Critique my complex(ish) mech plan - 2 floor UFH, 2x ASHP, 2x dedicated ventilation..

[puntloos]

One errant though that I can't quite square with the whole extraction thing is that a device like this

 

Needs zero fans. if 'effectively' the network closet would be like this, with a large-sized pipe straight above it, wouldn't the heat simply drift up into my loft where I can "handle it" separately? Why do we need fans anyway?

 

Obviously the device gets a lot hotter inside than you'd want..

 

Another simple question perhaps:

- Does it matter if I have fans suck on a pipe, or push air into a pipe? Meaning, do I need the fans in the network closet or can I put the fans in the loft and pull on the pipe?

 

 

[Nickfromwales]

On 19/01/2022 at 22:13, ReedRichards said:

I have my DHW on a loop.  My cylinder has the secondary return port quite near the top and it does not seem to adversely affect the stratification.  That's good in winter but in summer I heat my cylinder with spare solar power, the immersion heater is half way up the tank and I could wish for destratification to take place.  If there was such a thing as a three port valve approved for drinking water I would send the return back via the cold feed in summer but such a valve does not seem to exist.   

https://www.google.com/shopping/product/1?q=manual+3+way+diverter+valve&prds=epd:15456469943751230827,eto:15456469943751230827_0,pid:15456469943751230827&sa=X&ved=0ahUKEwiq2ZHtkMb1AhXISsAKHaSFDwEQ9pwGCAU

[SteamyTea]

36 minutes ago, puntloos said:

Another simple question perhaps:

- Does it matter if I have fans suck on a pipe, or push air into a pipe? Meaning, do I need the fans in the network closet or can I put the fans in the loft and pull on the pipe?

where will they create least noise when on boost?

Edited January 22, 2022 by SteamyTea

[puntloos]

Just now, SteamyTea said:

where will the create least noise when on boost?

Yep that's where my question stems from, the loft is intended to be 'noisy', so I prefer to put the fans there...

 

[Dan F]

 

Quote

And here I am. Not saying I am in the right place necessarily but it's a logical path, no? ?

 

 

Yes it's all logical and I went through a similair process. What I did with the overheating and condensation concerns though, was to quantify them by getting the numbers to the cooling load and the cooling power of UFH, before deciding what else to add in.  When I saw that the cooling load was just 300W and UFH could suplly 3.5kW without any condensation that put me at ease.  I then turned my attention to how to best avoid the situation where the first floor is a couple of degrees cooler or warmer than downstairs (which is often reported) and looked at MVHR heat-battery vs. fancoils.  Ended up going with the heat-battery as it's a single unit next to UFH manifold, rather than needing one unit per room and a lot more plumbing.  MVHR can't deliver very much cooling at all, but given I knew the demand was so low, this wasn't an issue.

 

On the heating front, given UFH output way exceeded heat demand (2.5kW) on the ground floor, and I knew the MVHR heat battery could be as needed to delivery an additional 1kW to the first floor if needed, it was clear that using UFH on the first floor was completely unnecesary (have used electric mats in the bathrooms though).

 

What would I do specifically with your design?  It's hard to say without some calcs, but would probably:

- Drop first-floor UFH for sure.

- Drop ground-floor fancoils (or put in pipework for future-proofing instead).
- Keep first floor fancoils (rather than explore MVHR-based approach) if you want to be conservative.

- See if you can run DHW/UFH/Fancoils of a single ASHP to simplifiy things and reduce costs.  (there are some very good pre-insulated underground ducting products that can be used for for longer distance with minimal losses, which are used in europe for district heating systems.)

Edited January 22, 2022 by Dan F

[puntloos]

7 minutes ago, Dan F said:

 

 

Yes it's all logical and I went through a similair process. What I did with the overheating and condensation concerns though, was to quantify them by getting the numbers to the cooling load and the cooling power of UFH, before deciding what else to add in.  When I saw that the cooling load was just 300W and UFH could suplly 3.5kW without any condensation that put me at ease.  I then turned my attention to how to best avoid the situation where the first floor is a couple of degrees cooler or warmer than downstairs (which is often reported) and looked at MVHR heat-battery vs. fancoils.  Ended up going with the heat-battery as it's a single unit next to UFH manifold, rather than needing one unit per room and a lot more plumbing.  MVHR can't deliver very much cooling at all, but given I knew the demand was so low, this wasn't an issue.

