Anti Freeze in heating system?

Hi, I have a commerical heating system, not sure of capacity, but we have a potterton NXR3/37 boiler (210kw), we have had issues with pumping over which we have sorted (speed controller added to pump)
We are in the process of de-sludging our radiators and it was suggested we put anti freeze in the system instead of fernox, as fernox would cost about £800 for 50 litres. Not quite sure what to think?

Look forward to your comments

Peter

I would think you should look at fitting a pipe stat / frost stat rather than putting antifreeze in.

We use anti freeze inhibitor for outdoor boilers - when the customer is prepared to pay for it. Sentinel X500 for example.

In principle the frost stat etc should render it pointless....unless the boiler fails on a very cold day of course.

So for outdoor boilers it is a good idea, for indoor ones less so. I would not put normal anti freeze in a heating system without consulting the boiler manufacturer.

On a large system a microbubble deaerator and sludge pot would make more sense, Spirovent are one manufacturer you could look at.

Sentinel X500 costs around £20-£25 for 5 litres.

Fernos is a usually a corrosion inhibitor (but they make cleaning and anti-freeze solutions, as well). Anti-freeze will not replace the corrosion inhibitors. In fact, it makes them even more necessary. The anti-freeze oxidizes into an acidic compound in the presence of dissolved oxygen, which causes galvanic corrosion. You have a dissolved oxygen issue from the pumping-over problem. It would be daft to put anti-freeze in this, unless you need to stop it freezing. You'd be better off with a frost thermostat.

£800 worth of Fernox in a 210 kW system sounds excessive; are you sure you're not being conned? Get a commercial water treatment specialist in for a quote to compare.

Anti-freeze would usually need to be propylene glycol (expensive, non-toxic) rather than cheaper ethylene glycol (very, very, toxic), especially if the heating system heats a domestic hot water system.

We tend to use glycol in all our commercial installs,based on use and pipe configures dosage varies from 50% for roof mounted external runs(run round coils , condesr circuits) down to about 10% (standard heating circs) about £50 for 25litres was fridays price.

A bit pointless in UK at least as you can buy 5 litre of central heating inhibited antifreeze for under £20