Glycol vs Antifreeze valves?

[eniacs]

I'm in the sunny south in a town (Plymouth). Like you say for several years we haven't had very cold weather, but the past couple, we've had -5 for a few days. My pool heat pump system froze solid and when i found it I felt terrible thinking how stupid i was to forget it (plan was to run the circ pump in very cold weather). All the pipes/pump/strainer etc were solid. Luckily the heat pump protected itself and prevented its heat exchanger from freezing, which is a god send, otherwise the £2500 unit would be a bit of scrap.

 

I'll be doing my ashp soon and will be using freeze valves, over the lifetime of our previous heating system we've made multiple small changes requiring the system be drained and refilled.

[Dreadnaught]

11 hours ago, JohnMo said:

If you live in the sunny south in a town, not sure I would bother with either. 

 

Yes, I am in the south (Cambridge) and, after reading this very helpful thread and some of the links presented, especially that from Graham Hendra, I have decided to do without both when I commission my own heat pump. 

 

Then I shall pray that there isn't a power cut that lasts for more than 24h which coincides with freezing weather.

[Dan F]

21 minutes ago, Dreadnaught said:

 

Yes, I am in the south (Cambridge) and, after reading this very helpful thread and some of the links presented, especially that from Graham Hendra, I have decided to do without both when I commission my own heat pump. 

 

Then I shall pray that there isn't a power cut that lasts for more than 24h which coincides with freezing weather.

 

And if there is power-cut in freezing weather? Do you know how much the repair would be vs. what you save for valves/glycol?   Typically, if you don't take out an insurance policy, it's good to know what the costs would be that you'd have to cover in a worst-case scenario.

Edited April 25, 2023 by Dan F
spelling

[Dreadnaught]

28 minutes ago, Dan F said:

Do you know how much the repair would be

 

Oh, no I don't. No idea at all.

In reality, the probability of a power cut lasting 24h-duration is remote at any time.

And I am a natural risk taker  

[Dan F]

21 minutes ago, Dreadnaught said:

 

Oh, no I don't. No idea at all.

In reality, the probability of a power cut lasting 24h-duration is remote at any time.

And I am a natural risk taker  

So no house insurance, nothing? 🙂

 

We have the anti-freeze valves installed, the installer preferred them to glycol, and the manufacturer (Vaillant) was happy with it, so that's what we have.

 

Actually given our primaries are somewhat undersized at 22mm, I'm glad we don't have glycol else 22mm would have been even more borderline

Edited April 25, 2023 by Dan F
spelling

[JohnMo]

50 minutes ago, Dan F said:

Do you know how much the repair would be vs. what you save for valves/glycol

Possibly finding someone would be the issue, rather than the cost.  Cost may end up being a cost of a new unit.

 

We have a generator, big enough to run the heat pump, but I am still installing glycol. Worst case is away for the weekend and a power cut. Cheap insurance policy

[Dreadnaught]

18 minutes ago, Dan F said:

So no house insurance, nothing?

 

Haha, no comment but we each choose our own level of risk according to our own comfort levels 😄 

 

17 minutes ago, Dan F said:

Actually given our primaries are somewhat undersized at 22mm

 

Ah yes, I was just now buying the 28mm connection bits for mine (and have 32mm duo insulated pipe under my raft foundation).

 

[Dan F]

49 minutes ago, Dreadnaught said:

Ah yes, I was just now buying the 28mm connection bits for mine (and have 32mm duo insulated pipe under my raft foundation).

 

My M&E guy told me to use 25mm duo (plastic) which has roughly the same ID as 22mm copper.   Vaillant's view was it "wouldn't" work with 22mm, but the reality is it's fine, it achieves target flow rate,  and the fact the run isn't that long and I'm not using Glycol of course helps.

 

That said if we'd installed the 10kW model (with a significantly higher primary flow rate) this would have been a big issue.  7k is plenty though.

[GLPinxit]

What about corrosion inhibitor, I thought that came with glycol?

(And I'm currently up-sizing 3 rads in our 8 month old retrofit and that suggests that the installers' flush wasn't fully effective. In our last house I drained the system from time to time as I was making various changes and was used to a clear drain-down as I always put Fernox back in. Here a combination of cost and a sewage digester means I've just drained individual rads as I go.)

[ReedRichards]

On 25/04/2023 at 21:05, Dreadnaught said:

In reality, the probability of a power cut lasting 24h-duration is remote at any time.

 

 

Storm Arwen caused power cuts lasting 24 hours and much longer in my area.  But the weather was not too cold at that time so you would probably have been okay.  

[Dreadnaught]

30 minutes ago, ReedRichards said:

Storm Arwen caused power cuts lasting 24 hours and much longer in my area.  But the weather was not too cold at that time so you would probably have been okay. 

 

Yes. In the event of freezing weather and the realistic prospect of a power cut lasting 24-hours or more, I'd probably just turn the isolation valves and disconnect the pipes to the heat pump and let it drain. I have a ground-mounted installation which isn't up against a wall so simple to do with easy access. I will have a short length of 28mm Hep2O pipe (suitably well insulated and protected from UV) connecting the heat pump to the duo insulated pipe that emerges from the ground so won't even need a spanner, just a Hep2O key.

Edited April 28, 2023 by Dreadnaught

[sharpener]

35 minutes ago, Dreadnaught said:

 

Yes. In the event of freezing weather and the realistic prospect of a power cut lasting 24-hours or more, I'd probably just turn the isolation valves and disconnect the pipes to the heat pump and let it drain. I have a ground-mounted installation which isn't up against a wall so simple to do with easy access. I will have a short length of 28mm Hep2O pipe (suitably well insulated and protected from UV) connecting the heat pump to the duo insulated pipe that emerges from the ground so won't even need a spanner, just a Hep2O key.

 

That's all very fine until it happens when you are away. So I prefer the idea of antifreeze in the system.

 

Read yesterday that Viessman R290 units don't allow it, you have to enable their frost protection, also these units won't start from cold so there is a 6kW inline heater in the indoor unit to warm the compressor up to 20C before starting it up.

[dpmiller]

5 hours ago, sharpener said:

6kW inline heater in the indoor unit to warm the compressor up to 20C

 source for that info?

[sharpener]

41 minutes ago, dpmiller said:

 source for that info?

 

Viessman Technical Guide available here says on p85 the following:

 

If frost protection mode is permanently enabled (e.g. in a holiday
home), the secondary circuit temperature can drop below the mini-
mum heat pump flow temperature. The heat pump compressor
does not then start independently.
As a result, even with a mono mode heat pump design, an additional
heat generator must always be included in the design; e.g. an
instantaneous heating water heater.

 

Also on p88 it says not to use antifreeze. I can't now find the reference to 20C min compressor temp but I am sure I read it somewhere as recently as yesterday.