 

On the heating front, given UFH output way exceeded heat demand (2.5kW) on the ground floor, and I knew the MVHR heat battery could be as needed to delivery an additional 1kW to the first floor if needed, it was clear that using UFH on the first floor was completely unnecesary (have used electric mats in the bathrooms though).

 

What would I do specifically with your design?  It's hard to say without some calcs, but would probably:

- Drop first-floor UFH for sure.

- Drop ground-floor fancoils (or put in pipework for future-proofing instead).
- Keep first floor fancoils (rather than explore MVHR-based approach) if you want to be conservative.

- See if you can run DHW/UFH/Fancoils of a single ASHP to simplifiy things and reduce costs.  (there are some very good pre-insulated underground ducting products that can be used for for longer distance with minimal losses, which are used in europe for district heating systems.)

Thank you Dan. I certainly will do the exercise around making the things you just listed 'optional'. It's one of my crucial design principles that - if somewhat cost effective - I at least make it easy to add upgrades later.

 

But I'll have to say, the extra cost for 1st floor UFH and ground floor fancoils are pretty low if I have everything else anyway. It adds up I guess... 

[joth]

14 hours ago, puntloos said:

Obviously the device gets a lot hotter inside than you'd want.

Exactly. The element gets red hot, about 600°C. So at that temperature it only needs to move 2 l/s to dissipate 1000W.

For another extreme example, imagine (just got a moment) me on my indoor stationary bike. My body can't deal with overheating by more than a couple °C so even though I'm only putting out a couple hundred watts, I need a gale force strength fan to keep cool. 

[joth]

18 hours ago, puntloos said:

This meant the fresh air connections are connected directly into a return air plenum fixed to the FCU. The return air plenums are also connected to the two return air grilles by ductwork.

 

If the FCU is off, the fresh air travels along the return air ducts into the bedroom below. 

Indeed, I understand how the design works, the fact each FCU is a closed system per room makes it elegant in many ways, but just saying unless you already have someone lined up to install it that has done this before, don't be surprised when there's lots of head scratching at install time, and potential for screwups. Tbh the whole M&E install will need a lot of oversight, if you're heating guy is on it that great, or maybe he's just specing it extra complex to ensure he's retained for the duration, I can't tell.

 

Btw I was distinctly underwhelmed by the MelCloud app, and if it can intelligently coordinate across controllers then it is doing so via the cloud so be aware your heating may go wild if the internet is down/server maintenance/they discontinue the service.

Unfortunately the FTC6 only has one controller connection port, so it's WiFi *or* modbus control, the latter being far more appropriate for a real BMS brains to drive it via.

 

[joth]

13 hours ago, puntloos said:

But I'll have to say, the extra cost for 1st floor UFH and ground floor fancoils are pretty low if I have everything else anyway. It adds up I guess... 

You're still in the pre-tender design stage, so aside from the time investment there's little downside in leaving all these luxury items in, and then value optimising them if needed post tender. That's the best way to get the data you need to cost/benefit it all.

 

(There maybe some indirect signalling to the tendering companies that, with this much luxury items, they should change a few % more on every item as you obviously can afford it (like the old adage about hiding the Mercedes before getting a trade around to quote), but TBH I think they can get 98% of that signal from floor area+postcode alone.

I mean, it's not like you're including a basement swimming pool or something)

Edited January 23, 2022 by joth

[puntloos]

3 hours ago, joth said:

For another extreme example, imagine (just got a moment) me on my indoor stationary bike. My body can't deal with overheating by more than a couple °C so even though I'm only putting out a couple hundred watts, I need a gale force strength fan to keep cool. 

Yep, thanks for.. visualizing.. that for me. Good to connect those dots.

 

3 hours ago, joth said:

Indeed, I understand how the design works, the fact each FCU is a closed system per room makes it elegant in many ways, but just saying unless you already have someone lined up to install it that has done this before, don't be surprised when there's lots of head scratching at install time, and potential for screwups. Tbh the whole M&E install will need a lot of oversight, if you're heating guy is on it that great, or maybe he's just specing it extra complex to ensure he's retained for the duration, I can't tell.

