Grant Vortex Outdoor Boiler and Frost Stat

smjm · 08-03-2017 11:42AM #1

Morning All!

If I understand things correctly, the Vortex Outdoor models have a built in frost stat which start the boiler and pump running when the temperature inside the casing reaches 5 degrees, in order to stop the boiler itself from freezing. Obviously that wouldn't be helpful if no valves were open for the water to flow, so the frost stat has to be wired (somehow) to open a valve for either the hot water or a radiator zone or, as I've read, a separate 'bypass' circuit. Is that correct?

My question then is: what form would the bypass take? Can it simply be thought of as a separate zone? Is it just a length of pipework with its own 2-port valve and, if so, are there certain requirements for the length and location of the pipework, and is there anything special about the valve?

Also, is it necessary to install a pipe stat on the return pipe to one of these boilers, to prevent it running constantly in cold conditions, or does the simple operation of the boiler raise the internal temperature of the casing sufficiently that the frost stat will turn off the boiler and pump (and also close the bypass or other valve)?

If you were installing one of these boilers from scratch, how you would go about setting things up with regard to the frost stat?

Hope that makes sense. Please excuse my layman terminology!

aujopimur · 08-03-2017 02:02PM

Fit an automatic bypass valve.

smjm · 08-03-2017 09:13PM

aujopimur wrote: »

Fit an automatic bypass valve.

Thanks --- that gives me something to read up on.

Does the bypass valve have anything to do with the frost-stat/pipe-stat interaction though, or would a pipe stat actually be required?

agusta · 08-03-2017 11:32PM

The original frost stat in the vortex was preset[fixed] at 4 to 5 degrees approx.afaik ,the frost stat is now pre set at 1 to 2 degrees,which to me makes more sense.

aujopimur · 08-03-2017 11:39PM

smjm wrote: »

Thanks --- that gives me something to read up on.

Does the bypass valve have anything to do with the frost-stat/pipe-stat interaction though, or would a pipe stat actually be required?

The frost stat will do, the auto bypass comes with instructions.

smjm · 09-03-2017 12:52AM

aujopimur wrote: »

The frost stat will do, the auto bypass comes with instructions.

Cheers. Still slightly muddled though after reading this on the Grant FAQ:

"We recommend that Outdoor Boilers should have a Frost Stat fitted. The Grant Vortex Module range is factory fitted with a Frost Stat set at 5ºC plus or minus 1ºC. A permanent live is required with a frost stat

For added frost protection on Grant Vortex Modules, fit a pipe thermostat on a return pipe, set at 30ºC and wired to number 5 & 6 on the control panel. This will prevent the boiler heating the house unnecessarily. A bypass must also be fitted when wired as above."

(http://grantengineering.ie/installers-information/faq-information-on-grant-boilers/#toggle-id-3)

Wish there was more information out there. Details seem to be in short supply!

Wearb · 09-03-2017 01:28AM

What the first part of that means (frost stat), is that (assuming everything is wired as expected) the frost stat is only protecting the boiler and not the rest of the pipework etc.. In that situation a bypass is not needed for that function.

The part about the pipe stat, is to protect the pipework from frost and in that case a bypass is needed.

smjm · 09-03-2017 01:48AM

Wearb wrote: »

What the first part of that means (frost stat), is that (assuming everything is wired as expected) the frost stat is only protecting the boiler and not the rest of the pipework etc.. In that situation a bypass is not needed for that function.

The part about the pipe stat, is to protect the pipework from frost and in that case a bypass is needed.

