Cooling with an A2W ASHP and radiators

Hi all, I’m pondering cooling with my air-to-water heat pump system (10 wet radiators, 2 bedrooms, 2 storey house, designed for a flow temp of 48C).
As I understand it, the air source heat pump unit itself has enough capability to do a useful amount of cooling, but it won’t be able to put that cooling power through the radiators for two reasons.

  1. You cannot have a low flow temperature running through the system as water will condense on the pipes, causing mould and damp. Options here include switching to underfloor heating so that a certain flow temperature has a more powerful cooling effect, getting a dehumidifier (but this has a heating effect), or getting MVHR to get rid of water as much as possible. None of these are really attractive to me.

  2. The other problem is that my radiators are connected at the bottom on each side, so cold water would just flow across the bottom of each radiator. As it just flows along the bottom it won’t mix with the hotter water above, reducing the heat transfer and preventing the cooling power. So my thought is this: if I add a baffle / upwards flow diverter inside each radiator, would that improve the cooling power of the radiator by forcing the cold water to flow upwards and mix with the hotter water in the radiator? Would that provide better cooling? Would that have a detrimental effect on the pump that has to move water around the system? Would that have an effect on the ability of the radiator to heat normally during winter? Has anyone tried this?

I understand that this won’t provide all the cooling power you could want, but I’m just wondering if adding flow diverters would make it better.


You are correct that you will get condensation on your pipes. You will also get it on the radiators. As an absolute minimum you will need to invest in drip trays for your radiators and to find some way of emptying them.

Thanks for the warning! Would I still get condensation even if I stayed a few degrees above the dew point?

Logic says you shouldn’t get condensation but I’m not sure that the long term results would be particularly good. Remember that the maximum of the target range for humidity is 60%, so if you exceed that you can still get mould and your timber will be more vulnerable to insect attack.

I think the guys at @Heatgeek did a bunch of experiments during the hot days earlier this year. They will probably not recommend doing this but you may as well tap their knowledge.

1 Like

Ok that’s helpful to know too. We are sometimes above 60% so maybe I should keep more an eye on this.