Ha, it's worth keeping in mind. But yes, I think even a simpler M&E install (such as just A2W with a water fancoil or 2) probably would benefit from a good team setup with a clear person holding the bag. But on the plus side, people can inspect in detail what they're tendering for. If they don't understand it they probably shouldn't tender.. 

 

3 hours ago, joth said:

Btw I was distinctly underwhelmed by the MelCloud app, and if it can intelligently coordinate across controllers then it is doing so via the cloud so be aware your heating may go wild if the internet is down/server maintenance/they discontinue the service.

Unfortunately the FTC6 only has one controller connection port, so it's WiFi *or* modbus control, the latter being far more appropriate for a real BMS brains to drive it via.

Hmm strange. So while buying gear we'd have to pick one or the other? Or can I switch at will, just not use both? Indeed modbus would then be the way to go..

 

2 hours ago, joth said:

You're still in the pre-tender design stage, so aside from the time investment there's little downside in leaving all these luxury items in, and then value optimising them if needed post tender. That's the best way to get the data you need to cost/benefit it all.

 

(There maybe some indirect signalling to the tendering companies that, with this much luxury items, they should change a few % more on every item as you obviously can afford it (like the old adage about hiding the Mercedes before getting a trade around to quote), but TBH I think they can get 98% of that signal from floor area+postcode alone.

I mean, it's not like you're including a basement swimming pool or something)

 Swimming pool, you say.... ? - maybe I can start considering those industrial 4-pipe ASHPs... j/k 

 

But you're right, it's certainly possible that they figure they can add a bit - but they'd still be tendering against a few others. But hopefully the way we frame it ('this is the intended design but we probably initially only will do A2W, just making sure that A2A can be plugged in easily' - something along those lines..) 

[joth]

9 hours ago, puntloos said:

can I switch at will, just not use both? Indeed modbus would then be the way to go..

You can switch, but you have to buy new adapter at about £100 each. 

[puntloos]

5 minutes ago, joth said:

You can switch, but you have to buy new adapter at about £100 each. 

 

OK, but can they run in parallel? I took from your point it's one or the other?  Either way, I think I'll stick with modbus. Like yourself I prefer to be mostly non-cloud

Edited January 23, 2022 by puntloos

[joth]

9 hours ago, puntloos said:

 

OK, but can they run in parallel? I took from your point it's one or the other?  Either way, I think I'll stick with modbus. Like yourself I prefer to be mostly non-cloud

No, by switch I mean replace, exchange, unplug one and plug the other one in instead.

FTC has a Single port so you can only plug in a single adapter at any given moment in time. 

 

[puntloos]

Small update, but my heating guy came up with a proposal:

 

1/ merge the network closet with our service shaft. (so our service shaft is straight above the gear)

2/ Attach 20L/sec MVHR capacity to this shaft for normal operation

3/ Separately, use an AC infinity fan and temperature sensor to detect peak heat and turn on the tornado. E.g. the 100L/sec inline fan (to be clear: not into the MVHR, this is a separate run)

 

Will I run into balancing problems if the 100L/sec effectively starts pulling at the same air the 20L/sec MVHR inlet also tries to grab

 

 

And then:

4a/ Duct the 100L/sec directly outside, possibly up through the shaft, or maybe even at ground floor level

• concerned about adding a hole in my roof, cold bridging etc.

4b/ Duct the 100L/sec into the loft, then if the loft gets too hot, open the roof window

• To my layman-self this feels more elegant, and we could even do the 20L/sec extract in the loft itself, so fewer conflicts (as above) 

4c/ Duct the 100L/sec into the loft, which has slots into the hallway, and the hallway has a skylight we can then open?

• Perhaps the most elegant, using my entire hallway as a chimney. 

 

Which one would you do? Or an alternative option/

 

As.a reminder. Ground floor- but integrating the network closet rather than right-next-to (not a huge diff really, but it would draw fresh air from the hallway, whole-house!)

 

 

Loft: (which has its own skylight, or we could open slots high up the plant room, or even powered ventilation, and open skylight if things get toasty..

 

 

Edited January 25, 2022 by puntloos

[dpmiller]

Might there be fire protection implications to a ventilated riser like this?

