frost protection valve, air temp triggered, or water in pipe?

[Danny42]

Does anyone know either way if frost protection valves are triggered by air or water? If by the air temp then it seems that the frost-protection mode of running water through the pipes all the time when the temp is low outside is a bit pointless as the valves will dump all the water. Thing is, I'm still working on the system, I have got it up and running to get hot water (we only had oil before this and it was £1.70 a litre due to awkward narrow road, so couldn't afford to do anything but rappidly swap out system - now have lots of cheap hot water from ecodan, yay!) but the heating side is still a work in progress, it works, but need to swap out all the rads (they are tiny, pinholed, single skinned and hugly as hell), and a lot of pipework (micro currently).

Anyway, thats a lot of babbling, essentially I still have work to do and will be emptying and refilling a lot over the next 6 months, so £200 each time to get to 25% glycol, only to also reduce the efficiency seems a bit much, so I'd have to be pumping it out rather than dumping it etc. All a total pain. Seems a lot of folks just use frost protection and frost protection valves. If the power fails while its -4 outside the valves save the outside unit from ice damage by dumping the water, from the lowest, coldest most exposed bit of pipework. Sounds like a great idea.

They only concern I have, is that having watched a video from altecnic about how you SHOULDN'T insulate the valve, however counter-intuitive that is, to ensure it's sensors are exposed, that rather implies they go by the air temp. Well if thats the case even though the mains is up or the batteries still charged and despite the frost protection mode or the actual normal heating cycles keeping the water warm despite all that, the valves will dump the water because the air is 3C. Seems silly. I'm clearly missing something here, like either thats not how they work, or maybe it is and people only put them on houses which never go below 3 (but thats nowhere in UK isnt it, we always get to below 3 many times each winter even in south).

One thing I do know, or at least have been told: having read online that mitusbishi warranty still fine if frost protection mode enabled and set to 6C trigger, and valves in place, I called them, they confirmed, enabled at 6C and valves installed and warranty fine.

[JamesPa]

53 minutes ago, Danny42 said:

Does anyone know either way if frost protection valves are triggered by air or water? If by the air temp then it seems that the frost-protection mode of running water through the pipes all the time when the temp is low outside is a bit pointless as the valves will dump all the water. Thing is, I'm still working on the system, I have got it up and running to get hot water (we only had oil before this and it was £1.70 a litre due to awkward narrow road, so couldn't afford to do anything but rappidly swap out system - now have lots of cheap hot water from ecodan, yay!) but the heating side is still a work in progress, it works, but need to swap out all the rads (they are tiny, pinholed, single skinned and hugly as hell), and a lot of pipework (micro currently).

Anyway, thats a lot of babbling, essentially I still have work to do and will be emptying and refilling a lot over the next 6 months, so £200 each time to get to 25% glycol, only to also reduce the efficiency seems a bit much, so I'd have to be pumping it out rather than dumping it etc. All a total pain. Seems a lot of folks just use frost protection and frost protection valves. If the power fails while its -4 outside the valves save the outside unit from ice damage by dumping the water, from the lowest, coldest most exposed bit of pipework. Sounds like a great idea.

They only concern I have, is that having watched a video from altecnic about how you SHOULDN'T insulate the valve, however counter-intuitive that is, to ensure it's sensors are exposed, that rather implies they go by the air temp. Well if thats the case even though the mains is up or the batteries still charged and despite the frost protection mode or the actual normal heating cycles keeping the water warm despite all that, the valves will dump the water because the air is 3C. Seems silly. I'm clearly missing something here, like either thats not how they work, or maybe it is and people only put them on houses which never go below 3 (but thats nowhere in UK isnt it, we always get to below 3 many times each winter even in south).

One thing I do know, or at least have been told: having read online that mitusbishi warranty still fine if frost protection mode enabled and set to 6C trigger, and valves in place, I called them, they confirmed, enabled at 6C and valves installed and warranty fine.

They are made of conductive metal so, if it's cold and the water isn't running, will trigger in good time.  If the water is running enough heat will reach the sensor to keep them closed.

 

The logic of not insulating the valves is that, if you do, they might take too long to trigger also the water has to go somewhere not into the insulation 

[Danny42]

Thanks james, that makes a lots of sense!

I just watched a video from: https://www.intatec.co.uk/product/anti-freeze-valves/#:~:text=Designed+to+discharge+when+the,costly+damage+to+the+system.

And their one explicitely says it triggers from the water temp, so I think it'll be fine. Interestingly, another video (by altecnik, I think, probably spelling that wrong), says to NOT insulate it, while the one I link above not only say you can but actually sell a little custom insulation jacket for the thing.

I think I'll err on the side of not insulating it. The parts inside the heat pump aren't insulated very much and can see them freezing pretty quickly, would rather the dump valve got cold faster and dropped the water quickly in the event of cold+powercut. Even if that does mean a tiny bit of heat loss just there.

