low loss header questions

[lame plumber]

right team, I have been out to a leaking 35 kw boulter camrey, knackered hex, down to acidic water from borehole in all likeleyhood, seeing as pump engineer also appeared today to replace that side of their system.

So had a look round and found it was all underfloor heating dating back 20-25 years.

Initial query related to the flow and return coming off the boiler and being immediately linked by a pump, bit like where you would find a bypass in some setups. I presume this is instead of a low loss header set up to ensure even temps and flow around the boiler.



so had a chat with grant (putting in a vortex pro 26/35) about this and got told it would kill the condensate hex quickly. I understand that it would never get a temp drop so needs to go, but do i need a llh instead.

further along the flow goes to another pump for HW) then one for flow (in 35mm pipe) and then another pump on the return (in 35mm as well).
the heating is all underfloor, some 20 2 ports on the system, no obvious sign of any blending valves/mixer anywhere.





so it must be like walking on a rad when it is all on, but they are happy with it and dont want anything apart from a new boiler.

Right my main question is, will it be better to bin the llh/pump next to the boiler and rely on the other 3 pumps to do the circulation, at least there will be a partial temp drop over the flow n return so the boiler may even condense. or will a llh be required.

Need a bit of current thinking on llh and condensing boilers from the green machines out there.
-+

 

[ShaunCorbs]

i would install a proper llh with a decent set of pump (does the underfloor have its own but higher up in the pic?)

must be a big place with 20 + rooms

 

[Norcs]

Might be more than one loop to certain larger rooms.
Looks like they fitted a shunt pump to protect the boiler return temp. But looking at the image the cable seems to be hanging in mid air.

With a set up like this if the pipes are in a screed when the UFH is started up the return will remain below 40c for much longer and Grant advise maintaining the return @ or above 40c.

 

[lame plumber]

Might be more than one loop to certain larger rooms.
Looks like they fitted a shunt pump to protect the boiler return temp. But looking at the image the cable seems to be hanging in mid air.

ha ha never noticed that cable was disconnected, it was dark under there, so shunt pump does? I presume it keeps flow and return temps similar to prevent cold shock to boiler.

flow n return both have their own pumps, and I expect several rooms have more than one loop.

what I dont get about a low loss header, is that I understand they keep flow and return temps similar so boiler isnt working too hard, but then you dont get a 20 delta T so a new boiler wont ever condense, so whats the point of a llh on this system.

 

[ShaunCorbs]

ha ha never noticed that cable was disconnected, it was dark under there, so shunt pump does? I presume it keeps flow and return temps similar to prevent cold shock to boiler.

flow n return both have their own pumps, and I expect several rooms have more than one loop.

what I dont get about a low loss header, is that I understand they keep flow and return temps similar so boiler isnt working too hard, but then you dont get a 20 delta T so a new boiler wont ever condense, so whats the point of a llh on this system.

yes normally about 10-20 dc

and have a read

Best Practice: Low Loss Headers - CIBSE Journal February 2014

 

[Nostrum]

Low return temp has probably rotten the boiler out through internal condensation.

I'd say the first pump was probably designed to keep return temperature high, but it's been disconnected.

It looks like a good bit of engineering, but I'd be wanting to know the control aspect of it before recommending a replacement. Without a mixing valve I'd be worried !

 

[Norcs]

so whats the point of a llh on this system.

No point. Just connect the new boiler up direct.

 

[Nostrum]

What was the boiler stat set to?

 

[lame plumber]

What was the boiler stat set to?

havent looked, at stat, but reason for corrosion is more likely to be the highly acidic water, water softener system, pump from borehole etc etc all being replaced. the pump is disconnected as its seized up, needs replacing according to the owner and my thoughts were it was to keep return temp high on an old style boiler. re controls and mixing valves, found a hw programmer, there are no mixing valves i have found!!! but its worked for 20 plus years.............. so I understand.

my thoughts are to remove the llh/pump and rely on the flow and return temps allowing the boiler to work reasonably.

