Direct slab heating with ASHP

[JIH]

After much heart ache, time and tears I'm looking for some advice from you guys regarding my heating system, which is completely separate from DHW. 

 

I plan to directly heat my slab with ASHP using Willis heaters as back up.  Hydraulically does this look ok?

 

Input much appreciated.

 

[Jilly]

So, I'm not at the point of choosing an ASHP, but...you need extra heaters?? TBH it was troubling me how it would work in the really cold weather...

[JIH]

  On 11/07/2020 at 16:28, Jilly said:

So, I'm not at the point of choosing an ASHP, but...you need extra heaters?? TBH it was troubling me how it would work in the really cold weather...

Expand  

Jilly -   I'm happy that my ASHP will be adequate to heat my house, which has a high level of insulation and air tightness.  You may be correct that additional heat could be required in extreme conditions - but this could be achieved with a fan heater and does not need to be part of the system design in my case.

 

 

 

[PeterW]

  On 11/07/2020 at 16:28, Jilly said:

So, I'm not at the point of choosing an ASHP, but...you need extra heaters?? TBH it was troubling me how it would work in the really cold weather...

Expand  

No the Willis heaters are there for a backup if the ASHP breaks 

 

Sizing an ASHP is fairly simple, the difference is getting used to running it on off peak power such as E7 or E10. You use the floor as a big storage heater, pump lots of heat in and then it radiates through the day. E10 allows you to give it a boost later in the day. 
 

 

[JIH]

  On 11/07/2020 at 15:50, JIH said:

 

 

Expand  

 

Can anybody help me here?  Does this look ok?  Correct to have circulating pump on the flow side?  Should it be as far from the UFH manifold as possible?

[joe90]

My pump is on the manifold on the flow side as designed by the manufacturer.

[PeterW]

Only thing I would potentially add is a buffer and then just put the immersion(s) as a backup in the buffer tank itself. 

[JIH]

  On 13/07/2020 at 19:01, joe90 said:

My pump is on the manifold on the flow side as designed by the manufacturer.

Expand  

 Yes, thanks @joe90 I have a pump attached to the manifold (as shown in the diagram in the box on right), but  I thought I would need another  pump in addition to the UFH circulating pump.

 

[JIH]

  On 13/07/2020 at 19:04, PeterW said:

Only thing I would potentially add is a buffer and then just put the immersion(s) as a backup in the buffer tank itself. 

Expand  

Thanks @PeterW, I don't have room for a buffer tank in the space unfortunately and have already bought the willis heaters. 

[PeterW]

So you need a bypass somewhere here after the pump and before the UFH manifold. If all the zone valves shut you will get a closed circuit and no flow. 

[joe90]

  On 13/07/2020 at 19:09, JIH said:

 Yes, thanks @joe90 I have a pump attached to the manifold (as shown in the diagram in the box on right), but  I thought I would need another  pump in addition to the UFH circulating pump.

 

Expand  

my ASHP does not have a pump within it (some do) so I have a pump externally to give flow to the buffer or DHW tank as dictated by the controller/stats etc. The manifold pump circulates water from my buffer and around the UFH loops.

[JIH]

  On 13/07/2020 at 19:15, PeterW said:

So you need a bypass somewhere here after the pump and before the UFH manifold. If all the zone valves shut you will get a closed circuit and no flow. 

Expand  

Thanks @PeterW, just a simple connection across as above?  Does this need a valve?

[JIH]

  On 13/07/2020 at 19:44, joe90 said:

my ASHP does not have a pump within it (some do) so I have a pump externally to give flow to the buffer or DHW tank as dictated by the controller/stats etc. The manifold pump circulates water from my buffer and around the UFH loops.

Expand  

 

Thanks @Joe90, I think I shall therefore try and position my pump as close to the ASHP as possible.

[PeterW]

No it needs a bypass valve. 

[PeterW]

  On 13/07/2020 at 19:55, JIH said:

 

Thanks @Joe90, I think I shall therefore try and position my pump as close to the ASHP as possible.

Expand  

Check the MIs for the ASHP - some need it on the return not the flow for some reason .!!

[JIH]

  On 13/07/2020 at 19:55, PeterW said:

No it needs a bypass valve. 

Expand  

 

  On 13/07/2020 at 19:56, PeterW said:

Check the MIs for the ASHP - some need it on the return not the flow for some reason .!!

Expand  

Thanks @PeterW, you're a ?

[joe90]

  On 13/07/2020 at 19:56, PeterW said:

Check the MIs for the ASHP - some need it on the return not the flow for some reason .!!

Expand  

yes, @JIH What ASHP do you have?

[JIH]

  On 13/07/2020 at 20:04, joe90 said:

yes, @JIH What ASHP do you have?

Expand  

 

I have a Kingspan Aeromax Plus 6kW @Joe90.

 

 

 

Looking at this diagram in the blurb it seems the pump should go on the return for the Kingspan, thanks @PeterW

[joe90]

Ha, I have the Kingspan Aeromax 4kW 

[joth]

  On 13/07/2020 at 19:56, PeterW said:

Check the MIs for the ASHP - some need it on the return not the flow for some reason .!!

Expand  

 

I always assumed this was more for the benefit of the pump rather than the ASHP: it gets to spend its  working life pumping away at room temperature rather than at the heating supply temperature, but I don't have any evidence that's necessary or helpful or even relevant.

 

[JIH]

  On 13/07/2020 at 20:32, joe90 said:

Ha, I have the Kingspan Aeromax 4kW 

Expand  

 

I hope you're pleased with it!  Did you use the controller to set the temperature?  I remember reading you had problems.  I've not tried mine yet.

[joe90]

  On 13/07/2020 at 21:11, JIH said:

  I remember reading you had problems.  I've not tried mine yet.

Expand  

OH YES. I am not the best when it comes to programming stuff but I found this very difficult to understand. (And so did Jeremy, and he is a boffin) Frankly I managed to set a couple of parameters and left it alone ?. I am very pleased with the ASHP and it’s performance. ?