UFH not getting hot on vented system

[ejkilby1]

Hi folks, I’m in need of some sound advice.

We have recently had a ground floor extension and have had underfloor heating (company: JK UFH) installed throughout most of the downstairs. We have a few rads still left downstairs and the entire upstairs is still heated through rads.

We have a vented (gravity fed) central heating system (about 0.3 bar), heated from an oil fired Thermecon boiler. The header tank is in the loft and the boiler in the garage. It’s an S plan setup with two 2 port valves that control the flow to the CH and to the water heater tank (immersion).

The plumbers have just connected the UFH as a direct T -off from the flow (just after the boiler) and the return just before the boiler, as the UFH manifold is in the garage also.

The UFH has not been placed on a separate thermostat or controlled with a separate port valve, therefore it’s a dumb system and will only receive hot water if either the hot water tank or the CH are calling for heat. My plan is to get it on its own zone, however as things stand, I simply can’t get it to get hot at all. The best I’ve managed is 30 degrees while the boiler is running.

The pipework from the boiler to the manifold and CH is 22mm and all rads are on 15mm

My understanding is that I have the following options, however I’m a little in the dark as to the best course of action, so any advice and opinions would be welcome.

1. I’m told that an additional pump is needed to get the hot water sent to the UFH manifold, however where would this pump go? before or after the T-off to the UFH manifold? Also, would a second pump run the risk of over pumping into the header tank, adding crap into the system? Or should this pump replace the current one on the first floor.
2. Install more valves to enable the UFH to be diverted all hot water at the times it requires it, therefore going from a 2 valve to a 3 valve system. I’m thinking this will mean that the UFH will only get hot if the others are not calling for heat.
3. Make the CH system unvented (pressurised) with an expansion vessel and filling loop. My worry here is that pressurising the system might find weakness in the pipework (house was built in 1990). Also I’m guessing that even after this is done, I still need to zone the UFH onto its own circuit.
4. I’ve read that Installing a plate heat exchanger to the UFH would add pressure and get the heat through the system, however I’ve no Idea if this is a valid option and I’m assuming I still need to zone the UFH off.
5. Some combination of the above

I have attached an image of my setup. I’m not a plumber so please let me know if I have missed some crucial piece of information here.

Edd

 

[Deleted member 120897]

Have you thought about getting the company back who installed the ufh system? Challenge them with the questions asked on here, as they’ve now left you with a system that doesn’t heat up as you want.

 

[exedon2]

If your pipework layout is as you have sketched it out it's wrong .
Get installer back to sort it.

 

[ejkilby1]

Have you thought about getting the company back who installed the ufh system? Challenge them with the questions asked on here, as they’ve now left you with a system that doesn’t heat up as you want.

The company that installs the system unfortunately don't connect them to your existing system, they leave it for you to get plumbers into connect it. The company is jk-gb.com I have had some plumbers in to connect it, but they didn't do anymore than T-off from the main line and as you have to bring it up to temp very very slowly, they wouldn't have known on the day if it was or wasn't really heating well (it does get up above 25 degrees). The plumbers used are now booked up for months and I'm keen to get some advice on options. I will either be getting the same plumbers back or see if I can get a UFH engineer to come and advise, but struggling to find someone with availability. I have spoken to JK and they have suggested an additional pump and valve, but not suggested where, and I've no idea of their ability to suggest this, not really knowing much about my setup. I won't be doing anything myself, but it would be useful to get some opinions on what might seem like a sensible solution, given there seems to be so many options.

Cheers

Edd

 

[ejkilby1]

If your pipework layout is as you have sketched it out it's wrong .
Get installer back to sort it.

Are you able to elaborate on specifically what you have seen that's wrong? It would be helpful to know ready for when someone does come back.

 

[Deleted member 120897]

If it were me, I’d be checking to make sure it works as part of commissioning.

 

[exedon2]

Connection to underfloor needs to be after existing pump with it's own zone valve and control.
Strictly speaking the underfloor return needs to be connected in before the cylinder return.
Advising a second pump shows a distinct lack of knowledge. could easily cause problems.
Converting to sealed system is worth considering move pump next to boiler tee in underfloor bring cylinder return back to make it last connection.

 

[ShaunCorbs]

Basically the plumbers don’t know what there were doing how is the manifold supposed to get flow / hot water from the system as it’s before the pump

Ask for a refund and get another heating engineer in

Best to seal the system eg unvented

Move the pump to before the ufh manifold and a plan plus the system

Then use heat miser controls for the ufh system

 

[ejkilby1]

Connection to underfloor needs to be after existing pump with it's own zone valve and control.
Strictly speaking the underfloor return needs to be connected in before the cylinder return.
Advising a second pump shows a distinct lack of knowledge. could easily cause problems.
Converting to sealed system is worth considering move pump next to boiler tee in underfloor bring cylinder return back to make it last connection.

Thanks that's very helpful, are you able to explain further about the cylinder return coming last? what effect does this have? I have attached an image of what I think you are proposing, is this accurate?

 

[ejkilby1]

Basically the plumbers don’t know what there were doing how is the manifold supposed to get flow / hot water from the system as it’s before the pump

Ask for a refund and get another heating engineer in

Best to seal the system eg unvented

Move the pump to before the ufh manifold and a plan plus the system

Then use heat miser controls for the ufh system

Thanks for this. It's probably hard to advise, but what's the likelihood of me having issues if I pressurise the system. It's probably hard to say, but as plumbers is it a common issue to get issues changing from vented to unvented?