Under Floor Heating

[jst008]

I have just connected to my central heating system a JG ufh Single Room Heating Pack which was laid in my extension that I have been buidling for the last 12-18 months. I installed in independantly from the rest of the house so that it can come on by itself via it's own motorised valve & programmable room stat.

For ease I broke into the flow & return just before / after the boiler in the kitchen. The main central heating pump & HW / CH valves are upstairs in the airing cupboard.

The problem I'm having is that the main CH pump which forces the hot flow from the boiler to the CH & HW & then back to the boiler as the return, is forcing hot water up the "return" pipe from my ufh kit. As the ufh kit only turns on when the flow reaches 40 degrees this does not happen. By bypassing the flow switch in the ufh kit with a specific electrical link in the box, the pump fires up & in an instance drags the water round in the correct direction.

Should I have taken the flow & return up to the airing cupboard & connected there? And is a loop at the end of the loop not the done thing?

 

[ChrisR]

Er, well you haven't connected it right, then.
You're taking the flow for the UFH AFTER the rads??
No motorised valve?
It should be like this:

 

[jst008]

no, I have not connected the flow for the ufh kit after the rads.

I said I installed it independantly of the central heating & hot water, with it's own motorised valve & programmer.

Instead of connecting in the airing cupboard after the pump adjacent to the ch & hw motorised valves I connected for ease near the boiler. The motorised valve though is adjacent to the ufh kit for ease of future maintenance. Therefore this loop at the end of a loop does not flow like I thought it would.

 

[ajrobb]

Novice speaking:

I suppose it depends on the system, but I thought that UFH can have another circulating pump and be connected between the radiator return and the boiler return with an additional connection to the feed (to keep the temperature up to 40ish).

 

[jst008]

It does depend on the type of ufh kit you buy.

Mine is a John Guest Single Room Heating Pack for areas upto 30m2. It does have it's own manifold & circulating pump - BUT this pump only fires up when the temp of the flow reaches 40 degrees, & turns off at a lower temperature. This kit can be connected in a standard rad circuit or as I have done with it's own motorised valve & programmer - it can then turn the boiler on regardless if the rest of the central heating is on.

 

[greemyamochop]

where have you connected the return??

 

[Rhondo]

Sounds like another typical diy bodge up.

 

[jst008]

The return is connected also adjacent to the boiler approx. 1m away.

Thanks for your reply Rhondo, sounds like you haven't a clue what I'm talking about & opted for the usual retort instead of offering any useful advice or comments - which is what this web site is about.

 

[Norcon]

If the T's for the underfloor circuit are before the primary circulator then its wrong.
The reverse circulation back through the ufh return would lead me to think the zone valve is fitted in the wrong location also.

When actuaters are fitted to the manifold and no zv, as is common then a nrv needs to be fitted on the bypass port (cold side) to the tmv other wise the tmv acts as a by-pass back to the primary return.

 

[Onetap]

The problem I'm having is that the main CH pump which forces the hot flow from the boiler to the CH & HW & then back to the boiler as the return, is forcing hot water up the "return" pipe from my ufh kit.

You'd need a diagram to clearly explain that.

A cross-over header is the thing you may need. Connected as for a radiator on the primary system with an isolating and regulating valve as for a rad, but with a straight pipe connecting the two valves, instead of a rad. Water flows through the header at a constant rate when the primary circuit is on, whether or not the UFH secondary circuit is on.

The secondary UFH flow and return to the mixing valve and secondary pump are taken from/to closely spaced tees from the header. Because they're closely spaced tees, there's negligible pressure difference between them and so no nuisance flow induced by the primary pump.

The disadvantage is that primary unused flow water is routed straight back into the return, and reduces the efficiency of a condenser.

Hope that helps, if not, too bad, too much to do.

 

[Rhondo]

A cross-over header is the thing you may need

YOU'D need a diagram to explain that to the OP.
It's not needed though. The OP's JG tmv will most likely regulate on one port thus it needs positive pressure applied to that port via the primary circulator ideally with the by-pass fitted close to the mixing arrangement.
Google Rehau systems (I've fitted them so know how they operate) and whilst you're scouring the net have a look at how an UFH tmv operates and how it interacts between the primary and secondary system.

 

[ajrobb]

It sounds like you have connected it across the boiler. This would be fine if the boiler included the main circulation pump (many do), but you say the pump is in the airing cupboard. You need to connect the feed AFTER the main circulation pump and before the other zone valves. The UFH pump only circulates water under the floor, it relies on the main circulation pump to provide feed pressure.

 

[Onetap]

A cross-over header is the thing you may need

YOU'D need a diagram to explain that to the OP.
It's not needed though. The OP's JG tmv will most likely regulate on one port thus it needs positive pressure applied to that port via the primary circulator ideally with the by-pass fitted close to the mixing arrangement.
Google Rehau systems (I've fitted them so know how they operate) and whilst you're scouring the net have a look at how an UFH tmv operates and how it interacts between the primary and secondary system.

Don't you just love being told how to do your job by a clueless DIYer.
See his post on PTFE on compression fitting threads.

Cross over headers and low loss headers are all over the internet and it's adequately explained above. Hydraulic disconnection of the primary and secondary circuits is what they achieve and that is what he wants.

I did Rehau's course 5 or 6 years ago, I have their manuals. Why would I scour the net? Why would I look at how a UFH TMV works? I don't use them. Thermostatic mixing valves? Get real.

Have a look at how proper motorized mixing valves work. Tell me something about mixing valves in diverting mode, injection mixing valves or injection pumps and I may take some notice.

 

[Rhondo]

Don't you just love being told how to do your job by a clueless DIYer

Well it's a dirty job but someone's gotta do it.

btw you're all singing all dancing "cross over header" with "closely spaced T's" won't work with the OP's system.

 

[Onetap]

btw you're all singing all dancing "cross over header" with "closely spaced T's" won't work with the OP's system.

Why not? Provide the technical details for your (note spelling) answer.
It works on every other system.