Vaillant Frost / Freezing Protection Statement

[Delta925]

The manual for my Vaillant Ecotec Plus 832 states that if the internal temperature drops to 12C frost protection will be activated but, to me anyway, it is not clear exactly what the protection is so I contacted Vaillant. Below is their response for reference:-


The frost protection cycle will begin stage one at 12 degrees internal flow temperature. This will run the pump for 30 minutes and if the appliance hasn't reached 15 degrees, it will bring the burner on based off the heat impartial load output. Alternatively, should the appliance drop below 8 degrees, the burner will come on until the boiler reaches 35 degrees internally, this would be stage two. The diverter valve will sit in mid position during this, so heat should go through both the plate heat exchanger and down the heating flow pipe. It is not designed to protect the pipework / system, only the boilers internals.

 

[oldbuffer]

I would read this as:

Protects the boiler's internal parts but no guarantee on anything outside the boiler.

 

[martygturner]

If you are worried about CH pipes getting frosted up use sentinel X500 as it contains both an inhibitor and antifreeze. We use it on a small holiday let that lies empty over winter, never had a problem even though its exposed and as its a conversion of a stone building can get pretty nippy. Yes the anti frost cycle is to protect the boiler not the CH system.

 

[Madrab]

The manual for my Vaillant Ecotec Plus 832 states that if the internal temperature drops to 12C frost protection will be activated but, to me anyway, it is not clear exactly what the protection is so I contacted Vaillant. Below is their response for reference:-

Not sure it's clear, just what is it you wish to understand?

A boilers built in frost protection is purely to protect the boiler, wouldn't ever be anything else. If you want to protect the rest of the system then a frost stat system would be added to the system pipework, so if the ambient temp at any exposed location drops below the set temp (~5Deg) then the system fires up and runs until the return temp reaches ~30Deg

 

[Delta925]

Not sure it's clear, just what is it you wish to understand?

A boilers built in frost protection is purely to protect the boiler, wouldn't ever be anything else. If you want to protect the rest of the system then a frost stat system would be added to the system pipework, so if the ambient temp at any exposed location drops below the set temp (~5Deg) then the system fires up and runs until the return temp reaches ~30Deg

Vaillant could very explicitly state some like ' The integral frost / freezing protection does not protect any external pipes '.

If I was designing a boiler controller I would at least include the option to circulate water through the heating circuit if the boiler detected either the feed or the return temperature dropping below say 10C. Raising up until the return temperature exceeds 15C would not be a high energy cost.

With a combination boiler the problem is nothing can automatically be done to run tap hot water and so draw cold feed water.

Hence

If you are worried about CH pipes getting frosted up use sentinel X500 as it contains both an inhibitor and antifreeze.

is only partial protection.
My installer added Fernox F1 when filling my system.

I am going to run trace heating cable along both pairs of pipes with the integral 5C thermostat on the cold feed pipe.

 

[Madrab]

If I was designing a boiler controller I would at least include the option to circulate water through the heating circuit if the boiler detected either the feed or the return temperature dropping below say 10C. Raising up until the return temperature exceeds 15C would not be a high energy cost.

Yeah - I see where you're coming from, only issue with that would be that then If that didn't work and there was a burst would they be held responsible, I'm sure that's why they wouldn't take responsibility for anything other than their own hardware. .

I am going to run trace heating cable along both pairs of pipes with the integral 5C thermostat on the cold feed pipe.

if the concern is there of the system being exposed to sub zero temps, then there is an established system standard for CH, designed to protect the whole system and is as described, a frost stat and pipe stat working in tandem that overrides the controller and starts the boiler. The boiler runs until the pipe stat registers 30Deg @ the return warming up the whole system then the boiler shuts down.

 

[martygturner]

Vaillant could very explicitly state some like ' The integral frost / freezing protection does not protect any external pipes '.

If I was designing a boiler controller I would at least include the option to circulate water through the heating circuit if the boiler detected either the feed or the return temperature dropping below say 10C. Raising up until the return temperature exceeds 15C would not be a high energy cost.

With a combination boiler the problem is nothing can automatically be done to run tap hot water and so draw cold feed water.

Hence

is only partial protection.
My installer added Fernox F1 when filling my system.

I am going to run trace heating cable along both pairs of pipes with the integral 5C thermostat on the cold feed pipe.

