Extended S plan with 5 channels 2 pumps

[ToolGuy]

In a large old house with 22 radiators with pressurized system need to replace the boiler and install controls. Plan on installing Worcester Greenstar 40 CDi or Vaillant ecoTEC plus 438 boiler. Thinking of Danfoss Tp9000Si Programmable Room Thermostat upstairs, Sunvic Select 307XL 3 channel programmer downstairs.


It has Megaflow DHW with its thermostat and pump and due to the layout of the house the only sensible CH zoning will be to have three sub zones off one main heating one using S plan plus.


Plan is separate pump for CH then 2 port valve to all the heating with 3 other 2 port valves separating secondary zones off this. The 1st primary zone can provide general background on ground floor, 2 zones can independently add extra rooms on the ground floor, the 3rd zone add in heating for upstairs.


Plan a 2 channel room stat to control upstairs CH and DHW. Three channel programmer and 1 room stat to control the 3 zones (main background plus the extra rooms). Question is how to wire it to prevent feedback loops to zone valves and allow pump overrun for the correct pump (DHW or CH) while holding open only the correct valve.


None of the programmers seem to have enough sense built in to handle this sort of situation so suggestions on programmers also welcome.


Thanks.

 

[doitmyself]

In a large old house with 22 radiators with pressurized system need to replace the boiler and install controls. Plan on installing Worcester Greenstar 40 CDi or Vaillant ecoTEC plus 438 boiler.

How did you size the boiler?

Thinking of Danfoss Tp9000Si Programmable Room Thermostat upstairs, Sunvic Select 307XL 3 channel programmer downstairs.

the 307XL is only a programmer. How will the temperatures be controlled in the three zones downstairs?

 

[ToolGuy]

How did you size the boiler?

Thanks for the response. The boiler was sized on heat loss calculations having to make rather a lot of assumptions on stone walls, brick walls and insulation levels (some yet to be done).

the 307XL is only a programmer. How will the temperatures be controlled in the three zones downstairs?

The three zones downstairs use a common hall which will effectively act as a reference temperature for a single hopefully intelligent room thermostat (some radiators also have TRVs).


I know the system isn't the normal one due to sub-zones, but its about the only logical plumbing way to set it out with existing pipework in place. Actually the right way even with new pipework considering the expected usage of rooms. Expect to need relays.


With the new building regs requirements for zones and people wanting better control of heating the whole control schema is going to have to become much more complicated than currently catered for.

 

[doitmyself]

Thanks for the response. The boiler was sized on heat loss calculations having to make rather a lot of assumptions on stone walls, brick walls and insulation levels (some yet to be done).

Must be a big old house with that heat loss.

The three zones downstairs use a common hall which will effectively act as a reference temperature for a single hopefully intelligent room thermostat (some radiators also have TRVs).

So the downstairs sub-zones are time-controlled only? Why do that?

With the new building regs requirements for zones and people wanting better control of heating the whole control schema is going to have to become much more complicated than currently catered for.

Presumably your floor area is over 150 sq m.

 

[Gray0689]

Each zone needs it's own stat

 

[doitmyself]

Each zone needs it's own stat

That would seem logical; I'm waiting for the OP to confirm this. Then we can provide a solution.

 

[ferret]

what you are trying to achieve is bordering on light commercial , if you have room i would install a 54mm loop header in the boiler room with each zone branching off this controlled via individual programmable room stats and zone valves , with the header on its own programmer . this would give a constant temp and control.

 

[Gray0689]

what you are trying to achieve is bordering on light commercial , if you have room i would install a 54mm loop header in the boiler room with each zone branching off this controlled via individual programmable room stats and zone valves , with the header on its own programmer . this would give a constant temp and control.

A bit over kill

 

[ferret]

A bit over kill

not as complicated as the post and far more efficient ,

 

[TheGasEngineer]

... i would install a 54mm loop header in the boiler room ...

I think this a very good idea. I ticks all the boxes and you could buy the header if you look around the net. However...
I bet if you sized all the rads and hot water carfully they would not be anywhere near 40kW, and...
The smaller the boiler the smaller the gas pipe... Even if the property needs 40kW, if you've only 20kW of rads and 10kW for water there's no point in buying 40kW.

 

[ToolGuy]

Yes the house is reasonable size, about 300 sq m plus a bit. I have tried to find the original heat loss calculations done 17 years ago for original system and individual rad outputs but can't find this in the paperwork. The system originally had two boilers.

I didn't explain properly on downstairs having one temperature reference point meaning it would have a single room thermostat as some of the rooms might simply want different timing control but from same temperature referance.

