Hot rads upstairs, cold downstairs.

duckypoohs

Looking for a solution folks to my heating. Got my boiler replaced,swopped out like for like. Now if i turn on rads upstairs , downstairs stay cold. But if i turn off upstairs downstairs lovely. Have valves upstairs 1/4 turn on and they heat alsmost straight away but downstairs takes ages to get warm.

I tried bleeding the system when hot and cold, also turned off every rad and switched on a rad one at a time bleeding as i went, but still same situation, If upstairs opened more than 1/4 turn downstairs loses heat. Standard 3 bed semi.

Any help greatly appreciated as upstairs like a sauna!!!!!

shane0007

How many rads in total in your house?
What is the kw output of the new boiler?
Do the pipes feeding the downstairs rads come out of the walls or do they rise from the floor?

duckypoohs

Total of 9 rads, 5 double and 4 sigles. New boiler is 24kw while old was 18 so thats not issye. Plumbed through joists between ground floor ceiling and 1st floor. T off for each rad. Working ok now but if i adjust upstairs open any further i lose rads downstairs. Must be an air pocket somewhere?

Irish Steve

OK,from the description, the pump is struggling to provide the flow required to get upstairs and down again.

Are you familiar with balancing, in other words, using the valve at the other end of the radiator to restrict the flow regardless of how much the valve with the head on it has been opened. From the desocription you've given, it sounds as if the check valves are all wide open, so the hot water is taking the line of least resistance back to the boiler, and not getting to the more distant radiators,

So, the plan will be to close all the check valves, and then open them fractionally, maybe no more than 1/8th of a turn, and see what sort of temperatures you get in each rad with the service valve fully open. If a radiator heats up real quick, then the check valve is open too much, if it doesn't heat, try opening the check valve a bit more, and if that doesn't work, the pump may not be running fast enough, depending on the model of pump that's installed.

In some cases, 1/16 of a turn on the check valve is the difference between working and too much, so if several of the upstairs rads are open too much, which your description certainly implies, then that's the first level of attack, close the check valves down on them and see what happens. Once you have them working better, that should force the water to get to the downstairs rads again. They are at a disadvantage, the flow is coming from above the radiator, so a longer path to get to them, and getting air locks out is more difficult.

In passing, when getting air out and bleeding, it will be worth making sure that both valves are fully open on the radiator that you're working on, if the check valve is closed a long way on the downstairs rads, the air may get out of the rad but not the lines feeding it, the flow to the rad may not work once the other rads are back on line if there is still air trapped in the line, the only way to be sure is to open both valves fully with all the others closed off. Takes time, but will be worth checking given the drop down routing.

Last slightly desperate thought Is the pump horizontal or vertical. If the pump is horizontal, it is just possible that the flow rate is being reduced due to air trapped in the body of the pump. Long shot, but worth checking, there should be a small screw on the body of the pump that will be visible on the top. Loosen it a little and see if any air comes out.

Hope that makes sense and helps to diagnose what's happening.

shane0007

duckypoohs wrote: »

Total of 9 rads, 5 double and 4 sigles. New boiler is 24kw while old was 18 so thats not issye. Plumbed through joists between ground floor ceiling and 1st floor. T off for each rad. Working ok now but if i adjust upstairs open any further i lose rads downstairs. Must be an air pocket somewhere?

As I said where do the pipes come from for the ground floor rads? Walls or floors?
Also what make & model boiler is it?

duckypoohs

New boiler is 24kw while old was 18 so thats not issye. Plumbed through joists between ground floor ceiling and 1st floor. T off for each rad. <<<<<<<<<From previous post,

so in other words across ceiling and down through walls to downstairs and up through floor boards to upstairs rads.

Irish Steve,
Well used to basics of plumbing and did all that you suggested before i started posting here. At moment downstairs is nice and warm and upstairs checkr valves barely open. Just dnt undrstand why if i open checkers any furtyer upstairs i lose downstairs. I understand that it will take the path of least resistance but sure the rads downstairs should not go cold regardless of settings upstairs????

Irish Steve

Upstairs will get some natural gravity circulation with heat rising and cold falling, but the downstairs are totally depending on the pump to force hot water down to the radiator, with natural "gravity" flow fighting that, and trying to go back up against the flow of the pump, and in the same manner, cold water will tend to drop rather than rise, so the pump has to work to force that to go where it is supposed to.

thinking back to the last boiler I put in, the return in the elbow at the bottom had a restrictor in it to accellerate the flow into the boiler, the intention being to aid gravity circulation on the larger flow ports.

Is there any chance that the new boiler has some sort of flow restrictor in the body of the boiler that is restricting the total flow in comparison to the old boiler you took out?

Was the pump changed at the same time as the boiler? If it was, is it the same capacity as the old pump, and is it set to the same speed as the old pump?

I'm not altogether surprised that the upstairs rads are locked down pretty tight, I have a similar scenario here, with underfloor pipes on both floors, getting the hot water to the lower floor takes more effort than to the upper floor for similar reasons.

As long as all the radiators are hot, and the boiler is happy with the flow and return temperatures, I don't think you've not got anything significant to worry about, even if the check valves seem to be a long way closed.