knows when the room temp is to low, and so can provide power to the boiler only when it needs it.
Michael Chare
Are you able to confirm from personal experience that this is how it
*actually* behaves?If so, it should do what the OP wants.
If it does do this, it must have some internal switching logic which achieves the same thing as I was suggesting doing with an external relay.
In message , Michael Chare writes
nothing at all
but a load of stuff under the sig separator
Please try learning to post
clue - everything under "--" is treated as your signature
The information contained in this post may not be published in, or used by
Right. This sounds a bit more intelligent than your average programmer plus room stat on a gravity hot water system.
However, without a zone valve in the HW circuit, it still can't prevent the HW from overheating when the CH is on - or, indeed, when just HW is on. Maybe you could solve the HW-only problem by inserting a cylinder stat in the boiler feed - but you'd have to find a way of by-passing it when CH was required.
So you found a minor error in my posting. Not the greatest contribution to the understanding of central heating programmers that I have read!
Your own posting would be improved by the use punctuation.
Michael Chare
In message , Michael Chare writes
Hardly a minor error - it means that nobody can reply to your posting without cutting ands pasting what you put under the sig sep.
Learn to post correctly and you might get a useful reply
The information contained in this post may not be published in, or used by
You are wrong to say 'nobody'. Whether or not you have to C&P depends on the newsreader you are using (and maybe how you have it configured.)
In message , Michael Chare writes
Everything below the sig separator is removed when replying. That's what it's for
please learn a) not to top post and b) to leave the body of the message above the sig sep, snipping what is not relevant
And by being correct; it's "-- ". The space is important.
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