Inadequate Circulator Pump?

[JC22024]

Will explain general calcs tomorrow which you might find interesting.

Re d/stairs, are some of the lock shield valves throttled in and have all got TRVs fitted?

I fitted quality liquid Drayton TRV valves throughout house a few years back. Except for the rooms which have the digital stat. (Living room GF and master bed FF)

Many of the radiators (+50%) are new Myson also. Each time I decorated a room I renewed the rad too.

Yes lockshields are in roughly balanced but will balance it correctly over holidays now.

I wonder do I need a bypass valve now too as I can hear noise in water flow upstairs due to bigger pump. Not terrible but noticable. As the house would heat up and TRvs shut could get worse.

 

[John.g]

You can reduce to sped2 which is a 6M setting which should reduce noise as the TRVs will be opened more and apart from that a interesting exercise to see if all the rads would still get hot.

 

[ShaunCorbs]

Would just let the system run for a few weeks before messing anymore with it eg let it settle etc

 

[John.g]

Calculations for boiler flow rate etc.
Flowrate (LPM) = (boiler output (KW) X 860) / (boiler dT X 60)
LPM = 26 X 860/33.3/60, 11.2 LPM. (boiler dT, 81.1-47.8, 33.3C)
The above calculation need no other input(s).

Re rad outputs, all modern rads are sized based on a "50 Deg" basis which is the mean rad temp-the required room temp (generally taken as 20C). the mean rad temperature is the (flow temp+the return temp)/2. In your case above IF the rad(s) flow and return temps are 81.1/47.8 then the mean rad temp is, (81.1+47.8)/2, 64.5C, if the room temp is 20C then you effectively have a 64.5-20, "44.5 Deg" rad so it will emit 86% of a "50 Deg" rad (44.5/50)^1.3 X 100, (86% of its rated output.)
However, because the huge dT means the boiler has to be run at almost full flow temp available, 80C. to obtain this performance, if you reduce the boiler temp to 70C then there will be a marked reduction in the rad(s) output.
You might measure the dT across a few of your rads sometime as I am amazed at the very poor flow rate with a 8M head and 28MM flow&return piping. I have a 20kw firebird with 10 rads and the flow rate is 16LPM based on the boiler dT of 18C, this flowrate is achieved at a pump head of 3.5M. I have 22mm piping. If I installed a 8M pump then my flowrate would be , 16*sqroot(8/3.5), 24LPM which is what I expected to see from your system at least. Even one rad, with fully open valves will flow 4/5LPM so I am wondering if your TRV's are somehow restricting the flow through the rads, you might remove the actuators from 3 or 4 of them and check that the pins are fully out.

However, you do have a comfortably heated house for the first time in your life so well done.

 

[JC22024]

Thanks for comments above! I did try the pump on setting 2 and all rads appear to be heating about the same including the furtherest one.

Over the holidays I will get time to try properly balancing the rads and see if setting 2 is enough when they are set at 11c drop.

I did clean the mag filter again and noted more buildup than normal. Note it is new install mag too. Probably because the water is now actually circulating properly! I did order more X800 cleaner so will use that again now the water is going through all rads just to make sure all is clear and should dissolve any rust buildup which may exist.

The overflow for the heating header tank dropped into the water tank for the house. This meant any time it overflowed etc it dumped rusty chemical laden water into where you brush your teeth from!! So I redirected that overflow pipe this morning so it discharges externally and not into the other tank anymore.

Whilst in there I noted the main tank ballcock is dribbling constantly so I'm going to go get a new one today and install tonight. That means both ball cocks will be new.

Now for the bad news- noticed the water level in the heating tank is indeed rising. When switched on and overflowing. However I believe this system has done this for years too and I think it is coming from the stove circuit which is teed in just before the circulator. I will do more testing to be sure and for now maybe add 2no full bore 28mm ball valves on those pipes to shut them off.

