Mixing Pressure Problems

[Savdefriz]

Morning,
The pumps should be pumping as you have indicated John, and the circled valve is indeed the manual bypass. The problem as I understand it is that if the manual bypass will push the same volume of water back into the primary loop as the pump injects out of it. I've fiddled with this and I can get hot water down to the injector pump but only when the flow back to the primary loop is massively restricted. If I open up the bypass essentially the cold water pushes back past the t junction where the injector pump branches off, and all that happens is that the cold water gets re-injected into the UFH. I've found some old schematics, and the picture of my manifold is there (actuators taken off as I wanted to make sure none of those were causing flow to stop).

 

[John.g]

I'd say you would need a magician to get that going in its present form, there is no injected water control or return to the primary system to keep the system(s) balanced.
You might be able to install a thermostatic mixing valve and utilise the Alpha2 as the manifold pump, you might then be able to use the existing boiler circ pump to provide the hot water and remove the 8M grundfos. Depending on the hot (boiler) flow temp, the mixed flow temp and the manifolds return temps the boiler circ pump may be able to do this or upgrade it, if you had 70C/40C/30C respectively then you only need the boiler circ pump to provide 25% of the mixed flow, for example you may have say a total UFH heating demand of 20kw which will require a manifold circulation flow of 29 LPM but will only require 7 LPM from the boiler circ pump.
I'd say exedon2 would point you in the right direction.
The attachment is a good depiction of the above and shows that whatever hot water flows into the mixer is returned to the boiler to maintain the balance.

 

[Savdefriz]

I think the Kanmor box is supposed to control the pump that injects water. The bypass valve I believe is supposed to be passive as its job is essentially just to allow a flow back equal to the amount of water injected and that's how the water returns back to the primary system.

I thought that I might be able to play about with the pump settings and valve and coax the hot water round but there are too many variables for me to play with.

Cheers for the help though, I've often been told that the system I have is a bit different!

 

[exedon2]

As John ,g has said never going to work!
I would just go for sorting it properly by fitting a pump/ blender unit to each manifold each feed by a dedicated zone valve. Get rid of current underfloor pump if the one shown is only bypass on system change it for a auto bypass .
On the picture of the manifold all the actuator heads have been removed I take it they do work?

 

[Savdefriz]

There's a bit of a delay as my posts seem to take an age to get through moderation (probably because I'm new). The actuators have been taken off to make sure that I was getting flow everywhere. The Alpha 2L injector is supposed to be controlled by the Kanmor 361 controller box. I've fiddled with it again and managed to persuade a little hot water to come down through the pipe to the injector, but I was hoping that swapping the bypass valve to an auto bypass might have been the answer, looks like it might be a bit more costly!!

 

[exedon2]

Yes I'm afraid some cost involved but it's not much use as it is!
Correctly working ufh is lovely to live with .
Make sure you get a heating engineer who is familiar with ufh both pipework and its correct wireing.

 

[Savdefriz]

No it's not much use as it is at all. The problem is that the bloke who built the house used non standard parts for everything, from the boiler to the manifolds. I've just had a good read of the pack and need to change some settings on the mixer controls... You never know, it can't do any harm!
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I think I've got it sussed. Checked the system and there are 2, 2 zone part valves going to the DHW and primary loop. When the system calls for DHW the boiler loop loses pressure and the cold water from the UFH pushes back into the primary loop via the bypass. When the valve opens to supply hot water back to the primary loop, the hot water struggles to overcome the pressure of the cold water coming back through the bypass and can't reach the injector pump. If I play with restricting the manual valve I can usually resume the flow of hot water to the injector but it's very sensitive. I think If I replace the manual valve with an auto valve and then rebalance it might solve the problem..... Well here's hoping (and I hope that all makes sense as I'm a science teacher and not a heating engineer and before Monday knew nothing at all about UFH systems!).

 

[John.g]

Despite our reservations, it is certainly a very interesting challenge. logically, one would think that it should work in some fashion or other, if not perfectly, some design guru went to the trouble of putting this package together with the Kanmor 361 and the injection pump etc, if you have any links to its setting up you might post them.
Re the injection pump control which is one of the key components, the speed/frequency is controlled by the Kanmor but this is only designed for the older type of circ pumps (see quote) some of the newer types can be externally controlled, but only by a PCM (pulse width modulation) signal which is plugged into the pump motor. I wonder was your injection pump changed out sometime for the present Alpha 2L which cannot be speed controlled IMO by the Kenmor.

Quote:
HVAC Systems
The Mixing Control 361 is designed to operate a mixing pump using Outdoor Temperature Reset. It can be used in applications ranging from in-floor radiant to commercial baseboard systems for Boiler Return Protection with full reset. This control regulates a single heating water temperature through Mixing Outdoor Reset. It provides mixing by speeding up or slowing down a single permanent capacitor (standard wet rotor) circulator, and provides control of the mix system pump. Unquote.

 

[Savdefriz]

Despite our reservations, it is certainly a very interesting challenge. logically, one would think that it should work in some fashion or other, if not perfectly, some design guru went to the trouble of putting this package together with the Kanmor 361 and the injection pump etc, if you have any links to its setting up you might post them.
Re the injection pump control which is one of the key components, the speed/frequency is controlled by the Kanmor but this is only designed for the older type of circ pumps (see quote) some of the newer types can be externally controlled, but only by a PCM (pulse width modulation) signal which is plugged into the pump motor. I wonder was your injection pump changed out sometime for the present Alpha 2L which cannot be speed controlled IMO by the Kenmor.

Indeed it was...... I'm off to work, but I'll post settings when I get home.
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Despite our reservations, it is certainly a very interesting challenge. logically, one would think that it should work in some fashion or other, if not perfectly, some design guru went to the trouble of putting this package together with the Kanmor 361 and the injection pump etc, if you have any links to its setting up you might post them.
Re the injection pump control which is one of the key components, the speed/frequency is controlled by the Kanmor but this is only designed for the older type of circ pumps (see quote) some of the newer types can be externally controlled, but only by a PCM (pulse width modulation) signal which is plugged into the pump motor. I wonder was your injection pump changed out sometime for the present Alpha 2L which cannot be speed controlled IMO by the Kenmor.

Quote:
HVAC Systems
The Mixing Control 361 is designed to operate a mixing pump using Outdoor Temperature Reset. It can be used in applications ranging from in-floor radiant to commercial baseboard systems for Boiler Return Protection with full reset. This control regulates a single heating water temperature through Mixing Outdoor Reset. It provides mixing by speeding up or slowing down a single permanent capacitor (standard wet rotor) circulator, and provides control of the mix system pump. Unquote.

Add

Indeed it was.... I'm off to work, but I'll post settings when I get home.

I've got the full plumber/electrician pack with all the settings. We might get this thing figured out eventually. John you seem to know a lot about the pumps (of which I know nothing), do you think that maybe changing the Alpha's setting might help in the short term?