Advice on heat pump for under floor heating only

[Ceridunn]

Good evening to all. I have a 1930's bungalow which I have reroofed to create a new dormer, insulated walls and floors so had ufh installed on the whole ground floor. Decided to start future proofing the heating system by installing heat pump for the ufh and keeping existing combi for water. But I am struggling to find advice on how to install heat pump just for ufh, most people go for dhw as well which is a more complex system. Any advice would be most welcome. Cheers

[PeterW]

Depending on the heat loss, it’s as simple as pick one to match about 125% of the load, 2 port buffer and standard UFH from there on. Not much more to it ..??

[Ceridunn]

9 hours ago, PeterW said:

Depending on the heat loss, it’s as simple as pick one to match about 125% of the load, 2 port buffer and standard UFH from there on. Not much more to it ..??

Hi, thanks for that, you make it sound so easy! Octopus quoted for us at 1 point and that included a 7kw HP so I've been out and bought Samsung 8kw. UFH is already installed approx 700m of pipe from memory. Do I need a buffer tank do you think? I'm also under the impression that I connect the flow and return directly onto the manifold with no need for the pump as the heat pump does this itself(or is this wrong?) Do I need expansion vessel as I see on installations with dhw or are they only for dhw and radiator circuits? 

[JohnMo]

You need to meet minimum manufacturer heating system, which is normally around 30 to 40 L, which you should exceed, as long as you don't zone and leave it as an open system. Min volume, is the smallest zone plus interconnected piping.

 

My install will be open on a single zone no buffer. 

[Ceridunn]

23 minutes ago, JohnMo said:

You need to meet minimum manufacturer heating system, which is normally around 30 to 40 L, which you should exceed, as long as you don't zone and leave it as an open system. Min volume, is the smallest zone plus interconnected piping.

 

My install will be open on a single zone no buffer. 

Thanks, I will check this, already planned 5 zones for the ufh, so maybe a rethink in order

[JohnMo]

Most efficient way to add volume is either a 2 port buffer, that sits in parallel to heating system, or a volumiser, it sits in either the flow or return piping and flow passes through it - it is connected to only flow or return, not both. Neither add hydraulic separation, so only a single pump is required.

 

One zone - no wiring centre needed, single thermostat (normally your heat pump controller), no buffer/volumiser, simple system is all that's required for heating only, couple of isolation valves (use a filter ball valve in the return). Get your rooms where you need them by balancing loop flows.

[Ceridunn]

3 hours ago, JohnMo said:

Most efficient way to add volume is either a 2 port buffer, that sits in parallel to heating system, or a volumiser, it sits in either the flow or return piping and flow passes through it - it is connected to only flow or return, not both. Neither add hydraulic separation, so only a single pump is required.

 

One zone - no wiring centre needed, single thermostat (normally your heat pump controller), no buffer/volumiser, simple system is all that's required for heating only, couple of isolation valves (use a filter ball valve in the return). Get your rooms where you need them by balancing loop flows.

OK, let me see if I have this right, if I keep my zones I need a buffer and will need to fit the pump that came with my manifold. If I have just 1 zone then I don't need the buffer, but in this instance will I need the pump or will the heat pump do that job? (I was under the impression I wouldn't need the pump on the manifold if going direct onto a heat pump). Cheers

[JohnMo]

My view and there are others that will say no.

 

Your heat pump is not doing cylinder heating, so there is no need to have a mixer to protect the floor from 55 deg flow. So use pump that comes with the ASHP and no mixer or pump on the CV UFH manifold.

[Ceridunn]

15 minutes ago, JohnMo said:

My view and there are others that will say no.

 

Your heat pump is not doing cylinder heating, so there is no need to have a mixer to protect the floor from 55 deg flow. So use pump that comes with the ASHP and no mixer or pump on the CV UFH manifold.

Thanks, let's see if others comment  but I was told I wouldn't need the pump on the manifold solely for ufh. There is more to this than I originally thought as I have already set up the 5 zones etc so maybe that idea will fall by the wayside. Looks like I have more reading up to do. 

 

Cheers John. 

 

Ps Any other tips please share. 👍

[JohnMo]

Are you talking loops or zones?

 

5 loops as a single zone is easy, just remove the actuators, they stay open loops as a single zone. If you want to keep the zones, you need a volumiser to stop short cycling and allow defrost, when you only have a zone open.  Grant do a couple of nicely designed ones.  A volumiser doesn't need an additional pump, nor does it does it effect efficiency of the heat pump.

