Wiring Pump & boiler with T-stat

[martyc]

Hi there,
Currrently have no stat on CH system and relying on TRV's.
Picked up a wireless stat and was wondering about wiring the pump.(no mention of it on MI's)
Should i wire the pump so that it is on all the time i want the house heated or should i wire it so that it only comes on when the stat calls for heat?(do i twin it with the boiler or the timer)

its currently set up so that its on all the time (ie an hour in the morning and a few hours in the eve)
But if i was to change it so as to let the stat do all the work then the pump would be on 24/7 and i guess that aint ideal.

Cheers,
Marty.

 

[bengasman]

Your system is designed wrong and installed wrong. Chances are it is wired up wrong as well, if you add diy wireless stats to that list, you could be in for a few surprises

 

[martyc]

Fair enough...
This is a basic boiler,vented system.
When should the pump run??...all the time i would like my house heated or only when the boiler is firing?....thats my question essentially.
It may be designed wrong but i intend to put it right!!
Cheers,
MArty.

 

[D_Hailsham]

1. What boiler do you have (make & full model no)?
2. Where is the pump connected to at the moment?

 

[DP]

Chances are you have a gravity hot water system. If that is so, if you were to select CH, HW channel is also activted.

If above is correct, for HW only boiler is energised. For CH, pump is enegrised by the programmer. Pump running by itself, will not heat the rads, only circulate water through the system. To fire the boiler, an internal link activates HW channel when CH is selected (HW channel supplying power to the boiler)

For you to use your wireless programmer, wiring would have to run the pump AND fire the boiler for CH demand and also ONLY fire the boiler for HW demand.

Be aware, above is just one configuration (be it quite common), but you have to give more information to get precise details on how to instal the new unit.

 

[martyc]

Just to clarify,
Its a pumped system, vented, gravity top up via F & E tank.
Trvs an all rads.
Hot water is heated via a cylinder in airing cupboard(both electrically and by heat exchange when the heating is on )
It is not a combi boiler...there are no zones...nothing fancy, no 3 way valves to open/close nothing!!...the boiler is only for heating the house.

Hi DP,
From your reply i think i am right in saying that i only need my pump on when the boiler is actually heating?
Im well aware that the pump only circulates the hot water but should it not remain on for a short period after the boiler heats up to empty the boiler of hot water and replace it with cooler water from the return?


Its currently setup with a real basic timer, and once its between on times eg 6:30 and 8:00 in the morning the pump runs continuously...and the boiler cycles on and off when its own stat tells it to....is this right or wrong?

I have the option now of changing how its wired...whether or not the pump continues pumping when the stat does not call for anymore heat?

Cheers,
MArty.

 

[Terrywookfit]

Glad you finally got all your other problems sorted !!!

 

[D_Hailsham]

When should the pump run??...all the time i would like my house heated or only when the boiler is firing?

It all depends on your boiler.

Generally the pump only needs to run when the boiler is on but some boilers need the pump to run for a few minutes after the flame goes out to cool the heatexchanger down; this is called pump over-run.

What boiler do you have? Make and exact model would help.

Hot water is heated via a cylinder in airing cupboard(both electrically and by heat exchange when the heating is on )

What do you mean? Is the hot water heated by an immersion heater only or is the HW cylinder in the circuit from the pump?

 

[martyc]

D Hailsham,
The boiler is an ideal classic NF 50.
I understand what pump over run is but my boiler is quite basic and does not have any way of telling the pump "ive stopped firing but run for another 30 seconds"..or whatever the required time would be.
Once my house is up to temp my boiler cycles a bit...maybe a minute on a minute off in the current mild weather were having.

The way it is and i guess has been wired for the last 15 years is mains into timer...and 2 cables out of timer, one to pump and one to boiler so the pump is running all the time even when the boiler cycles off due to reaching its own stat setting.
I am aware that this is the way it HAS to be with the current hardware as the boiler doesnt have a module on it to control the pump in unison with its own stat.

However i have the opportunity now change this as i can control the pump either after the timer but before the RF receiver(essentially how it is now) or else after both the RF receiver and the timer meaning it would only be on when the boiler is actually heating water.


Terry...got a brand new PCB for it on ebay for £20 and it sorted it out...running great since so i got a T stat for it for Xmas!!

Cheers,
Marty.

 

[martyc]

D_hailsham...
Didnt answer 2 of your questions..............
Pump is near the boiler but after the vent to F&E(its in the airing cupboard)
My HW cylinder is in the circuit from the pump AND electrically heated which is handy in the summer etc.
My boiler is old...no fancy channels for switching..it literally plugs in!!
Cheers,
Marty.

 

[D_Hailsham]

My HW cylinder is in the circuit from the pump

Wow! It is basic. Don't you have any way of controlling the temperature of the Hot Water coming out of the tap? (Apart from turning the boiler temp down.) If you don't, you should consider converting the system to S-plan or Y plan. As your boiler does not need pump overrun, the pump should be wired to run only when the boiler is alight; as in these diagrams.

Y PLan Layout and wiring:

S Plan Layout and wiring

 

[DP]

If your last post is factual, I would connect one side of the new programmer to mains spur that powers the heating system (fused 2amp) and the other contact to the motorised valve (assuming you have one fitted otherwise your heating would be on everytime you ask for hot water). So, when heat is called for, motorised valve energises. When valve is fully open, switch within the motorised valve would power pump and the boiler.

 

[D_Hailsham]

If your last post is factual, I would connect one side of the new programmer to mains spur that powers the heating system (fused 2amp) and the other contact to the motorised valve (assuming you have one fitted otherwise your heating would be on everytime you ask for hot water). So, when heat is called for, motorised valve energises. When valve is fully open, switch within the motorised valve would power pump and the boiler.

DP
The OP appear NOT to have a motorized valve. In any case, a midposition valve has 5 wires, how is he expected to know how to wire it up doh

 

[DP]

He does not say he does not have a motorised valve, nor does he say he has gravity hot water system. He also has not said if the heating is on whenever he asks for HW (in which case he will not have a diverter valve).

My assumption is based on the post where he says the HW loop is pumped. In such an installation to not have some kind of isolating device (be it a gate valve) on the heating circuit would result both circuits going active when boiler is activated.

Where did the midposition diverter enter the picture? A two port zone valve has five or six wires (28mm valve). What is so complicated about wiring such a valve? Blue is N, Brown goes to programmer, green/ yell goes to earth, orange to Live and grey to boiler and pump.

 

[martyc]

DP..he is right i have no motorised valves.
nothing fancy!!...even the electrical side of my cylinder has no timer just an on/off switch with a preference for bath or sink(2 heating elements)

If i turn on the tap and there is no hot water..its tough s£$T!!!...If i turn it on and its boiling its also tough !!!...No control over hot water other than a flow control through the cylinder which i have limited right down so as not to be over working the boiler yet i still have enough hot water.
HW is NOT linked in anyway to boiler...this is pretty much the norm here in Ireland!!...Very few people have combi boilers here, most people have electric showers and emersion heaters on timers.

So if im reading you right i would do better to only have the pump going when the house calls for heat from my new stat...ill set the boiler to max thaqt way it will always come on when the house calls for heat(well at least it should!!)

I might also try looking into a TRV of sorts for the HW cylinder as thats effectively short circuiting my heating system.
Cheers,
Marty.