[sharpener]

4 hours ago, Danny42 said:

I still have work to do and will be emptying and refilling a lot over the next 6 months, so £200 each time to get to 25% glycol

 

Well at least the system will be well flushed. Don't see why you would now need glycol until September, why not just use inhibitor over the summer? Or 10% Fernox HP-5C at most, see link below.

 

3 hours ago, Danny42 said:

another video (by altecnik, I think, probably spelling that wrong), says to NOT insulate it, while the one I link above not only say you can but actually sell a little custom insulation jacket for the thing.

 

By co-incidence I watched this vid from Glyn Hudson yesterday, at 11'30" in he puts an elbow over the top of the AFV specifically to let the air get at it. [Edit - I see that is to break any vacuum, not to expose it to the OAT.] Also has only one valve, mostly I thought they were fitted in pairs, that's what Midsummer Wholesale supply by default. If you buy two it costs as much as a good load of glycol.

 

Personally as I will need ~50 litres I am waiting for Hydratech to bring out their 5 deg protection product as per this thread.

 

 

Edited March 25 by sharpener

[JamesPa]

1 hour ago, sharpener said:

Also has only one valve, mostly I thought they were fitted in pairs

My understanding too, presumably to let air in one and water out of the other.   One alone would release the pressure from the pipes which may suffice, particularly if the cold ones are plastic (this is imho a good argument for plastic pipes on the outside, but I guess that the pipes inside the pump aren't plastic!).  

Edited March 25 by JamesPa

[HughF]

You need one, at the lowest point of the system.

 

Glycol should be resigned to the bin, horrible stuff. 

[dpmiller]

9 hours ago, HughF said:

Glycol should be resigned to the bin, horrible stuff. 

because?

[sharpener]

19 hours ago, JamesPa said:

My understanding too, presumably to let air in one and water out of the other.   One alone would release the pressure from the pipes which may suffice, particularly if the cold ones are plastic (this is imho a good argument for plastic pipes on the outside, but I guess that the pipes inside the pump aren't plastic!).  

 

13 hours ago, HughF said:

You need one, at the lowest point of the system.

 

So you are happy to rely on a single £30 Chinese copy valve to protect a £000s installation. I would not be confident that with only one valve it would allow enough air into the pipework to make sure all the water emptied out of the outdoor unit. Especially if the system is off and all the two-port valves are shut.

 

Seems to me an ideal setup would isolate everything that is outside the house and then empty just that. To be independent of the mains it would need e.g. spring-loaded valves connected with bowden cables. Not easy to engineer to be reliable at reasonable cost though.

 

Intatec valves in the video upthread look reasonably well thought out but as with all valves you cannot be sure they are not going to be stuck shut just when you need them to open. Then if they do you still have the hassle of re-filling the system before you can use it. And if it is < +3C how do you get the valves to stay shut for long enough to get the system running again, do you need an assistant to keep pouring hot water over them?

 

For all these reasons I prefer to think in terms of glycol as per this thread.

Edited March 26 by sharpener

[Nickfromwales]

49 minutes ago, sharpener said:

Especially if the system is off and all the two-port valves are shut.

Not ever a real world scenario or design particular, so completely moot tbf  

 

If the system is off and the valves are closed (which they should NEVER be in normal service) then it would be because a service / maintenance issue has occurred and somebody had shut them purposefully (so therefore in winter they'd also drain accordingly).

[HughF]

1 hour ago, sharpener said:

 

 

So you are happy to rely on a single £30 Chinese copy valve to protect a £000s installation. I would not be confident that with only one valve it would allow enough air into the pipework to make sure all the water emptied out of the outdoor unit. Especially if the system is off and all the two-port valves are shut.

 

Seems to me an ideal setup would isolate everything that is outside the house and then empty just that. To be independent of the mains it would need e.g. spring-loaded valves connected with bowden cables. Not easy to engineer to be reliable at reasonable cost though.

 

Intatec valves in the video upthread look reasonably well thought out but as with all valves you cannot be sure they are not going to be stuck shut just when you need them to open. Then if they do you still have the hassle of re-filling the system before you can use it. And if it is < +3C how do you get the valves to stay shut for long enough to get the system running again, do you need an assistant to keep pouring hot water over them?

 

For all these reasons I prefer to think in terms of glycol as per this thread.

Yep, more than happy to trust my install to a £30 valve I got from AliExpress….. I see the chance of a power cut, when the house is empty, in the winter, for more than a day, such a tiny chance, that it’s hardly worth loosing sleep over.

[HughF]

5 hours ago, dpmiller said:

because?

Because of the efficiency hit…. As simple as that. Same as buffers and llh’s, all best designed out of a system.

