new build - ineffective CH


Postby Silver_back90 » Wed Jan 14, 2009 7:16 pm

Hi, I'm looking for some advice please, we have a new build house (detached 3 storey), and I dont think the heating is very effective.

Basic prob is that If we set the stat to 20 degrees it don't cut out! I have had heating on today for 4 hours (raising temp in hallway from 17 to 19 degrees), it seems to me the heat is being funneled up the stairs.

The thermostat is in hallway, (which is approx 6m x 2m long with steel front door at one end and stairs at other), and the rad here is rated at 2109 btus. The rad is by the front door and the stat is on the opposite wall at the stairs end.

The other complication is that the system has two zones with the 2nd and 3rd floor controlled by a stat on the 2nd floor. However the landing on the 2nd floor appears to be getting heated up from below so need stat up here to be set at over 21 degrees to enable the bedrooms to be heated!

I have looked at some rough rad size charts and some of my rads appear to be far too small.

sorry for the long post (I hope it makes sense) any advice would be appreciated.
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Postby ericmark » Thu Jan 15, 2009 11:17 pm

My son had a problem with his. Worked A1 until he turned temp down at Christmas then seemed it would not heat up again.

Turned out to be settings on lock shield valve. New boilers don't just switch on and off but they adjust their output to match the demand this is worked out by the temp of return water.

If the house is up to temp as each room cools the radiator TRV opens and closes so the return water is cool.
But if the house is cold the radiator TRV is wide open so unless the lock shield valve is set correct the hot water goes straight through radiator and returns hot to the boiler and so turns boiler output down. As a result to start with only some radiators get hot. As the rooms with hot radiators heat up the TRV starts to work and water is forced through other radiators in the system and so long as the heating is not turned off in the end all rooms will warm up.

But it the heating is turned off at all the cycle starts all over again.
Running zones from a variable boiler also causes problems to ensure one zone does not close down boiler before another one is up to temperature.

Being fair to installer very hard to set correct during the summer.

First step must be to ensure lock shield valves are set to give 10 to 15 degs temp drop across every radiator when they are all on. i.e. TRV wide open.

For a condensating boiler to work the return water must be cool enough so the old ON/OFF method will no longer work they have to be variable output type.
ericmark

Postby Silver_back90 » Sat Jan 17, 2009 9:01 am

Thanks for replying,
I think I've probably not explained the problem properly, sorry!.

When I said it won't shut down I meant the CH pump is continuously running and although the hallway rad is on full, the temp in the hallway doesnt rise suffieciently to switch the themostat off (set to 20 deg).
It seems the rad is too small for the area, any warm air is rising to ceiling and then being funnelled up stairs without being able to radiate towards thermostat.
This then means the next landing is warming up (where the 2nd zone stat is) which means I have to have this stat set to about 22deg or else the bedrooms rads wont work!
Given the sizes above would we be better off with a double rad in hallway?
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Postby ericmark » Sat Jan 17, 2009 1:41 pm

I had a similar problem with my own house. I removed the radiator up-stairs on landing and fitted an extra radiator down-stairs.

But you say down-stairs radiator not getting warm so I wonder about lock shield valve setting and bleeding.

Second although I can see a point in timed zone up-stairs not sure about temperature control!

My up-stairs radiators all have TRV which stop up-stairs getting too warm with down-stairs on normal room stat.

But with my sons house he has a modern boiler which gives variable output so the whole of the house is controlled with TRV's and the thermostat's only job is to switch off system in summer months to stop cycling.

With my house the thermostat controls the circulation pump but with his house the boiler controls the pump and thermostat only shuts down boiler.

To fit zone valves to switch between bedrooms and living rooms at different times of the day makes very good sense but with modern systems the thermostat position is completely different to with old systems.

Placed in cool area but where it can be warmed by morning sun. Even outside as all the room temperature control is done with TRV's the only function for the thermostat is to switch off system when we have the odd nice day.

Modern boilers have a crude anti-cycle built in and they measure the return temperature of the water but it is easy for the system designer to mess up.

