Frost stat back feed??

froshtyv

Just a quick question,

I will be wiring a frost stat to a boiler,

My question is, when the frost stat sends a signal to the boiler to turn it on, will i not get a back feed to one side of the N/O contact in time clock in the house which would normally bring on the boiler?

At the moment there is a fuse spur in the shed to give power to the pump and boiler when there is call for heating from the time clock,

M cebee

yes
but i don't think it matters

assuming stat is wired from heating spur or circuit

froshtyv

M cebee wrote: »

yes
but i don't think it matters

Thanks for the reply,


I didnt think it mattered myself, just something i hadnt thought of before, i cant think of any other way of doing it without sending power back to the time clock.

M cebee

froshtyv wrote: »

Thanks for the reply,


I didnt think it mattered myself, just something i hadnt thought of before, i cant think of any other way of doing it without sending power back to the time clock.

ya if you had an apt timer with neon
the neon would light when stat kicks in

froshtyv

M cebee wrote: »

ya if you had an apt timer with neon
the neon would light when stat kicks in

Ya your right, its a digital time clock so thats not a problem,

I now get to enjoy wiring in a 2 stage frost protection, with the pump coming in first and then the boiler if it gets colder, along with an on timer and a delay re-start timer to stop the boiler from cycling at night.

Best of all a motorised valve needs to be opened first on the heating circuit to stop my pump from burning out.

M cebee

froshtyv wrote: »

Ya your right, its a digital time clock so thats not a problem,

I now get to enjoy wiring in a 2 stage frost protection, with the pump coming in first and then the boiler if it gets colder, along with an on timer and a delay re-start timer to stop the boiler from cycling at night.

Best of all a motorised valve needs to be opened first on the heating circuit to stop my pump from burning out.

is that not over-complicated
whats your setup
zones, valves, boiler type, location

frankmul

froshtyv wrote: »

Best of all a motorised valve needs to be opened first on the heating circuit to stop my pump from burning out.

Normally there is a boiler bypass to eliminate that issue?.

M cebee

frankmul wrote: »

Normally there is a boiler bypass to eliminate that issue?.

if you're protecting a boiler i think a bypass
might do
if you're protecting the the house itself though you would need to open a valve

Robbie.G

Just wire the frost stat to the boiler and then a pipe stat so when the frost stat calls for heat you only heat to a low heat that the pipe stat then breaks stops all the complication also if a bypass isn't fitted one will need to be to stop the pump going against nothing

M cebee

Robbie.G wrote: »

Just wire the frost stat to the boiler and then a pipe stat so when the frost stat calls for heat you only heat to a low heat that the pipe stat then breaks stops all the complication also if a bypass isn't fitted one will need to be to stop the pump going against nothing

if you mean the boiler abv's used for boiler frost protection and pump overrun-that wont protect the house and any incoming pipework from shed will it?

Robbie.G

M cebee wrote: »

if you mean the boiler abv's used for boiler frost protection and pump overrun-that wont protect the house and any incoming pipework from shed will it?

You can fit a abv just before any motorised valves internally that way boiler and circs will have frost protection.
You don't need the house to heat on frost protection it will cost a fortune to run and do you want heating on 24/7 during cold spells.
The pipe stat just lets the boiler heat slightly by fitting on the return and setting at 25
degrees

M cebee

Robbie.G wrote: »

You can fit a abv just before any motorised valves internally that way boiler and circs will have frost protection.
You don't need the house to heat on frost protection it will cost a fortune to run and do you want heating on 24/7 during cold spells.
The pipe stat just lets the boiler heat slightly by fitting on the return and setting at 25
degrees

with frost stat near boiler,return stat,and abv indoors the boiler and incoming pipework is protected


why would the heating need to be on 24/7
can't you also add a frost stat set low in the coldest part of the house that can respond to temp rise, and open a zone valve

what if you happened to be away and frost set-in in the unheated house

im sure there's other ways of doing it

frankmul

Is a frost stat on a boiler used mainly to protect the boiler from freezing by running the boiler?
A pipe stat to protect the pipe work from freezing by running the circulating pump?
To protect the house, is it not a frost protection on a room stat that overrides the time control and bring on the heating for that zone?
Are things getting too complicated by trying to interconnect everything?