ONE THOUGHT, took me a while to fathom it out, dual coil cyl, with a hot flow n return, from the bleedin aga, so hot hot temps not an issue, so I presume the boiler has been running at lowest setting to allow them to walk on the floor.

 

[Nostrum]

The pump isn't anything like a LLH lame.

A LLH provides hydraulic separation for different circuits. For example; a boiler may need a minimum flow rate which cannot be achieved through the heating circuits.

The pump is a crude way of semi controlling the returning water temp, which as you say, would ruin the condensing capability of a new boiler.

If the boiler was on low, they'd also affect he hot water unless always provided by the AGA?

Definitely bin the shunt pump, I'd add a blending valve if you can't find one.

 

[lame plumber]

suspect the aga never goes out on this one. re the shunt pump, i was going to bin that based on others advice. beginning to understand llh now, being more hydraulic separation ,not temp control.

blending valve seems a good idea, although how I get one in is a thought, customers dont seem to want any change as they like what they have had for 20 years!

 

[Millsy 82]

The problem they may have is if the boiler has been set on low so it would not overheat the floor, then grants have a very limited temp range so they won't be able to turn it down or walk on there floor. Lol.

 

[oz-plumber]

Geez Lame, that's 'old-school' heating setup.

I would hazard a guess that the pump under the boiler was setup like a llh. It was installed to maintain a flow through the boiler when the zones shut down. ( Primary pump )
Does the boiler modulate or is it on / off.

I have a suspicion that the pump on the return may have been installed as an after thought, due to the pump on the flow not being large enough for the full system load.

I would probably set up a new boiler with a llh.
Keep the primary pump between the header and the boiler probably put a larger pump on the system side of the llh.
To counteract the larger pump a pressure differential by pass valve could be installed between the flow and return headers to maintain a decent flow through the larger pump.

I try and post a drawing for you

Oz

 

[lame plumber]

it already has a diff bypass on flow and return, had a chat with the lady owner, husband is away. Floors dont get hot, cant understand why as no mixure valves! most of the room stats/2 port valves are broken so they have them permanently open on manual setting. I asked to speak to the old man on wed!!! could be interesting this one

 

[Norcs]

Boiler stat turned down low probably. Would be interesting to see what its set at.

 

[Norcs]

UFH pumps are notorious for seizing during the summer months, which is why good controllers have "exercising" parameters built in.
The second pump/s may have been an after thought with the system initially underperforming.
Two pumps in series boosts the head and are usually fitted close together.

No balancers or flowmeters either by the look off it. So no way of setting the flow rate accurately.
Then you have loop lengths?

 

[Unregistered]

husband called back, insists on a new boiler, everything else ok. Flow rates controlled by gate vales on 2 ports, no heat control through mixers but not an issue. Oh apart from the favt when it all went in first, and they turned it up nice and warm, the oak planking downstairs all lifted one night!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Gonna write a contract, boiler only not responsible for ought else..............

 

[Norcs]

The maximum turn down on a grant steamer is 65c. Looks like the floor is in for another roasting.

 

[Millsy 82]

Run away!!! When the floor gets messed up and the family cat cooks on the floor your name will be mud.

 

[lame plumber]

just written a disclaimer in with the estimate, work is on boiler only, flush and clean system, replace pumps as req but not responsible for heating system due to its none compliance with current design requirements. Oh and estimate is twice my normal rate

 

[oz-plumber]

Sound like you went in on the cheap side Lame.
Hope you break even!

 

[lame plumber]

Sound like you went in on the cheap side Lame.
Hope you break even!

you havent seen my normal pricing structure then I break even on the deposit!!!!!!!!!!!!!!

 

[Norcs]

It wouldn't require a lot to put this system right.
An ESBE CRA 140 which is a combined actuater/controller and HG series boiler connection valve.
Then you have two two mixing operations being supervised. The boiler return and the UFH circuit.
Oventrop sell the unit with all the bells and whistles.