Setting up and balancing y plan

[danmickread]

Hi everyone,
i have just bought a house which has a y plan central heating system with an oil fired conventional boiler. The house was prob built in the 60's, I'm not sure how old the system is but my guess is it's been in a while. The boiler is Wallstar 12/14. The radiators take a while to heat up and don't seem that hot and takes a while to heat the house. There is a bypass valve which is right open and also the gate valve on the cylinder return is right open. Right now your all thinking just get a plumber in to sort it out!! As you all know so many plumbers don't even bother to balance systems properly and i would like to understand myself so I can set it up best I can so the system is working most efficiently. Firstly I will probably get the system flushed out.
Now I have done a lot of reading already regarding balancing radiators and the said 11 degree c drop across them but I'm struggling to fully understand how pump speed, boiler temperature, radiator temperatures, temperature drops across radiator and boiler, cylinder flow, bypass valve position, boiler kWt rating, radiator Btu's etc are all related and how you set them up. I appreciate that this is prob quite complex if you want it to be but there must be a fairly simple explanation and set of guidelines that can be followed in order to set a system up? Also in the future I would like to upgrade rads to double convector to heat the house better but obviously I don't want to increase the total btu output of all rads too much and then the boiler cant keep up. Also what temperature would the radiator have to be in order to achieve the btu output of a rad that is stated by the manufacturer?
Sorry for the long post but some help would be much appreciated.
Thanks
Dan.

 

[Simon F]

so do you have some radiators that heat up quicker and hotter than others?
simple answer to balancing, the radiators closest to the boiler are only just open the furthest away are fully open, so that the same level of resistance to flow is achieved.

does the system need balancing?
new pump? adjustment to speed setting?
powerflush?
bigger boiler?
alteration to the bypass valves??
new motorised valve??

 

[danmickread]

Hi thanks for the reply. Upstairs rads get hotter than downstairs but all rads are slow to heat up so my guess is there's too much water flowing round the cylinder and bypass.
How do i know what the pump speed should be on?
How do I know where to set the cylinder gate valve and bypass valve?
How long should it take on average for the HW to get to temperature? I guess this is dependent on the gate valve position?
should I be looking for the 11 Deg drop across radiators?
what temperature should boiler be set at?
What should temperature drop be across the flow and return at boiler, should this be same as rads?

 

[mountainman]

You don't need a by-pass on a Y plan system, turn it off.
Close the cylinder balancing valve fully then open it one turn.
Should be good to go then.

 

[Ermintrude]

I would leave bypass open on Ch just so there is flow.

 

[danmickread]

Thanks mountain man. How long on average would you expect the hot water to heat up? Would this be related to the gate valve position?
I don't have any pump overrun but do have trvs fitted to every rad so I do believe I need the bypass don't i?

 

[mountainman]

Thanks mountain man. How long on average would you expect the hot water to heat up? Would this be related to the gate valve position?
I don't have any pump overrun but do have trvs fitted to every rad so I do believe I need the bypass don't i?

With trv's you do need a by pass open a crack.
An average cylinder should heat in less than an hour.

 

[AWheating]

put the hot water on for an hour before the heating so when the heatings running the hot water has no demand and the pump pushing around the heating.

 

[doitmyself]

Now I have done a lot of reading already regarding balancing radiators and the said 11 degree c drop across them but I'm struggling to fully understand how pump speed, boiler temperature, radiator temperatures, temperature drops across radiator and boiler, cylinder flow, bypass valve position, boiler kWt rating, radiator Btu's etc are all related and how you set them up.

Are you talking about the theory? If so, how long have you got?

there must be a fairly simple explanation and set of guidelines that can be followed in order to set a system up?