I don't understand the idea of a loop header. It sounds sort of like what is present. A main zone with zones looping off it? All with zone valves, though had thought of room stats only for upstairs and one shared one downstairs where the rooms are all off a common hall.

Isn't the idea of loop header on its own programmer the same as being on a separate channel on a multi-channel programmer? Yes, might be bordering on light commercial ideas.

 

[TheGasEngineer]

Ah, well this is where understanding how central heating *really works* helps. The way heating technology is totally under-represented at a higher level of eductation results lots of "rules of thumb" and plainly inappropriate ideas being passed from generation to generation by old plumbers with no eduction themselves. I've entered the trade late in life but as an engineer in my own right I set about finding out what the technology really is. I was horrified to find out what is going on in our plumbing industry. I'm not surprised heating in the UK is in such a mess with plumbers having such a bad name. Sorry - bee in the bonnet...

And with the best will in the world, if an installer has not been taught the technology, and taught it properly, this sort of project would be a big ask.

The first thing to find out is "did the old heating do the job?". Then find out if improvements are wanted. Then work out if any others are needed (this is where your knowledge of heat flow, controls, efficiency and people comes in). Then work out the heat output for the rads taking note of the 25% reduced output moving to a condensing boiler.

Are the rads all panel? I will get back later about the header loop. It's a great way of sorting out the hydraulics as the other guy indicated.

 

[ToolGuy]

From what I know the system worked well before, but not completed as the kitchen wasn't done and would have a fan convector kick board heater to be installed. It wasn't zoned so as the family changed down to one person areas could not be centrally turned off but only rad by rad. Then one boiler, an Ideal Turbo 2 (12KW) condensing gave up after 5 years with parts unavailable. The Potterton Prima F evidently gave up a year after again with parts evidently not obtainable.

All the rads are panel, all parallel, about half with TRVs (rooms often with 2 rads, 1 with TRV one manual).

When first posting I wasn't trying to make a big issue on boiler (as not actually decided yet, no new calcs done, boiler choice as much to do about how it handles control as anything else) but more interested in how to control the system.

Human element: House will be occupied by couple plus part time(?) lodger. Two rooms as office use, guest bedrooms less used. The suggested zones were as close as could be predicted for expected usage pattern.

 

[doitmyself]

Yes the house is reasonable size, about 300 sq m plus a bit.

That's a bit of an understatement!

I didn't explain properly on downstairs having one temperature reference point meaning it would have a single room thermostat as some of the rooms might simply want different timing control but from same temperature reference.

So the zone valves will be controlled from a timer, not a thermostat? Presumably there will be TRVs on the rads in those zones?

I don't understand the idea of a loop header. It sounds sort of like what is present. A main zone with zones looping off it?

I think a loop header is what is usually called a low loss header. See Headers

 

[TheGasEngineer]

300m^2 is about 3-4 times the size of a typical 3-bed semi. I suggest you start from the beginning. Look at what the calcs say the heat requirements are; look at what you have got; If the difference is positive ie heating needs adding then u factor in how comfortable the customer is with the existing and then estimate the additional and see if the cost is OK. See the EST heating tools to calculate the heat losses [DLMURL="http://www.energysavingtrust.org.uk/business/Business/Housing-professionals/Interactive-tools/Domestic-heating-sizing-wizard"]Energy Saving Trust - Domestic heating sizing wizard[/DLMURL]
Use a low loss header if the hydraulics are difficult eg adding a two-pipe system to one that already has a one pipe. The header allow you to pump each circuit independently. Or use one if the zones are so big that one pump will not supply all of them. For the headers see V A Heating Ltd contact us
I am amazed that your customer said they were warm enough with 12kW in a house that size. It doesn't look right to me.
You will chose a programmer + stat or programmable room stat depending on how they live. Always put the stat in a living room / lounge where air changes are not too great. No TRV there and TRVS everywhere else. If there isn't a header you will need an automatic bypass and auto-air vents at the top of all inverted pipe loops; Maybe a magnaclean but a good powerflush should do the job; and make sure the return from each rad is at about 55degC in normal running conditions; and then make sure the return to the boiler is about 55degC as well.
If the rads are panels, get a rad brochure and calculate their total heat load. As I said, it's likely to be much less than the old boiler output.
Choose the controls on the basis of whether a centralised multi-zone control is needed or whether the customer is happy to have separate programmers. I suggest you use Honeywell and their wiring centre. Take the sw/l from each wiring centre to a junction box and then one cable to the boiler.
Honeywell also offer CM-Zone, a product with wireless trvs. TRVs are added to a logical zone on the control unit so you might have , for example, two rooms upstairs and one downstairs controled as one zone (which rooms are controlled like this depends on the occupancy) and the remainder on another zone.