Okay, I can understand that, but .... now I'm back to my original post! :P

When the frost stat starts the boiler and the pump, (which I presume it does, but I'm open to correction), the water has to flow somewhere. I thought that was the idea of the bypass circuit, but you're saying a bypass isn't needed when only protecting the boiler? So what exactly should the frost stat do that protects the boiler? You said "assuming everything is wired as expected" -- I suppose that's the information I'm after, i.e. exactly what is expected?

aujopimur · 09-03-2017 10:29AM

It you fit the auto bypass after the outdoor pipework, ie where it enters the house, no MV is required.

agusta · 09-03-2017 11:07AM

The frost stat activates the boiler at 1 to 2 degrees.It starts the boiler and the pump.
The frost stat is fitted behind the control panel on the top of the boiler.The boiler will generate heat inside the boiler casing and the frost thermostat will sense the temperature rise and cut out the boiler.
Your correct,the water does need somewhere to circulate.
The motorised valves will be closed so the pump will be unable to circulate the water.This is bad for the pump and you will most certainly get nuisance trip outs on the hi-limit thermostat.
So an auto-bypass is required.fitted between the boiler and the motorised valves.If its fitted inside the house ,its gives the boiler and the outdoor pipework full protection

smjm · 09-03-2017 11:44AM

agusta wrote: »

The frost stat activates the boiler at 1 to 2 degrees.It starts the boiler and the pump.
The frost stat is fitted behind the control panel on the top of the boiler.The boiler will generate heat inside the boiler casing and the frost thermostat will sense the temperature rise and cut out the boiler.
Your correct,the water does need somewhere to circulate.
The motorised valves will be closed so the pump will be unable to circulate the water.This is bad for the pump and you will most certainly get nuisance trip outs on the hi-limit thermostat.
So an auto-bypass is required.fitted between the boiler and the motorised valves.If its fitted inside the house ,its gives the boiler and the outdoor pipework full protection

That makes sense, cheers!

One last question then. In a setup where we're just relying on the frost stat to start and stop the boiler according to the internal casing temperature, how often might a boiler switch itself on and off during a night? For instance, if the temperature reached 1 degree at midnight, causing the frost stat to kick in, and the external temperature remained constant for the next 6 or 7 hours, would the boiler be likely to run for 5 minutes every hour, or something like that? Given that the water was only circulating around the bypass, I'd expect the internal temperature of the casing to rise fairly quickly, causing the frost stat to stop the boiler after not too long a period -- but I've no idea how long it would take the temperature to drop again to the point where the frost stat started the boiler again. I'm only looking for a rough idea on this, of course.

K.Flyer · 09-03-2017 12:41PM

Depends on how cold it is and how long the temperature stays at that level.
So say if it was less than zero degree, then the boiler will activate until the internal of the casing is warm enough to turn off the stat, then the external cold will cool the boiler back down and repeat the process until the the external temperature rises above the frost stat set point.
An alternative, which I have seen done, is to wire the frost stat through one of the zone valves. Although this will run the boiler for a little longer, if the external temperature is very low it will introduce some heat into the house at the same time.

agusta · 09-03-2017 01:03PM

definitely not 5 mins every hour,The boiler itself will still be giving off heat for a long time after the first cut out.at a guess it might kick back in for a few mins a few hours later if it was a constant zero degrees outside

Wearb · 09-03-2017 01:16PM

agusta wrote: »

The frost stat activates the boiler at 1 to 2 degrees.It starts the boiler and the pump.
The frost stat is fitted behind the control panel on the top of the boiler.The boiler will generate heat inside the boiler casing and the frost thermostat will sense the temperature rise and cut out the boiler.
Your correct,the water does need somewhere to circulate.
The motorised valves will be closed so the pump will be unable to circulate the water.This is bad for the pump and you will most certainly get nuisance trip outs on the hi-limit thermostat.
So an auto-bypass is required.fitted between the boiler and the motorised valves.If its fitted inside the house ,its gives the boiler and the outdoor pipework full protection

It is a long time ago since i did an install of one of these, but I thought that -when wired in a particular way- that the frost stat called for boiler heat without running the pump. Am I remembering this incorrectly?

aujopimur · 09-03-2017 01:39PM

Wearb wrote: »

It is a long time ago since i did an install of one of these, but I thought that -when wired in a particular way- that the frost stat called for boiler heat without running the pump. Am I remembering this incorrectly?