You can set as system up without knowing the theory behind it. Here's how you do it:

1. Remove all TRV heads and set wheel valves to full open
2. Close all LSVs (turn clockwise, like a tap) then open 1/2 turn
3. Set pump to speed 2
4. Set programmer to Heating only. The cylinder must not heat up during balancing.
5. Turn on boiler and set temp to 75C or thereabout
6. Wait for system to heat up (make sure rooms stat is set high so boiler doesn't go off)
7. Wait 5-10 minutes for the system to settle down
8. Check all rads are warming up, even if not all by the same amount. If some rads are stone cold, set the pump to speed 3. (You may be able to set it back to 2 later.)

9. Go to each rad and feel the two pipes. It's the cooler pipe we are interested in; that's the Return.
10. Make a note of which rad has the coldest Return. That will normally be the one furthest from the pump.
11. Find the rad with the hottest Return pipe and close the LSV by 1/12th turn.
12. Check if the Return in step 10 has got any warmer.

13. Repeat steps 9 to 12, until the returns on all rads feel approximately the same. Which one is the hottest/coldest will vary on each pass.

14. If they are all approximately the same, but the difference between flow and return is very small, set the pump to a lower speed. (The boiler may start cutting out on its own thermostat if the differential is too small as not enough heat is being extracted from the water, so the flow temperature rises.)


Do NOT expect perfection.

15. Turn HW ON at programmer and set cylinder stat to call for heat.
16. Adjust gate valve on the cylinder return until the cylinder Return temp is approximately the same as the radiator returns.


Replace all TRVs and set to desired temperature.


If you have something to measure the pipe temperature with, it does make life easier.

Also in the future I would like to upgrade rads to double convector to heat the house better but obviously I don't want to increase the total btu output of all rads too much and then the boiler can't keep up. Also what temperature would the radiator have to be in order to achieve the btu output of a rad that is stated by the manufacturer?

The first thing to do is to use the Baxi Whole House Boiler Size Calculator to find out if your existing boiler is big enough. (There are other versions of the same calculator, but this one is more user-friendly.)

Radiator outputs can be obtained from many on-line sources. Make sure they state the the outputs are measured using BS EN442. This Standard measures outputs at a Flow temp of 75C, Return Temp of 65C and when the room temp is 20C.

There is only a few percentage differences between manufacturers for the same size rad and you can obtain outputs for not standard sizes by proportion.

If the boiler is too small, there's only one solution. (I'm assuming insulation can't be improved).

If the rads don't total what is required, you can add/change rads to give the same output as the boiler.

If the rads add up to more than the boiler, that's OK. They will give out the maximum heat which the boiler is capable of providing, but the radiator flow and return temperatures will be lower.

 

[danmickread]

Thank you all for your responses so far and thank you doitmyself for your detailed informative response.
Last night I let my heating get up to temperature and took some measurements of temperatures across rads. I bought a digital differential thermometer that clamps on both flow and returns and measures difference etc.
Doitmyself if you could answer some of the following questions I would be very grateful.
Firstly the boiler stat is on half way. This gave a flow temperature straight from boiler of 57 degrees c. Is this too low and should I turn up the stat to get 75?
The return to the boiler was around 50 so I am only getting a 7 degree drop across the boiler flow and return. I noticed that once every thing is up to temperature the boiler cycles on and off every 2.5 minutes. Is this normal or is this because the return temp is too high?
I assume that when taking flow and return temperatures it has to be when the boiler is actually fired up and you wait until it reaches its maximum as as soon as the boiler goes off the flow temperatures drop straight down again?
I also measured rad temperatures and the 3 downstairs rads had flow temps ranging from 52-55 with temp drops of 10-17 respectively.
The 3 upstairs rads had flow temps of 53-55 with drops of 4-7 respectively.
So as you can see the water is flowing faster around the upstairs rads. In order to balance this better would I shut down the upstairs rads to push more the downstairs and then would this increase the overall difference between flow and return at boiler as the flow around the whole system has been restricted?
Should I be aiming for a 11 degree drop across rads and boiler pipes and why is it 11 degrees is this the optimum flow rate for the rad to extract the most heat out of water and achieve specified btu rating?
i think that's enough questions for now.

Thanks
Dan