[sharpener]

1 hour ago, Nickfromwales said:

Not ever a real world scenario or design particular, so completely moot tbf  

 

If the system is off and the valves are closed (which they should NEVER be in normal service) then it would be because a service / maintenance issue has occurred and somebody had shut them purposefully (so therefore in wthe inter they'd also drain accordingly).

 

No, the schematics for my proposed system (as approved and drawn up by Vaillant tech) re-use the existing n/c S-plan valves inc DHW  to save the need to replace any of them with a diverter valve. So in a power cut all 4 circuits will be shut off.

 

The only other flow path is an automatic bypass, but if the HP is not running there will be no differential pressure to open it.

 

Thinking about some more, this is not a peculiarity of my system. The normal published Vaillant schematics have a HW diverter which defaults to the heating circuits, and then if these are more than one there are either zone valves or UFH actuators or both, all of which will shut off in a power cut.

 

 

Edited March 26 by sharpener

[JamesPa]

4 hours ago, sharpener said:

Seems to me an ideal setup would isolate everything that is outside the house and then empty just that. To be independent of the mains it would need e.g. spring-loaded valves connected with bowden cables. Not easy to engineer to be reliable at reasonable cost though.

 

I have seen this recommended.  Basically a couple of motorized valves (ie zone valves) kept open by electricity, which therefore close if the power fails.  As @sharpener says they can (depending on physical layout) replace the diverter valve (applying Occams razor).

[JohnMo]

Except wouldn't your expansion vessel just push it's contents out the freeze valve anyway? Once it's depleted nothing else is likely to come out the system away.

[JamesPa]

7 minutes ago, JohnMo said:

Except wouldn't your expansion vessel just push it's contents out the freeze valve anyway? Once it's depleted nothing else is likely to come out the system away.

I guess that depends on whether the zone valves can resist the pressure differential and whether there is a 'way in' for air toreplace water.

[JoeBano]

No glycol no anti freeze valves for me, just have the frost protection activated. I can see the last coal power station from my bedroom window, I don’t think I’ve had a power cut longer than 2 minutes ever. 

[markocosic]

9 hours ago, sharpener said:

So you are happy to rely on a single £30 Chinese copy valve to protect a £000s installation.

 

Pah.

 

Use underfloor heating.

 

Mount the monobloc high enough to be clear of the snow.

 

Ensure that the pipework rises from your floor to the monobloc.

 

It will then thermosyphon (cold water falls into the house; warmer water rises into the monobloc) even if the power happens to be off. 🙂

 

 

 

Even if it goes tits up...

 

There shouldn't be much hard pipework outdoors; flexis ought to survive

 

The critical plate separating out the refrigerant will likely survive half a dozen oopsies too; especially if the rest of the monobloc is made of cheese

 

 

 

 

Or better yet use an air to water split system...or an air to air split for the ultimate in walk away peace of mind.

 

 

I've been debating whether or not to use glycol in the case of a power cut in our cabin (e.g. RCBO trip when -20C out) where the entire building drops below 0C. I'm hoping that the most vulnerable pipework (that in the walls) will also thermosyphon the cold water down into the radiators and can be maintained at temperature e.g. by running the woodstove if the poop hits the fan. The potable water freezing and screwing the pipework / unvented cylinder / water filters would be a pain even if the heating didn't freeze.

 

Question is how you'd know if you weren't there and the power were off.

 

 

With a mixed work / personal hat on I'm looking at these:

 

https://teltonika-gps.com/products/trackers/fmc125

https://teltonika-gps.com/products/trackers/fmm125

 

- SIM card

- 12-24V DC supply

- Built in backup battery and charging circuitry (so you'd know if the house were powered down provided that the mobile cell site still had power form it's backup battery)

- Can measure temperature/humidity via bluetooth or temperature via onewire

- Can flip a relay

- Can also do RS485 (if one wanted to read a heat / elec meter or indeed heat pump where those use RS485)

 

https://teltonika-gps.com/products/accessories/sensors-beacons/eye-sensor-standard

https://teltonika-gps.com/products/accessories/other/temperature-sensor

 

I think there's a product offering in the works here for monitoring houses and heating.

 

 

Waffling.

 

 

In a UK climate in a house that's regularly occupied I probably wouldn't even both with an antifreeze valve. Just let it thermosyphon in the event of a power cut, and rely on the house being warm enough to avoid it freezing up. In all other scenarios the circulator pump is running or the internal trace heating is active. If it ever gets cold enough to freeze!

 

[sharpener]

40 minutes ago, markocosic said:

Question is how you'd know if you weren't there and the power were off.

 

Some low tech solutions:

 

A security camera will send you an email or pics every x hrs e.g. pics of your indoor/outdoor themometer.

