Willis pumps and pressures

[Barnboy]

I'm needing to run my ufh heating screed before I can get an ashp,

I'm going to build a willis setup and I've been looking at all the talk about this on here but still have some questions.

 

* What pressure should I be setting everything to when initially filling it up and maintaining?

 

* Do I need a circulation pump and pre circuit as well as the pump on the manifold.

 

* What size expansion vessel should I be getting, 10% of complete volume?

 

* Do I need a prv ?

 

Sorry I know these sorts of things have been covered before but I've seen all arrangements and can't afford to get it wrong or spend money that I don't need to

 

Thanks

 

[JohnMo]

3 minutes ago, Barnboy said:

I'm needing to run my ufh heating screed before I can get an ashp,

Obvious question why?

 

3 minutes ago, Barnboy said:

Do I need a circulation pump and pre circuit as well as the pump on the manifold.

No, manifold pump will circulate. But why do you need a mixer and pump with ASHP?

 

4 minutes ago, Barnboy said:

What size expansion vessel should I be getting, 10% of complete volume?

 

* Do I need a prv ?

Just use normal sizing calculations and you need prv and filling loop.

 

[Barnboy]

@JohnMo I need to comission my screed and don't have my outside area anywhere near ready for an ashp yet so need to run it on Willis heaters and I might run it on them for rhe winter depending on running costs to save shivering for a couple of months.

[Conor]

You don't need to commission screed. Let it dry normally.

 

We used portable heaters and dehumidifiers to keep the house a sensible drying temperature (16c) before moving in. You get a COP of about 1.5 from a dehumidifier, so cheaper to run. Much simpler and cheaper than building a Willis arrangement. We sold the dehumidifiers on at £80 each, they cost £115.

 

We set our ASHP on a base of loose laid concrete blocks. We still haven't sorted a permeant hard standing three years later lol

Edited February 5 by Conor

[Nickfromwales]

11 minutes ago, Barnboy said:

@JohnMo I need to comission my screed and don't have my outside area anywhere near ready for an ashp yet so need to run it on Willis heaters and I might run it on them for rhe winter depending on running costs to save shivering for a couple of months.

OK. You keep saying "commission", do you need to commission it or just turn it on to get heat? Big difference, as one makes sense and the other doesn't  

Some folk have their tilers recommend thermally 'shocking' a newly laid slab / raft foundation to provoke it into hairline cracking ahead of tiling, but it depends on if it's a screed, a slab / raft, and how long this has had to dry.

 

So do you just want heat? 

[Barnboy]

@Nickfromwales I need to commission it, its an Anhydrite screed that the spec is to heat it up gently until at running temp and then turn off to let it cool again. It's supposed to force the last of the moisture up to the surface as well as force any expansion cracks to occur.

It would also be nice to maybe use it for some heat possibly later on as I have no power to where the ashp will go.

[Barnboy]

I'm going to be filling the system with a pump out of cans of water that I've sent through a reverse osmosis and DI filter so I won't jabe mains pressure to set the system pressure, what should I be setting the system pressure to and what pressure prv should I add to my willis setup ?

Thanks