[puntloos]

9 minutes ago, dpmiller said:

Might there be fire protection implications to a ventilated riser like this?

I actually asked exactly the same thing to my heating guy. I don't know. To be clear the riser was designed with my explicit instructions to pay attention to that, and my arch assured me his design was made to comply with them... so the riser minus the network closet is fine.. but I don't know if that closet changes things.

 

Edited January 25, 2022 by puntloos

[joth]

On 25/01/2022 at 19:32, puntloos said:

1/ merge the network closet with our service shaft. (so our service shaft is straight above the gear)

 

So this bit ^ I definitely like.

 

How the shaft is ventilated is the tricky bit. It needs a different strategy for mid winter vs mid summer.  If I was doing this, my own inclination would be:

1/ vent the shaft into the loft

2/ use a high power variable speed fan to purge the shaft into the loft as/when needed

3/ ensure there's a clear "return path" from loft back to the network cupboard via the hallways and living spaces, so this excess heat gets best chance to percolate around the building a bit in winter. This maybe just a dedicated open grill from upstairs hallway into the loft, or use the service void all around the perimeter of the house, or something else.

4/ have the 20L/s MVHR extract in the loft rather than in the shaft, to keep the systems somewhat isolated (avoid risk of shaft purging reversing the MVHR flow) but still allow MVHR to contribute to moving this excess heat around.

5/ have an automatic opening roof window in the loft to stack purge the whole lot overnight in summer. Ideally this is coupled to another automatically opening window/door somewhere downstairs to maximise the stack vent effect. (An electric opener on a small fanlight window somewhere might do it. Ideally something hard for cats / burglars to get to)

6/ Think a bit about how FCUs can help if there's a genuine heat wave (>25ºC overnight for several days) and the loft is never getting cooled.

 

By no means is that lot ^ a proclamation of how you should do it! Just working through my own thinking process on it.

 

Edited January 27, 2022 by joth

[puntloos]

The 'heart' emoji goes out to the solution I was thinking myself roughly. I bounced between simplicity ("if hot then blow it out a hole in the roof") and elegance ("keeping the precious heat away from living quarters, but doing helpful things with it"). Maybe recover, maybe put towards cold places, etc.

 

Not to mention that somehow using an FCU, running power to de-heat the heated air, feels distasteful vs just venting it.

 

But indeed the brains of the smart home will at some point gain sentience and kill us all so .. hm.

 

 

[joth]

On 27/01/2022 at 13:46, puntloos said:

But indeed the brains of the smart home will at some point gain sentience and kill us all so .. hm.

 

Going OT for this topic, but if you're thinking of KNX light switches (and dimmers?) I'd definitely recommend considering Loxone for the heating control, and it's ~easy to link the KNX systems into it if you decide you want to combine systems as you get comfortable with it. This might be quite a nice system with lighting being autonomous to Loxone, but available for automations if desired.

As @Dan F says it'd be quite a fun project to tune the heating system in loxone, and a lot more accessible for DIY tuning over time than most of the KNX homeservers (Gira et al) appear to be

 

 

[puntloos]

On 27/01/2022 at 11:21, joth said:

So this bit ^ I definitely like.

 

How the shaft is ventilated is the tricky bit. It needs a different strategy for mid winter vs mid summer.  If I was doing this, my own inclination would be:

1/ vent the shaft into the loft

Why not simply have the shaft going straight up to a dedicated vent or skylight in the roof? 

On 27/01/2022 at 11:21, joth said:

2/ use a high power variable speed fan to purge the shaft into the loft as/when needed

How would this fan be connected to the shaft if it has no cap? Why would you need it if it vents naturally through a vent at the top of the shaft.

On 27/01/2022 at 11:21, joth said:

3/ ensure there's a clear "return path" from loft back to the network cupboard via the hallways and living spaces, so this excess heat gets best chance to percolate around the building a bit in winter. This maybe just a dedicated open grill from upstairs hallway into the loft, or use the service void all around the perimeter of the house, or something else.

We should probably avoid holes or vents in the shaft at first floor level but provide a relatively large vent near the floor in the hall, this vent would help the rising hot air to move using its natural buoyancy by introducing relatively cold air at the bottom of the shaft.