M cebee

frankmul wrote: »

Is a frost stat on a boiler used mainly to protect the boiler from freezing by running the boiler?
A pipe stat to protect the pipe work from freezing by running the circulating pump?
To protect the house, is it not a frost protection on a room stat that overrides the time control and bring on the heating for that zone?
Are things getting too complicated by trying to interconnect everything?

pipe stats limits water temp to conserve oil

frost stat near outdoor boiler protects boiler
frost stat indoors protects indoors imo

frankmul

How does the pipe stat limit the water temperatur?. Is it that it switches off the circulating pump when water pipe temperature is above it's set point or does it stop the boiler somehow

M cebee

frankmul wrote: »

How does the pipe stat limit the water temperatur?. Is it that it switches off the circulating pump when water pipe temperature is above it's set point or does it stop the boiler somehow

turns off boiler

M cebee

frankmul wrote: »

How does the pipe stat limit the water temperatur?. Is it that it switches off the circulating pump when water pipe temperature is above it's set point or does it stop the boiler somehow

if you have the setup robbie g described
you're covered, long as the heating timer etc is set to prevent house freezing-which you normally would anyway
i don't know much on it myself

M cebee

i just keep it simple myself

-frost stat outside north facing
-pipe stat return
-i've oil boiler in shed and no motorized valves

froshtyv

Cheers for all the input.

What im basically doing is;

1: only turn the pump on to circulate water to prevent freezing,
to prevent burning out the pump i am opening the motroised valve for the heating circuit

2: If the temperature gets colder, the boiler turns on for 30-40 mins, to stop the boiler being on all night or cycling when it

turns off it will not be allowed to come back on for say 2 hours.

This way then protects the boiler which is in an outside shed, and the pipes in the house also.

M cebee

froshtyv wrote: »

Cheers for all the input.

What im basically doing is;

1: only turn the pump on to circulate water to prevent freezing,
to prevent burning out the pump i am opening the motroised valve for the heating circuit

2: If the temperature gets colder, the boiler turns on for 30-40 mins, to stop the boiler being on all night or cycling when it

turns off it will not be allowed to come back on for say 2 hours.

This way then protects the boiler which is in an outside shed, and the pipes in the house also.

if you just want the boiler on 30min every 150 in frost, you might be as well with stat outside then

if thats the setup you want

froshtyv

M cebee wrote: »

if you just want the boiler on 30min every 150 in frost, you might be as well with stat outside then

if thats the setup you want

The reason I was timing it to run for 30-45 minutes was to allow the boiler to get to temperature so that it will be at its most efficient, and i dont want it turning on and off every few minutes wasting old all night.

The frost stats are in the shed where the boiler is located.

The cables are mostly all there i may have to run in another few cores for the aux signals coming from the valves when they open.

frankmul

Will opening a valve not run the boiler anyway. The auxiliary contact on the valve is normally used to signal the boiler.

froshtyv

frankmul wrote: »

Will opening a valve not run the boiler anyway. The auxiliary contact on the valve is normally used to signal the boiler.

Opening either valve will bring on the boiler under normal conditions.

But if there is a call from a stat along with the signal from the motorised valve the pump will only run,

Or if both frost stats are calling then the boiler will be switched on along with the pump and run for the desired time.

frankmul

There Is a lot of relays and timers involved there, I'd love to see the circuit diagram when your finished.
Did you ever look into getting a programable controller and wiring all through it. It might be easier to get it to work how you want

2011

frankmul wrote: »

There Is a lot of relays and timers involved there, I'd love to see the circuit diagram when your finished.
Did you ever look into getting a programable controller and wiring all through it. It might be easier to get it to work how you want

Modern heating systems can get more involved with motorised valves, relays, zones and timers. Although it cost more to install it is worth it IMHO as the end user ends up with better control and a far more efficient system. This was less important in the days that energy costs were so much less.

Bruthal

M cebee wrote: »

if you mean the boiler abv's used for boiler frost protection and pump overrun-that wont protect the house and any incoming pipework from shed will it?

One way is a frost stat, and pipe stat to keep boiler to a low heat cycle.

Have them bring on a relay(s) which can energize all zone valves. Simple enough. And protects everything. No bypass setting up needed.

froshtyv

frankmul wrote: »

There Is a lot of relays and timers involved there, I'd love to see the circuit diagram when your finished.
Did you ever look into getting a programable controller and wiring all through it. It might be easier to get it to work how you want

Its a PLC that i will be using to control the system.