Yes.

smjm · 09-03-2017 09:00PM

agusta wrote: »

definitely not 5 mins every hour,The boiler itself will still be giving off heat for a long time after the first cut out.at a guess it might kick back in for a few mins a few hours later if it was a constant zero degrees outside

Excellent. Thanks to you and everyone else for the help!

jimf · 09-03-2017 11:47PM

Wearb wrote: »

It is a long time ago since i did an install of one of these, but I thought that -when wired in a particular way- that the frost stat called for boiler heat without running the pump. Am I remembering this incorrectly?

if wired this way you would most likely run the risk of tripping the hl stat

Wearb · 10-03-2017 12:02AM

jimf wrote: »

if wired this way you would most likely run the risk of tripping the hl stat

I don't know where the idea I had came from Jim.
Though I suppose a frost stat would cut boiler out before it got hot enough to trip hi stat.

jimf · 10-03-2017 12:11AM

quite possible I suppose wearb

but if the run stat was set at max the static water in boiler would probably continue to rise in temp

Wearb · 10-03-2017 01:49AM

jimf wrote: »

quite possible I suppose wearb

but if the run stat was set at max the static water in boiler would probably continue to rise in temp

Don't think the boiler stat comes into play when fired by frost stat. Wouldn't even be a live feed to boiler stat unless there was another call for heat. It's late and perhaps I have this all ar$eways.

jimf · 10-03-2017 09:16AM

its me that probably has it arseways as usual

K.Flyer · 10-03-2017 10:35AM

Heating Fused Spur ===> Frost Stat ===> Switched Live Going to Boiler (or Brown on a zone valve).
Depending on how the system is set up, the feed from the frost stat will connect to the switched live going to the boiler, so that the boiler"s own thermostat still controls the boiler.
To connect after the boiler thermostat means you would have by-passed its main safety device.

Wearb · 10-03-2017 02:02PM

K.Flyer wrote: »

Heating Fused Spur ===> Frost Stat ===> Switched Live Going to Boiler (or Brown on a zone valve).
Depending on how the system is set up, the feed from the frost stat will connect to the switched live going to the boiler, so that the boiler"s own thermostat still controls the boiler.
To connect after the boiler thermostat means you would have by-passed its main safety device.

I have looked at the Vortex wiring diagram (should have done so at the beginning of the thread). I see now that frost stat is wired in series with both boiler stats. As KF said it needs to be like that for safety.

So Jim you're not the one who got it ar$seways after all.

I must have just noticed that it could be wired to work only through the frost stat way back then, not that it was done that way. Frost stat is likely to cut out boiler long before it gets hot enough for hi limit trip. Though it needs that for safety.
Thanks All.

jimf · 10-03-2017 02:28PM

I suppose if you actually think about it we could make scenarios why it needs to be this way

cover off boiler allowing heat to disperse to the outside thus only allowing the frost stat to kick in

Wearb · 10-03-2017 02:30PM

I heard you the first time Jim

jimf · 10-03-2017 02:31PM

Wearb wrote: »

I heard you the first time Jim

:P:P

smjm · 10-03-2017 03:14PM

Quick question, seeing as the thread is still running!

Would the frost stat normally be tested on boiler commissioning/servicing, and how would that be done (other than waiting for some cold weather!)

agusta · 10-03-2017 05:03PM

No,the frost stat on the vortex cant be adjusted,its preset at 2 degrees,plus or minus 1 degree.so it wont be checked during commisioning or servicing.

smjm · 10-03-2017 07:42PM

agusta wrote: »

No,the frost stat on the vortex cant be adjusted,its preset at 2 degrees,plus or minus 1 degree.so it wont be checked during commisioning or servicing.

Ok, thanks. I can see why it might be difficult; thought there might be some sort of test mode to simulate it though.

Dtp1979 · 12-03-2017 07:37PM

No harm wiring the frost stat through a pipestat on the return set to 25/30. That way the bypass circuit doesn't need to get so hot. Frost stat does a more efficient job then

smjm · 12-03-2017 09:05PM

Dtp1979 wrote: »

No harm wiring the frost stat through a pipestat on the return set to 25/30. That way the bypass circuit doesn't need to get so hot. Frost stat does a more efficient job then

In layman's terms, what's the sequence of events in such a set up please?

Grant Vortex Outdoor Boiler and Frost Stat

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