Central Heating system help

[deema]

I’ve recently bought a new house in which the central heating has me stumped. Some of the radiators arn’t working properly possibly due to an air bubble or something else?. I don’t understand how it’s been plumbed and would welcome any insights.

This is the system in the plant room.

Valve A is closed
Valve B is open

1,2,3 Zone control valves are for Downstairs, Upstairs and hot water tank respectively.

4 is a Vortex Z152 timed pump for circulating hot water out of the tank I believe through the system so that the hot water taps run hot quickly.

I’ve put arrows to show what I believe is the flow of water

Pump C pushes the heated hot water towards the three zone control valves.
Pump D seems to be pump on the return, it looks to have two pipes feeding into it as well as a connection to the heated water flow which is cut off by valve A


Upstairs is all radiators, whilst downstairs is radiators and a single manifold feeding an underfloor heating system.

All of the radiators have temperature control valves on them, some on the outflow rather than the inflow which I think are likely to be forced closed by the water flow and need moving so the flow through them is the correct way…..is this idea correct?

Having two pumps one on the outfeed and the other on the return smells like the the installer got the pump sized wrong, and tried to create a greater head / flow by doubling up the pumps? Is there another reason for adding two pumps?

I can’t think why there would be two returns to pump B, should Valve B be open or closed? Why have a shut off on only one leg?

Why would you have a connection through valve A?

The return from the hot water tank heating coil seems to go into the flow side of the upstairs radiators after the zone control valve, is this normal rather than returning to the boiler?

 

[Alli]

Just a quick thought, you mentioned an air bubble. your first photo looks like it got a air vent at the top, is this a manual one that needs opening to release the air?

 

[deema]

@Alli, yes its a manual air vent, I’ve opened it and also been around all the rads checking them for air. The system is I believe two years old and I can’t find an automatic vent near the boiler or in the plant room or indeed a sludge trap, which also needs adding.

 

[Alli]

Ahhhh, great. I got caught out once thinking it was an automatic one when it was manual, a quick turn got the system working.

Just another thought, some radiator TRV can be bi-directional so don't need to be on the flow. If you take the TRV off do all the pins move freely? I've been caught out where the pins get stuck in the shut position. A drop of oil and pushing the pin downwards got it freed off. What ever you do, don't try and pull the pins upwards with pliers or similar, you could pull the pin right out them its a real PITA. Ask me how I know!!!!

 

[deema]

@Alli That’s really useful to know, I didn’t know they did bidirectional TRVs. Good advice on not pulling with pliers……that was on my list of things to try…..until now

 

[Woody Alan]

the water flow and need moving so the flow through them is the correct way…..is this idea correct?

As Alli says some are Bi directional and I have had some Danfoss I think that have to be set (at installation)for the flow direction.

 

[deema]

Just a thought whilst I’ve been mulling it over. How do you balance the flow to the underfloor heating manifold? Does the water temperature value at the manifold have a restrict or within it? Could valve B be there to restrict the flow to the underfloor heating system and act as a balance?

 

[deema]

the water flow and need moving so the flow through them is the correct way…..is this idea correct?

As Alli says some are Bi directional and I have had some Danfoss I think that have to be set (at installation)for the flow direction.

I suspect I have little flow through the radiator circuits so I’m thinking it’s either air trapped somewhere in the pipes, or the pump shut of valuing isn’t set correctly / pumps not working correctly. However, both pumps are set on level 3, or the top head pressure and both indicate and ‘feel’ to be on. I’m guessing having both fu-barred is unlikely, but don’t understand why there would be two.

 

[Sideways]

You don't show your boiler but my condensing job has an expansion vessel built into it - a pancake thing that takes up one entire side of the boiler casing - and an auto bottle style airvent fitted in the boiler's pipework above this, so close to the ceiling you would need steps to check...

Even though you have separate expansion vessels there might still be components built into the boiler.

 

[deema]

This is the underfloor heating manifold, it has a Reliance mixer, having had a look through the manual, it doesn’t appear to have any form of flow restriction, it does give the flow for various static heads.

 

[Woody Alan]

Just a thought whilst I’ve been mulling it over. How do you balance the flow to the underfloor heating manifold? Does the water temperature value at the manifold have a restrict or within it? Could valve B be there to restrict the flow to the underfloor heating system and act as a balance?

The system is certainly confusing, you should have a blender valve which takes the "hot" water from the heating primary and blends it with the cold return from the underfloor until it reaches the optimum underfloor temp set by the blender valve, this will be pumped around by the underfloors own heat pump. is it not with the UF manifold? something strange about the whole install for 2 years old, who uses gate valves anymore, horrible things. 2 expansion vessels however big is your cylinder? was this a refurb of an old system?

edit your pic answers some of the question

edit not familiar with the manifold but those valves with th red and blue on should adjust th flow in each section

 

[deema]

@Sideways, it’s a Worcester Greenstar 40CDI a superseded boiler but still git a very good efficiency rating. It doesn’t appear to have any expansion systems built in.

