UF Heating dedicated pump switching.....

[Lazlo]

Is it OK to wire a dedicated UF heating pump to the switch live from the programmer to the Zone valve (usually brown) as I can't use the switch live to the boiler (usually orange) or it will fire up other zones when not required. I am worried about pump operating slightly before the UF heating valve is opened. If I need a relay, what type and how is it wired?
Ta

 

[davesparks]

It's not a very good idea to wire it directly from the programmer as then it will be pumping all of the time that the programmer is on regardless of what the thermostat and valve(s) are doing.
You will probably be better off using a relay to give you a separated switched live to the boiler.

 

[Lazlo]

Sorry I didn't mean programmer I meant stat, it's a wireless system, what type of relay would you use and how would you wire it?

 

[davesparks]

Sorry I didn't mean programmer I meant stat, it's a wireless system, what type of relay would you use and how would you wire it?

I'd use the normal IMO industrial 10A plug in relay and base that the wholesalers keep in stock.

 

[Lazlo]

Picked up an 8 pin Relpol relay with base for UFH pump....

Just checking before I install....

Switch live from Zone valve for UFH (orange) to A1 of coil on relay, N to A2..
Perm. Live to 1(11) and 8(21) to common on contacts...
Switch live to Boiler control from one side of the NO contacts 3(14) and another switch live to the UFH pump from the other NO contact 6(24). Ignore the NC contacts as these will be live when coil is not energised...

Think that's right...

 

[EvilDrPorkChop]

Wiring the Pump live to the Switch Live of the Zone Valve (The S/L from the Stat - Brown wire on Zone Valve) shouldn't be a problem - this is all that the Wiring centres for Underfloor modules do by Polypumb and Speedfit. You'd then just use your Orange/Grey wires for your switch live to the boiler.

 

[davesparks]

Wiring the Pump live to the Switch Live of the Zone Valve (The S/L from the Stat - Brown wire on Zone Valve) shouldn't be a problem - this is all that the Wiring centres for Underfloor modules do by Polypumb and Speedfit. You'd then just use your Orange/Grey wires for your switch live to the boiler.

it will work that way, but it is better to have the pump switched once the valve is confirmed as being open rather than before as there is the possibility that the pump will be pumping against a closed valve for a brief period while the valve opens and also if the valve fails to open for any reason it will be pumping against a closed valve for a long time making the problem worse.

 

[Leesparkykent]

The Honeywell u-plan shows the individual pumps wired to the orange of each valve which in turn switches the relay on the coil. Reason being if the valve fails to open the the pump wont be going against a closed valve. Saying that though I've come across a few valves in the past where the microswitch has been stuck closed which would cause the pump to go against the closed valve if it was wired as the U-plan diagram.

 

[EvilDrPorkChop]

it will work that way, but it is better to have the pump switched once the valve is confirmed as being open rather than before as there is the possibility that the pump will be pumping against a closed valve for a brief period while the valve opens and also if the valve fails to open for any reason it will be pumping against a closed valve for a long time making the problem worse.

If the Valve failed to open then the pump would pump it round the underfloor heating circuits as the actuators would still open even if the Zone valve failed - so I don't see that being an issue.

You'd be pumping against a closed valve for a very brief period of time - nothing that would effect the lifetime of the pump. I've seen many systems wired up like this before and none have had any issues.

 

[EvilDrPorkChop]

In that situation then yes it would be right to do it that way. But as the OP is talking about a UF heating pump, which would be located after the zone valve then it wouldn't be an issue as it would just pump it round the UF circuits.

 

[davesparks]

If the Valve failed to open then the pump would pump it round the underfloor heating circuits as the actuators would still open even if the Zone valve failed - so I don't see that being an issue.

You'd be pumping against a closed valve for a very brief period of time - nothing that would effect the lifetime of the pump. I've seen many systems wired up like this before and none have had any issues.

What actuators? What would the pump circulate? We have no further information than that there is a valve and pump in series as far as the hydraulic part goes. To assume what other components may or may not be present could be a mistake.

I agree it could work perfectly well as you have suggested, but a better design to ensure that the pump only operates after the valve has opened.

It is two different ways of achieving the same operation, but one goes a little further than the other to reduce the possible side effects of one component failing.
Also should the valve fail then a temporary operation of the system can be achieved by latching the valve open and operating the pump via the manual override of the relay and adjusting the boiler flow temperature to avoid overheating.
Personally I prefer to design a system which, as far as I can foresee will minimise disruption and cost should it go wrong. This is partially a product of spending time fixing systems which have been installed with a 'as long as it works ok that'll do' attitude.

 

[EvilDrPorkChop]

Maybe I was jumping to an assumption that it was Underfloor heating manifold with a pump, mixing valve and actuator heads, however it is highly unlikely that it is just a pump and a motorised valve.

While I agree that your way a better design and best practice the way the OP asks (wired from the stat) is achievable. As far as I can see if it is a Underfloor heating manifold no damage could be caused to the pump if the zone valve failed as it could still pump it around the underfloor circuits.

 

[davesparks]

Maybe I was jumping to an assumption that it was Underfloor heating manifold with a pump, mixing valve and actuator heads, however it is highly unlikely that it is just a pump and a motorised valve.

While I agree that your way a better design and best practice the way the OP asks (wired from the stat) is achievable. As far as I can see if it is a Underfloor heating manifold no damage could be caused to the pump if the zone valve failed as it could still pump it around the underfloor circuits.

Achievable is not necessarily the same as desirable or sensible.

If it is a single zone system for just one room then it may well just be a valve and pump with a blending valve in the mix somewhere.