Heating Partial Load

[blowlamp]

Why don't you get some bigger radiators fitted? It sounds like it would help with the constant boiler cycling and give you a warmer home too.

[rs1987]

Why don't you get some bigger radiators fitted? It sounds like it would help with the constant boiler cycling and give you a warmer home too.

I plan to try this, but my landlord is pretty unreasonable. When I moved in here there was absolutely no heating control at all. No timer on the boiler, no thermostat.

I proposed to the landlord that I fit Evohome, entirely at my own expense, as well as replacing the existing Honeywell valve bodies with new Honeywell valve bodies. Zero outlay on his part.

He refused.

Only after I cited the 2015 building regulations that do not allow a landlord to unreasonably withhold consent for energy efficiency improvements if they're funded by the tenant did he finally agree, and grudgingly so.

So I don't have an expectation that he will agree, even if I pay for these radiator upgrades myself (which I would do, since the cost of moving house is vastly more expensive with removal companies, end of tenancy cleaning, etc. etc, and anyway, I happen to really like this property except for the dismal heating performance).

I am currently looking at some radiator upgrades, although in one case the available space does not allow for a large enough radiator (it's about 2000 BTU short of requirements) and another case the existing radiator is a very strange width of 950mm and I can't find any type 22s that are 950mm in width and higher than 600mm. The pipework won't allow a wider radiator.

[blowlamp]

Anything suitable here?

[mtmcgavock]

Yes, I turned Evohome back to its normal set point. It only anti-cycles, and infrequently, when the rest of the zones are up to temperature and there is only one rad open. It's a big improvement.

You're correct that the rads are undersized in some rooms. So I have a double problem: oversize boiler and undersize rads. The main hallway rad is on pretty much permanently just to maintain the zone at 19 degrees. The living room rad is too small for the room but eventually manages to get the room to 21 degrees after a few hours, although it then is also on pretty much permanently in order to maintain the temperature. The conservatory (double glazed) which serves as a dining room has a woefully undersized radiator that cannot even maintain a 15 degree set-point in this weather, so I leave it off and heat with a 3kw electric radiator during the times I need to use the room.

I'll experiment with different flow temps to check what the gas usage as. I really need to run at a higher temp to compensate for these undersized rads. I'm a little fearful of the result though, as I recall before I put in Evohome I had a gas bill of £200+ for 30 days usage in one month when running a flow temp of 65 degrees and only a few rooms in the house were actually being heated.

Yeah with small/undersized rad sizes you need to be ideally running it at 75oc. You're possibly having the opposite effect running at lower temperatures - as the boiler not meeting/maintain set points it's just running constantly using more gas than it would at a higher flow temp. I'd run it at 75oc and see if it makes a difference - take meter readings and see.

I wouldn't say the boiler is oversized massively when you think a normal system you'd have a demand of at least 50% in normal use which would equate to more than 5kw which it can modulate down to, i'd probably just the wrong boiler for the property. Sounds like it needed a system boiler and Unvented cylinder.

So next step it seems is to have an engineer come and close down my bypass valve from the default to about 3/4 closed, if I recall your instructions correctly.

If you've got bypass radiators such as towel rails etc. i'd be tempted to just close it completely.

[rs1987]

Anything suitable here?

Hmm, you're right. I didn't think that this was perhaps an imperial size radiator I have in the hallway. All the others are metric. Looking at the sizes in this chart it appears to be a 37 inch. That said, the ones in this brochure are not tall enough to make any difference as my existing one is 600mm high and the highest on offer in this catalogue is 690mm. I really need something about 900mm high.

I'll have to investigate whether a 900mm x 900mm or a 1000mm x 900mm could fit with a slight bend in the pipes on either size or perhaps a small shim for the 900mm wide radiator.

[rs1987]

If you've got bypass radiators such as towel rails etc. i'd be tempted to just close it completely.

I do. Two towel radiators and one in the dressing room that I've opened to max to allow for some heat dumping to prevent anti-cycling.

Surely closing these rads off would make the system go into anti-cycle mode more frequently?

[mtmcgavock]

No, I meant you can close the internal bypass completely. Think you misunderstood.

[rs1987]

No, I meant you can close the internal bypass completely. Think you misunderstood.

Ah right, gotcha - I did misunderstand. Thanks for the clarification.

[blowlamp]

Hmm, you're right. I didn't think that this was perhaps an imperial size radiator I have in the hallway. All the others are metric. Looking at the sizes in this chart it appears to be a 37 inch. That said, the ones in this brochure are not tall enough to make any difference as my existing one is 600mm high and the highest on offer in this catalogue is 690mm. I really need something about 900mm high.

I'll have to investigate whether a 900mm x 900mm or a 1000mm x 900mm could fit with a slight bend in the pipes on either size or perhaps a small shim for the 900mm wide radiator.

Yes, a 900mm wide radiator with a pair of these to get the right fit.

[bruce_miranda]

No, I meant you can close the internal bypass completely. Think you misunderstood.

Just make sure you don't have a Zone Valve on the CH that shuts off before even the first radiator. That's when the bypass is really needed.