 

[deema]

The system is certainly confusing, you should have a blender valve which takes the "hot" water from the heating primary and blends it with the cold return from the underfloor until it reaches the optimum underfloor temp set by the blender valve, this will be pumped around by the underfloors own heat pump. is it not with the UF manifold? something strange about the whole install for 2 years old, who uses gate valves anymore, horrible things. 2 expansion vessels however big is your cylinder? was this a refurb of an old system?

edit your pic answers some of the question

This is a house that was ‘refurbished’, the entire heating system is supposed to be new. The tank is a 300 litre Kingspan Tribune XE it has a built in expansion tank at the top of the cylinder. Hot water is taken about 300mm below the top. The literature states that this is to reduce thermal losses. The expansion vessels are for the heating system only I believe.
Looking at the spec I’ve downloaded for the Reilance valve on the UFH system manifold it is a blender with a Grundig pump just above it to circulate the UH system. It does have a Heatmiser UH4 the standard wired system rather than the Wi-Fi system.

 

[Sideways]

@Sideways, it’s a Worcester Greenstar 40CDI a superseded boiler but still git a very good efficiency rating. It doesn’t appear to have any expansion systems built in.

View attachment 154762

Yep. No expansion vessel but there is a bottle type auto air vent. #20 . The topmost cap of this should be loose to let it vent.

And we see flow is on the left and return on the right as you face the boiler. Now it's possible that these are crossed over in the ground floor plumbing, but with the advantage of having seen the position of your boiler vs the picture of your tank cupboard, I would check in case your red arrows for the 28mm flow and return pipes both need to be reversed in the second photo.

Gate valve A could be a bleed valve between flow and return to maintain minimum flow through the boiler if all the rads and UFH thermostatic valves closed down ? If so it should be nearly but not quite closed. Make a mark then check what fraction of a turn is needed to close it fully, then return to where it is now.

 

[deema]

@Sideways well spotted, hadn’t noticed the auto vent

 

[ian33a]

This is the underfloor heating manifold, it has a Reliance mixer, having had a look through the manual, it doesn’t appear to have any form of flow restriction, it does give the flow for various static heads.

View attachment 154761

You appear to have a four zone UFH system with six circuits. It looks like one zone (kitchen) has three circuits so those three actuators will go to the same controller channel. This is done when the pipe runs are lengthy - each circuit having a specified maximum pipe length for a given pipe bore. The three at the right hand end appear to be separate zones.

The flow to each zone is done by adjusting to balance the gauges on the top of the red section of the manifold. It's supposedly easy to set the balance up using these. Our system doesn't have them and, because each circuit keeps the zones warm enough, I leave them as they are.

The black pump provides the flow around the system - hot water directed in the top, colder water returning through the bottom. The reliance unit is a thermostatic mixer valve which blends incoming hot water with warm water coming back through the return. It also provides a return of cold water to the tank or thermal store for reheating.

With ours, we have temperature gauges on both halfs of the manifold and can adjust the mixer to suit. TBH, they aren't very effective and a thermal camera does a far better job. The temperature on the flow side doesn't need to be especially high - too high and it can damage wood flooring, too cold though, and the heat wont permeate carpets. The differential temperature between flow and return is often quite low. Really though, the return needs to have a low enough temperature that it causes the boiler to condense.

Some pumps have a variety of modes to set defined speeds or rates of flow or power consumption. Many UFH system pumps have electronic control to select a mode and level of performance to suit the UFH design.

 

[davethebb]

Deema, Just a general safety comment. You should perhaps mount the cable JB that's on the floor on the wall just in case you have a leak!

 

[XTiffy]

Deema,
I would get a plumber that knows his stuff to survey your installation. To my mind that is the work of a bodger. The underfloor heating installation seems to be tidy, so probably different installers. Agree with davethebb, what installer would mount an electrical box on the floor.

 

[Pedronicus]

@Sideways well spotted, hadn’t noticed the auto vent

It's not an auto airvent but a manual one.

 

[Spectric]

it’s a Worcester Greenstar 40CDI a superseded boiler but still git a very good efficiency rating. It doesn’t appear to have any expansion systems built in.

It won't because it is a nice simple uncomplicated system boiler with no valves or pumps etc built in, they are good.

you should have a blender valve which takes the "hot" water from the heating primary and blends it with the cold return from the underfloor

it has a Reliance mixer, having had a look through the manual, it doesn’t appear to have any form of flow restriction, it does give the flow for various static heads.

That is what the Reliance mixer does, and once the supply temperature reaches setpoint the pump will run continously, either just moving water round the loops or pumping it to the return via the mixer when it opens to let more hot water into the system.

what installer would mount an electrical box on the floor.

A heating engineer, they are often trained to install electrics for a heating system and plumbing is there main job with electrics almost like an added hassle.

I have seen heating electric's in places that you are lucky to be able to shine a torch on let alone gain access, in fact I can recall jobs where cylinders and pipe work have had to be removed to get access for changing zone valves.

I notice that you have a smart circulating pump, how have they accomodated the bypass loop ? I had a similar issue because you cannot use an automatic type pressure bypass valve with a smart pump because it has proportional pressure control. My solution was to use a three way valve but you can also use setter valves and this is just another area you may or may not have an issue.

The attached docs might be worth reading.

Your next course of action is to either get a heating engineer to take a look or take some time and draw up the system so you have a diagram which shows all the components and this will greatly help explain things and assist with fault finding.

You also need to bear in mind that this being a sealed system comes under different regulations which used to be G3 and there are some components that are safety devices and not all heating engineers may have the required knowledge.