On 27/01/2022 at 11:21, joth said:

4/ have the 20L/s MVHR extract in the loft rather than in the shaft, to keep the systems somewhat isolated (avoid risk of shaft purging reversing the MVHR flow) but still allow MVHR to contribute to moving this excess heat around.

I was wondering how well 'natural convection' would work here - can we enhance the convection that would occur naturally using displacement ventilation (cool air in at the bottom, hot air out at the top). If the shaft is open to the MVHR it may be counter-productive and wouldn’t work well? I think @SteamyTea or @jack spoke about this somewhere but I can't find it anymore

On 27/01/2022 at 11:21, joth said:

5/ have an automatic opening roof window in the loft to stack purge the whole lot overnight in summer. Ideally this is coupled to another automatically opening window/door somewhere downstairs to maximise the stack vent effect. (An electric opener on a small fanlight window somewhere might do it. Ideally something hard for cats / burglars to get to)

Actually the automatic opening vents (AOVs) are more or less standard thing but are they are normally opened by a smoke detector rather than a thermostat. AOV or smoke vent shafts are shafts with an automatic opening vent (AOV) at the top and vents at each floor level to clear smoke from staircase landings. They are used in blocks of flats to let the smoke out of the staircase in a fire. Many companies make equipment for these shafts for example https://www.kingspan.com/gb/en-gb/products/smoke-control-systems/natural-shaft-ventilation.  The shaft could have a velux window instead of a louvre if you prefer. 

 

The AOV would need to be opened and closed by a small electric actuator controlled by a thermostat but that seems pretty simple to me. Obviously you would need it closed in cold weather and when there was no heat build up, but that is easy to achieve.

 

On 27/01/2022 at 11:21, joth said:

6/ Think a bit about how FCUs can help if there's a genuine heat wave (>25ºC overnight for several days) and the loft is never getting cooled.

I guess I don't care too much for the (plant room in the) loft. If it's truly smouldering we can open the skylight, or stop pulling heat from the network closet (and open the door) but that must be an emergency

 

[joth]

9 hours ago, puntloos said:

Why not simply have the shaft going straight up to a dedicated vent or skylight in the roof? 

If you have an AOV that probably makes sense, but with a glazed window I thought you'd want it in the loft to get the benefit of the light and solar gain in winter. 

 

AOV aren't much on my radar as it's hard to get airtight / high U value, passive house certified ones? But makes sense on a non-certified project.

 

Displacement ventilation sounds another way of saying stack ventilation? Either way it's using the chimney effect ?

 

[puntloos]

10 hours ago, joth said:

If you have an AOV that probably makes sense, but with a glazed window I thought you'd want it in the loft to get the benefit of the light and solar gain in winter. 

AOV aren't much on my radar as it's hard to get airtight / high U value, passive house certified ones? But makes sense on a non-certified project.

 

https://www.lamilux.com/skylights/solutions/smoke-and-heat-exhaust-ventilation-shev/smoke-and-heat-exhaust-ventilation-units/flat-roof-window-shev/smoke-lift-glass-skylight-f100.html has an U-value of 1.. might work? 

 

10 hours ago, joth said:

Displacement ventilation sounds another way of saying stack ventilation? Either way it's using the chimney effect ?

 

I think so.. indeed I still can't quite figure out if a chimney would be able to cool a network hub properly but indeed house air coming in from the bottom and a vent at the top. I guess one thing I don't quite understand about convection is that I always assumed you need a loop, it doesn't work nearly as efficient with just a pipe. So either the vent is 'always open' which is not ideal, or it's closed and the cooling would be insufficient. - but that's just my gut feel.

[puntloos]

One quick update - I'm still debating the full hot water return (past most, or all of my relevant hot water taps) or only hot water return with a presence detector actuated pump. 