 

[ToolGuy]

The plumbing is all two pipe, flow and return, rads run parallel not serial. The original system had 2 boilers, the small condensing boiler was in use when outside wasn't too cold, the second boiler came in in cold conditions only.

Yes, I know I need to go back and calculate what is their and what is needed, but going on the comment from previous owner that said temp was OK with the two boilers.

Wanted control of DHW and one heating area upstairs, 3 heating areas on ground floor. Yes, thermostats both upstairs and ground floor. Honeywell only do a 2 channel programmer, not 3 or 4. With any larger house this is now not even going to meet regs (separate DHW & 2 zones). The wireless systems are all over budget.

 

[doitmyself]

Yes, I know I need to go back and calculate what is their and what is needed, but going on the comment from previous owner that said temp was OK with the two boilers.

You could start by working out the total rad output. Use the Stelrad Elite Catalogue or the [DLMURL="http://www.pipecasings.co.uk/downloads/download%20files/A%20Guide%20to%20Radiator%20Sizes%20and%20Heat%20Output.pdf"]Guide to Radiator Outputs[/DLMURL]. The boiler shouldn't be much larger than this plus 2 or 3kW for the HW cylinder.

The EST calculator may not be suitable as it is only meant to be used for boilers up to 24kW and standard houses, which yours doesn't appear to be.

The wireless systems are all over budget.

Which ones have you considered?

 

[ToolGuy]

Yes I know I need to go through and work out possible heat output as well as do the heat loss calculations before actually dealing with the boiler. But the controls have been more of a concern. Would be same control design whatever size the boiler is.

For wireless looked at Honeywell, Danfoss, Drayton and and a few others. The network enabled would be great but can't really seeing justifying a spend more than on hard wired as that will be easy wiring runs.

Have been looking at programmers, thermostats and a wiring center from Speedfit Underfloor Heating with warm water | The Speedfit Underfloor Heating System which has 8 channels. Looks like it is much more adaptable than the more common ones on the market for about same cost.

 

[doitmyself]

Can we clear up a confusion over exactly what you are trying to achieve on the heating side, particularly on the ground floor?

This is how I understand it:

First Floor: One heating zone, controlled by a timer and thermostat and one zone valve.

Ground floor: the whole controlled by a master timer, master thermostat and a master zone valve. Certain radiators will be controlled by secondary timers and zone valves.

If the above is correct, then all the secondary timers are doing is opening and closing a zone valve; they have no control over the temperature of those zones and therefore no control over when the boiler is alight. This is done by the master timer/thermostat/zone valve.

This means that the secondary timers need to be connected to the master timer, but not powered by it; i.e they need to be volt-free timers. There is no point opening a secondary valve if the master timer is not ON and the master stat is not calling for heat. That means the Sunvic 3 channel timer is not suitable, but the Horstmann H37VXL can be used.

 

[ToolGuy]

First Floor: One heating zone, controlled by a timer and thermostat and one zone valve.

Yes, correct.

Ground floor: the whole controlled by a master timer, master thermostat and a master zone valve. Certain radiators will be controlled by secondary timers and zone valves.

Yes. Hopefully with the secondary being able to still call Boost or Advance function which would also open the zone valve for the main basic/master zone. Can't see a situation occurring when one of the ground floor sub areas would want extra heat without also wanting it in the basic/master zone.

they need to be volt-free timers. There is no point opening a secondary valve if the master timer is not ON ....., but the Horstmann H37VXL can be used.

Exactly, the secondary do want to be secondary, the reason for the design. Sounds good. I've used the H37XL before but hadn't spotted the volt-free contact version. So the valves are controlledvery much as normal.

So, to clarify my thinking on CH side, The basic/master valve auxiliary switch controls the boiler, everything else is dependent on that. OK, but boiler controls the pump and want that valve open for pump over run (better than using a bypass but maybe not possible). Boost or advance control just their own circuits (main or sub) not allowing sub-circuits requests to be also sent to main as can't separate advance function from boost function.

Getting there, not quite as controllable as ideally wanted (problem with pump over run probably needing to use bypass valve instead of delay in valve shutting).

 

[doitmyself]

Yes. Hopefully with the secondary being able to still call Boost or Advance function which would also open the zone valve for the main basic/master zone. Can't see a situation occurring when one of the ground floor sub areas would want extra heat without also wanting it in the basic/master zone.

