Heatpump with Stelrad Radiators

BuzzFish

Hi folks,

In the process of purchasing a house and upgrading the heating from Gas to and A2W system. Too late for under floor heating at this point. The house was up to 1st fix when we decided to purchase.

The plans for the house were sent to Daikin who have sent back a pretty thorough 43 page document but there is one question I was hoping folks may be able to help me with as I'm meeting the plumber tomorrow.

Daikin have spec'd various sizes of StelradCompact radiators throughout the house. They are over-sized and looking at the delta values they look to be sufficient for the outputs required per room. However, I would have expected that aluminium rads would have been specified. I have no issue really with the rad sizes in itself but just curious about the fact steel rads have been recommended.

Should I question this or are Stelrad compact radiators sufficient to get good efficiency from a Daikin Altherma 3 7kw system?

Calahonda52

Are Alu rads not more expensive so unless you asked for them, anyone will quote the lower cost option when its a tender.

I would do so iff I was alked as a lot of folk will just look at the bottom line number and bin it if it seems to high.

When you say oversized, what do you mean?

What flow/return temps are they using?
What room temps are in the design?

BuzzFish

Thanks for the reply.

45/35 flow return.
Room temps between 21 in living spaces back to 18 in bedrooms.

When I say oversized I mean that in the spec the rads are documented at 1500w (for example) at delta 50. For me they'll output 460w in the spec.

Mainly my question is whether using Stelrad radiators will be more inefficient than aluminium rads?

antoinolachtnai

BuzzFish wrote: »

Thanks for the reply.

45/35 flow return.
Room temps between 21 in living spaces back to 18 in bedrooms.

When I say oversized I mean that in the spec the rads are documented at 1500w (for example) at delta 50. For me they'll output 460w in the spec.

Mainly my question is whether using Stelrad radiators will be more inefficient than aluminium rads?

There is no difference in efficiency between rads!

A 460w rad (at a particular delta) is a 460w rad no matter what it is made of.

An aluminum rad will certainly heat up faster than a steel rad when you turn system on. But it will also lose its heat much faster when you turn system off.

froshtyv

BuzzFish wrote: »

Hi folks,

In the process of purchasing a house and upgrading the heating from Gas to and A2W system. Too late for under floor heating at this point. The house was up to 1st fix when we decided to purchase.

The plans for the house were sent to Daikin who have sent back a pretty thorough 43 page document but there is one question I was hoping folks may be able to help me with as I'm meeting the plumber tomorrow.

Daikin have spec'd various sizes of StelradCompact radiators throughout the house. They are over-sized and looking at the delta values they look to be sufficient for the outputs required per room. However, I would have expected that aluminium rads would have been specified. I have no issue really with the rad sizes in itself but just curious about the fact steel rads have been recommended.

Should I question this or are Stelrad compact radiators sufficient to get good efficiency from a Daikin Altherma 3 7kw system?

I find it strange that a heat pump manufacturer are sizing radiators?
Do they have PI insurance to stand over their design?

Aluminium radiators are normally used with a heat pump due to their low water content and high emissivity value.

A correctly sized radiator will work, once it is producing enough heat output to meet the rooms heat loss.

At a 45 degree flow temperature from the heat pump, you are going to loose a certain amount of efficiency.

Any COP or outputs for the heat pump in question, will all be based on a flow temperature of 35 degrees.