Rads and HW problem

[inmarset]

Hi All,

I am not highly experienced in Plumbing having just passed my level 2 but will be taking relevant NVQ’s etc.. (Wanted to make it clear I do not know it all!)

What I describe is more for an experienced Plumber but it’s a friend of a friend I am helping so it is more for experience. (He is happy for me to cut my teeth!)

Situation is this ‘friend’ has a very large house with 23-24 radiators. Worcester Bosch Greenstar 40 CDi conventional boiler for the heating and a Megaflo 250cl for Hot Water. This is a three storey house. Boiler and Mega in Basement where there is one other room with 3 rads. Then there is first floor with no heating problems at all. Second floor is a different story and the main problem, all rads are fine apart from the three rads in three bathrooms. All three of these rads are those towel warmer rads and even the flow and return pipes going into them do not get hot!! Up until three months ago they were fine apparently. The only thing to change in that time is one of those rads was replaced but when the plumber left it was working fine. First I thought airlock but is it not spookily strange that all of the conventional rads on the second floor are piping hot and the three bathroom rads are cold. I tried to drain the system down today and in a nutshell the rads in the basement and first floor drained but not on the second floor. I was just going to try and drain and refill and see if that shifted anything. (Rads have of course been bled previously and are full of water no air.)

I guess my question is, does anyone have any idea of firstly why these three rads could be playing up and secondly why it did not drain?

Second problem is that again up till a few months back hot water was nearly instantaneous throughout the house. It now takes about 30-40 seconds to come through in the kitchen which is near enough above the megaflo and about 1 minute to get hot in the farthest point of the house. I drained and refilled the megaflo (I know I can’t do too much to it as I am not unvented) as per user instructions/guide. Once refilled pressure was good and hot was at outlets within about 10 seconds but a few hours later it’s back to being cold then hot. It appears that the cold is balanced supply but I think as most taps are mixers the cold is somehow being drawn into hot pipe before hot pushes it out! I was thinking a non return valve on the hot and cold just after the megaflo may be an idea, I think Heatrae Sadia also think this (not 100% though).
Any ideas on this as well as the rad issue! (Possibly a powerflush, water is dirty’ish but not sure whether it would be justified).
Many Thanks in advance.
Gav

 

[danielp]

are the towel warmers on the heating or hot water?

if on heating turn the other rads off and let it just circulate around them

 

[stevetheplumber]

if one floor doesent drain id be looking for zone valves and possibly a gate on the return on the hot water question is there a secondary pump thats failed ?
its always hard to diagnose without seeing the job
can you trace pipework to see how far the heat is getting ?its possible that somethings got in yhe system at some point and caused a blockage polystyrene is a bugger for this as it floats up in system
But always think simple to start with when fault finding its easy to get carried away with fancy ideas

just re read the problem and i would definatly look at a secondary pump with the towel rails being on this circuit maybe a pump valve is shut

 

[migoplumber]

hot water problem is due to dead legs, indicating a problem with secondary return pump on mega flo.

heating, turn off every radiator in the house, at least one of the towel rads will get warm, if it dosn't then last plumber in has changed the pipework incorrectly, if towel rads get warm then balancing, the replace rad probably has lockshield fully open stealing all the primary heat.

good luck

 

[inmarset]

Many thanks for the replies. I believe the rads are on the hot water run now so the pump idea sounds logical as they do have the CH pump and the bronze/yellow pump.

Again, thanks
Gav

Fellas

I just came back from the house. The pump makes the sound of it working but doesnt mean it is so will try and service it myself tomorrow. Interesting thing is the pump gets hot but pipe either side is stone cold. There is a double check valve underneath the pump and a gate valve above, could either of these be an issue. Gate valve appears to be okay is there any way of checking the double check valve?

Also how exactly does the pumped hw flow into the system? The pump is not on the Direct Hot Water pipe above the megaflo it is on a seperate pipe, how then does it make the HW flow round the system? Do they meet up somewhere?

Gav

 

[migoplumber]

soundslike the pump. they get hot from working and displace that heat into the water flowing through it, helps keep them cool.

check valve could be seized if its been unused for a whille.

take the screw out of the pump, and check you can spin it freely with the power off.
turn the power on and have a look make sure its spinning

check the gate valve is open.

 

[inmarset]

Ok,

I have taken the pump off and checked the rotor, it seems to be working fine although possible not spinning as fast as I would have thought but that is an opinion only. I replaced the gate valve above the pump and replaced the check valve. The old check valve was definitely worn and I am pretty sure not working correctly.

With the new gate valve and single check valve the pipes actually got very hot either side of the pump which is an improvement over the cold pipes yesterday. However whilst one of the three towel rads got warm' ish the other two are still not playing ball. Have drained again and refilled. I do not believe there is any air in the system as all draw off points are fine and water is flowing. Just doesn't make sense as even when I bleed them the water coming from the bleed valves is not hot yet the tap hw is perfectly fine and hot. If they are on the same run should they not be hot?

Could it be that whilst the pump is working it is not working at optimum (1 speed only) and time has just taken its toll and it needs renewing or uprating. (5 yeasr old we think).

Interestingly when the system is drained and the megaflo refilled HW is fairly quick to the bathroom taps but after a day or so it goes back to normal taking a while for HW to come through again. Can this be a loss of pressure somewhere, The Megaflo does have a fair amount of limescale around the HW outlet on top and there is slight dampness.

(not sure if this helps but apparently this all started after a new shower temp mixer was installed along with a new bathroom towel radiator, this bathroom also appears to be first on the loop on the second floor).

Gav