The stove is connected to heating in the boiler room. Then loops up into attic, into gravity rad and drops down into stove. Trouble is I do not believe there is a link to the header tank to that stove circuit. It relies on atmospheric pressure to fill with water from boiler room. Maybe another outlet teed into that circuit from header tank would balance it and stop the water head being pulled down into the boiler room which is what I believe is happening but need to test more.

It didn't happen the first night because there was probably still air in the stove circuit which slowly vented out and filled and the problem re-surfaced. Literally!!

This house used to also pump water up out of the overflow vent but was cured years ago by moving the circulator pump to the boiler outlet side VS where it was pumping into boiler casing from return.

 

[John.g]

Its nigh impossible to make any comment on your set up without at least a schematic to show how the two systems are integrated and how recirculation through one system is prevented with either system in use, the potential for very dangerous conditions exist if these systems are not properly installed, I would strongly advise not to use the stove until problems addressed.

 

[JC22024]

Yes I plumbed the stove in about 5 years ago. It is absolutely safe I made sure of that hence why I wanted to do it myself. Eg, large capacity gravity rad which was sized per manual to soak away the heat if fhe power went out in use and heating not circulating. In conjunction with high and low pipe stats and a thermostatic damper on the stoce which at that time was special order. (Now it is legal requirement as I understand it and all new stoves should come with it.

But... here is an update. When I changed the ball cock in heating tank I noted it was too high. Set about 2 inches below the outlet.

So the new ball cock heating tank level is only a couple inches above the outlet to allow for expansion.

So that was yet another error in the system.

But the main error it appears when I thought about it is the actual vent pipe itself. This house has the old school heating plumbing whereby if you wanted hot water it switched the boiler on and no pump hence it raised up the pipe and fell back down warming the cylinder coil.

That is a 22mm pipe which goes from the boiler and loops over and down into the hot press. With a 15mm vent pipe teed off that mid point and above heating tank.

Years ago when I was upgrading the controls in the house I may have made an error of judgement I fitted a cylinder stat and control valve to the hotpress 22mm pipe.

I was thinking about this and did a test there by turning on hot water to permanent on (I normally use economy 7 electric on immersion heater all year around) and switch heating on and off.

Bingo- now the heating tank water level stays AOK doesn't rise. Sits at correct level. Could be speaking too soon but before I opened that it was pumping up and out the overflow then filling back up again a little when shut down. Now it stays level. Will it creep up still? Time will tell.

I guess this is just how the house was plumbed and I need to remove that valve, the only downside being that there will always be a degree of hot water from normal space heating running but that's OK.

 

[JC22024]

So just to make this clearer, I belive the expansion tank puking out water has been a long term problem. The overflow is out the back of the house and I'm usually never out there. But I recall before seeing it putting bursts of water out of the pipe and thinking "I need to look at that" but never did.

After the old boiler burst and working on system in recent weeks I noticed the high water level in the heating expansion tank. And thought must be ball valve. I renewed that and lowered the water level.

But it wasn't the ball cock. It was the fact that one end of the 22mm vent / feed pipe was effectively capped in the hot press.

So in that state when you turn the heating on and all is bled properly the lower feed pipe in the header tank backfeeds water and rises the level in the tank until it overflows a couple litres out the overflow pipe.

Now with the hot press valve overrode/ powered on this does not happen. There must be a small head in the water, perhaps intentional that travels down into the HW cylinder when the system is operating. And since it couldn't go that route through the cylinder it was instead being pushed up into the header tank.

So I'll leave the HW valve permanently on for a few days and report back If heating tank water level / puking issues are now resolved.

Space heating is superb Pump on setting 2. Overflow from heating tank also now bypassing the drinking water tank. And I did renew the second ball cock in the main loft tank today as it was actually constantly leaking.

 

[ShaunCorbs]

Can you roughly draw the set up also feed and vent positions

 

[JC22024]

Can you roughly draw the set up also feed and vent positions

Yes I will in coming days and will post. Will monitor heating tank and see if this went away also.

If it doesn't next step for me will be to temporarily cap the stove pipes in boiler room to remove it from equation.