OK folks, I've tried to answer this question myself by reading what I can on the but whatever I read seems to bring up more questions!
Basically we have a smallish 3 bed mid terrace, currently with one bathroom. boiler was recently (last couple of years) changed to a system boiler (at least I think its a system, theres an expansion vessel mounted near the HW cylinder and a teeny cistern in the loft next to the CW tank), and the unvented cylinder upgraded to a slightly bigger one, I don't have size details handy right this minute.
We are now planning a loft conversion, and are hoping to add an extra bedroom and shower-room up there. Our builder seems very keen on changing us over to a combi system so we can eliminate the cold water expansion tank in the loft, but I'm hesitant to go that route, as I've heard that combis have problems meeting demands when more than one tap is open at a time, and the whole point of putting the shower-room in upstairs is to prevent queues in the mornings!
So as far as I can tell that leaves us with the options of sticking with our existing (gravity fed?) cylinder, and adding a pump to get hot water up to the loft and improve the shower pressure in the existing bathroom, or switching to a mains pressure system like an unvented cylinder or thermal store, and I have some questions:
a) Vented cylinder - is there a minimum distance between the expansion tank and the cylinder? We should have enough height in the loft after conversion to build a closet to store the cylinder directly under the CW tank (and so improve the flow in the 1st floor bathroom without a pump there, leaving just the loft shower-room needing pumping) but I'm not sure if this will give enough "head height" for the cylinder to work properly.
b) Unvented cylinders and thermal stores - pros and cons? I can't seem to find a decent comparison of these two on the web anywhere, all the info seems horribly skewed one way or the other. If we were to go this route, the thermal store looks more likely, but I can't find any truly critical reviews on the web so would welcome opinions!
c) Are we being idiots and have combis in fact improved to the state where we'd be nuts to stick with our existing system?
Thanks guys, I know this is a big ask and hope you're able to shed a bit of light on the situation!
Basically we have a smallish 3 bed mid terrace, currently with one bathroom. boiler was recently (last couple of years) changed to a system boiler (at least I think its a system, theres an expansion vessel mounted near the HW cylinder and a teeny cistern in the loft next to the CW tank), and the unvented cylinder upgraded to a slightly bigger one, I don't have size details handy right this minute.
We are now planning a loft conversion, and are hoping to add an extra bedroom and shower-room up there. Our builder seems very keen on changing us over to a combi system so we can eliminate the cold water expansion tank in the loft, but I'm hesitant to go that route, as I've heard that combis have problems meeting demands when more than one tap is open at a time, and the whole point of putting the shower-room in upstairs is to prevent queues in the mornings!
So as far as I can tell that leaves us with the options of sticking with our existing (gravity fed?) cylinder, and adding a pump to get hot water up to the loft and improve the shower pressure in the existing bathroom, or switching to a mains pressure system like an unvented cylinder or thermal store, and I have some questions:
a) Vented cylinder - is there a minimum distance between the expansion tank and the cylinder? We should have enough height in the loft after conversion to build a closet to store the cylinder directly under the CW tank (and so improve the flow in the 1st floor bathroom without a pump there, leaving just the loft shower-room needing pumping) but I'm not sure if this will give enough "head height" for the cylinder to work properly.
b) Unvented cylinders and thermal stores - pros and cons? I can't seem to find a decent comparison of these two on the web anywhere, all the info seems horribly skewed one way or the other. If we were to go this route, the thermal store looks more likely, but I can't find any truly critical reviews on the web so would welcome opinions!
c) Are we being idiots and have combis in fact improved to the state where we'd be nuts to stick with our existing system?
Thanks guys, I know this is a big ask and hope you're able to shed a bit of light on the situation!