Err that's a thermostats job, if you are worried set the thermostat to min

 

[Madrab]

With a combination boiler the problem is nothing can automatically be done to run tap hot water and so draw cold feed water.

Ah, so to protect the hot water pipes to the outlets? If there is a risk of them freezing then they should be insulated. Are we talking about a property that would be left empty for an extended period of time over the winter? If that's the case then the recommendation and standard would be to isolate and hot and cold water supplies and drain them down and implement the system frost/pipe stat setup.

 

[Delta925]

Err that's a thermostats job, if you are worried set the thermostat to min

.... logically it should be but all the Vaillant internal 12C protection thermostat does is circulate water within the boiler.

If the concern is there of the system being exposed to sub zero temps, then there is an established system standard for CH, designed to protect the whole system and is as described, a frost stat and pipe stat working in tandem that overrides the controller and starts the boiler. The boiler runs until the pipe stat registers 30Deg @ the return warming up the whole system then the boiler shuts down.

Fine for the heating circuit but even if this ran continuously since no flow in cold water feed or tap hot water outlet pipes these could still be frozen solid.

Ah, so to protect the hot water pipes to the outlets? If there is a risk of them freezing then they should be insulated. Are we talking about a property that would be left empty for an extended period of time over the winter? If that's the case then the recommendation and standard would be to isolate and hot and cold water supplies and drain them down and implement the system frost/pipe stat setup.

The installer has put standard grey lagging on all four pipes - cold water feed, tap hot water output, central heating output, central heating return.

Primarily simply talking about the overnight temperature dropping to say -10C and daytime temperature only 0C. Back to 1980's overnight dropped to around -20C, low enough for diesel to become too thick for vehicles to run.
Even if alarm was set to wake up every 2 hours and run tap hot water the cold feed water would be close to freezing so potentially not take long to freeze.
If daytime temperature was only 0C or didn't even reach 0C cold feed and hot tap outlet could freeze during the day even if heating pipes stayed above 0C because house thermostat intermittently kicked in.

Leaving the property unattended is scenario I had not thought about. With a combination boiler can the water stop tap be turned off and a both a cold and a hot tap opened to at least partly drain the pipes then left open so a volume for remaining water to expand yet the boiler be left on and the house thermostat set at 5C or even 10C? Or would the boiler lockout in a fault condition because the cold water feed pressure was zero?


I still see fitting trace heating wire with the thermostat on the cold feed pipe as the best / safe option. So long as it keeps the pipes, lagged remember, above 0C, which I presume is how it is designed and and rated, then the freezing risk is eliminated so long as the boiler looks after itself and the house thermostat set at say 10C keeps the internal pipes all above 0C.
Just putting the trace heating wire on the cold feed and tap hot water outlet would probably suffice given the heating pipes have to drop to 0C but a 10m kit is £50 and a 20m kit is £78 so might as well cover all 4 pipes. Since the cable is self regulating if the heating pipes are warm much less heat would be added to them than the cold feed and tap outlet pipes. Two kits are another option but more cost and need two wall sockets as for what is a permanent installation using a 2-way splitter or extension lead even if only 0.5m long not a good idea and reduces reliability.

 

[Why Not Indeed]

Leaving the property unattended is scenario I had not thought about.

If all this is about an occupied property then I suspect you're over-thinking this. Is your boiler in an unheated outbuilding or something?

 

[helplessowner]

Leaving the property unattended is scenario I had not thought about. With a combination boiler can the water stop tap be turned off and a both a cold and a hot tap opened to at least partly drain the pipes then left open so a volume for remaining water to expand yet the boiler be left on and the house thermostat set at 5C or even 10C? Or would the boiler lockout in a fault condition because the cold water feed pressure was zero?

Yes, you can turn off the cold water at the stop tap and drain the taps and leave the combi on without problem. The central heating is a sealed system, not affected by using tap water. We always turn the water off when going away, and leave the heating thermostat on a low setting.

With regard to the earlier post, if somebody does not understand the words:
"It is not designed to protect the pipework / system, only the boilers internals."
Then they are also unlikely to understand the words:
"The integral frost / freezing protection does not protect any external pipes"

 

[Delta925]

If all this is about an occupied property then I suspect you're over-thinking this. Is your boiler in an unheated outbuilding or something?

The boiler is in the garage attached to the house on the single brick rear wall. The pipes run at roof level on the joists ... see the thread I started.

 

[Why Not Indeed]

OK, as you were then