[PeterW]

I still prefer pump and blender as you can use it to recirculate heat around the building if you get plenty of solar gain on one floor area.

 

I would go minimum 20 litre low loss header and manifold pump and you should be fine 

[Ceridunn]

6 hours ago, JohnMo said:

Are you talking loops or zones?

 

5 loops as a single zone is easy, just remove the actuators, they stay open loops as a single zone. If you want to keep the zones, you need a volumiser to stop short cycling and allow defrost, when you only have a zone open.  Grant do a couple of nicely designed ones.  A volumiser doesn't need an additional pump, nor does it does it effect efficiency of the heat pump.

Tell me if I'm wrong, but when you say loops do you mean pipe runs, if so I have 7 loops that were going to be 5 zones. Although I've already prehung the controller, and purchased a WiFi hub and 5 wireless stats, I guess I could leave off the actuators and keep it at 1 zone, but will look at the volumiser. I have now found the installation manual for the heat pump, it was inside the casing, not easy to get in to it without the instructions! 😂😂. I hope the plumbing side will be simple enough. The Samsung controller seems not so straight forward, but as I'm only running ufh I hope this will simplify its installation as some of the wiring to it won't be necessary. 🤞🤞🤞

[Ceridunn]

40 minutes ago, PeterW said:

I still prefer pump and blender as you can use it to recirculate heat around the building if you get plenty of solar gain on one floor area.

 

I would go minimum 20 litre low loss header and manifold pump and you should be fine 

Hi Peter, excuse my dumbass question, what do you mean by 20 litre low loss header? 

[JohnMo]

9 minutes ago, Ceridunn said:

Tell me if I'm wrong, but when you say loops do you mean pipe runs, if so I have 7 loops that were going to be 5 zones.

You are correct.

 

 

[Ceridunn]

Good evening all, 

On 26/01/2023 at 14:21, JohnMo said:

My view and there are others that will say no.

 

Your heat pump is not doing cylinder heating, so there is no need to have a mixer to protect the floor from 55 deg flow. So use pump that comes with the ASHP and no mixer or pump on the CV UFH manifold.

Hi there, decided to follow this as a quick method installation to get the heat pump up and running to make sure the floor is dry so I can start tiling. Connected everything up but the heat pump doesn't seem to create a flow, so I get a flow error. Do all heat pumps have internal pumps? Or have I managed to find one of the only ones on the market that doesn't

[JohnMo]

Not all, but most do - read the instructions, if it shows an external pump between the hp and a buffer you need to add a pump. Pump can be in flow or return, whichever is easier, just make sure it's facing the correct direction. The power and control for the pump will come from the heat most likely

[Wil]

On my HP I had to short the flow sensor for initial commissioning to get it running and bubbles out of the system. Since then and removing the short, it’s been fine.

 

Or post the make and model and someone will fairly quickly tell you if it has a pump…

Edited February 1, 2023 by Wil
additional para

[Ceridunn]

5 hours ago, JohnMo said:

Not all, but most do - read the instructions, if it shows an external pump between the hp and a buffer you need to add a pump. Pump can be in flow or return, whichever is easier, just make sure it's facing the correct direction. The power and control for the pump will come from the heat most likely

Hi, thanks will check tomorrow. Just out of interest would the introduction of a pump need something like a buffer, volumiser, expansion tank? 

[Ceridunn]

5 hours ago, Wil said:

On my HP I had to short the flow sensor for initial commissioning to get it running and bubbles out of the system. Since then and removing the short, it’s been fine.

 

Or post the make and model and someone will fairly quickly tell you if it has a pump…

Hi, thanks, what's the easiest way to short out a flow sensor? The model of heat pump I have installed is Samsung 8kw R32 Monobloc Air Source Heat Pump. Cheers

[Wil]

Mine’s a Cool Energy unit with some lovely labelled terminals in the outdoor unit. I just googled Samsung 8kW R32 Monobloc and got this manual from Midsummer:

https://midsummerwholesale.co.uk/pdfs/samsung-ae050rxydeg-eu-manual.pdf 

 

No idea if it’s the same as yours but it seems to imply a low flow error is on the controller. Do you have a central heating pump at all? Or are you expecting the pump in the monobloc to do all of the flow in the house? Turning the heating pump on to ‘pull’ a bit of water through in line with the heat pump water pump would also help get the flow going.

 

I can’t see any obvious terminals to short but the control section of the manual tells you how to interrogate the display to see what the pump is up to. If you’re not confident stepping through the manual, might be time for a heating engineer Callout.

 

Good luck!