Hot water re circulation pump

[Perci]

I am currently wiring at s-plan plus (s plan with underfloor heating) the system also has a hot water recirculating pump. This pump is because the house is so large it would take the hot water along time to get to the taps. I am planning on putting a 1 hour time delay on the pump from the hot water program so that the boiler isn't trying to heat recirculating water. Has anyone else done one of these pumps if so how did you control it?

 

[snowhead]

The DHW Secondary pump needs to run permanently whilst the property is occupied otherwise you're defeating the point of having it.

Alternatives would be to have PIR's in every room with taps in controlling it,
Or control it from the intruder alarm when it's not set.

 

[davesparks]

The normal way to control it is to put it on its own timeswitch and set it to run when the house is likely to be occupied.

 

[Perci]

Yea I was thinking about using just a timer but then they would have in total 12 timers controlling their central heating system. 1 for HW 1 for CH 1 for pump 9 for each UFH loop. I'm trying to make it as simple as possible. PIRs in each room would make it efficient but they would never agree to the extra cost. The plumber has told me that it shouldn't be circulating when the cylinder is trying to get to temperature.

 

[chris murphy]

"Hello Perci",

This information may not be of much help to You but I thought that I should explain this as it seems from your brief description of the System that it is quite a `complicated` and hopefully well designed one - BUT the Plumbers comment might well be because the Hot Water CIRCUIT [Circulating Hot Water throughout the Home] MAY NOT be correctly installed [?] - here are my reasons for mentioning that:

In order to adhere to the Energy Efficiency Regulations regarding preventing Heat Loss from Hot Water Cylinders and Pipework the Hot Water CIRCUIT Pipework MUST be installed so that it can be CORRECTLY Insulated with a `Superior Quality` Pipe Insulation [for example Armaflex] - which has a very large external diameter to prevent MOST of the Heat Loss - because of that large external diameter there are OFTEN problems with the Pipework Installation methods allowing enough room to apply the Insulation correctly.

The Insulation MUST be Installed in a VERY Professional manner - NO Splits / Holes / Gaps and it and ALL Joints / Manufacturers Splits MUST be without any Gaps and be Glued with the appropriate adhesive.

IF the Hot Water CIRCUIT Pipework IS correctly Insulated there would not really be an issue about whether the Hot Water CIRCUIT Pump was running during the Cylinder Heat Up periods as the Heat Loss from the CORRECTLY INSULATED PIPEWORK during the Cylinder Heat Up periods would be negligible.

As another Member correctly stated the Hot Water Circuit Pump needs to be running throughout the periods when People are likely to be using Hot Water - IF this is going to be at any time during the Day or Night there would be an issue with constantly circulating the Hot Water from the Cylinder because even `negligible heat loss` during the Cylinder Heat Up periods would add up to a significant lowering of the Hot Water temperature in the Cylinder over for example a 16 Hour period.

That scenario would require quite a Large Capacity Hot Water Cylinder and an additional Heat Up period perhaps mid way through the Hours of the Day / Night when Hot Water is being used or a more suitable time determined by the Hot Water usage times.


WHEN A HOT WATER CIRCUIT IS INSTALLED THE AVAILABILITY OF CORRECT TEMPERATURE HOT WATER IS TOTALLY DEPENDANT ON THE HOT WATER CIRCUIT DEFINITELY BEING INSULATED CORRECTLY WITH SUPERIOR QUALITY [E.G. ARMAFLEX] PIPE INSULATION.



An incorrectly installed / incorrectly insulated Hot Water CIRCUIT can CAUSE the Hot Water Storage / Production be totally inadequate for the Hot Water requirements of the Household / Business !

IF the Hot Water Circuit is NOT correctly Insulated the Pumped Circuit will quickly dissipate the Hot Water temperature within the Hot Water Cylinder.


Just in case there IS a problem with the Hot Water CIRCUIT Pipework / Insulation / Hot Water Cylinder being rapidly cooled down - You should ask the Plumber or your Client to SPECIFY how they want the Pump to be controlled - although really a 7 Day programmable Timeswitch is the only realistic option Cost wise - I would suggest that the more On / Off periods that can be programmed in the better regarding options for the Occupants.


I hope that this is not too `Boring` - and that my comments may be of some help to You and other Members / Readers.


Regards,

Chris

 

[davesparks]

Yea I was thinking about using just a timer but then they would have in total 12 timers controlling their central heating system. 1 for HW 1 for CH 1 for pump 9 for each UFH loop. I'm trying to make it as simple as possible. PIRs in each room would make it efficient but they would never agree to the extra cost. The plumber has told me that it shouldn't be circulating when the cylinder is trying to get to temperature.

But once the timer is set then that's it, done and dusted.

And why so many time controls for the underfloor?