In my daughters house the previous owners changed the closed gas fire for an open gas fire looked great with glowing coals just like a coal fire. But this meant the chimney was open and it had the chimney effect and sucked the heat out of the room and went to help the globule warming. But it was not noticed in the living room as it was drawing in warm air from hall but the hall was very cold. My son-in-law tried all sorts fitting an extra door between hall and front door etc. And like you considered a bigger radiator in hall. But cure was a simple bin bag over living room fire. As soon as he can afford it he will swap fire for a closed type.

It can be very misleading as to causes to problems.

Eric
ericmark

Postby Silver_back90 » Sun Jan 18, 2009 3:55 pm

System is basically all working as it should, all rads are getting hot and both thermostats (Hallway and 1st floor) have been cross checked with other thermometers.
With an outside temp of about 8 degrees I noted following internal temperatures:
Hallway 17deg
Ist floor landing 18.5
I set the hallway stat to 20deg left the 1st floor stat at 18deg, and an hour later I checked the temperatures:
Hallway 19deg
1st Floor landing 19.5
The hall thermostat had not clicked out at all and the system had been running constantly for the hour.
I took a temp reading at the ceiling by the stairs: – 25 degrees!
Therefore it seems to me (IMHO) that most of the heat from hallway rad (2109 btu )is being funnelled up stairs and heating 1st and 2nd floor landings without being able to warm up the hallway sufficiently to trip the stat. This means the heating system is going constantly (and costing me a fortune).
The other downside is that to get any heat into the bedrooms (1st and 2nd floor) I have to have 1st floor stat set to 22/23deg!
This just does not seem right for a new build house, and I was wondering if any Heating Engineers on here could give their opinion.
Sorry it’s a long post, but I just wanted a 2nd opinion before I contact the builder
Thanks
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Postby ericmark » Sun Jan 18, 2009 8:46 pm

I would copy and paste and re-post once answered fewer people look.
It does seem set-up wrong. With zone control the system can get complex and I am only an electrician.
ericmark

Postby plumberathome » Mon Jan 19, 2009 9:15 pm

[quote="Silver_back90"]System is basically all working as it should, all rads are getting hot and both thermostats (Hallway and 1st floor) have been cross checked with other thermometers.
With an outside temp of about 8 degrees I noted following internal temperatures:
Hallway 17deg
Ist floor landing 18.5
I set the hallway stat to 20deg left the 1st floor stat at 18deg, and an hour later I checked the temperatures:
Hallway 19deg
1st Floor landing 19.5
The hall thermostat had not clicked out at all and the system had been running constantly for the hour.
I took a temp reading at the ceiling by the stairs: – 25 degrees!
Therefore it seems to me (IMHO) that most of the heat from hallway rad (2109 btu )is being funnelled up stairs and heating 1st and 2nd floor landings without being able to warm up the hallway sufficiently to trip the stat. This means the heating system is going constantly (and costing me a fortune).
The other downside is that to get any heat into the bedrooms (1st and 2nd floor) I have to have 1st floor stat set to 22/23deg!
This just does not seem right for a new build house, and I was wondering if any Heating Engineers on here could give their opinion.
Sorry it’s a long post, but I just wanted a 2nd opinion before I contact the builder
Thanks[/quote]
Hi just been reading about your problem are other radiators downstairs getting as hot as upstairs rads if not then the zone valve for the ground floor could be part closed and not allowing enough flow thru also try balancing system on lockshield valves start nearest boiler and just crack open about quater turn then move to next and adjust in the same way but open slightly more do this with all rads you shouldnt need to do this but it may help .If other rads downstairs are hot you could have a pipe that is restricted to the hall radiator if pipework is micro bore it could be a flattened bend or a kink in the pipe.Another cause could be the way the feed to the rad is branched off the main pipework sometimes it can pump past the branch and cause problems ,It could of course be simply that the rad is too small .By the way the room stat normally is placed in the coldest place in a building or where there is chance of air temp change ie opening of external door that is why it is in the hall.
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Postby Silver_back90 » Mon Jan 19, 2009 10:55 pm

thanks for the reply,
no all the rads are getting hot enough, the problem appears to be that the hallway rad is too small to heat up the hallway sufficiently to make the thermostat cut out. The wall directly above the rad gets really hot, and the air at the ceiling by the stairs gets to about 25 deg. The stat is placed about 8' away from rad diagonally and most of the heat generated by rad seems to be going up the stairs, the rad is about 2100 btus, would a double rad be more suitable given the conditions I've previously described?
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