Thermostats

[warmadmax]

Hi Guys,

Looking at my current system, there are no thermostat controls other than the 0 to 4 dial on the front of my Baxi bermuda

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So other than the programmer turning various parts off at set times, there isn't anything to regulate the temperature, we quite often find ourselves with scorching hot water and a "too hot" upstairs.

Turning the boiler down to 2 hasn't solved it so i'm looking into thermostats.

I've looked at the installation instructions for my programmer (horstmann 425 Tiara) and looks relatively straight forward to add the controls.

Planning on adding a cylinder stat and a room stat at the same time on the upstairs landing, with the stat on a wall away from the airing cupboard I presume? (airing cupboard on landing next to bathroom)


Wiring wise, I'm comfortable doing the work (have done keypad door controls with the gibberish they supply)
and the install looks to be
1) cylinder stat to interupt boiler On unless called by room stat
2) room stat to interupt pump ON


are there any pitfalls to watch for?

The programmer can be setup to supply mains AC to the stats.

Cheers
Matt

 

[flameport]

1) cylinder stat to interupt boiler On unless called by room stat
2) room stat to interupt pump ON

It won't be as simple as that.

Is the hot water circuit gravity or pumped?
Any zone valves (2 or 3 port)?

 

[warmadmax]

It's gravity fed hot water,
Pumped central heating,

No zone valves at all, only controls are visible in picture.

Old council house with baxi Bermuda and upstairs hot water tank with f&e tank

 

[warmadmax]

just added some images to the album showing the hot water tank.

System is laid out the same as the install instructions as far as i can tell
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heating pipework
View media item 37905 View media item 37906which then runs under the stairs...
View media item 37867 View media item 37866
water supply pipe work (mains cold, gravity hot)
View media item 37902 View media item 37903 View media item 37904

 

[xr4x4]

You need a zone valves to use thermostats.

I'd get a 2 port and put it in the feed pipe to the rads, drain down, cut and put it in and leave the hot water as is.

 

[flameport]

Your option 2 will work (a thermostat to interrupt the pump live). This will control the heating (radiators) only.

You can't use a cylinder thermostat with the current arrangement, because switching off the boiler when the cylinder is hot will also prevent the central heating from working. You will end up with a cylinder full of hot water and a freezing cold house.

 

[warmadmax]

Zone valve sounds like an good idea, as even with the pump off, some radiators get warm to the touch.
I'm not sure were i'd site it, after the pump further up the pipe work??
i'm also looking to put a magnabooster in, presumably on the pipe immediately above the pump, see here


I appreciate what your saying about the cylinder stat, however the install instructions for the Horstmann show the stat wired up "back to front" from the norm?
View media item 37907
terminology used in the install instructions is "Call"ing for fire up and "Sat"isfied heat need

with the "call" coming from the HW ON,
the "satisfied" being joined to the room stat's "Call"
with the common going to the boiler on

that way, if the cylinder is up to temp and flicked over, but the room stat says "turn on", the boiler will still operate??[/u]

 

[Space cat]

To control your cylinder temperature while still allowing the central heating to function independently, you need a zone valve in the RETURN pipe from the cylinder coil. (You can't put it in the feed because you must keep an open path to the vent at all times.)

When we moved into this house, we found pumped heating controlled by a room stat and a zone valve controlled by a cylinder stat. There was only one problem - the idiot who put the zone valve in didn't see fit to shut the boiler off when it closed! Result: When the cylinder got up to temperature, the boiler was left cycling on and off on its own internal stat - in an outhouse!

It's getting late and I haven't got time to explain how you get around this, suffice to say that it can be done. I'll be back later - unless somebody else gets in first.

PS: You can expect some gravity fed heating in your upstairs radiators while the boiler is on for hot water.

 

[warmadmax]

Been having a read, thanks for the pointer Space Cat

looks like I need to use "C Plan"
as i've got gravity HW and pumped CH


1) 28mm zone valve
2) Cylinder Thermostat
3) Room thermostat


Presume the only place i can install the zone valve will be next to the tank here
View media item 37906
as I can't block the vent pipe (for obv. reasons),
and shouldn't block the cold feed as it tops up the radiators
View media item 37868

 

[Space cat]

Presume the only place i can install the zone valve will be next to the tank here

Correct! Down near the floor where you can hardly get in - but, unless you reroute the feed/expansion pipe, that is your only option.

 

[45yearsagasman]

No, you can put it on the 28mm return near the boiler under the stairs.

 

[Space cat]

you can put it on the 28mm return near the boiler under the stairs

I stand corrected. Filling/expansion will still take place through the cylinder coil.

 

[warmadmax]

Doh, yes that makes sense

Thanks guys you've been a real help,
i'll post back when i've done the work