I can't find any data on Danfoss's site (as an example).
As a general rule, is the microswitch in a zone vale suitable for switching a pump directly, or is a relay advised?
Ta - Tim
PS - can anyone recommend a simple UFH mixer/pump unit for 2 UFH circuits? Dumb as possible (no wiring centre) as I'll be controlling it from an external system.
Absolutely normal practice to switch pump and gas valve directly. I think they are rated at 10A
They're good for several amps - AC (less for DC). They can easily switch a pump and boiler demand without additional relays.
Bear in mind that the entire CH system is usually protected by a 3A fuse, so nothing takes all that much current.
Thanks Roger, and yes I know about the 3A. However, pumps do have a significant of a switch on surge (well, used to - not sure if any of the electronic ones are softer?) - some 6-10 x nominal for an induction motor, albeit only for a few cycles.
That's what I was worried about. I have one Z-Wave switch that explicitly says "do not control a pump directly" as its relay is reckoned to suffer.
???
Yup.
switched live via timer to Thermostat(s) to zone valve(s) to neutral
Wire OR those to a relay and the UFH pump/reducer
Switched live to relay SC, NO terminal to boiler (pump) in parallel with normal CH motorised valve output. Boiler pump to neutral
Important to have relay to make UFH independent of CH
I don't think there are any relays in my S-Plan system; just a chock-block connector. So I guess the thermostats and valve switches must be switching the pump directly.
You need a relay when you have a separate pump for UFH.
Otherwise the standard CH will always make the UFH come on
Understood - relays for logic. I'll be doing that. I'm merely wondering if I can save relays by assuming UFH actuators and zone valves have switches that don't mind inductive loads.
My plan is to take the controls to the boiler, UFH pump, and 2 actuators from a gridswitch bank - each circuit runs through 2 switches:
Switch 1: Off vs "On demand"
Switch 2: "Auto" vs "Manual On"
Good for clearing the air, testing and if the automatics go wrong.
The input to the "auto" switch input would come from relays driven by programmers (the programmers would be an integrated Z Wave solution).
At least, when it goes wrong, I'll be able to force various part sof the system on, or off.
Depends how it's wired. My roomstat switches on my UFH pump in parallel with the motor of its zone valve - and the zone valve's auxiliary contacts switch on the boiler and main pump - just like those for the other zones. I don't have any relays.
Snap.
Actually I do have relays for the rest of the house, but that is only because I wanted to run all those thermostats on 12Vac, as I have timer/stats and motorised valves for each room and (at least until each room was due for redecorating) I wanted to run stats off alarm cable surface run up the edge of door frames for neatness.
A useful side-effect was that I could have a timer/stat in the bathroom due to the 12Vac and isolating transformer.
SteveW
Blimey. You run a pump off the stat contacts?
OK - that was my initial thoughts, hence the question...
Right, I think, given the lack of data on some of the microswitches, probably best to shove relays in everywhere. Just got to browse the Omron section in RS and find a nice beefy DIN mount one, but not silly beefy :)
Room stats will easily switch domestic pumps. Modern programmable stats use a relay anyway so why bother with making the system less reliable by using more?
my boiler control (internal) operates the pump. This allows the pump to continue running for a short period after the demand has ceased. This allows the heat to be taken away from the boiler thus preventing the overheat thermostat from closing down then boiler. My bolier is nearly 30 years old, so it's not a new idea. Someone had to add a similar facilty to our village hall boiler as long ago as the 1970s.
I was asking about the microswitches in zone valves (and later UFH actuators).
Also, the Horstmann Z-Wave boiler relay explicitly will not switch a pump directly.
I need relays anyway to mix several signals down (2 UFH actuators, OR'ed to the blender pump, then that OR'ed with the main radiator demand relay to signal the boiler. So a couple more won't matter.
I can't see where it says that in the manual.
It must work with motors as zone valves are motors.
Why not? That was how a tradition gravity HW, pumped CH system worked.
It was in the Heatgenius literature (they use that part in their system).
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