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Are antifreeze valves essential for a glycol free ASHP system?

 
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Air Source Heat Pumps (ASHPs)
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 Mike H
(@mike-h)
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Topic starter 13/02/2024 11:04 am  

During a recent upgrade to my 12kW Samsung ASHP set up, the glycol was removed as requested. I expected one or more antifreeze valves to be fitted, but I was told on good authority that these were not required. So I wondered if anyone had any views on the pros and cons of fitting antifreeze valves? If fitted, is one on the return flow sufficient or should there be one on the leaving flow too? Is anyone in the same position, having no glycol and no antifreeze valves?

I must admit to feeling a little anxious when all occupants of our three terraced cottages were away at the same time after Christmas, when it went very cold and any power cuts would have gone unnoticed!



   
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Mars
 Mars
(@editor)
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13/02/2024 5:21 pm  

Great question. @heacol will know the answer.


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 Brendon Uys
(@heacol)
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13/02/2024 5:39 pm  

According to Samsung, you either have to have antifreeze valves or glycol. As glycol will add 20%+ to your heating bill, it is not really an option. In reality, if you want top install them, 1 will suffice on the lower pipe, however, it is nearly impossible for ice to damage the Samsung unit as the internal connecting pipes are rubber, and will expand on freezing. 

It is up to you, I have about 600 units in the field, of all makes, and no glycol or antifreeze valves, and have not, in the last 15 years, had a single unit damaged by ice.

 



   
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 Mike H
(@mike-h)
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Topic starter 13/02/2024 10:39 pm  

@heacol Thanks Brendon, that is very helpful.



   
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Mars
 Mars
(@editor)
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14/02/2024 9:09 pm  

@heacol I’ve also wondered how that worked. Will the system remain protected if there’s a big winter storm with temperatures below zero and power lines get taken down, and we’re without power for a few days. Wouldn’t that do some damage and wouldn’t stuff that shouldn’t freeze, freeze?


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 Brendon Uys
(@heacol)
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15/02/2024 7:32 am  

@editor I am not saying the units will not freeze in some conditions, and I have seen many, however it is the design of the unit it'self that will determine if there is any damage. Units that have standard circulator pumps in them such as Valiant, Midea/Clivet and others are vulnerable as standard circulators can easily be damaged by freezing, some units with pumps like Panasonic are not affected as they have taken the time and effort to make their own pump. Units that have no pump, like Samsung and Mitsubishi, are not usually affected.

As I said, it is your choice. My choice is Panasonic hands down, it is so far ahead of the pack for many, many reasons.



   
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Abernyte
 Abernyte
(@abernyte)
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15/02/2024 7:59 am  

Posted by: @heacol
↑

As glycol will add 20%+ to your heating bill,

Really? That is an enormous claim, citation required.  I am aware of talk around a small increase,  but 20% plus ( by how much plus) is astonishing.



   
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 David I
(@david-i)
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Joined: 2 years ago
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16/02/2024 8:29 am  

@abernyte Difficult to get specific figures but I work on

Water 4.184kj/kg.K. 

Monopropylene glycol 3.884kj/kg.K (@30%)

Monoethylene glycol 3.712kj/kg.K. (@30%)

Pump at say 50W will cost 1p/hour to run, with glycol added 1.1p/hr.


I work for a manufacturer of heat pumps and boilers.


   
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Mars
 Mars
(@editor)
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16/02/2024 8:36 am  

@david-i interesting. Thanks for sharing. So do you avoid glycol in systems too?


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Toodles
 Toodles
(@toodles)
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16/02/2024 10:08 am  

@editor No Glycol in our Daikin installation but we do have two antifreeze valves. When the ‘Boss’ came to do a little ‘snagging’, he was surprised (and I think, a little miffed due to their cost) that his installers had fitted them in both pipes rather than just one. I was rather pleased that they had fitted them in both as surely, if the pipes are both very cold, isn’t better that they both drain? (Or is not how this precaution is supposed to work perhaps?). (Daikin are coming today to carry out the first annual service) Regards, Toodles.


Toodles, heats his home with cold draughts and cooks food with magnets.


   
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 AllyFish
(@allyfish)
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16/02/2024 11:25 am  

Anti-freeze valves provide some guarantee of a fail safe if the system is unpowered for a long period and all other forms of frost protection such as the unit pump circulating water and/or frost protection heating in the circuit fail. You are into double jeopardy however - a long power failure coincident with extreme prolonged low temperatures. Anti-freeze valves should be on both outdoor unit supply and return pipes at the lowest point. Glycol isn't really required in the UK provided external pipework is properly insulated and protected.

Glycol lowers the specific heat of water with increasing concentration, it's the renewable parallel of adding hydrogen gas to mains gas methane, which lowers the calorific value of the resulting blend. That's why using H2 for domestic heating is a dumb idea, aside from the cost of producing it and the safety issues it creates.



   
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Abernyte
 Abernyte
(@abernyte)
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16/02/2024 11:58 am  

Which does not get us anywhere near a 20% plus energy cost increase caused by using glycol.



   
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