Central Heating Mystery

[john west]

We had a new Ideal Logic Heat 18 Boiler installed some weeks ago. (To replace a Bosh Greenstar 18 ).

After installation of this new Ideal it caused the pump upstairs in the water cylinder cupboard to run non-stop for two weeks until an Electrician rewired the Boiler connections and then it stopped.

Now the system (a traditional type with a hot water cylinder upstairs) has become erratic with the boiler cycling up to 80 degrees then cooling to 40 then repeating this cycle endlessly. To stop this I had to switch the electric switch off below the boiler.

I am told that to fix this is that either the pump is not working properly and it needs a new pump and that the system and radiators being at least 30 years old needs a flush through as dirt might be upsetting the boiler.

It does heat up the radiators sometimes, but this can be erratic with some radiators getting barely warm sometimes.

One thing that puzzles me involves the new Programmer a Drayton Lifestyle LP722. When it is set to heating continuously and when the radiators do heat up it also strangely also heats the Hot Water even though the hot water is switched off at the Programmer ?

Any ideas as to what is likely going on here ? Grateful for any suggestions for any next types of action.

[SH]

that sounds like a three port valve issue.... Do you have a 3 port valve?

Do the upstairs radiators get hot but the downstairs radiators remains cold? This is a sympton of a failed pump.

[Brian]

Certainly a flush wouldn?t be a bad idea. Crud does collect in systems in a lot less than 30 years. Ours was power flushed when we had a new boiler fitted maybe 15 years back. It has been drained several times since, radiators flushed when thermostatic valves were fitted etc, kept topped up with inhibitor, flushed with cleaner, all the right things. Yet, when I needed to replace an element in the bathroom rad ( it has an electric element for use in the summer etc), the rad still had crud in it.

That aside, other things to look at.

I assume you have a room thermostat? It is rare not to but not unknown. That could be part of the problem - setting the boiler stat right is critical without one.

Is the divert valve ( valves) working? These direct the hot water in the primary circuit to the rads, the coil in the water tank, or both. Some systems have one, others have two.

Next, are the rads balanced? Basically, this means are they all getting a ?fair share? of the hot water from the boiler in the heating circuit. Ideally you adjust this with thermometers on the in and out pipes of each rad. However, you can do it without. Turn all rads except one off at one end. Go around, turning one on at a time just enough to see which pipe gets hot first. Note, that is your ?in?.

Open all your outs, close all the ins except the one furthest from the boiler. Open it one turn. Work towards the boiler, opening the ins a bit less each time. The nearest one will probably be a fraction of a turn. You should find all the rads get warm. Check for air in the system.

If any rad seems cold, open the in a touch. If one seems hotter, close a touch. If the system settles down, you can go around an open every in a touch but try to keep them in ratio.

That approach isn?t perfect but it works quite well. It takes time.

When a system has been refilled, it can require a few bleeding cycles. Plus, of course you need inhibitor. If it won?t bleed, check the header tank is full and the pipe from it to the heating loop isn?t blocked - not uncommon on old systems.

[Andrew]

Any decent CH engineer should have thoroughly flushed the system to comply with the manufacturers warranty. Combined with the wiring error for the pump, it sounds like you got some bloke down the pub to fit it.

[alan_m]

If the pump was incorrectly wired perhaps the valve(s), controller and thermostat have been incorrectly wired.

Don't morn boilers all have a pump overrun so wiring to the pump should be a no-brainer?

[Harry Bloomfield, Esq.]

alan_m was thinking very hard :

Yep, the modern boiler controls the pump and in some cases pump speed, to run the pump to get maximum heat out of boiler once it stops burning.

It does read as if the guy who put the boiler in was clueless, was he actually gas qualified to touch a gas boiler?

[Dave Plowman (News]

Sadly being gas qualified doesn't seem to extend to understanding electrics...

[Harry Bloomfield, Esq.]

on 14/12/2021, Dave Plowman (News) supposed :

True, but he should have an idea about basic boiler control. My concern was if he couldn't manage the controls, what sort of job has he done on the gas boiler install?

[Roger Mills]

I agree with others that it appears to have been installed by a cowboy.

In order to diagnose the problems, we need more information.

Is it a vented system, with a small fill & expansion tank (not to be confused with the large cold water header tank) in the attic - or is it a sealed (non-vented) system with a filling loop and expansion vessel?

How many motorised valves are there, and what type are they - 2-port with two inline water connections, or three port with three water connections arranged in a T formation?

Is there a room thermostat? Is there a cylinder thermostat on the hot water cylinder?

[alan_m]

On a 30 year old system I'm surprised that the boiler installer didn't recommend a flush before removing the old boiler. The manfacturer of the boiler may have also recommended that a (magnetic/particle) filter in the return line be fitted. Was this done.

However I suspect that who ever gave you the above advice doesn't know what is wrong. From the limited description of your system and problems I would guess that as the pump was incorrectly wired something else is also incorrectly wired. Perhaps the rewiring of the pump is still incorrect. Does the pump run at all times when you select central heating and when you select hot water. Does the pump still run for a short time after the controller stops requesting heating or hot water?

You possibly need to narrow down the problem? Do the radiators get hot when you only ask for central heating? Do they only get hot when you select hot water as well as central heating? Do they get hot when you only select hot water?

If the valve(s) are incorrect wired you may get this.

[Dave Plowman (News]

These days, they only seem to be able to cope with system boilers.

A basic one with bits like the pump elsewhere needs more knowledge.

[Mike Rogers]

Could be air lock in the pump. Bleed via the big screw in the centre, it can take quite a lot of bleeding.

Do tell us what the cure was.

Mike

[Steve Walker]

It it is that, it is well worth fitting an air separator before the pump. Our system used to be an absolute pig to bleed after any work on it, but since fitting one, it's easy.