 

[Perci]

But once the timer is set then that's it, done and dusted.

And why so many time controls for the underfloor?

There has to be a separate thermostat and timer for each room as that is the only efficient way to run a underfloor heating system. Normally you would have a TRV on each rad.

Thanks Chris very useful! I've being struggling to find any info about it, the pipe work is insulated but just with the standard 10mm thick gray stuff but it is mainly run through the attic under the insulation and insulated stud walls, would this mean it doesn't need the special insulation?

 

[chris murphy]

There has to be a separate thermostat and timer for each room as that is the only efficient way to run a underfloor heating system. Normally you would have a TRV on each rad.

Thanks Chris very useful! I've being struggling to find any info about it, the pipe work is insulated but just with the standard 10mm thick gray stuff but it is mainly run through the attic under the insulation and insulated stud walls, would this mean it doesn't need the special insulation?

"Hello Perci",

I know that You are probably NOT going to get involved in having the Hot Water Pumped Circuit Pipework Insulation replaced - But here are my thoughts on the matter in case it would be helpful either on the Job that You are on or to other Members / Readers in future:


Running the Hot Water Pumped Circuit through the `Attic` / Roof Space actually makes the situation worse - despite the Loft Insulation which strange as it might seem has to be disregarded when it comes to Insulating Pipework in Roof Spaces - ALL Pipework in Roof Spaces MUST be Insulated to AT LEAST the Standards imposed by Water Bylaw 49 regarding the Wall Thickness of the Pipe Insulation to prevent Freezing and Heat Gain in Cold Water Pipes.


Briefly this means `Bylaw 49 Approved` Pipe Insulation with a minimum Wall Thickness of 25mm on MAINS WATER Pipework [15mm & 22mm Pipework] - and `Bylaw 49 Approved` Insulation with a minimum Wall Thickness of 19mm on COLD WATER SERVICES Pipework [28mm & 22mm]

There are various Pipe Insulation products which are stated to be compliant with Bylaw 49 - BUT in MY opinion if the Insulation cannot be Glued along the Splits and Joints I personally would NOT allow it to be installed because I would state that Splits and Joints that were NOT completely sealed would make the whole Pipework Insulation `Fail` the Bylaw 49 specifications.



In MY Professional Opinion the Hot Water Pumped Circuit on your Job SHOULD be Insulated to a minimum Wall Thickness of 25mm - with a Superior Quality Pipe Insulation such as Armaflex.

This is above the requirements of Bylaw 49 because that Bylaw is just for preventing Freezing of the Pipework and preventing the Cold Water Services heating up in Spring and Summer - it does NOT cover Heat Loss from Hot Pipework.

For a Hot Water Circuit circulating Hot Water from the Cylinder through a Roof Space I would recommend that MY OPINION above be checked with the Armaflex Insulation Technical Department - they MAY state that a Wall Thickness of 19mm Armaflex is suitable.


* As I mentioned previously - Pipe Insulation with a Wall Thickness of 25mm on a 22mm Pipe = a external diameter of 72mm. [IF Armaflex stated 19mm Wall = 69mm]

On the 15mm `Return` Pipe = 65mm External Diameter.

IF there is 28mm Hot Water Supply Pipework then obviously the Pipe Insulation External Diameter would be 78mm.

You can see from these External Diameters that `Retrofitting` these sizes of Pipe Insulation can be extremely difficult - the Insulation needs to be allowed for when the Pipework is being installed.


The Insulation installation method is crucial on a Hot Water Pumped Circuit Pipework - the Insulation must NOT Squashed down at any point and the Insulation MUST be installed in a Professional manner - All Joints mitred / fitting perfectly and the joint seams / Splits GLUED to prevent ANY Gaps.


The Hot Water Pumped Circuit needs to be Insulated to this level because there will be periods of time [possibly long periods] when the Hot Water from the Cylinder will be circulating around the Pipework circuit without the Cylinder being Heated by the Boiler - ANY Heat Loss from the pipework is constantly lowering the Hot Water Temperature in the Cylinder - there will still be some Heat Loss but it needs to be prevented as much as possible.



The Grey Foam 10mm Wall Thickness Pipe `Insulation` that You described is USELESS for Insulating the Hot Water Pumped Circuit !


This should be obvious to the Plumber as it should ALWAYS be done:

The Hot Water Pumped Circuit MUST be insulated along its entire length AND the draw off pipework to Taps / Showers / Washing Machine insulated underfloor and as close to the draw off points as possible.

ALL Pipework connected to the Cylinder MUST be insulated from the Cylinder to where it goes into the Floor or through the Wall or Ceiling - this is to prevent Heat Loss from the Cylinder by radiation from the Cylinder Pipework.