It makes things alot easier to wire and i can write my own programs for it.

frankmul

froshtyv wrote: »

Its a PLC that i will be using to control the system.

It makes things alot easier to wire and i can write my own programs for it.

And there I was thinking about the fun you would have with back feeds. Best way to go if you want to design a system that goes beyond the basic setup.

Bruthal

frankmul wrote: »

And there I was thinking about the fun you would have with back feeds. Best way to go if you want to design a system that goes beyond the basic setup.

This backfeed thing is often a statement used without much thought about what will backfeed. Relays will keep different parts separate from each other. Its easy enough to setup a frost protection system without much complication.

frankmul

robbie7730 wrote: »

Relays will keep different parts separate from each other. Its easy enough to setup a frost protection system without much complication.

I agree for a simple system.

Bruthal

frankmul wrote: »

I agree for a simple system.

Even the most complex system with PLC`s will still use relays to isolate the frost stat control from the heating control circuit when the frost stat is not in use, even if its just PLC output relays.

But there is not much complexity in frost protection of a domestic heating system.

Even if it was a complex enough non PLC setup, it would be simple to keep different circuits separate with relays.

I guess a PLC makes it easier to wire, and alter later, but my point was, I would`t have had any concerns about the "backfeed" thing, which then disappear when hearing its a PLC going to be used. If this was going to be a job for someone, it certainly would be done without a PLC.

It might be an interesting micro-controller project just the same.

froshtyv

If I was installing a frost protection system for someone else I wouldnt be going into as much detail.

But seeing as its for myself and its not too difficult to setup id said why not.

Also with the PLC i have the option of installing a GSM module in the future to activated the heating system via a text message.

I will be wiring it at the weekend as im picking up my PLC tomorrow from a local heating supplies company (uni-therm)

The PLC does allow me to prevent back feeds to motorised valves etc by separating out each output

Bruthal

froshtyv wrote: »

If I was installing a frost protection system for someone else I wouldnt be going into as much detail.

But seeing as its for myself and its not too difficult to setup id said why not.

Also with the PLC i have the option of installing a GSM module in the future to activated the heating system via a text message.

I will be wiring it at the weekend as im picking up my PLC tomorrow from a local heating supplies company (uni-therm)

The PLC does allow me to prevent back feeds to motorised valves etc by separating out each output

I was not being critical of using a PLC. Its a good idea.

The PLC is preventing back feeds/cross circuiting by virtue of using output relays. It still ends up being kept separate via relay contacts, the same as doing it by hard wiring would.

How much will the plc cost? Again, not for reasons to be critical of using one, just wondering the price of them.

froshtyv

robbie7730 wrote: »

I was not being critical of using a PLC. Its a good idea.

The PLC is preventing back feeds/cross circuiting by virtue of using output relays. It still ends up being kept separate via relay contacts, the same as doing it by hard wiring would.

How much will the plc cost? Again, not for reasons to be critical of using one, just wondering the price of them.

Didn't think you were being critical at all, for most people a simple supply to the boiler from a frost stat would be fine,

The Plc will be around 200 quid, saves me having to run more cables and buying relays and timers not to mention the jumble of wires I'd be left with!

Bruthal

froshtyv wrote: »

Didn't think you were being critical at all, for most people a simple supply to the boiler from a frost stat would be fine,

The Plc will be around 200 quid, saves me having to run more cables and buying relays and timers not to mention the jumble of wires I'd be left with!

Yea that doesn`t sound too bad.

Pete67

Could you post some details of the PLC please - I can think of several uses for one of those. Does it come with programming software?

froshtyv

Pete67 wrote: »

Could you post some details of the PLC please - I can think of several uses for one of those. Does it come with programming software?

The programming software is free to download,

The units come in 2 types,

The zone 4 controller has 6 inputs and 4 outputs,

The zone 8 controller has 12 inputs and 8 outputs

I dont have any other info on them

230 volt supply, and the outputs can be volt free depending which way you wire them.

http://www.uni-therm.net/controls.html

Thats the only picture i could find on them.

frankmul

How did things go

froshtyv

frankmul wrote: »

How did things go

I havint wired the system yet,

Im planning to do it on saturday morning,

I have the PLC programmed and ready to go.

Pete67

Any details on the PLC now that you have it in your hand - make / model etc? How is it programmed, I guess a USB cable to laptop? Would you have a link to the programming software?

Many thanks!