Do you mean 25/80? I suggested that earlier.
Is it a sealed system?
You can't just stick pumps anywhere on the circuit, fine if you can get them off the main flow but access might not be possible.
central Heating Pump Size
- Thread starter agsaunders
- Start date
Do you mean 25/80? I suggested that earlier.
Is it a sealed system?
You can't just stick pumps anywhere on the circuit, fine if you can get them off the main flow but access might not be possible.
Sponsored Links
Who said anything about 28mm pipe? Not sure what you mean.
.Sponsored Links
G
gaswizzard
Yep , you can only try to educate Lee but it falls on deaf ears.
40kw/(0.320 x 4.2) = 29c dt.
Thanks for all the responses, i have been through the manual and it clearly shows 22mm pipework for the boiler flow and return and for the gas.
I would love to rip up the house and fit the ideal installation but unfortunately thats a bit excessive and would require a lot of expensive floor replacement. I have rebalanced the system and have some improvement but really feel that teh radiators are of insufficiant capacity for a 38m2 room with approx 7m2 og upvc double glazing. They are old Myson round tops double concector 500mm x 1140mm.
I was planning on replacing the kitchen flooring anf piping in water underfloor heating a year down the line but would like to make the best of the current system for this winter. If it means a better light commercial or 15 60 pump or bigger radiators or a combination of both that would suit me. What would you recommend.
Hi,
sorry a typo on my part.
its not a sealed system. Y plan layout, pump is located as per Y plan layout.
I have spent more time balancing the system with a bit of improvement. Seems the radiators at 1140 x 500mm double convectors are too small to heat up 38m2 room with 7m2 glass. Unfortunately teh layout of the room requires settees in front of ( but a foot away from ) teh radiators which is hardly ideal.
Appreciatting all the tech info and on a steep learning curve.
- Joined
- 19 Feb 2006
- Messages
- 31,235
- Reaction score
- 10,557
- Country
The boiler may well have 22mm connections and that's all the instructions care about.
22mm pipe will carry 40kw but it will be outside the design performance of 1m/s.
The next issue is the 3port.. 22mm 3 port isn't designed for 40kw.
22mm pipe will carry 40kw but it will be outside the design performance of 1m/s.
The next issue is the 3port.. 22mm 3 port isn't designed for 40kw.
I appreciate that but unfortunately i am in a catch 22, house requires approx 34kw for its current radiators, i cant change all the pipe work realistically( well not before xmas) How can i make the best of the best of the current system ?
That may be true if you are running with an 11C differential, but it's OK with a 20C differential.
Honeywell recommend 26kW max; but that was when the differential was 11C, so a flow of 34 litres/min, which gives a pressure drop of just over 1m
40kW @ 11C = 52 litres/min, which means a pressure drop across the valve of approx 3m.
But 40kw @20C = 28 litres/min, which is only a pressure drop of approx 0.5m. This is well within Honeywell's recommended max drop of approx 1m.
Pressure drops have been read off the Flow Characteristics graph provided by Honeywell. The 22mm has a KV of 6.
You said you had tried balancing the system.
1. How far open were the LS valves when you finished balancing?
2. What temperature differential (flow/return) were you aiming for?
3. What is the flow/return differential at the boiler?
You said that the online calculator recommended a 32kW boiler. What is the total output of your radiators?
Use Stelrad Elite Catalogue page 31 (pdf page 2) to find out.
1. How far open were the LS valves when you finished balancing?
2. What temperature differential (flow/return) were you aiming for?
3. What is the flow/return differential at the boiler?
You said that the online calculator recommended a 32kW boiler. What is the total output of your radiators?
Use Stelrad Elite Catalogue page 31 (pdf page 2) to find out.
Radiator output approx 34kw, The previous owners added 5 large vertical tube radiators and 3 large towel heaters, the 30kw ferolli sigma may have coped prior to that but it died 2 weeks after we moved in. ( British Gas contract serviced !? a few months earlier)
1. Most are around 1/4 to a half turn
2 12 deg C to 15 deg c at the moment
3.Flow 71 deg Return 45 deg c
So you need a 32kW boiler which, assuming it includes 2kW for the HW cylinder, means a heating load of 30kW. Your rads add up to 34kW, but that's when running with a 50°C ΔT. If the ΔT is lower the rad output will be lower. It's not a linear relationship. Reducing ΔT by 20% to 40C will reduce the output by 25%.
A quick explanation: ΔT is the difference between the mean water temperature and the room temperature. Rad outputs are measured with a flow temp of 75C, return of 65C and room temp of 20C. The mean water temp is therefore 70C and ΔT is 70-20 = 50C.
1 and 2 are good, but why is there such a large drop at the boiler? I would have expected the return to be about 55-56C. Is there a large run of pipe from the boiler to the first rad?
What are you using to measuring the temperatures?
rechecked boiler flow and return after its been on for couple of hours.
Flow 72 deg c return 56 deg c using a raytek IR thermometer gun.Boiler set at 75 deg c.
tks
Andy
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
Similar threads
