Manifold sizing

[JackofAll]

Have received 3 different quotes for same job. First one specs 9 port and 7 port manifold, second 11 and 6 while the third one specs 7 and 7. Am confused tbh, I asked the supplier of the 3rd quote why they are specing a 7 and 7 and was told its plenty good as per the program they use for the size of the house. Anyone shed some light on this please, thanks.

[JohnMo]

They all use standard programs and it's rubbish in rubbish out generally. Fill the whole floor space with pipes, the variation will possibly be pipe spacing, or how they have laid the pipes out and run lengths.

 

I assume you have UFH on ground and 1st floor with all those loops?

[JackofAll]

2 hours ago, JohnMo said:

They all use standard programs and it's rubbish in rubbish out generally. Fill the whole floor space with pipes, the variation will possibly be pipe spacing, or how they have laid the pipes out and run lengths.

 

I assume you have UFH on ground and 1st floor with all those loops?

It's a bungalow John.

 

[JohnMo]

That's a lot of pipe in the floor.  It may be worth putting up you favoured plan for some feedback.

 

Would be worth adding floor area, floor buildup and heat source. If you know the building loss that is also benificial.

[Thorfun]

is one of those suppliers Wunda? I had discussions with them over the course of designing our ufh and asked them to reduce the number of loops to fit a sized manifold which they did. they were also happy to design at whatever pipe spacing I wanted and also to design as a single zone or 2 or 3 zones throughout the entire ground floor.

[JackofAll]

1 hour ago, JohnMo said:

That's a lot of pipe in the floor.  It may be worth putting up you favoured plan for some feedback.

 

Would be worth adding floor area, floor buildup and heat source. If you know the building loss that is also benificial.

That's based on 150mm centers,  179m2, 300mm eps in floor 150mm concrete and an 8.5kw ASHP. As far as heat loss goes, take it I add up each components heat loss figures, AFAIK the report doesn't give an overall figure.

[JackofAll]

1 hour ago, Thorfun said:

is one of those suppliers Wunda? I had discussions with them over the course of designing our ufh and asked them to reduce the number of loops to fit a sized manifold which they did. they were also happy to design at whatever pipe spacing I wanted and also to design as a single zone or 2 or 3 zones throughout the entire ground floor.

Never tried wunda, wrong side of the pond, did try BPC, around 2k dearer that the quote above, could be providing better quality gear hence the difference, they asked if I would send on the attached quote which I did, awaiting response.

[JohnMo]

Looks a big heat pump, your floor is a similar insulation value to mine, I am in 100mm concrete.  I just have 7 loops in 194m2.

 

Pert-al-pert, I have found a little easier to install than pex-al-pex.

 

I would suggest you look at the thermostat hysterisis, you need one with a very small hysterisis, with a thick floor, otherwise you will get wild swings in operation if the thermostat ever works. I'm using 0.1 deg hysterisis.

 

You will need to take a look at how the rooms are mapped for UFH - do all rooms need it etc.

 

 

[JackofAll]

11 hours ago, JohnMo said:

Looks a big heat pump, your floor is a similar insulation value to mine, I am in 100mm concrete.  I just have 7 loops in 194m2.

 

Pert-al-pert, I have found a little easier to install than pex-al-pex.

 

I would suggest you look at the thermostat hysterisis, you need one with a very small hysterisis, with a thick floor, otherwise you will get wild swings in operation if the thermostat ever works. I'm using 0.1 deg hysterisis.

 

You will need to take a look at how the rooms are mapped for UFH - do all rooms need it etc.

 

 

Apologies, 200mm centres, just confirmed with supplier. Pipes will be in 150mm concrete. Had a mate check out heat pump size based off the BER assessment, he came back with 7.5kw so 8.5 ain't a kick in the arse away. Will have to check out hysterisis meaning. Am not sure why a room wouldn't need ufh?

Edited July 28, 2023 by JackofAll

[JohnMo]

Room may not need UFH in it if lots of UFH pipes already pass through that area. For example our utility has the manifold in it so has no dedicated UFH loops, same with the hallway. If you have a DHW cylinder in the utility, again no need for UFH. Have seen plans with UFH in a plant room, plenty of heat there already without adding more.

 

Hysterisis is the off set between the set point and reaction point. A 0.5 deg hysterisis with a set point of 20. Will switch off the heating at 20.5 and back on again at 19.5. Now concider your floor will take circa 12 hours to change room temp 1 deg. So a normal hysterisis thermostat is just too slow. Room temps will vary by 3 to 4 degs which is less than ideal.

 

We started with a 0.4 hysterisis thermostat and that just didn't cope, so upgraded to 0.1.

 

Have you thought about cooling, you may not think you need it, but can be a zero cost adder with the right ASHP. Ruining cool water through the floor loops certainly helps in summer, if you have PV running costs can be close to zero. We added 1kWh to a our daily electric bill having cooling on from 8am to 5pm.

[JackofAll]

47 minutes ago, JohnMo said:

Room may not need UFH in it if lots of UFH pipes already pass through that area. For example our utility has the manifold in it so has no dedicated UFH loops, same with the hallway. If you have a DHW cylinder in the utility, again no need for UFH. Have seen plans with UFH in a plant room, plenty of heat there already without adding more.