If what I described is NOT carried out there WILL be a problem with the Hot Water production and availability because it is certain that the Hot Water from the Cylinder will lose too much temperature while being pumped around the circuit.

Even with what I describe being carried out - IF the Hot Water Cylinder is not large enough to contain enough Hot Water to allow for some Heat Loss during the possibly long periods that the Hot Water is being pumped around the circuit and still have enough Hot Water capacity to satisfy the usage - that will be a problem requiring an additional Heat Up period programmed in to the system.


I have gone into detail here and my other message Perci just in case the information is useful to You or the Plumber.

BUT I can Guarantee that He or the Builder / Client will NOT be pleased to receive it !


Regards,

Chris


P.S: Please excuse all the RED Highlighting - those points are particularly important.

 

[davesparks]

There has to be a separate thermostat and timer for each room as that is the only efficient way to run a underfloor heating system. Normally you would have a TRV on each rad.

Thanks Chris very useful! I've being struggling to find any info about it, the pipe work is insulated but just with the standard 10mm thick gray stuff but it is mainly run through the attic under the insulation and insulated stud walls, would this mean it doesn't need the special insulation?

Why does it need a seperate timeswitch for each room?

The use of zones/stats for each room is obvious but why seperate time control? All of the systems I have worked on have a stat in each zone and a single time control which controls peak and set-back time periods for all zones.

After all it isn't exactly an instant heat is it!

 

[driverman]

I'm just off out, not read every thread.......but in hospitals etc some have a ring plumbing pipework to all the hot pipes. I'm assuming done by flow return pipe stat controlling pump. The idea behind it is, that when hot water reqd it's on tap as it were! No need to run off a lot of cold water until the hot arrives.

 

[Perci]

Why does it need a seperate timeswitch for each room?

The use of zones/stats for each room is obvious but why seperate time control? All of the systems I have worked on have a stat in each zone and a single time control which controls peak and set-back time periods for all zones.

After all it isn't exactly an instant heat is it!

The system has been designed by john guest and they always have separate timers for each room so that you can program each room separately. But I agree it would easier to have one timer for all the underfloor heating.

 

[Perci]

Thankyou Chris for you time and effort on this post. I thought very much the same about the heat loss on the loop as this would make the boiler have to work for longer periods to get up to temperature hence my idea of using a time delay. I would set this so that after an hour after the programmer is set to heat hot water it will start to circulate to allow for time to get to temperature. The cylinder is 300l and is all plumbed in 28mm speed fix pipe work and a 15mm return on the hot water loop.

 

[chris murphy]

I'm just off out, not read every thread.......but in hospitals etc some have a ring plumbing pipework to all the hot pipes. I'm assuming done by flow return pipe stat controlling pump. The idea behind it is, that when hot water reqd it's on tap as it were! No need to run off a lot of cold water until the hot arrives.

"Hello driverman",

I realise that You are responding to Perci`s question - what I wrote will not be of any interest to You as it is not relevant to His actual question - apart from that the Hot Water Circuit may actually cause there to be NO Hot Water available at certain times of the Day.


You mentioned that You thought a pipe thermostat might be used to control the Hot Water Circuit Pump how do You imagine that would work on the basis of having Hot Water available at the draw off points when it is required - as You mentioned without having to draw off tepid / cold water first - ?


Hospitals would have Zones for both Heating and Hot Water and obviously a well designed `Energy Efficient` System would have Controls to prevent for example circulating Hot Water around the Building in areas and at times where there was NO Demand for it but Pipe Thermostats are very unlikely to be part of the Controls.

Regards,

Chris

 

[jaypp]

Taps close to the cylinder would waste a negligible amount of water (in relation to 'ring' hot water) I think. Is there a way to install a 'call' button adjacent to taps so the hot water circulates when pressed?

 

[chris murphy]

Thankyou Chris for you time and effort on this post. I thought very much the same about the heat loss on the loop as this would make the boiler have to work for longer periods to get up to temperature hence my idea of using a time delay. I would set this so that after an hour after the programmer is set to heat hot water it will start to circulate to allow for time to get to temperature. The cylinder is 300l and is all plumbed in 28mm speed fix pipe work and a 15mm return on the hot water loop.

"Hello again Perci",

I hope that my `Wall of Text` explanations did not confuse You about what I was trying to describe.

I did not go into all those details just to suggest that the Hot Water Circuit Pump should not be running during the Hot Water Cylinder Heat Up periods - the situation is FAR more Complicated than that - although I know it is NOT Your problem.


My main point is that unless the Hot Water Circuit is Insulated as `Professionally` as I described the circulation at the Cylinder Heat Up periods causing the Cylinder to take longer to Heat Up will be the LEAST of the Hot Water Problems !

If the circuit is NOT Insulated correctly the Pumped circulation of the Hot Water WILL dissipate the Temperature of the Hot Water / Hot Water Cylinder contents in a relatively short time.

