Vaillant 837/937 frost protection

[Tipper]

My Vaillant 937 is located in my garage and I have been a little concerned about frost protection.

I know it has a built in frost stat to protect the inner workings, presumably on the PCB, and the pipework to and from is insulated but what about the chassis pipework that is visible through the plastic grille on the underside? It's effetively open to the very cold air in the garage. The Magnaclean is also uninsulated.

What I have done is tape a couple of layers of cardboard underneath to give some level of protection and so that this exposed pipework is drawn into the body of the boiler. I may upgrade this to a piece of insulation like polystyrene or even an old tank jacket.

Any safety or other issues with doing this? What do you think?

 

[Deleted member 105431]

any pipes in the garage should be lagged but the boiler opens up the ch circuit in frost protection mode so no need to worry.

 

[Tipper]

But won't the pipework outside the boiler see the low freezing temperatures before the internals of the boiler?

Surely the pipework below the boiler will be more at risk the the boiler itself!

 

[gas4you]

As said, just insulate as close to the boiler as possible.

This has a 2 stage frost protection, pump runs as temp drops, then boiler fires if it really gets cold.

Running water takes a lot more to freeze than staic water.

 

[Tipper]

Thanks for you responses guys but I'm not convinced.

I've seen, as I'm sure you have, outside taps blown apart by ice right next to insulated pipework so I still feel that the exposed pipework below the boiler is at risk.

I acknowledge that the boiler has this 2-stage protection but it's sensing the temperature inside the boiler where it will always be warmer and not outside the casing around it. It will probably be better to fit a conventional frost stat close to the boiler to ensure the boiler fires with low temperatures in the garage rather than just inside the boiler casing.

If I do this can this be connected to the 'conventional' CH demand conections, ie bridged connections 3 and 4, as I am using the eBus with a VRT 360f.

 

[Deleted member 105431]

Thanks for you responses guys but I'm not convinced.

I've seen, as I'm sure you have, outside taps blown apart by ice right next to insulated pipework so I still feel that the exposed pipework below the boiler is at risk.

I acknowledge that the boiler has this 2-stage protection but it's sensing the temperature inside the boiler where it will always be warmer and not outside the casing around it. It will probably be better to fit a conventional frost stat close to the boiler to ensure the boiler fires with low temperatures in the garage rather than just inside the boiler casing.

If I do this can this be connected to the 'conventional' CH demand conections, ie bridged connections 3 and 4, as I am using the eBus with a VRT 360f.

It's completely pointless but if you insist fit a frost stat (set to 5 deg C) wired in series with a pipestat (set to 30 deg C) fitted on the ch return.

Honeywell are good quality.

 

[Dan Robinson]

I've seen, as I'm sure you have, outside taps blown apart by ice right next to insulated pipework so I still feel that the exposed pipework below the boiler is at risk.

I have yet to see an outside tap fitted with a frost stat though.

As Dangermouse said - fitting a frost stat is totally pointless here - why introduce two more things to break?

From your original post I see you are worrying about the pipes IN the boiler- exactly where the internal frost protection is...

 

[Tipper]

You've obviously not seen the underside of a Vaillant 837/937!

If you look up and under the boiler you will see all the CH, HW and cold feed pipework external to the boiler AND through a thin plastic grid on the underside the uninsulated connecting pipework which then feeds into the boiler.

I'm not concerned about the internals of the boiler as they are adequately both insulated and protected by the OEM's frost protection and anyway the internals are unlikely to see the same low external temperatures due to the high level of insulation of the boiler casing.

The house side pipework insulation stops at the plastic grid. Therefore all connecting pipework, etc, in the exposed under belly of the boiler is uninsulated and I consider this at risk of freezing because the boiler is in an unheated garage.

I'll ignore your comments about frost stats and outside taps......

Coming back to the electrics.....which connections should I be using for this frost stat/pipe stat scheme? Does using the suggested connections (3&4) compromise the use of the eBus for system control? (My electronics knowledge of multiplexed control systems is a bit rusty since I retired!)

 

[gas4you]

Can't see an external frost stat working with the VRT360.

This will already have terminals 3 & 4 bridged for the 360 to work.

Try changing the frost settings in the 360, or am I thinking of the VRC400

 

[Deleted member 105431]

Tipper your right, I have never seen underneath a Vaillant boiler.

What do they look like? What do all the pipes do? Does it look pretty?

 

[Dan Robinson]

Anyone would think a heating engineer would get confused by all those different boilers....

What was I thinking?

 

[The831Bunny]

Didn't want to get drawn into this but...

My ecotec is in the garage, has been for nearly four years, ecomax before that for a good few years. NEVER a problem, even when the kids leave the side door wide open overnight

The frost protection is measured from the flow and return ntc sensors so I doubt there would be a 10 degree difference in 400mm or so of pipe.

Just insulate to the required standard for the garage.

Can't remember the last service cock I changed for frost damage...

Bunny

 

[The831Bunny]

Next thing the OP will be saying he has a \DV fault 'cos the heatings on in the night

 

[Tipper]

Sorry to disappoint but I'm not as stupid as some posters!

 

[JoeMar]

Tipper

I have my 937 (+ magnaclean) installed in the loft and have not had any problems with freezing pipes although i have lagged the c**p out of them.

The answer to your problem is to set the CH Circulating pump to run for 15 - 20 minutes every 2 hours during the night. this way warm water from the house will stop your pipes from freezing (this is exaclty what the boiler does in its 1st stage frost protection by the way). Im not sure if this feature is available on your particular controller - i have the VRC430.

Edit: I've just had a quick look at the specs for the VRT360 and i looks like it is possible to set time windows for the circulating pump.

Like it has already been said the 937 does a very good job at protecting it's pipes and you are worrying a bit too much about it.