ASHP manifolds setup Help

[Can_Do]

Hi all

 

We are midway through our GF extension adding around 110m2 on 3 sides of our house. After almost giving up on the idea of ASHP, we finally took the gamble to go with a local MCS approved plumber but with little experience of heat pumps installations. The decision was based on low cost and flexibility in choosing pump/cylinder (Mitsubishi Ecodan 11.2kW + Joule 300l high gain cylinder). The original house had radiators throughout, however 4 years ago, I installed wet UFH on first floor covering small bedroom, landing and bathroom with the intent to do the same in the remaining two bedrooms at the time of extension. I used Warmup manifold with mixing valve and grundfos pump which is controlled through couple of actuators, heatmiser app and a single neo-air thermostat. Since then I have been using the heatmiser app as timer to call for heat from the boiler with no other thermostat installed.

 

As part of the extension works, all the radiators are now getting removed and replaced with wet UFH throughout ground floor and first floor. The outdoor Ecodan unit will sit at the corner of the extension with 9m straight run of 28mm copper pipes (elbow at each end) to the Main utility cupboard where the pipes will connect to the water tank and primary UFH 8 port manifold. The total pipe run connected to this manifold will be approx. 750m using 16mm PERT pipes buried in 65mm cement sand screed over 120mm PIR insulation. There will be two Tee off, first one feeding to a secondary 4 port manifold under the stairs on the other side of the house (approx 8m run using 22mm copper pipe). Total pipe length connected to this manifold will be around 350m. The second Tee off will be to the existing manifold in the first floor airing cupboard again using 22mm copper pipes which will feed all of the first floor heating.

 

Based on my research to date, my plan has been to keep all GF UFH as open loop (total pipe length 1100m) which should be sufficient to not need a volumizer or a buffer tank. The main heating setup will be based on weather compensation curve and offsetting function through the FTC6 Controller. I intend to then disable the mixing valve function in the FF manifold and continue to use the grundfos pump and the heatmiser app just to call for the heat for the first floor using the thermostat or timer function which ever will work better.   

 

The plumber has started the work today with installation of the water tank. He has brought an ASHP pump pack along with the GF manifolds and other kit. His view is this additional pump would be needed to circulate all the water through the large lengths of underfloor pipes connected to the manifolds. Based on my research (basically watching some Heatgeek videos on Youtube), the pump within Ecodan unit should be sufficient for the GF pipes and the FF manifold already has a pump attached. I am also not sure if this additional pump will have an impact on Frost cycle as there is no volumizer in the system.  The chat with him today morning has made it clear to me that we are both bit novice with heat pumps and doing it for the first time which is the reason for this post.

 

Can yo please share any advice on the ideal pipe configuration for all the 3 manifolds e.g. Tee off sequencing for flow and returns, need for additional pumps etc. to ensure that the overall system is balanced and performs the way it should. I have tried to keep the system as simple as possible but it seems there is still scope to get it very wrong. Hopefully it all will work out in the end. 

 

Thanks in advance.

 

Kind regards            

 

[sharpener]

30 minutes ago, Can_Do said:

The plumber has started the work today with installation of the water tank. He has brought an ASHP pump pack along with the GF manifolds and other kit.

 

You cannot design an HP installation on the hoof like this and expect it then to work well or indeed at all. Stop and think. Plan the work then work the plan.

[JohnMo]

Your post is long and a little confused, can you say in a couple of simple sentences what you want to connect, what has pump and what doesn't 

 

Defrost, doesn't really care if there are loads of pumps or no pumps, as they will be on if you need to defrost, so it will just take it needs from the return water.

 

Heat pumps are just a heat source. The plumbing is the same really. You have asses dT and with that the required flow rate, to get the kW output needed. Then make sure your pump can handle the volumetric flow at that head loss. UFH loops are parallel loops, so the pressure drop on a manifold is the longest loop length only.

 

Multiple manifolds in different floor buildups are likely to have different flow temp requirements, if these are minor you can adjust the flow rates to balance the system, but most likely you will need mixers and pumps.

 

The offsetting function is really for radiators, could lead over and undershoot of room temp with UFH so be careful.

 

But as stated sit down and work it all out, or rather the MCs contractor is obliged to do this prior to starting work.

 

 

[ProDave]

the heat pump will have a minimum flow rate below which it will throw an error.  Fit a manifold circulating pump to be sure, or if you want to wing it, just try it, you might get lucky but if your HP throws a flow rate error be prepared to add another pump or 2 somewhere.

[JamesPa]

I thought ecodans came without a pump (which seems to be the concern) in which case it's surely just a case of picking a sufficiently high capacity pwm pump for the plumbing (working out the flow requirement based either on dt5 or what it says in the hp manual) and letting the hp sort it out.  That isn't anything that the plumber should be too worried about as it's the same as in any ufh system sofaik.  Or am I missing something?   Plus perhaps some valves allowing balance between the three manifolds to be adjusted)again surely necessary on any ufh system with multiple manifolds - although I admit to knowing nothing about ufh systems, but logic says some balancing must be needed))

 

Whilst I agree with the advice that the 'proper' way to do it is to work it all out, if the plumber is onsite there may be not much choice in which case perhaps following @ProDave s suggestion is not such a bad idea in the situation in which op finds him/herself

Edited April 30 by JamesPa

[Can_Do]

Hi All

 

Thanks for your prompt responses and helpful advice. Apologies for delay in coming back as had a busy week working with the Builder and ASHP Installer together. The Installer originally had brought individual pumps for the two manifolds which gave me the doubt as haven't seen these being used before. He spoke to Mitsubishi Technical Support next day who confirmed that Ecodans don't come with a pump (as JamesPa mentioned above). He has since installed a Grundfos 25-80 180 variable speed pump on the main incoming flow from the heat pump. According to him, this pump would be sufficient to cover flow requirement for both the ground floor manifolds. The first floor manifold already has a pump installed to it along with a Heatmiser UH8-RF controller. He has installed a 3 port valve for water tank/UFH and an additional 2 port valve to the supply line for first floor. In addition he has installed few extra valves which he may need to balance the overall ufh system as the build progresses with the second manifold and more loops are added. His initial install is almost done and tested. Awaiting couple of parts arriving next week which would allow start of heat pump. Looking forward to it now. 

 

To be fair, the installer has been very accommodating with the project requirements as the overall ufh system will be build in stages up to next 3-4 months by the Main Builder. The Installer will have to wait till then to fully finish his install.   

 

Kind regards