What's the temperature of the return pipe, just before it goes into the boiler(s)?
If it's hot (like 10-20 degrees below the flow) and you have some unhot radiators, you have a balancing problem.
If it's not hot, the heat is being lost , so check the gas rates on the boilers. If they've modulated back, they think they're hot enough. Read the manual to see if you can alter that.
If the boilers are flat out and the return's cool, they're undersized (unlikely).
If as seems likely, your boilers are modded back, and your rads aren't hot enough, then you're short on pumping. An external bypass would make things worse. What I suspect you'll have to do is wind up the internal bypass pressures, to something like 0.4-0.5 bar ( 4-5 metres) in order to get the hot water round the system.
I've had to do that when using a pair of combis in big houses.
An alternative is to CLOSE the internal bypasses, and put in your own externally, right at the END of the system, ie across the last rad.. Think about it - if all the rads get shut, then you still have the bypass protecting the boilers, but it can't starve the rest of the system of pressure.
If it's hot (like 10-20 degrees below the flow) and you have some unhot radiators, you have a balancing problem.
If it's not hot, the heat is being lost , so check the gas rates on the boilers. If they've modulated back, they think they're hot enough. Read the manual to see if you can alter that.
If the boilers are flat out and the return's cool, they're undersized (unlikely).
If as seems likely, your boilers are modded back, and your rads aren't hot enough, then you're short on pumping. An external bypass would make things worse. What I suspect you'll have to do is wind up the internal bypass pressures, to something like 0.4-0.5 bar ( 4-5 metres) in order to get the hot water round the system.
I've had to do that when using a pair of combis in big houses.
An alternative is to CLOSE the internal bypasses, and put in your own externally, right at the END of the system, ie across the last rad.. Think about it - if all the rads get shut, then you still have the bypass protecting the boilers, but it can't starve the rest of the system of pressure.
B
Bodd
I think I really should get somone who has a little more idea than I do.
As much as I apprieciate every ones advice I think I'm more confused than I was before. Which is a good thing as I could have waited a lot of time and in the end would habve been my problem.
I can think of a couple of fellas who would know more so I think I would work along side and learn but not earn
Happy new Year and thank you all
Bod
As much as I apprieciate every ones advice I think I'm more confused than I was before. Which is a good thing as I could have waited a lot of time and in the end would habve been my problem.
I can think of a couple of fellas who would know more so I think I would work along side and learn but not earn
Happy new Year and thank you all
Bod
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Guy's i've just had a read back to the first post.
20rads at per say 1KW=20KW
2 x 210 litre unventeds (based a vailant cylinder that would be 44KW)
if all calling form cold theres trouble.
House is 1920's, 3 floors over 5 levels.
System boiler pumps not likely to be any bigger than 15-50.
Not a cat in hell those pumps can shift their heat at the correct flow with that sort of resistance.
Non of you guys would fit such a small pump to a 3 story house with that much demand.
Lets ignore the arguemnet of turn on the hot water an hour before the heating.Size for worst case.
20rads at per say 1KW=20KW
2 x 210 litre unventeds (based a vailant cylinder that would be 44KW)
if all calling form cold theres trouble.
House is 1920's, 3 floors over 5 levels.
System boiler pumps not likely to be any bigger than 15-50.
Not a cat in hell those pumps can shift their heat at the correct flow with that sort of resistance.
Non of you guys would fit such a small pump to a 3 story house with that much demand.
Lets ignore the arguemnet of turn on the hot water an hour before the heating.Size for worst case.
(ie.Isometrics and shading)
B
Bodd
Norcon
I will let you know what happens. Diagram is not far off ie zoning but no bypass.
Very impressive thanks
Bod
I will let you know what happens. Diagram is not far off ie zoning but no bypass.
Very impressive thanks
Bod
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