Totally depending upon the occupation of the House during the Day and the Hot Water usage this MIGHT be able to be `overcome` by programming an additional Heat Up period for the Hot Water Cylinder BUT that would completely against the Energy Efficiency Regulations because it would be required BECAUSE the Hot Water Pumped Circuit Pipework Insulation was NOT applied correctly / to adhere to the Energy Efficiency Regulations.



Using a Timeswitch is really the only inexpensive way to control the Hot Water Circuit Pump and is how it is almost always done.

I don`t know what the maximum number of programmable periods there are available in various models but if I was deciding on the Timeswitch I would try to get one that could be programmed for 3 time periods per Day Monday to Friday / Saturday & Sunday to give the maximum flexibility to the Home`s occupants for setting the Pump run times.


I hope that You did not mind Me going into such detail about circumstances that are not directly related to Your question.

You would be surprised at the number of times that I have had to carry out a LOT of Work to rectify exactly the problems that I described in my messages which were caused by `Plumbers` / `Heating Engineers` who simply did NOT know what I described about the Professionally Insulated Hot Water Circuit / correctly sized [and insulated] Hot Water Cylinder & Pipework.

Regards,

Chris

 

[stimpy]

Domestic set up - Just put a 24hr timer on it and set to run during day or customer requirements. No point it running all night unless customer requires.

As to the U/fl/htg it is customary to either stick with 1 programmer then seperate stats, or more commonly 1 programmer (Master off - Part L) and 'programmable room stats' in each room.

 

[chris murphy]

Taps close to the cylinder would waste a negligible amount of water (in relation to 'ring' hot water) I think. Is there a way to install a 'call' button adjacent to taps so the hot water circulates when pressed?

"Hello jaypp",

When a `Ring` Circuit of Pumped Hot Water is installed - for `Energy Efficiency` purposes ALL of the attached Pipework requires Insulating.

The pipework to the Taps / Shower etc. would NOT have to be insulated with the `Superior Quality` Pipe Insulation [Armaflex] that I suggested for the Hot Water Circuit but it has to be insulated to prevent Heat Loss by `Heat Creep` [my term] along the draw off pipes FROM the Hot Water Circuit Pipework.

Although that `Heat Creep` would usually not go more than about a Metre from the Hot Water Circuit - Heat Loss / Cooling of the Water in the Pipe `Leg` serving the Hot Tap / Shower etc. is NOT desirable - and although I cannot find a specific reference in the Regulations for this situation I can assure You that insulating the Pipe `Legs` is required.

IF what You described about a `Call Button` could be configured - causing the Hot Water Circuit Pump to come on - one would have to be installed at every Hot Water draw off area - Bathrooms / Kitchen / Utility.

AND this would still mean wasted Water - instead of having to wait for the Hot Water to be drawn from the Cylinder all the way through the Hot Water pipework to the Tap / Shower etc. by Gravity / Mains pressure - the same amount of Tepid / Cooled Water would be wasted - it would just arrive at the Tap / Shower etc. quicker than with Gravity.


Although people might think that Pumped Hot Water Circuits are JUST for the Comfort and Convenience of the Household - there are Water Regulations which prevent large draw offs of Water before the Hot Water reaches the outlets.


Regards,

Chris

 

[jaypp]

Hi Chris, obviously haven't seen install and was only suggesting a possible compromise to an obviously already poorly installed set up. i.e. that it will be the farther points that would benefit from circulation of hot water. Hope you find a solution and find time to post it.

 

[chris murphy]

Hi Chris, obviously haven't seen install and was only suggesting a possible compromise to an obviously already poorly installed set up. i.e. that it will be the farther points that would benefit from circulation of hot water. Hope you find a solution and find time to post it.

"Hello jaypp",

I hope that You did not misunderstand the tone of my reply to You - I was not trying to be pedantic when I responded to your suggestion about a Call button.

I have been involved with situations in very large properties where some Bathrooms were at the furthest point in the House compared to the Hot Water Cylinders / Tanks - these Bathrooms had their Hot & Cold Water pumped to the Taps / Showers by pumps that had Flow Switches - Open a Tap / turn On Shower and the Pump Flow Switch is tripped by the small flow of Water and turns On the Pump - the Pump stops when the Tap / Shower valve is closed.

By the way I am not the OP of this thread - that is Perci - I don`t have a problem to solve - I have written the MASSIVE `Wall of Text` messages to Him / other Members / future Readers to explain the possible problems that an Incorrectly Insulated Pumped Hot Water Circuit can cause.

What I intended to be a couple of `reasonable length` messages developed into what You can see above !

Regards,

Chris

 

[jaypp]

Sorry Chris, my mistake!