Ufh And By-Pass Pump

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steptoe

of course Im wrong, ask my wife™
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been out to look at another dodgy UFH tonight,

problem was the by-pass pump keeps tripping the RCD,

what does this pump actually do, its running even when all the actuators are open,

there is also another loop beside it with a temp gauge, so Im stumped as to what the pump is for,

pump is controlled via a pipe stat, and comes on, on rise.

again, no proper wiring centre, but client wants a price to tidy everything up and install proper panels, one on each floor, basement, ground and 1st, (a radiator in loft room is on 1st floor manifold)

the other thing I noticed was its only one single little pump driving the whole system, is it powerful enough?

customer says 1st floor or loft never gets warm, dodgy by-pass pump is on 1st floor manifold,

 
deffo by-pass, there is one on every floor at the manifold linking the flow and return legs of the manifold,

my phone battery went, but I'll do a sketch.

 
It's not a bypass pump. It's the circulating pump for each set of UFH pipes.

I think the theory is that with the amount and length of the UFH pipes, a simple circulating pump at the boiler would not create enough flow.

So each UFH manifold has it's own pump to push the water through the UFH pipes for that manifold.

Every system I have seen, the manifold pump runs all the time when any zone is calling for heat. That's done by the proper mainfold control box which will energise a relay to turn on the pump when one or more zones calls for heat.

The bypass valve is a thermostatic valve.  That mixes hot water from the flow coming in, and cooler water returning from the UFH pipes, to regulate the temperature of the water flowing through the UFH to a much lower temperature than the raw hot feed out from the boiler.

In every one that I have seen, the pipe stat on the manifold is there to STOP the pump if the water gets too hot, i.e to prevent over hot water flowing if the thermostatic mixer has failed.

The internal flow of water through the various bits of an UFH manifold is not always obvious as what may look like a through connection isn't always.

 
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I've just had a look at my manifold to refresh my memory.

It LOOKS like a bypass pump, because it's between the flow and return legs of the manifold.

But next to it will be the thermostatic mixer.

Think of it at equilibrium, where the water in the UFH is up to the temperature set by the mixer valve.  The mixer valve will be shut. So no water will be entering or leaving the system.

In that case, the pump sucks water out of the return manifold and pumps it down the flow manifold.  The water then flows round the UFH pipes back to the return.

so it may look like a bypass pump, it is in fact the circulating pump.

As the water in the UFH pipes cools down (becaue they are heating the floors) the flow temperature drops, so the mixer valve opens to let hot water in from the boiler flow to get back to equilibrium.

So the pump MUST run whenever any zone calls for heat.

 
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brilliant Dave, thanks for that, I actually got confused cos attached to the pump was a little leaflet of setting instructions, one of those was 'when using as UFH by-pass set speed to 3'

OK, so I deffo need this pump running then in order to help the pump in the basement move the water round the system, or rather, to move the water round the pipes once up to temp and the valve closes and makes it a loop.

so, its the circulating pump and the pump in ther basement merely pushes the water to the manifold point.

now Ive got my head round it thanks to your description its all starting to make a bit more sense to me now.

 
It's not a bypass pump. It's the circulating pump for each set of UFH pipes.

I think the theory is that with the amount and length of the UFH pipes, a simple circulating pump at the boiler would not create enough flow.

So each UFH manifold has it's own pump to push the water through the UFH pipes for that manifold.

Every system I have seen, the manifold pump runs all the time when any zone is calling for heat. That's done by the proper mainfold control box which will energise a relay to turn on the pump when one or more zones calls for heat.

The bypass valve is a thermostatic valve.  That mixes hot water from the flow coming in, and cooler water returning from the UFH pipes, to regulate the temperature of the water flowing through the UFH to a much lower temperature than the raw hot feed out from the boiler.

In every one that I have seen, the pipe stat on the manifold is there to STOP the pump if the water gets too hot, i.e to prevent over hot water flowing if the thermostatic mixer has failed.

The internal flow of water through the various bits of an UFH manifold is not always obvious as what may look like a through connection isn't always.
+1 on that Dave, the pipe stat is a High Limit Stat arrangement, I think from memory the water must not exceed 30 degrees, some are preset others are adjustable.

 
OK, Ive just rang the 'plumber'/handyman that originally 'fixed' it, he DID change the stat settings,

and then he 'bled' the pump, thats when it tripped out the RCD, while he was loosening the bleed screw, Im assuming he means the big screw in the centre of the pump,

should he have done that while the pump is running? I dont know either way, this is why I DONT DO plumbing,  :C

 
this guy actually wants a proper panel fitted, [uH3 ? ]

problem is, the way it is currently wired Im not seeing any benefit [apart from tidying it up], unless I pull in some more cables, and the plumber fits some zone valves,

3 floors, manifold and mess of wires on each floor, currently all thats been wired is a 3core from Boiler linked between each floor, L N & Sw , then the stats for each floor are bodged into this box,

so, am I right in thinking I really need a clock for each floor wired to a zone valve for the floor to have this done properly?

and, as Its one pipe T'd to manifolds on basement and ground I'd need a mid position on those, basement mid controlled from ground and 1st, ground mid controlled from 1st.

that might actually be doable using the 3rd core I already have at each manifold,

or can someone see a massive flaw in my thinking?

 
Despite being accused of spouting *?!# and being called names not acceptable to the forums T&C’s and being of not a proper spark.. all the gear no idea or something.??? 