 

Hysterisis is the off set between the set point and reaction point. A 0.5 deg hysterisis with a set point of 20. Will switch off the heating at 20.5 and back on again at 19.5. Now concider your floor will take circa 12 hours to change room temp 1 deg. So a normal hysterisis thermostat is just too slow. Room temps will vary by 3 to 4 degs which is less than ideal.

 

We started with a 0.4 hysterisis thermostat and that just didn't cope, so upgraded to 0.1.

 

Have you thought about cooling, you may not think you need it, but can be a zero cost adder with the right ASHP. Ruining cool water through the floor loops certainly helps in summer, if you have PV running costs can be close to zero. We added 1kWh to a our daily electric bill having cooling on from 8am to 5pm.

Thanks John,

Never thought about the rooms that have pipes running through eg, utility and hall. The 3 or 4 degree variation in room temp that you mention John, is that due to solar gain? re. cooling will have to check if the unit we have selected has a cooling option.

[JohnMo]

 

21 minutes ago, JackofAll said:

The 3 or 4 degree variation in room temp that you mention John

That's all to do with energy flow through the floor. Nothing to do with solar gain.  You are heating lots of tonnes of concrete, which in turn gives heat to the room. If you let the floor have to much heat, it takes for ever, for the heat to be given up and the room continues being heated.  Same when the room is cooling, by the time you have lost 0.5 deg in room temp the floor is way to cold to react quickly, so the room continues to loose heat until the UFH has caught up.

 

Solar gain - If your room temp is targeted at say 20 deg, the floor surface temp will be in range of 21-23 deg. If you get solar gain and the room starts to exceed 20 degs, the floor to room deltaT reduces, so the floor gives off less kW of heat. If the room goes above the floor temp, the floor stops giving of heat and could start to absorb it. A thermostat does nothing to help control solar gain.

[JackofAll]

7 hours ago, JohnMo said:

 

That's all to do with energy flow through the floor. Nothing to do with solar gain.  You are heating lots of tonnes of concrete, which in turn gives heat to the room. If you let the floor have to much heat, it takes for ever, for the heat to be given up and the room continues being heated.  Same when the room is cooling, by the time you have lost 0.5 deg in room temp the floor is way to cold to react quickly, so the room continues to loose heat until the UFH has caught up.

 

Solar gain - If your room temp is targeted at say 20 deg, the floor surface temp will be in range of 21-23 deg. If you get solar gain and the room starts to exceed 20 degs, the floor to room deltaT reduces, so the floor gives off less kW of heat. If the room goes above the floor temp, the floor stops giving of heat and could start to absorb it. A thermostat does nothing to help control solar gain.

Forgive my stupidity John, if the pipe temp is say 23deg surely the floors in all the house heat up uniformly or is it that the pipes for the farthest rooms lose some of the 23deg temp through conduction?

[JohnMo]

Your pipe surface temp is say 25. This heat dissipates outwards (up, down and sideways). At 200mm centres, this heat transfers out sideways 100mm, it will never get to 23 as a 16mm pipe is the source of heat. The further from the heat source the lower the temp. The concrete in the floor is pulling heat and spreading it out over a much bigger area. The heat continues to be consumed to make up for the house heat loss. It's a bit like standing in front of a radiator its hot, take a step or back you don't feel the heat - it's still there just spread out.

 

[JackofAll]

@JohnMo just looking at another quote that we got. I take it that there will be no need for an 8 zone wiring center if the whole house is on a single zone. So just a wiring module for 1 zone. Or is the hot water cylinder counted as a zone in which case a 2 zone wiring center will be required.

Edited July 31, 2023 by JackofAll

[JohnMo]

Hot water cylinder is a different control to the house heating.

 

If you are running a single zone you may be able to run the whole lot from the ASHP circulation pump (I do). Then you don't need a wiring centre at all, or any actuators, no pump or mixer on the manifold.

 

Depending on the control for your ASHP you may be able to just use the thermostat to control when the ASHP gets a start permissive.

 

I use a wireless thermostat (with time and temperature), the output of the thermostat says ASHP start or stop, the weather compensation curve says what temperature to flow at.

 

Cylinder heating, a temperature probe in the cylinder tells the ASHP if it needs heating.  The ASHP, will stop UFH, move the 3 port valve towards the cylinder, once the cylinder is satisfied the 3 port valve moves back to UFH.

[JackofAll]

11 minutes ago, JohnMo said:

Hot water cylinder is a different control to the house heating.

 

If you are running a single zone you may be able to run the whole lot from the ASHP circulation pump (I do). Then you don't need a wiring centre at all, or any actuators, no pump or mixer on the manifold.

 

Depending on the control for your ASHP you may be able to just use the thermostat to control when the ASHP gets a start permissive.

 

I use a wireless thermostat (with time and temperature), the output of the thermostat says ASHP start or stop, the weather compensation curve says what temperature to flow at.

 

Cylinder heating, a temperature probe in the cylinder tells the ASHP if it needs heating.  The ASHP, will stop UFH, move the 3 port valve towards the cylinder, once the cylinder is satisfied the 3 port valve moves back to UFH.

Thanks John.