This is getting more complicated. The master zone valve is controlled by the master timer and thermostat; but all you have on the secondary is a timer. If the master thermostat has reached temperature, the master valve is closed. Someone presses the Boost button in a secondary, which immediately overrides the thermostat and opens the master valve. How then is the temperature controlled?

The basic/master valve auxiliary switch controls the boiler, everything else is dependent on that. OK, but boiler controls the pump and want that valve open for pump over run (better than using a bypass but maybe not possible).

An automatic bypass is better for the pump overrun as it can be adjusted to give the correct flow through the boiler irrespective of which zone valves are open/closed.

Boost or advance control just their own circuits (main or sub) not allowing sub-circuits requests to be also sent to main as can't separate advance function from boost function.

This is contradicting what you said earlier about Boost opening the main valve.

 

[TheGasEngineer]

If I am wiring multiple zones I take the valve switched live to a common terminal and one wire from there to the boiler. Then when any valve opens the boiler fires. Each valve can be controlled by any arrangement of programmers and timers including a H37XL (which is, after all, just three switches in a box). The programmers can be one multi-channel unit or separate, it depends what's appropriate but they are only switches.

I suggest wiring each zone and its room stat to its own Honeywell wiring centre. The cylinder stat and timer can be wired into one of them as well. Job done...

An automatic bypass should be used. It might never operate but it's there to stop the boiler over heating (and possibly being wrecked).

 

[doitmyself]

If I am wiring multiple zones I take the valve switched live to a common terminal and one wire from there to the boiler.

I would agree, if the OP wanted four traditional zones, each one completely independent of the others; but that's not what he wants.

 

[ToolGuy]

Yes, secondariness just controls time on own zones. Had hoped to do a bit more, but just doesn't look feasible.


For instance: master sets temp to 20C, time to 8 to 12. Secondary from 9 to 10 so boost will extend it to say 11, has nothing to do with temp. Same as on any other boost - only affects time on programmers (as TheGasEngineer says, programmers are just glorified time switches). Had hopped to set it up so boost in a secondary would override the master for time (not temp). I started to realize this would cause real confusion if Advance was used instead of using Boost as one location could close the master and another try and open it. Still both Boost and Advance work for the secondary as the sub zone. i.e. control on time now comes down to human not machine.


Trying to gain more control would mean major pipework changes which would like to avoid - expense and space limitations on pipe runs. As both TheGasEngineer and doitmyself imply starting from scratch one would do things differently, but not starting from that point.


Pump overrun to remove excess heat from boiler: seemed like putting that heat out to a useful circuit would be better than trying to dissipate it in a small short circuit. I accept automatic bypass will have to be the way.

 

[doitmyself]

I know it's a bit late in the day, but have you made sure that the pipe layout on the ground floor will allow you to create the sub-zones? All the rads on each sub-zone will have to be on branches from the main downstairs loop.

 

[ToolGuy]

Yes, its that layout which has partly dictated using sub-zones. Just went back last night to see if any could be easily changed. Might be able to move the upstairs off the basic zone with some tightly fitted 22mm. Would become like your attached jpg.

 

[doitmyself]

Yes, its that layout which has partly dictated using sub-zones. Just went back last night to see if any could be easily changed. Might be able to move the upstairs off the basic zone with some tightly fitted 22mm. Would become like your attached jpg.

I had assumed, from what you said in previous posts, that the upstairs was already piped so it could be a separate zone.

Here is a wiring diagram:

 

[TheGasEngineer]

I've not spent a great deal of time trying to understand the detail of this problem until now but after seeing it drag on and on I have reveiwed the whole thread and realised what I suspected all along is that ToolGuy has not started at the beginning but in the middle of a design process. The control design is being pieced together based on a limited understanding of heating system technology and heating controls which is leaving everone in a muddle.

I suggest starting at the beginning:
1) State what pipework, rads and zone valves are in place.
(NB DHW is a zone)
2) State what the premises will be used for and...
3) From the use determine what heating profile is needed (how much heat and when)
4) Compare (3) with (1) to determine if the existing system has the capability to provide the heating profile
5) If not, look at the feasible changes to (1) and (3) to make them converge.
6) Then... design the controls.

So, can you answer (1) & (2) ignoring everything that has gone previously and ignoring all you attempts to design the control system?
If so we can then look at (3)...