I will still, for what it’s worth, add my tuppence on this topic..

When looking at any problems on any existing domestic heating system it must be remembered not to assume it was wired and working correctly before,  IMHO you always need to…

1/ know what the customer is trying to do..

2/ what the actual physical components you have got can do..

3/ and how the manufactures have designed them to work…

Most plumbers struggle if the wiring gets more complex than a boiler, a thermostat & pump.

So it’s often the case that an existing system may not be wired or working to its full potential or how the customer would like it to work...

UFH pipe temperature..

As Steve mentioned if the pipes are laid in solid floor the heat must be strictly controlled otherwise you can end up cracking the floor screed.  So you cannot just run water from the boiler as you do to radiators.

Manifold..

A  heating system may include multiple UFH manifolds and/or traditional radiators as well. Each group of UFH pipe loops are balanced within their own manifold, and it is the manifold pump that then circulates water at a regulated temperature around the loops.  Obviously if the manifold loops are not balanced individual rooms would be too hot / cold when all zones on that manifold are active.

When setting up the UFH the flow rate around each loop is adjusted and balanced with the flow gauges on the top bar of the manifold..  

e.g.  the little red bar in the window of each zone gauge,

MANIFOLD1.JPG

or

MANIFOLD2.JPG

Obviously the physical lengths of individual zones affect the flow rate around zones, shorter pipe loops least resistance more water flow.!

The actuators to operate a particular zone sit on the bottom bar of the manifold..

So when a zone calls for heat, its actuator opens and water flows to that room..

Thermostats and operating times..

Traditional radiators put a block of intense heat on wall of a room that circulates up and around the room ..

typically heating the air above waste level.. (heat rises)

UFH puts a low level heat across a wide floor area that rises from floor upwards. Too much heat at upper torso & head level can leave a person feeling uncomfortable. Less heat at lower torso level is far more concussive to making a person feel comfortably and warm without being stifled.

UFH is designed to bring a comfortable uniform temperature to the lower torso level of a whole room, (not just one wall i.e. no cold patches at the parts furthest form a radiator),  without wasting energy heating ceiling level where people do not sit or move around!

BUT it is also designed with a longer lag time to get the room up to temperature..

Also it generally has to heat through a floor covering, boards/concrete/tiles/carpets etc. not just open pipe or rad in free air.

Some customers think having the heating on for a long time is wasting energy & money…

But as it is a lower heat for a longer time NOT the same intense heat that traditional radiators uses

and the UFH should be put on well before the time that normal rads would be set to come on.

Clearly if only one pump was running the whole heating system and there is only one thermostat for the whole property,   the heating will probably be on at the wrong times and if or when other rads or manifolds were on there is a greater probability that some floor zone are not getting the heat they need.

Your thinking about a separate clock per floor is on the right lines as again with the basic concept for energy saving... .

You only want to start warming up the rooms you are using..

In an ideal world you would want one of the individual programmable room thermostats for each UFH zone..

So they can all have their own times/ temps and/or manual override..

This is why you normally need separate thermostats and timer clocks to get the most out of UFH..

The JG control boxes are designed to combine multiple rooms stats/prog timers back to one group of manifold zones and control its associated pump and boiler heat call in one self contained box.

But that all depends on how much the customer wants it tidied up..

And what budget they are working with…

230v version http://www.screwfix.com/p/jg-speedfit-jgprte-programmable-room-thermostat-240v/26761#product_additional_details_container

12v version..

http://www.screwfix.com/p/jg-speedfit-programmable-room-thermostat-12v/36700

The 12v version can be wired with CAT5, Alarm or Phone cables if you are going to do a major overhaul of the system..

I can never understand why a customer paying for UFH to be installed dosn't pay for sufficient room controls to get the most out of the system..?.

Like buying a car...  but only ever sitting on the drive in it! 

Disclaimer:

I am in no way stating this information is the only way any UFH system can be configured or that it is the only global way that every UFH system in the UK has to work..

Merely trying the expand a bit more on the concept of what the manifold pump does in a UFH system, as the question was raised earlier in the thread and it may be of some help to other reading this topic as well.

what does this pump actually do, its running even when all the actuators are open,

there is also another loop beside it with a temp gauge, so Im stumped as to what the pump is for,

 
I don't see how an UFH system can work properly with a home made junction box like the one Step's posted in post #13

While in principle, each zone thermostat could directly switch the actuator for that zone, you are missing out on the switching for the circulating pump, which as I have said before, needs to come on when ANY zone calls for heat, and stop when no zones are calling for heat. That needs one or more relays to achieve that.

I guess at the moment the pump runs all the time, so pumping into a dead end if none of the zones are calling for heat.

You don't need a seperate timer for each manifold, unless you want to. in our house one timer turns on both manifolds, upstairs and downstairs.

I assume this rcd tripping thing when he bled the pump was merely water escaping from the bleed port and getting into the terminals and will never happen again.

 
Is the pump mounted upside down so any seepage from the bleed valve goes into the connections? Otherwise it shouldn't be able to cause any tripping when bleeding, unless there are other electrical connections below it as well?

Doc H.  

 
I don't see how an UFH system can work properly with a home made junction box like the one Step's posted in post #13
Steptoe said earlier that the customer wants it done correctly "this guy actually wants a proper panel fitted, [uH3 ? ]" so its sounds as though the customer reaslises this as well.

Doc H.

 
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