F gas A2A and A2W

[Oz07]

Talking to a plumber tonight. He is F gas certified. He was explaining the difference with these heat pumps to the standard ones to me. It's all a bit beyond my understanding. Anyway I was asking him if I could have wet UFH on GF then air to air units upstairs to do heating if needed and cooling in summer, also probably 1 or 2 air units downstairs to cool. All off 1 outdoor unit. I think he is more in with Daikin and said they are bringing out something soon, however Samsung appear to do the perfect solution with the TDM plus / climate hub. Outdoor pump, pre plumbed cylinder and air to air units. It looks good, no doubt very costly?! Does anyone have any experience with this set up. Seems simpler to a luddite like me. I suppose cost will be the trade off for simplicity i've no doubt others like @JohnMo can knock something up just as good performance wise for a lot less dough, maybe even have 2 seperate outdoor units. It's just beyond my pay grade though. I wonder what cost would be for this and 5 or 6 indoor air con units and the cylinder. https://samsung-climatesolutions.com/gb/b2c/our-solutions/home/heat-pump-solutions/heating-cooling/tdm-plus.html

[SimonD]

Lots of ifs and buts on this one. There are only really three practical ways of moving the heat into and out of the building: water, air, refrigerant. Air specific heat capacity is poor so you need lots of volume and flow, refrigerant needs its own specific pipework, qualifications etc. with lots of limitations to things like pipework length. Water is definitely the most effective way to move the heat. The aircon units will probably also need condensate drainage so added complexity there.

I don't think the solution is that simple, or not as simple as the Samsung marketing department makes it look. Maybe okay for a new build, but for a retrofit? I'm not so sure. Like with all these things, the complexity lies more in the cooling than in the heating, especially if you want aircon type cold.

[JohnMo]

The F gas solution doesn't look cheap, may be wrong. Could be a good system, but I would go A2W and have fan coils (water to air) in bedrooms and normal wet UFH.

 

A pragmatic design could be pretty simple. Design for heating, accept cooling may not be perfect but way better than not having cooling. UFH will make house feel way cooler than the air temperature is. The fan coils in bedrooms will leave rooms for a comfortable sleep.

 

First job is looking at heat loss and sizing an outdoor unit. Then room by room heat loss. Design UFH (not some cut and paste job by UFH suppliers). Size fan coils to provide room heating at under 30 degs. Then run everything as a single zone. Fan coils will modulate fan speed to keep room temperature stable. 

 

The above assumes you are talking about a low energy house.

[Oz07]

The build will be relatively low energy, not approaching passive but certainly lower than most. I have to admit the air con type cooling does appeal to us. After I built our last house I said i'd never build another without aircon. It's a small luxury that I'd be happy to pay for. I suppose what I need to do is compare prices of a normal ashp for 1500 odd sq ft house versus this f gas system. I'm sure fan coils and UFH would have ok cooling capacity but would it be as good as a2a air con?! I think with the umbrella scheme the grant could be claimed either way. I asked AI and I think it was estimating the installation at 12-20k with the cost for the samsung gear estimated at 7-12k. I did ask AI about the distances of air con units from the pump and it was saying quite long, 7.5-10m. I imagine they are decent if Samsung market this as 1 unit can serve whole house. I'm a fair way off heat calcs yet as resubmitting a new planning app but will deffo be one to keep an eye on. The plumber was saying to me that with the f gas you don't get any heat loss from the pipework to the unit whereas with the A2W you do?

[JohnMo]

1 hour ago, Oz07 said:

think with the umbrella scheme the grant could be claimed either way

Maybe not, A2A is ok for £2.5k only and almost no one is approved, so don't hold your breath on that one.

 

If you assume UFH is just part of house build cost. It all doesn't have to cost a lot to build a good performance system.

 

I never bothered with the grants, would rather pay myself than get ripped off.

 

Simple direct UVC for DHW, cheap as chips, save around £1000 compared to pre plumbed heat pump one. Charge on time off use tariff.

 

Would be surprised if you need more than a 4kW heat source, from size of house and assuming better than Building Regs.

 

If you want Aircon performance add a mixing valve to system and run fan coils at 6 degs, or just oversize the fan coils, decent fan coils have the output data for different flow temps.

 

Or do everything A2A, don't bother with UFH. Still do direct water heating.

 

Spend the money saved on a good system with good airflow regulation. Having lived in hot countries a number of years, the airflow became a thing of hate, once the novelty wore off.

[Nickfromwales]

11 hours ago, SimonD said:

Lots of ifs and buts on this one. There are only really three practical ways of moving the heat into and out of the building: water, air, refrigerant. Air specific heat capacity is poor so you need lots of volume and flow, refrigerant needs its own specific pipework, qualifications etc. with lots of limitations to things like pipework length. Water is definitely the most effective way to move the heat. The aircon units will probably also need condensate drainage so added complexity there.

I don't think the solution is that simple, or not as simple as the Samsung marketing department makes it look. Maybe okay for a new build, but for a retrofit? I'm not so sure. Like with all these things, the complexity lies more in the cooling than in the heating, especially if you want aircon type cold.

 

2 hours ago, Oz07 said:

The build will be relatively low energy, not approaching passive but certainly lower than most. I have to admit the air con type cooling does appeal to us. After I built our last house I said i'd never build another without aircon. It's a small luxury that I'd be happy to pay for. I suppose what I need to do is compare prices of a normal ashp for 1500 odd sq ft house versus this f gas system. I'm sure fan coils and UFH would have ok cooling capacity but would it be as good as a2a air con?! I think with the umbrella scheme the grant could be claimed either way. I asked AI and I think it was estimating the installation at 12-20k with the cost for the samsung gear estimated at 7-12k. I did ask AI about the distances of air con units from the pump and it was saying quite long, 7.5-10m. I imagine they are decent if Samsung market this as 1 unit can serve whole house. I'm a fair way off heat calcs yet as resubmitting a new planning app but will deffo be one to keep an eye on. The plumber was saying to me that with the f gas you don't get any heat loss from the pipework to the unit whereas with the A2W you do?

For a current (MBC PH TF) project, the decision has been made to go for fa refrigerant based setup for domestic heating / cooling (via UFH) plus DHW (all via a plate heat exchanger), and a second setup for all of the first floor space heating and cooling. 
 

There is some considerable distance between the external units (x2) and the internal units, and to overcome this it has been suggested that a manifolded system is utilised.

 

This is outside my wheelhouse as I mostly do wet (hydronic) systems, so am learning here too, but this certainly overcomes distance issues without a problem.

 

Sizeable dwelling, circa 400m2, but (apparently) the proposed Daikin setup will perform perfectly well here; I think the furthest 2/3 units are >20m from A-B.

 

Going for remote mounted chassis tucked into newly (purposefully created) closet / plant spaces vs units on the walls.

[SimonD]

2 hours ago, Oz07 said:

The plumber was saying to me that with the f gas you don't get any heat loss from the pipework to the unit whereas with the A2W you do?

This is pretty much irrelevant tbh. The 'losses' aren't really losses as they go into the heated envelope of the house, so do their bit on contribution.

Honestly, I'd wait and see what your heat loss calc says and then review from there as they may be so small if you're going near ph that even a 4kW heat pump would be too big. The other ball to chuck into the mix for a highly efficient house for heating is an exhaust air heat pump, which simultaneously deals with your heating, MVHR and DHW. The you can go multi-split for your air-con. Just make sure that the person doing your heat loss actually understands whole house MVHR and models the heat loss accordingly - lots don't and then calculate normal ventilation losses.