A burglar alarm - with its own battery backup - will phone or email you on break of a door circuit. This could be a relay contact held closed by the mains. Also if someone opens the cover of your HP.

A Victron inverter will email you if the grid fails (or a number of other fault conditions). You can configure it so the battery always has a minimum SoC for this eventuality. I think you can also get Victron central to email you if it loses contact with your inverter.

I am sure there are utility programs which would ping your router periodically and let you know if it is down.

 

Do not rely on only one method.

 

I worry about the migration of phone lines to VoIP, today's stats of 3.9M out of 35M smart meters not working properly does not fill me with confidence about national roll-out programmes.

 

[Nick Laslett]

10 hours ago, markocosic said:

 

In a UK climate in a house that's regularly occupied I probably wouldn't even both with an antifreeze valve. Just let it thermosyphon in the event of a power cut, and rely on the house being warm enough to avoid it freezing up. In all other scenarios the circulator pump is running or the internal trace heating is active. If it ever gets cold enough to freeze!

 

@markocosic, thank you for posting this. I have my ASHP on the wall and the pipe going down vertical 1m into the ground and coming up vertical into the house and through the insulated slab. When I looked at Intatec’s instructions for installing their anti-freeze valve, I could not see how it would work, as it wanted the valve to be at the lowest point in the circuit. I wasn’t going to bother with putting glycol in the system. I feel a lot better about my setup after reading your post. The average lowest temp according to Met Office where I live is -2°. 

Edited March 27 by Nick Laslett

[markocosic]

10 hours ago, sharpener said:

I worry about the migration of phone lines to VoIP, today's stats of 3.9M out of 35M smart meters not working properly does not fill me with confidence about national roll-out programmes.

 

I think physical phone lines are done for as far as voice is concerned. Voice comms are SIM cards and mobiles now. Physical lines are dumb data pipes.

 

No physical phone lines in this build anyhow. A SIM based widget with it's own battery that does temperature stuffs; and a router heartbeat for a SIM based router for other stuffs, is probably sufficient to avoid glycol. Only needs to give notice within a few days. 🙂

[markocosic]

1 hour ago, Nick Laslett said:

I have my ASHP on the wall and the pipe going down vertical 1m into the ground and coming up vertical into the house and through the insulated slab. When I looked at Intatec’s instructions for installing their anti-freeze valve, I could not see how it would work, as it wanted the valve to be at the lowest point in the circuit.

 

If just needs to drain the monoblock in order to prevent the monobloc from freezing. The ground is unlikely to freeze and would probably be reasonably resilient if it did (push water back into the house and expansion vessel rather than splitting pipe)

[sharpener]

2 hours ago, Nick Laslett said:

The average lowest temp according to Met Office where I live is -2°. 

 

It's not the average you need to worry about. For example the mean February figure for Plymouth is +6.2C

 

 

 

However to guarantee adequate HP performance the figure I need to use (from CIBSE Guide A) is -0.2C

 

 

But for frost protection purposes the lowest temp in Plymouth in the last 10 years is -4.9C.

 

And here on a tidal estuary just 20 miles away there was lying snow for a week in ?2009 and the river was iced over. Hence I would want to have protection down to -5C, and the Fernox HP-05 (or forthcoming Hydratech equivalent) seems well suited to this.

[Nickfromwales]

21 hours ago, sharpener said:

 

No, the schematics for my proposed system (as approved and drawn up by Vaillant tech) re-use the existing n/c S-plan valves inc DHW  to save the need to replace any of them with a diverter valve. So in a power cut all 4 circuits will be shut off.

 

The only other flow path is an automatic bypass, but if the HP is not running there will be no differential pressure to open it.

 

Thinking about some more, this is not a peculiarity of my system. The normal published Vaillant schematics have a HW diverter which defaults to the heating circuits, and then if these are more than one there are either zone valves or UFH actuators or both, all of which will shut off in a power cut.

 

 

Motorised valves should only be on the flows, and the return should remain common. That way the appliance always sees the expansion vessel etc.

 

[sharpener]

1 hour ago, Nickfromwales said:

Motorised valves should only be on the flows, and the return should remain common. That way the appliance always sees the expansion vessel etc.

 

 

Yes that is what I am proposing to do (and Vaillant have approved, with the filling loop and expansion vessel on the return as is their usual practice), but still with the zone valves shut and only one antifrost valve fitted à la @HughF there is no obvious way for air to get in so the water can get out of the external unit of the HP.

 

Edited March 27 by sharpener

[Nickfromwales]

6 hours ago, sharpener said:

 

Yes that is what I am proposing to do (and Vaillant have approved, with the filling loop and expansion vessel on the return as is their usual practice), but still with the zone valves shut and only one antifrost valve fitted à la @HughF there is no obvious way for air to get in so the water can get out of the external unit of the HP.

 

Air will enter via the automatic air vents.