Pro: hot water everywhere in under a second

 

But the cons:

- Some extra design/material cost I guess

- balancing of the circuits. Most plumbers don’t really understand balancing hot water circuits, so all of the water tends to circulate around the shortest circuit and water won’t circulate around the furthest branches. If anything changes the circuit goes out of balance and causes problems. Plumbers never use proper globe type balancing valves either which makes balancing even more difficult. Excessive hot water circulation creates more unnecessary complexity.
- Max pipe length is about 6m.  Hot water will be available at all taps fairly quickly. (how quickly?).
- If the pump is only running when hot water might be required, the circuit will not be wasting heat and will not be disturbing the hot water stratification in the cylinder. This maximises the Delta T in the cylinder improving the heat pump COP. (but frankly as we debated elsewhere the stratification thing isnt too crucial)
- Once the pipework is in it can’t be just switched off by closing valves. If you do shut off branches it would create ‘deadlegs’ which are against water regulations and would cause a legionella risk, the pipework would need to be removed. If the circuit is made more complex all of it must circulate equally.

 

Basically - is balancing of the circuits hard? 

[Bitpipe]

4 minutes ago, puntloos said:

One quick update - I'm still debating the full hot water return (past most, or all of my relevant hot water taps) or only hot water return with a presence detector actuated pump. 

Pro: hot water everywhere in under a second

 

But the cons:

- Some extra design/material cost I guess

 

Price of a pump, timer (or PIR) and a few m of piping & insulation. In my place, MVHR boost and DHW return pump are activated at same time (PIR in bathrooms).

 

4 minutes ago, puntloos said:

- balancing of the circuits. Most plumbers don’t really understand balancing hot water circuits, so all of the water tends to circulate around the shortest circuit and water won’t circulate around the furthest branches. If anything changes the circuit goes out of balance and causes problems. Plumbers never use proper globe type balancing valves either which makes balancing even more difficult. Excessive hot water circulation creates more unnecessary complexity.

 

In my 400m2 house there is one DHW circuit with the various taps / showers teeing off it. Pump is at the end of the loop just before it re-enters cylinder.

 

4 minutes ago, puntloos said:

- Max pipe length is about 6m.  Hot water will be available at all taps fairly quickly. (how quickly?).

 

For me, its a few seconds but not sure how long the longest run is to tap from the main loop.

 

More noticeable when the pump is not active (i.e. if I'm in kitchen) and it can take 2-3 mins to run hot.

 

4 minutes ago, puntloos said:

- If the pump is only running when hot water might be required, the circuit will not be wasting heat and will not be disturbing the hot water stratification in the cylinder. This maximises the Delta T in the cylinder improving the heat pump COP. (but frankly as we debated elsewhere the stratification thing isnt too crucial)

 

Well yes but it's going to be minimal.

 

4 minutes ago, puntloos said:

 Once the pipework is in it can’t be just switched off by closing valves. If you do shut off branches it would create ‘deadlegs’ which are against water regulations and would cause a legionella risk, the pipework would need to be removed. If the circuit is made more complex all of it must circulate equally.

 

Still not sure I get this - my DHW (and cold) is live to every tap with an isolator valve just before the fitting to allow for replacement / servicing. Why would you have entire legs isolated?

 

Very little of my pipework is even visible, just the major valves in the plant room, at the UFH manifold and that's about it.

 

4 minutes ago, puntloos said:

Basically - is balancing of the circuits hard? 

 

There is no balancing in a single loop system, why would you have multiple loops?

 

[puntloos]

On 14/02/2022 at 16:14, Bitpipe said:

 

Price of a pump, timer (or PIR) and a few m of piping & insulation. In my place, MVHR boost and DHW return pump are activated at same time (PIR in bathrooms).

 

 

In my 400m2 house there is one DHW circuit with the various taps / showers teeing off it. Pump is at the end of the loop just before it re-enters cylinder.

 

 

For me, its a few seconds but not sure how long the longest run is to tap from the main loop.

 

Can you give me a guess? The far run that the heatguy suggests to make the dedicated loop for is 12m or so, but the rest is 8-5m 

My calculations say that for 8m distance, 22mm pipe, 10L/minute flow rate - https://www.sensorsone.com/volumetric-flow-rate-and-diameter-to-flow-velocity-calculator/

On 14/02/2022 at 16:14, Bitpipe said:

More noticeable when the pump is not active (i.e. if I'm in kitchen) and it can take 2-3 mins to run hot.

Not ideal. Sounds wasteful too.

On 14/02/2022 at 16:14, Bitpipe said:

There is no balancing in a single loop system, why would you have multiple loops?

Not sure, will ask ?