HTH

 

[ToolGuy]

I suggest starting at the beginning:

I think I am virtually there in thinking through the design, but a description of house and pipes might be useful. House is 3 story plus basement (where the boiler is) and it has 3 levels of half landing rooms. Pipework and radiators are all in place, put in by a heating engineer 17 years ago and worked fine. Most rooms have two radiators, one without TRVs and 2nd with. No controls (had just on/off switching), but motorized valve and pump for DHW with all CH on one zone valve and separate pump. Also not yet used Zone valve separates landing rooms from kitchen, another Zone valve separates two ground floor rooms from rest.

28mm pipe out of boiler, split to 22mm Megaflow DHW with pump and valve located on middle floor. The 28mm pipe continues with Motorized valve separating off CH.

15mm T off 28mm in for ground floor toilet then 22mm T branch for kitchen and half landing rooms with second branch continuing in 22mm for ground floor, middle floor and top floor. This second branch has 22mm T for upper floors then 15mm T for hall and eventually splits with Ts for other ground floor rooms.

Its along this area where the pipes all run between a steel beam and wall where limited space prevents changing the pipe layout much if any. It might just be possible to get another length of 22mm in which could separate the middle floor from the rest of the CH.

The kitchen and two other main floor rooms plus one of the landing rooms all share a hall which would be convenient common area for a thermostat. Usage of rooms isn't yet known, except middle floor will have two office rooms plus bedroom (no one is yet living here, but expect 2 people plus a lodger). Two ground floor rooms may have little use, bottom landing room probably utility room so less frequent call for heating.

 

[TheGasEngineer]

I think you might find it easier to convey the above description in a drawing. Can I suggest you use PowerPoint? It's very easy to use. The one below took about 15mins but the resolution of the downloaded file is poor. I think you will find that once you have the drawing and you start making a list of the way the controls have to work, you will learn a lot. Email it to me at [email protected]

 

[TheGasEngineer]

OK I received your layout drawing. Thanks. I'm amazed. The idea of zones is that they are independent. I understand this is a family home. You want controlled heating and to make it efficient as possible, capital cost permitting.

The DHW is a zone in its own right and will therefore look after itself. I suggest you use a simple timer linked to the cylinder stat and probably located in the airing cupboard. I find that people rarely advance the hot water unless there is an unusual demand or if it is badly designed but that's another issue.

Unless there is an unusual heat demand in the various rooms or areas I suggest you ignore all the valves and only control the pump via a rooms stat / timer / programmer so that makes life ultra simple for you. A system should be set up so that when the control room (as I call it - the one with the stat) gets to temperature the balancing has ensured all the other rooms have already reached temperature. You banance rads (with a condensing boiler) by setting the return to 55degC. I do it by gauging the temperature of cold side of the rad by hand. The aim to get the return to the boiler down to 55degC or so.

The problem in a big house, when one room (one stat) determins when the heating is on/off, is that small inbalances can result in cold rooms. To improve the degree of control you need separate zones, but you haven't so you can't.

However, and this is where capital cost applies; Honeywell's CM-Zone will give separately zoned areas but all on the same pipe (like yours) but at a cost. I've not looked to see whether any of the limitations would limit its effectiveness for you.

There is a boiler with a flow sensor (like the BAXI 100HE - but leave that one alone!) which does not need a room stat to give the pump interlock. That's provided by the flow switch. It runs the pump periodically and if there is flow it fires. If not it hibernates for a few minutes. This allows all TRVS to be off manually or off because rooms are at temperature. It must be possible to rig up an flow switch box with a timer to fit to a heating system where the boiler does not have this switch. A good project. I would try using the flow switch from the Baxi 100HE; it would work a treat.
HTH

 

[doitmyself]

You balance rads (with a condensing boiler) by setting the return to 55degC. I do it by gauging the temperature of cold side of the rad by hand. The aim to get the return to the boiler down to 55degC or so.

I hope you take into account the reduction in radiator output when the return temperature is reduced. A rad with a 75C flow and 55C return will produce about 80% of the quoted output. So rads have to be upsized by about 25%.

 

[oldplumber]

why not simplyfy things and use programable trvs that are now available, reducing the need for addl valves and stats over several floors and rely on a more normal/simple system
Irealise u need 2 zones for 150m2 areas but it might be easier to work out on an older layout

 

[TheGasEngineer]

why not simplyfy things and use programable trvs...

See CM-Zone CM Zone - Honeywell UK Heating Controls

 

[fuzzy]

what you are trying to achieve is bordering on light commercial , if you have room i would install a 54mm loop header in the boiler room with each zone branching off this controlled via individual programmable room stats and zone valves , with the header on its own programmer . this would give a constant temp and control.

can you post a sketch of this please